Saiga 12 will not cycle low brass, I expected this but want to make su

[Mullet Man 2,114]

Let's see... If ya want to use a double hook trigger in a receiver like the Saiga with only one notch... do you :

A. Drill and cut another matching notch neatly on the other side of the trigger hole to clear the sear... or...

B. Hack out a huge square hole just because you can and some guy happened to post a tutorial on an AK forum saying to do that to fix the binding prob???

 

C: Neither, I would use the link in Gunfuns signature and set it up as an over travel limiter. Which is a really great idea actually.

 

Gas seal? You're trying to say that two pieces of metal, one threading into another that has a machined lip and no over lap of the female side, somehow creates a seal? Maybe we should write the big three and tell them they're wasting money on all the piston rings they keep installing on those internal combustion engines. It's not a press fit, there is no gasket or o-ring. Only threads.

Anybody can confirm this, please un thread your regulator and look at the carbon build up that encompasses the entire recessed ring around the circumference of the gas block. It will be filled with carbon on a dirty gun. I just verified this with mine and I didn't file into the recess to supposedly cause what you're claiming. There is no true "Gas seal" there because apparently, shit is getting into that ring.... but alas, my threads were clean and the Autoplug threaded out by hand, surprisingly easy too. Hmmm is it possible that the threads are the only form of a seal, maybe?!

 

  Once my camera battery charges, I will post up pictures. I'll even stick a pair of calipers on the Autoplug and on the factory regulator, in front of the threads, to see what difference resides there.

Edited October 17, 2013 by Mullet Man

[poolingmyignorance 2,191]

Looks like I have 4 ports, not 3.

 

Cane someone give me the size for a 4 port barrel? Also what size drill bit?

It will be fine for 4.  3/32= 0.0945 will be fine. yes it's a little bigger. If your nervous get a  (.0625) and drill all four out to that. and test. You can step it up as needed till you get the results you want.  Once you get the block off once it goes on and comes off with less fight. Only real risk is bending your pins. If you deform them you can just slightly bevel the end, to get it started.

If you go with the 3/32 you can add auto plug, or other after market plug if your concerned about over gassing. Don't go bigger than that, without some prohelp.

[Nephilim7 107]

Gas seal? You're trying to say that two pieces of metal, one threading into another that has a machined lip and no over lap of the female side, somehow creates a seal? Maybe we should write the big three and tell them they're wasting money on all the piston rings they keep installing on those internal combustion engines. It's not a press fit, there is no gasket or o-ring. Only threads.

 

I agree with your statement about the G2 trigger. Mine works very well as an overtravel limiter.

 

About the seal:

I don't know much about fluid dynamics, but I'll tell you what my gut tells me.

 

I would imagine that channel creates a zone of disruption right at the area that needs sealed. During the short pulse of high pressure gas impingement, the gas flows into the channel ring and moves in swirling motion. This creates a boundary layer of gas flowing across the seam instead of out of the gas block, blocking outflow similar to an o-ring. In effect, a temporary seal of high speed gas manifests for a short time as soon as high flow enters the chamber of the block, keeping much gas from escaping.

 

I also believe this is how the channel rings seal the gas puc during the power stroke.

 

This is all in my imagination and may be completely false. Just a guess really...

Edited October 18, 2013 by Nephilim7

[Mullet Man 2,114]

My gut tells me that there is way to much thought put into this and the only reason someone in particular wants the thread un stickied is because she thinks her thread is better. By the replies (often over the top rants), you can tell there is a bit of an ego that needs stroked.

 

I mean fuck, Bob Ash even said it was a great tutorial that needed stickied (post #12 in the D mod thread).

 

Anyway, my camera sucks, it has no macro setup, so close up pics turn out all blurry.

 

Nephilim, here me out for a second. If that zone of disruption needs to be sealed, then why is it a zone of disruption, if its suppose to be sealed off from the gasses? I don't know shit about fluid dynamics but I do know that if there is still a lip that creates the recessed channel between the threads and port window, it still allows gases into the recessed channel. This logically tells me that if there is no lip there (one files into the recessed channel like the D mod), that gases are still going to get into that recessed channel....at this point, I say to myself "what the hell does it matter if gases are getting into that channel regardless if there is a lip (seperation) or not???" Picking up what I'm throwing down?

 

That double hook trigger mod is an awesome idea and I wish I had thought about or known about it when I did all my conversions years ago.

[misterT 174]

To the OP for what its worth all I did to mine was polish the mating surfaces and it run great. I read a suggestion on here to try using a paper clip to feel all four gas ports. If they all feel unobstructed you should not need any porting just some careful polishing to reduce friction. The new FCG you installed should have had the hammer profiled already cobra has good pics on here of what it should look like. You can see in my gallery what I did following others advice on here and works great good luck

[gunfun 3,931]

Q:

A. Drill and cut another matching notch neatly on the other side of the trigger hole to clear the sear... or...

B. Hack out a huge square hole just because you can and some guy happened to post a tutorial on an AK forum saying to do that to fix the binding prob???

 

 

Answer:

C: file a little off of the underside of the second hook to eliminate the interference and leave the receiver alone.

Or D: file a little off of the underside of the second hook to exploit the interference as an overtravel stop. and leave the receiver alone.

 

Otherwise we agree.

[Terminator03 18]

You guys talking about that "gas channel" are way over thinking its importance for sealing. It was not designed to create a disruption in gas flow, seal, or any such thing. It is a simple machining technique used to break the threaded section so that the gas plug can screw all the way in and not be limited by the depth of threads that were cut. It's really that simple, its just a relief cut. On the topic of sealing the threads though, I have experimented with my setup when I had some FTEs with low brass, and found that the situation greatly improved by Teflon taping the threads on the gas plug. This tells me that I likely have to open my ports just a bit more as that simple experiment allowed more gas to remain in the system and it instantly "fixed" the cycling. My gun is already highly polished, smooth as glass cycling, .093 x 4 ports, etc., and runs great on almost everything, but I am trying to get it to run even the cheapest bird shot which is still not 100% (but close). I had zero failures on the next 50 rounds after taping so that tells me I'm pretty close now.

[Cobra 76 two 2,677]

Excellent pointsT-03. I've always used Never-Seez on my threads and it helps both retain compression and eliminates carbon getting in there and gluing the plug to where it's stuck.  If carbon is being blown up into the threads you can be damn sure some gasses are escaping though there, so either way...graphite grease of teflon tape, it helps for sure. That is one reason I think S-12s tend to run better after they have been shot a lot of times, and people start all those threads saying "what's wrong with my Saiga now? I cleaned it and now it won't cycle..." I have run mine with no cleaning at all for over a thousand rounds, and it kept working great til there was a giant carbon biscuit built up in there the size of my gas puck. You couldn't even see the puck when I unscrewed the plug. Had to knock it out from behind with a wooden down and hammer.

 

 As far as cutting back into the recess goes, it doesn't matter as much to me what it is for as much as it matters not to cut that much material away that otherwise increases the surface in the gas chamber. If the designers of the weapon had wanted to cut a giant gaping hole in there with square edges and corners to catch more crud and hold it, they would be making the gas blocks that way already. I just think it's dumb to go that far overboard with a totally unnecessary mod. Do ya really believe they would still be building Saigas and Veprs with as small an opening  as possible, beveled underneath to gain better access like they do, knowing full well it is causing problems in some guns they don't get it lined up right on? They could easily change one bit in one boring process from the bottom of the gas block, or even bore a little deeper, and there would be less S-12s coming out with gas delivery problems. Maybe Jeff D should apply for a job at Izhmash in the design dept if that's how all S-12s should be done. Hey while you are there tell em they are overbuilding bolts and there is a much better way... just takes a lot more time. All that the ports need is a clear opening the size of their own diameter. Of course others who have already done it to their guns will defend it to the end. Whatever... That doesn't mean it should be stickied and have every new guy who comes here doing it like it's a magic bullet that will fix their guns. I'm just saying it's total overkill when a very small bevel to remove a small amount of the lower side, is plenty enough to get just as much flow, and barely even change the size or shape of the hole as seen from the top.

 A certain other person who has it out for me will continue to claim I want it removed just to make some thread I don't even know where it is, but I have posted in, look better. Grow up dude. It has zero to do with me, and is only one of the stickied threads leading people to do unnecessary things to their S-12s with excessive dremel hacking. One is about the D mod and the other which is even worse, is quoting text and pics of this mod. My biggest concern the whole time has not even been Jeff's thread, it's that other one that apparently more and more people read and follow like a DIY book, and has people destroying their bolts & carriers after reading that nonsense.

THIS thread>>> http://forum.saiga-12.com/index.php?/topic/55377-my-saiga-12-from-start-to-finish/

OK now mullet go on tell everyone I only want that thread removed from sticky because it hurts my business by showing people how they should really be doing their own bolts & carriers. Wow man you never let up. Enjoy yourself and keep on defending your hacked up gas block mulletman. I have better things to do if people don't want to hear good advice and doubt if anyone cares what you are saying.

[Mullet Man 2,114]

Through your self proclaimed expertise on the subject, you can't or won't (most likely can't, since you've had multiple opportunities to tell why and fail to do so) provide a technical answer. All I'm looking for is a reason why and all you can come up with is that its "stupid" and "stupid is as stupid does". I've given an example as to why the "gas seal" doesn't make any sense to me and you can't counter with any sound reasoning or explanation as to why I'm wrong and why the mod itself is "destructive" or a "hack job".  I don't care about your business. But I expect an "expert" to be able to define why in some sort of technical form or data, especially with the claims you've made in this thread

.

What does "increases the surface in the gas chamber" mean?  

[Cobra 76 two 2,677]

Figure out what it means shirlock, I don't have time to take any more of your troll bait. Have a day.

[Mullet Man 2,114]

Gotta say, that wasn't not expected. Thanks for sharing your "expertise".

 

Edited to add quotations.

Edited October 19, 2013 by Mullet Man

[pedal2alloy 206]

Through your self proclaimed expertise on the subject, you can't or won't (most likely can't, since you've had multiple opportunities to tell why and fail to do so) provide a technical answer. All I'm looking for is a reason why and all you can come up with is that its "stupid" and "stupid is as stupid does". I've given an example as to why the "gas seal" doesn't make any sense to me and you can't counter with any sound reasoning or explanation as to why I'm wrong and why the mod itself is "destructive" or a "hack job".  I don't care about your business. But I expect an "expert" to be able to define why in some sort of technical form or data, especially with the claims you've made in this thread

.

What does "increases the surface in the gas chamber" mean?  

 

The mod increases the volume of the gas space which can reduce the energy of the gas pulse.  Also, it increases the nooks and crannies for crud to catch on.  But mainly it's that most guns don't have blocked gas ports.

[Terminator03 18]

 

Through your self proclaimed expertise on the subject, you can't or won't (most likely can't, since you've had multiple opportunities to tell why and fail to do so) provide a technical answer. All I'm looking for is a reason why and all you can come up with is that its "stupid" and "stupid is as stupid does". I've given an example as to why the "gas seal" doesn't make any sense to me and you can't counter with any sound reasoning or explanation as to why I'm wrong and why the mod itself is "destructive" or a "hack job".  I don't care about your business. But I expect an "expert" to be able to define why in some sort of technical form or data, especially with the claims you've made in this thread

.

What does "increases the surface in the gas chamber" mean?  

 

The mod increases the volume of the gas space which can reduce the energy of the gas pulse.  Also, it increases the nooks and crannies for crud to catch on.  But mainly it's that most guns don't have blocked gas ports.

 

 

This is exactly the correct answer, and even if Cobra didn't answer it in his latest posts, he has answered this before in this thread. It is simple physics that when you are trying to increase pressure, the volume needs to decrease when the source of that pressure doesn't, or can't increase (in this case cheap, low brass ammo). This is why in an internal combustion engine, they either add dome pistons, or REDUCE the size of the combustion chamber (or both) to increase compression on high horsepower engine builds. When you do the "D port" mod, it may very well work in your gun, but that doesn't mean that it will work in every case, and in some, it may actually make the situation worse by increasing volume, which decreases pressure, that is all Cobra was trying to point out. Once you remove all of that surface area it is also very difficult (not impossible) to put that material back, unless you are very good at TIG welding, and machining. This is why the guys that have played with these guns for a long time ALWAYS recommend removing material in small increments rather than just hogging the gas ports, or in this case, gas block out. I fully expect that the "D port" does in fact work on some guns, but I bet that they would have worked even without that, and the "D port" was done in combination with drilling the ports bigger so it was assumed that it solved the problem, when just drilling the ports alone had the biggest effect. I'm just glad that I personally took the time to study this platform and read as much as I could about it along with experimenting with each step separately as I progressed before just jumping in and cutting stuff because some guy on an internet forum thought it was a good idea. I agree that that thread should be taken down even though I have no personal, or business stake in this at all!

[burntpowder 23]

I really wish I would not have posted in this thread a few days ago.

 

Anyhow I too agree it (D-Mod Thread) should be taken down or allowed to be majorly edited.  I even posted in that thread long ago that it helped me out but what helped me was a step here and there and not the entire thing.  I have in no way been on this forum as long as others but what does that really mean?  When I first was looking into the S12 and came here looking for information about the firearm and what people liked/disliked about it and what problems I could run into so I made a mental note that the D-MOD was something I may have to do if I have FTE on low brass since it is the very first thread when you come into the S12 section so it has to be a community accepted modification to fix FTE or it would not be the very first thread, right?  Are highly controversial threads about making modification to a firearm which may or may not be needed always the very first thread you see when you go to a firearms forum?

 

Maybe put a disclaimer at the top of that thread that says something like, "you do not have to do all of this to your firearm but this thread has pictures and bulleted steps so since it is formatted beautifully we are keeping it stickied".

 

-bp

[Mullet Man 2,114]

 

The mod increases the volume of the gas space which can reduce the energy of the gas pulse.  Also, it increases the nooks and crannies for crud to catch on.  But mainly it's that most guns don't have blocked gas ports.

 

 

This is exactly the correct answer, and even if Cobra didn't answer it in his latest posts, he has answered this before in this thread. It is simple physics that when you are trying to increase pressure, the volume needs to decrease when the source of that pressure doesn't, or can't increase (in this case cheap, low brass ammo). This is why in an internal combustion engine, they either add dome pistons, or REDUCE the size of the combustion chamber (or both) to increase compression on high horsepower engine builds. When you do the "D port" mod, it may very well work in your gun, but that doesn't mean that it will work in every case, and in some, it may actually make the situation worse by increasing volume, which decreases pressure, that is all Cobra was trying to point out. Once you remove all of that surface area it is also very difficult (not impossible) to put that material back, unless you are very good at TIG welding, and machining. This is why the guys that have played with these guns for a long time ALWAYS recommend removing material in small increments rather than just hogging the gas ports, or in this case, gas block out. I fully expect that the "D port" does in fact work on some guns, but I bet that they would have worked even without that, and the "D port" was done in combination with drilling the ports bigger so it was assumed that it solved the problem, when just drilling the ports alone had the biggest effect. I'm just glad that I personally took the time to study this platform and read as much as I could about it along with experimenting with each step separately as I progressed before just jumping in and cutting stuff because some guy on an internet forum thought it was a good idea. I agree that that thread should be taken down even though I have no personal, or business stake in this at all!

 

To counter that, on high horsepower forced induction builds the pressure is greatly increased, as well as volume. Which is one reason low compression, dished pistons and enlarged valves and valve bowls are utilized. Air isn't being sucked in by a piston on the downward stroke on an S12, it's being forced in by the pressure of expansion because of the friction holding whatever projectile is still in the barrel. Which is why longer barrel S12's had fewer ports because of the increased dwell time the chamber had to be filled with.

To much pressure to fast in the gas chamber could have what effect? Timing perhaps, premature cycling of the action maybe?

[Terminator03 18]

 

 

The mod increases the volume of the gas space which can reduce the energy of the gas pulse.  Also, it increases the nooks and crannies for crud to catch on.  But mainly it's that most guns don't have blocked gas ports.

 

 

This is exactly the correct answer, and even if Cobra didn't answer it in his latest posts, he has answered this before in this thread. It is simple physics that when you are trying to increase pressure, the volume needs to decrease when the source of that pressure doesn't, or can't increase (in this case cheap, low brass ammo). This is why in an internal combustion engine, they either add dome pistons, or REDUCE the size of the combustion chamber (or both) to increase compression on high horsepower engine builds. When you do the "D port" mod, it may very well work in your gun, but that doesn't mean that it will work in every case, and in some, it may actually make the situation worse by increasing volume, which decreases pressure, that is all Cobra was trying to point out. Once you remove all of that surface area it is also very difficult (not impossible) to put that material back, unless you are very good at TIG welding, and machining. This is why the guys that have played with these guns for a long time ALWAYS recommend removing material in small increments rather than just hogging the gas ports, or in this case, gas block out. I fully expect that the "D port" does in fact work on some guns, but I bet that they would have worked even without that, and the "D port" was done in combination with drilling the ports bigger so it was assumed that it solved the problem, when just drilling the ports alone had the biggest effect. I'm just glad that I personally took the time to study this platform and read as much as I could about it along with experimenting with each step separately as I progressed before just jumping in and cutting stuff because some guy on an internet forum thought it was a good idea. I agree that that thread should be taken down even though I have no personal, or business stake in this at all!

 

To counter that, on high horsepower forced induction builds the pressure is greatly increased, as well as volume. Which is one reason low compression, dished pistons and enlarged valves and valve bowls are utilized. Air isn't being sucked in by a piston on the downward stroke on an S12, it's being forced in by the pressure of expansion because of the friction holding whatever projectile is still in the barrel. Which is why longer barrel S12's had fewer ports because of the increased dwell time the chamber had to be filled with.

To much pressure to fast in the gas chamber could have what effect? Timing perhaps, premature cycling of the action maybe?

 

 

Well, your analogy, while I see what you're trying to say is not as applicable as a naturally aspirated engine, since there is no method of forced induction. I understand the low compression thing well as my screen name reflects my current toy which is a 625 rwhp "Terminator" Cobra, which has a twin screw supercharger. As far as the effects on timing, I'm not an expert on that, but I don't believe that it has any effect on dwell time because the relative position of the ports is unchanged. I also don't think that the "D port" increases the velocity of the gas charge at all, in fact it likely slows it down with increased volume. I like using the internal combustion chamber analogy here because I feel these guns need to retain the same compression ratio, but increase the volume of gas available to operate effectively with low powered ammo.For this reason alone, I feel that removing too much material in the "combustion chamber" (gas block) will in effect lower the compression ratio to the point that you would need a "power adder" (or in this case a more powerful shell) to do the same work. I'm glad that the D port works in your gun, but to think that it would work for EVERY S12 is probably overoptimistic. Did you test the gun after opening the ports, but BEFORE doing the D port mod? My belief is that most people will do it all "while they are in there", and not in stages, so they never really know what part solved their problem.

[poolingmyignorance 2,191]

Well I'm not sure about the science surrounding the "D" mod. However wonder the logic behind grinding more metal than required to a alleviate obstructed ports. Perhaps an excessive quantity of overly sharpened Dremel carbides, that need to be dulled on Russian steel?

[Mullet Man 2,114]

I believe the forced induction analogy holds more weight here than NA does, for two reasons...

1: When the firing pin hits the primer and sends the projectile down the barrel, it's going through a sealed chamber (barrel) where the ever expanding gases have no escape, until they reach the gas ports at which point they are forced into the gas chamber simply because at that point it has nowhere else to go. Much like a Blower or Turbo forcing and filling (pressurizing) an intake manifold. It's continually forced or stuffed into the gas chamber until the projectile leaves the barrel and all pressure is released.

2. Naturally aspirated motors work off the downward suction of a piston pulling air and fuel out of the intake manifold and into the combustion chamber. They by nature make more power when everything in relation is larger like stroke, cylinder bore, valves, camshaft I/E overlap and especially aggressive timing.

 

I didn't say anything about the "D" mod increasing velocity at all. All I said is that it seems to have no noticeable effect on volume like some have claimed, see post #34 for my example.

 

No, I didn't test the gun after opening the ports and before the "D" mod. I was in there to do one thing, fix the gassing issue. However, I only opened two of the three ports that my particular S12 has (1 @ 5/64 + 2 @ 3/32). One of the two that were obstructed towards the threads and the lone port at the top of the triangle arrangement. So I guess I increased the volume of the gas block but didn't increase the flow enough to offset the increase in volume if you go by a typical recommendation for a 3 port gun of 3 ports @ .093"...

 

I'm a forced induction junky too I've played around a little bit with '86-'87 Turbo Buicks and currently own an '86 RX7 powered by a '00 LS1 with a single 76mm BB Turbonetics tc76 @ 14psi  and a solid axle 8.8 with a Watts link under the back end. 

[Terminator03 18]

I believe the forced induction analogy holds more weight here than NA does, for two reasons...

1: When the firing pin hits the primer and sends the projectile down the barrel, it's going through a sealed chamber (barrel) where the ever expanding gases have no escape, until they reach the gas ports at which point they are forced into the gas chamber simply because at that point it has nowhere else to go. Much like a Blower or Turbo forcing and filling (pressurizing) an intake manifold. It's continually forced or stuffed into the gas chamber until the projectile leaves the barrel and all pressure is released.

2. Naturally aspirated motors work off the downward suction of a piston pulling air and fuel out of the intake manifold and into the combustion chamber. They by nature make more power when everything in relation is larger like stroke, cylinder bore, valves, camshaft I/E overlap and especially aggressive timing.

 

I didn't say anything about the "D" mod increasing velocity at all. All I said is that it seems to have no noticeable effect on volume like some have claimed, see post #34 for my example.

 

No, I didn't test the gun after opening the ports and before the "D" mod. I was in there to do one thing, fix the gassing issue. However, I only opened two of the three ports that my particular S12 has (1 @ 5/64 + 2 @ 3/32). One of the two that were obstructed towards the threads and the lone port at the top of the triangle arrangement. So I guess I increased the volume of the gas block but didn't increase the flow enough to offset the increase in volume if you go by a typical recommendation for a 3 port gun of 3 ports @ .093"...

 

I'm a forced induction junky too I've played around a little bit with '86-'87 Turbo Buicks and currently own an '86 RX7 powered by a '00 LS1 with a single 76mm BB Turbonetics tc76 @ 14psi  and a solid axle 8.8 with a Watts link under the back end. 

 

Ok, I see your point with regard to the forced induction analogy, however, you left out one point. Normally, as you mentioned earlier, it is necessary to run lower compression by increasing chamber volume, dishing pistons, etc. because the power adder makes up for the lack of static compression. In the case of our guns, our power adder, in this example low brass, can't make up the deficit in compression loss, which is why we can't afford to lose that when adding more volume alone through porting. See what I'm saying?

 

That RX7 project sounds like a fun little ride!

[gunfun 3,931]

Well this poor guy's thread just went off the rails.

[burntpowder 23]

Well this poor guy's thread just went off the rails.

It should prolly be stickied......................

[Mullet Man 2,114]

 

I believe the forced induction analogy holds more weight here than NA does, for two reasons...

1: When the firing pin hits the primer and sends the projectile down the barrel, it's going through a sealed chamber (barrel) where the ever expanding gases have no escape, until they reach the gas ports at which point they are forced into the gas chamber simply because at that point it has nowhere else to go. Much like a Blower or Turbo forcing and filling (pressurizing) an intake manifold. It's continually forced or stuffed into the gas chamber until the projectile leaves the barrel and all pressure is released.

2. Naturally aspirated motors work off the downward suction of a piston pulling air and fuel out of the intake manifold and into the combustion chamber. They by nature make more power when everything in relation is larger like stroke, cylinder bore, valves, camshaft I/E overlap and especially aggressive timing.

 

I didn't say anything about the "D" mod increasing velocity at all. All I said is that it seems to have no noticeable effect on volume like some have claimed, see post #34 for my example.

 

No, I didn't test the gun after opening the ports and before the "D" mod. I was in there to do one thing, fix the gassing issue. However, I only opened two of the three ports that my particular S12 has (1 @ 5/64 + 2 @ 3/32). One of the two that were obstructed towards the threads and the lone port at the top of the triangle arrangement. So I guess I increased the volume of the gas block but didn't increase the flow enough to offset the increase in volume if you go by a typical recommendation for a 3 port gun of 3 ports @ .093"...

 

I'm a forced induction junky too I've played around a little bit with '86-'87 Turbo Buicks and currently own an '86 RX7 powered by a '00 LS1 with a single 76mm BB Turbonetics tc76 @ 14psi  and a solid axle 8.8 with a Watts link under the back end. 

 

Ok, I see your point with regard to the forced induction analogy, however, you left out one point. Normally, as you mentioned earlier, it is necessary to run lower compression by increasing chamber volume, dishing pistons, etc. because the power adder makes up for the lack of static compression. In the case of our guns, our power adder, in this example low brass, can't make up the deficit in compression loss, which is why we can't afford to lose that when adding more volume alone through porting. See what I'm saying?

 

That RX7 project sounds like a fun little ride!

 

 

But the low brass example you are using, does have the ability to make up the deficit as witnessed by the umpteen testimonials of people who have and have not done the "D" mod and who have increased the size and or amount of their gas ports, in all kinds of combinations of the above. Many a folks unable to cycle low brass before, were able to do so after. That is a hard fact to argue against. It's a rare occurance that you read topics on here of guys coming back after porting, saying there gun has not improved cycling. Some do report variances in the ability (marginally better, still issues with Win bulk etc.) but rarely have you read anyone saying its worsened the problem.   

It comes down to this (in my eyes), the power is always there with whatever shell you use, it's just whether or not it's able to get thru, into the gas block. Really the gas side of the S12 is not this complicated. 

 

RX7 is definitely fun, 2900lbs with driver and it does exactly what I want it to do....stomp Mustangs and imports.  

[montec 164]

Well, I may not have read all the posts here.  Seems his issue is possibly not a broken in gun.

 

Instead of throwing parts and doing dangerous mods, put all the stock parts back in and take it out and run some high brass or high power loads thru it and see if it functions with that.

 

I read this forum and looked @ the issues that I could have with buying one of these Guns.  First thing I did was take it out when I brought it home and fire some High Power/High Brass load thru it, about a 100 of them before I even attempted to shoot fed bulk pack.  

 

I had just recently tried some win target loads and they didn't function so I know to stay clear of that for now, but everything else runs in it.

 

I agree there is alot of bad info on here but there is also so much good and great info, you just have to spend the time reading thru threads to find the correct way to do something.  As we are mostly here, garage/kitchen table gunsmiths working on these things.

 

Read, Read, Read is all I can say before you start doing any drilling or grinding away on these as they are a pretty penny and sometimes hard to get ahold of and there isn't any way to get some replacement parts without buying another one.

 

I'd like to welcome the member here and hope he can find the correct and accurate information that he needs to get this functioning properly.

[mike989 1]

I had FTE with the cheap low base shells as expected from reading all the posts. I polished the bolt, I gently changed the abrupt angle which the bolt contacts the hammer when re setting the hammer for the next shot. It made working the bolt by hand much easier, but it did not fix the FTE with all stock parts. I read and read and read, decided to remove the gas block with a air hammer on a very low setting. Worked great. While the block was off I could clearly see all my slightly larger than 062 ports were un obstructed. A nice black ring around the diamond.I choose not to enlarge the port's, I add a 5th 062 hole in the middle of the diamond. With the stock gas plug I still had FTE 50% of the time, I installed a 3 position plug like the 5 position MD plug. Works 100% on the large opening with any low base, 7.5, 8 and 9 shot shell I've run through it. I adjust it to the smallest opening and it works great on slugs and 00 buck, but wont eject the low base shells. I've got about 800 round through it, about 200 round a session since the mod and it's runs great. I don't notice a lot more debris in the gas block area than before the mod, and I had about 500 round run through it before I did the conversion, and then the mod. I'm done with the mods until I get the paperwork back for the 12" SBS.