Carrier to frame impact...

[barely 5]

I discovered this today while shooting my Saiga 12. Using some blue painters tape, I wanted to see whether my carrier was hitting the frame upon recoil. Thought that I would share with everyone to see what others thought. I was NOT aware that the carrier was hitting the frame consistently during recoil as I'll show below and wanted to know your thoughs about whether this is normal.

 

Background of my Saiga 12:

- Bought Saiga 12 new a couple months ago and it has the manual BHO

- Has been converted with enough parts to allow high capacity magazines to be legal

- Original recoil spring, hammer spring, and gas puck is being used

- Pauly's "glassbolt" service was done after about 300+ rounds were used to break-in the firearm

- Pauly's "glassbolt" service gave me a set of gauges to check my gas ports. The 0.80 gauge will fit in all but 1 of my 3 gas ports. I believe that the 3rd gas port is slighly covered by the hole in the gas block. The 0.70 gauge will fit in this 3rd hole, but it is very tight. The 0.90 gauge will NOT fit into any of the 3 holes.

- Original gas adjustment plug and a TAC47 "auto-plug" was used.

 

 

I rolled a new piece of blue painters tape each attempt so that the sticky side was facing outward and pressed it against the frame where the carrier would impact as shown below:

 

 

I plan to use this firearm for 3-gun matches, so the ammo that I am using is what I have been using for matches with other shotguns. The #5 shot is about the lightest that I can get away with to knockdown steel plates, and still have enough shot for the occassional clay.

 

 

The next photos show the results of my testing. Working from left-to-right in both photos:

 

1) Gas setting on #2 using #5 shot

2) Gas setting on #2 using slug

3) Gas setting on #1 using #5 shot

4) Gas setting on #1 using slug

5) Switched to TAC47 Industries "auto-plug" using #5 shot

6) Switched to TAC47 Industries "auto-plug" using slug

 

- Gas setting #2 really hit the tape with both rounds and flattened the tape. Don't plan to do this anymore...

 

- Gas setting #1 still caused the receiver to hit the frame, but notice that the #5 shot did NOT crush the tape nearly as much as the slug. I expected the slug to recoil more heavily, but I did NOT expect the carrier to impact the frame on the #1 gas setting.

 

- Switching to the "auto-plug", the receiver still impacted the frame, but the tape was not crushed flat as all other attempts. Also, notice how both the #5 shot and the slug didn't seem to make a difference in how much the tape was crushed. I can only assume that the "auto-plug" was doing it's job to bleed off excessive gas.

 

 

 

One comment about the auto-plug, I've loosened the adjustment screw 1 full turn lighter than how it was provided from TAC47. This gun will NOT cycle anything lighter than these loads no matter what I try. I've tried several name brands of 7.5, 7, and 6 shot. The results were very unreliable with the majority of the problems being failure-to-extract problems. Total rounds through this gun is roughly 300+ and another 100+ with Pauly's "glassbolt" service.

 

Of course this is not the most scientific test, but it was done with what I had readily available at the range. So was it incorrect for me to be shocked that the carrier impacts on these loads?

[theorangeplanet 968]

Of course this is not the most scientific test, but it was done with what I had readily available at the range. So was it incorrect for me to be shocked that the carrier impacts on these loads?

 

Really good test with telling results. The tape idea is simple but effective... might try that out myself. Thats awesome to see the auto plug paying off the way its supposed to. If no one reports and longevity issues with them I'll definitely be picking on up for myself in about a year.

 

From what I understand, the carrier is going to strike the rear trunnion 95% of the time, which is fine. I mean, for the carrier to ride back just short of hitting the trunnion and still cycle properly would be a miracle of balance between your spring tension and power of ammunition (and would only work like that for that specific load). What you want to avoid is the carrier bashing, hammering, and obliterating the rear trunnion by overgassing your gun and shooting really hot loads hundreds of times... even then this has rarely caused any issues other than "Whoa, my trunnion is starting to looks like Bubb's smashed beer can."

 

The slug ate up the tape pretty good on either setting... but if you're still pretty much in the stock ports/puck setup, then I'd say its very unlikely to do any damage. Or just keep using that autoplug and you'll be in the clear either way.

[fauxknight 30]

One comment about the auto-plug, I've loosened the adjustment screw 1 full turn lighter than how it was provided from TAC47. This gun will NOT cycle anything lighter than these loads no matter what I try. I've tried several name brands of 7.5, 7, and 6 shot. The results were very unreliable with the majority of the problems being failure-to-extract problems. Total rounds through this gun is roughly 300+ and another 100+ with Pauly's "glassbolt" service.

 

From your own measurements it sounds like your holes are too small. I'd put getting that fixed up as your next priority for this gun, unless you like only running hotter more expensive ammo.

 

Nice test too, from my experience the gun won't cycle if it doesn't impact the rear trunion at least a little. Even a recoil buffer was too thick for my gun, causing light loads to bounce before they cycled. Getting the carrier all the way back there and not hitting it too hard is the goal.

[YOT 3,743]

What it tells me is that you've adjusted your auto-plug to an under-gassed gun. If you gas it right it will cycle anything.

[shades_of_grey 1,092]

...From what I understand, the carrier is going to strike the rear trunnion 95% of the time, which is fine. I mean, for the carrier to ride back just short of hitting the trunnion and still cycle properly would be a miracle of balance between your spring tension and power of ammunition (and would only work like that for that specific load). What you want to avoid is the carrier bashing, hammering, and obliterating the rear trunnion by overgassing your gun and shooting really hot loads hundreds of times... even then this has rarely caused any issues other than "Whoa, my trunnion is starting to looks like Bubb's smashed beer can."...

 

^ This.

 

People worry about trunnion impact too much. Unless you have the mythical "perfectly built" S-12, trunnion impact is going to happen, especially with certain loads. Assuming your gun isn't truly overgassed and the carrier isn't destroying the rivets and beating the trunnion out of the rear of the receiver, (pretty damn obvious if that's happening), there is no real problem.

 

The only time I've noticed a distinct mark from carrier impact on my S-12's rear trunnion was when I let my bro fire a 3" slugger without double checking his gas setting, (it was still on 2), and the shell was ejected ~25 ft. I immediately realized my mistake and stopped him before he fired another. I then field-stripped the gun and checked.. and there was a little bit of paint missing off the trunnion there, but no significant damage, (no dent etc).

 

This leads me to believe that you would have to do this, (fire hot high brass on a too-open gas setting), dozens if not hundreds of times before it would result in significant damage to the gun.. i.e. people worry too much about this.

 

ymmv.

Edited June 11, 2011 by post-apocalyptic

[barely 5]

Thanks everyone!

 

After my next 3-gun match, I believe that I'm going to experiment with opening the gas port holes. Although I try to read as many of these threads as possible, remembering the details is difficult and I recall reading that some have removed the front sight bead to get to the gas ports, and others have actually removed the gas tube. Anyone got a reason why I should lean towards one way verses the other?

[Paulyski 2,227]

Thanks everyone!

 

After my next 3-gun match, I believe that I'm going to experiment with opening the gas port holes. Although I try to read as many of these threads as possible, remembering the details is difficult and I recall reading that some have removed the front sight bead to get to the gas ports, and others have actually removed the gas tube. Anyone got a reason why I should lean towards one way verses the other?

Along with GlassBolt you get free tech-support.

When you're ready, call me.

I'll walk you through the dos & don'ts.

 

Drift the block.

Your sight bead is pressed in like a rivet.

 

It would take longer to do it that way anyhow. going through the sight bead won't get your ports angled right.

 

It'll take less than 2 hours to drift the block, clear your port obstruction & enlarge the first time.

 

The 2 most useful tips are to scribe reference points to get it back on just how it came off & use strips of 1200 grit in a sawing motion to polish it up slightly where the gas block sits before reinstalling.

That way you can fine tune it's position easily.

 

Fire a few mags & the carbon/wadding mixture will seal it right back up.

[evlblkwpnz 3,418]

Things that affect carrier travel and impact....

 

powder charge

shot weight

how the user holds the weapon

carrier dimensions (however subtle)

bolt fit in lockup

resistance of the action

weight of the weapon

wear of action

mods of action

hammer profile

carrier underside profile

smoothness or receiver rails

alignment of receiver rails

port size

number of ports

angle of ports

length of barrel

muzzle device (chokes, etc.)

strength of recoil spring

extractor resistance

strength of mag spring

 

ETA:

Position of gas regulator

gas regulator design

shooter weight

shooter strength

 

I have to go to work now and I'm sure that I missed at least a couple of things that affect carrier travel. Some of these things are obviously very subtle and affect the travel very little, but they do affect it. The point is that it would take a very delicate and precise juggling act of all of these variables to get that magical reliability while making the carrier stop its rearward travel just shy of the rear block. It is possible, but damn near unpossible Don't worry about it. Use the ability to regulate gas properly and your beloved weapon will be just fine. It sounds like you are undergassed. Friction reduction is an asset to reliability, but there is no substitute for gas in a gas operated system. Good luck and report back with some video of that thing running cheap and light loads. I'm sure Pauly can help you out.

Edited June 11, 2011 by evlblkwpnz

[G O B 3,516]

I have an older S-12. It regularly smacked the rear trunnion so Iput a BJ buffer in it and left it at that. No problems with the BJ buffer, the so far it cycles whatever it gets fed. All my Saiga's (S-12,S.308, and the wifes S-.410) have BJ buffers and all work well.

[Paulyski 2,227]

I'm sure that I missed at least a couple of things that affect carrier travel.

 

Barrel hood too thick or undersized chamber making steel based hulls jam in there & hard to extract.

 

(generally not a DIY fix)

 

But, yeah, there's a lot more to the guns than gas.

 

It'd be a damn shame if someone just kept adding gas when the above issue presented it's self.

[evlblkwpnz 3,418]

I'm sure that I missed at least a couple of things that affect carrier travel.

 

Barrel hood too thick or undersized chamber making steel based hulls jam in there & hard to extract.

 

(generally not a DIY fix)

 

But, yeah, there's a lot more to the guns than gas.

 

It'd be a damn shame if someone just kept adding gas when the above issue presented it's self.

Are tight chamber or thick hood common causes when light loads will not cycle reliably?

[Paulyski 2,227]

Are tight chamber or thick hood common causes when light loads will not cycle reliably?

I've only seen 1.

 

But this is NOT something that an average DIYer wants to fuck with.

Absolutely not, so I'll not go into detail.

 

I'd rather people have guns that don't run than have people fucking themselves up & permanently being blinded from screwing with that area & going too far.

A dremel seriously can fuck a person up around there.

 

We're only talking a difference of .002

(two thousandths)

[evlblkwpnz 3,418]

Are tight chamber or thick hood common causes when light loads will not cycle reliably?

I've only seen 1.

 

But this is NOT something that an average DIYer wants to fuck with.

Absolutely not, so I'll not go into detail.

 

I'd rather people have guns that don't run than have people fucking themselves up & permanently being blinded from screwing with that area & going too far.

A dremel seriously can fuck a person up around there.

 

We're only talking a difference of .002

(two thousandths)

I was thinking we could use it to scare the newbs.

[Scott Kenny 144]

Hell, you can make a .002" change in dimensions with a piece of red scotchbrite and about 2 hours *by hand*, maybe 5 seconds with a dremel. I've made that kind of dimensional change in aircraft-grade aluminum with green scotchbrite and about 30 seconds.

 

Thou shalt NOT FUCK with the chamber dimensions if you want to avoid blowing your gun up! Pardon my profanity, but that's too important to not get peoples attention that way.

[rockmup 12]

I'm sure that I missed at least a couple of things that affect carrier travel.

 

Barrel hood too thick or undersized chamber making steel based hulls jam in there & hard to extract.

 

(generally not a DIY fix)

 

But, yeah, there's a lot more to the guns than gas.

 

It'd be a damn shame if someone just kept adding gas when the above issue presented it's self.

Are tight chamber or thick hood common causes when light loads will not cycle reliably?

 

I had one come in with a hood that was under sized. It ate my lunch for some time. I did a happy dance when the light bulb went off. Chucked it up, cut it and never had an issue.

Edited June 12, 2011 by rockmup