Broken bolt carrier

[Spartacus 1,619]

Did the op rod have a lot of play in it before the cracks showed up?

 

Were you running the gun with that chip missing at the end?

[alistar 13]

Shooting a vast majority of skeet rounds through a generously gassed gun, my piston rod broke, which apparently is not so unusual. Replacing it with Mr. Cole's heavy duty rod seemed to be the best option, but it seems that there are bolt carriers that come from Izhmash a bit too brittle.

 

Unfortunately, after the first attempt, the pin loosened with shooting, after the second attempt, the bolt carrier began to show a crack. We then subsequently tig welded a new pin and all around the new piston rod and annealed the bolt carrier. But, alas, after only 192 skeet rounds, the bolt carrier is starting to crack apart, and the pin is again loose. There was absolutely no play with this (or the previous two) repairs

 

The design of the carrier results in very little metal around the threads of the piston rod, and if you happen to get a carrier that is brittle, or has a flaw, the heavy duty rod will only solve the immediate issue. A new bolt carrier is the only option for me at this point. Good luck with your repair.

[Sergii 142]

We tried to brew bolt carrier. Does not work. It breaks down again. We need to change a new one.

[ewoketeer 35]

Would it be possible to mill away the forward six or so inches and fabricate a new section and attach it via threading or welds or both using a more appropriate steel?

[Spartacus 1,619]

Anybody know about what it would cost to have a CNC shop make up a hundred carriers?

Under $100 per piece?

 

They could be done as a single piece I would think.... you make the op rod end a bit long and the customer can grind off the end for the right length. I would bet CSS would sell them off fairly quickly. I'd buy one.

 

 

Would it be possible to mill away the forward six or so inches and fabricate a new section and attach it via threading or welds or both using a more appropriate steel?

 

Yep, I was thinking the same thing..... hack off the whole rod piece up to the carrier body and make a new piece to attach to the body.

Edited November 2, 2011 by Spartacus

[poolingmyignorance 2,191]

Looks like that has been Bubba'd. The end is broken at a thread, the metal was over hardened and is quite brittle. Heat it red and let it air cool before you work on it, that will detemper the metal and make it soft enough to work on.If you can, screw a copper or carbon screw in before welding. That will save the threads. You may have to thread a copper rod, but that is the easiest part.

Instead of going through the trouble of threading a copper rod extra, just spin your tap in while you weld it. I wouldn't screw any sold rod in because the threads are likely to soften when heated. So use the tap and you'll just cut the soft away on the way out. I've use this trick for fitting thread o'lets on everything from copper, stainless and monel piping. Never had a failure with a tap, doing this.

[jdtravers 637]

Looks like that has been Bubba'd. The end is broken at a thread, the metal was over hardened and is quite brittle. Heat it red and let it air cool before you work on it, that will detemper the metal and make it soft enough to work on.If you can, screw a copper or carbon screw in before welding. That will save the threads. You may have to thread a copper rod, but that is the easiest part.

Instead of going through the trouble of threading a copper rod extra, just spin your tap in while you weld it. I wouldn't screw any sold rod in because the threads are likely to soften when heated. So use the tap and you'll just cut the soft away on the way out. I've use this trick for fitting thread o'lets on everything from copper, stainless and monel piping. Never had a failure with a tap, doing this.

 

That is an interesting technique. I would really be interested in seeing how this is done while the carrier is being TIG welded with a steel tap screwed into it.

[G O B 3,516]

IF you have a lathe, cut the bolt carrier off at the bottom of the threaded hole. Make a new nose for the bolt without the threaded hole. Make it long enough so you can turn the threaded end of the op rod down to a 1/8" X1/8" nub to center in the new nose. make a short hole in the new nose to match the op rod and weld it . This will be a ton stronger.

[Paulyski 2,227]

I'm still sayin' have the end of the carrier built up & dressed, then move the gas system way back & throw on a mid-barrel comp.

 

At least it'd be rather strong & not so jerry-rigged.

The weapon would at least have value again.

 

 

On a side note, I'll be adding these pictures to my library of fucked up carriers that I post every time I get into a debate with people advocating overgassing guns.

 

When I discourage it, it's really not because I want to be some "know-it-all-dickhead", it's because I see this stuff (never as bad as the 2 posters here until now) & figure it's better to go with properly tuning the guns & resistance reduction rather than overgassing.

[arjandommisse 0]

yes lukkely I have 2 of these guns so we will try shooting this one with the other carrier.

 

In the main time I try fixen the other one.

 

I'm wondering wy there are no spare parts for this one, you see the AK carrier for sale all the time.

 

Plus someone must have a screwd-up siaga 12 from a failed project sitting in the back of the machine shop.

 

well it's time to come out arcat@tampabay.rr.com is looking for you.

 

Thanks Adriaan

[Paulyski 2,227]

Shooting a vast majority of skeet rounds through a generously gassed gun, my piston rod broke, which apparently is not so unusual. Replacing it with Mr. Cole's heavy duty rod seemed to be the best option, but it seems that there are bolt carriers that come from Izhmash a bit too brittle.

 

Unfortunately, after the first attempt, the pin loosened with shooting, after the second attempt, the bolt carrier began to show a crack. We then subsequently tig welded a new pin and all around the new piston rod and annealed the bolt carrier. But, alas, after only 192 skeet rounds, the bolt carrier is starting to crack apart, and the pin is again loose. There was absolutely no play with this (or the previous two) repairs

 

The design of the carrier results in very little metal around the threads of the piston rod, and if you happen to get a carrier that is brittle, or has a flaw, the heavy duty rod will only solve the immediate issue. A new bolt carrier is the only option for me at this point. Good luck with your repair.

 

How many gas ports do you have & how big are they?

[jdtravers 637]

Generally the heat treating process is easy to control during the manufacture process of parts and without a Rockwell Hardness Tester you don't have a clue.

 

The primary reason for the failure rate of the carrier is because the op rod is not bottoming out inside the carrier. The op rod should not be supported only by the side walls of the carrier, it needs to be butted flush against the BOTTOM of the carrier. This will allow the energy to be transferred directly to the center line of the carrier rather than be deflected to the side which is the weakest point. The side walls have no structural integrity and are only designed to keep the op rod in alignment. If you take the measurements of the op rod and the inside depth of a failed carrier you will find that there will be an excessive gap at the bottom.

 

When the energy is transferred to the side walls of the carrier it is only a matter of time/cycles before metal fatigue sets in and the carrier will crack. Hotter loads/high brass will accelerate this process.

 

If you are concerned about preventing this, then remove your op rod and check the installed length and correct it as necessary or install a new aftermarket op rod and make sure it bottoms out. There exists a slight taper at the bottom of the carrier which can prevent the op rod from bottoming out, but it needs to be installed as far as it will go till it bottoms out in the threads or taper the op rod to clear the threads and make a flush contact with the carrier.

 

The new Tromix Op Rod for an SBS is of excellent design in the fact that the shoulder of the op rod will transfer energy directly in line with the carrier, without having to be bottomed out.

 

Jack

[poolingmyignorance 2,191]

Looks like that has been Bubba'd. The end is broken at a thread, the metal was over hardened and is quite brittle. Heat it red and let it air cool before you work on it, that will detemper the metal and make it soft enough to work on.If you can, screw a copper or carbon screw in before welding. That will save the threads. You may have to thread a copper rod, but that is the easiest part.

Instead of going through the trouble of threading a copper rod extra, just spin your tap in while you weld it. I wouldn't screw any sold rod in because the threads are likely to soften when heated. So use the tap and you'll just cut the soft away on the way out. I've use this trick for fitting thread o'lets on everything from copper, stainless and monel piping. Never had a failure with a tap, doing this.

 

That is an interesting technique. I would really be interested in seeing how this is done while the carrier is being TIG welded with a steel tap screwed into it.

It's pretty easy. remove the old piston. clamp carrier in vise (the fat end) screw tap into piston socket. weld cracks. yes it takes a good welder. no it's not hard. Maybe I'm not explaining correctly, but it's pretty simple. I don't really see how a tap would be any more intrusive than a rod. Just easier to remove and give you good clean fresh threads.

Edited November 10, 2011 by poolingmyignorance

[Rctreadaway 4]

The questioning comes from the possibility of the tap being welded to the carrier due to them being similar metals? The reasoning behind copper is that you can't weld copper to steel. It simply will not stick.

[jdtravers 637]

Looks like that has been Bubba'd. The end is broken at a thread, the metal was over hardened and is quite brittle. Heat it red and let it air cool before you work on it, that will detemper the metal and make it soft enough to work on.If you can, screw a copper or carbon screw in before welding. That will save the threads. You may have to thread a copper rod, but that is the easiest part.

Instead of going through the trouble of threading a copper rod extra, just spin your tap in while you weld it. I wouldn't screw any sold rod in because the threads are likely to soften when heated. So use the tap and you'll just cut the soft away on the way out. I've use this trick for fitting thread o'lets on everything from copper, stainless and monel piping. Never had a failure with a tap, doing this.

 

That is an interesting technique. I would really be interested in seeing how this is done while the carrier is being TIG welded with a steel tap screwed into it.

It's pretty easy. remove the old piston. clamp carrier in vise (the fat end) screw tap into piston socket. weld cracks. yes it takes a good welder. no it's not hard. Maybe I'm not explaining correctly, but it's pretty simple. I don't really see how a tap would be any more intrusive than a rod. Just easier to remove and give you good clean fresh threads.

 

I guess that is a technique,but here is what I would do: Like the gentleman posted earlier, you have to use a dissimilar metal as a backer/plug, in order to get enough penetration of the weld and build it up, otherwise you will be welding the tap into the carrier. I use bronze for the backing/plug materiel when it is required. Surface welding the cracks will not cut it. Really need to add new materiel from the bronze backer and build it back up. That is what I would do, otherwise you would be welding fatigued metal back in place if you only surface welded.

 

Yeah, you posted quicker than me. That is the problem!

[poolingmyignorance 2,191]

It is very possible to weld the tap to the carrier, but it won't be a good weld..the key is becareful. work your arc slow keep the heat low as possible for tie in. I'vee tried the copper threaded plugs on other stainless applications (granted the bolt carrier is 1 1/4 chrome alloy) and had them twist off inside the workpiece in the past. I've also had it work like a charm too. But I've never had the issue with the tap being welded to the work piece. Now in all fairness I've never done this exact repair on a "bolt carrier" but I have done nipples as small as 1/8" NPT. I'm not saying my path is THE PATH. It's just A PATH. Choose at your own discression.

 

Looks like that has been Bubba'd. The end is broken at a thread, the metal was over hardened and is quite brittle. Heat it red and let it air cool before you work on it, that will detemper the metal and make it soft enough to work on.If you can, screw a copper or carbon screw in before welding. That will save the threads. You may have to thread a copper rod, but that is the easiest part.

Instead of going through the trouble of threading a copper rod extra, just spin your tap in while you weld it. I wouldn't screw any sold rod in because the threads are likely to soften when heated. So use the tap and you'll just cut the soft away on the way out. I've use this trick for fitting thread o'lets on everything from copper, stainless and monel piping. Never had a failure with a tap, doing this.

 

That is an interesting technique. I would really be interested in seeing how this is done while the carrier is being TIG welded with a steel tap screwed into it.

It's pretty easy. remove the old piston. clamp carrier in vise (the fat end) screw tap into piston socket. weld cracks. yes it takes a good welder. no it's not hard. Maybe I'm not explaining correctly, but it's pretty simple. I don't really see how a tap would be any more intrusive than a rod. Just easier to remove and give you good clean fresh threads.

 

I guess that is a technique,but here is what I would do: Like the gentleman posted earlier, you have to use a dissimilar metal as a backer/plug, in order to get enough penetration of the weld and build it up, otherwise you will be welding the tap into the carrier. I use bronze for the backing/plug materiel when it is required. Surface welding the cracks will not cut it. Really need to add new materiel from the bronze backer and build it back up. That is what I would do, otherwise you would be welding fatigued metal back in place if you only surface welded.

 

Yeah, you posted quicker than me. That is the problem!

And thats a good point. Really if it was MY gun and I really wanted to make sure it was perfect. I'd fill the old socket up and re-drill & tap it. But heat treating is always a pain in the ass.

Oh and might I add. JT does this for a living. I'm a hobbist who's worked in the fabrication industry for 10 years..I have a general knowelege of maching and fabriaction skills...but These guys are the pros when it comes to guns. So they know the tricks and short cuts and what is effiecnt and achives sucessful results.

Edited November 10, 2011 by poolingmyignorance

[jdtravers 637]

Thank you, I am truly flattered!!

 

This would definitely be challenging, but not very cost effective to do, from a business perspective. Definitely a time and materiel job.

 

I have no idea how many broken carriers are out there, or if it would be worth the effort to build a fixture for the lathe or mill, which would clamp the carrier on center and allow you to both weld up the broken carrier and then do the necessary drilling, re-tapping required to clean/dress it up.

 

Jack

[dwnthehatch 14]

This thread has me concerned about my recently purchased 2011 Legion imported S12. I just shot 60 flawless rounds (Thanks Jack!) and went to clean it. Is the op-rod supposed to be loose? I can shake mine and it rattles back and forth.

[jdtravers 637]

Yeah, they pretty much all do. I have seen some tighter than others, but a little play generally develops.

[Bronc 0]

Generally the heat treating process is easy to control during the manufacture process of parts and without a Rockwell Hardness Tester you don't have a clue. The primary reason for the failure rate of the carrier is because the op rod is not bottoming out inside the carrier. The op rod should not be supported only by the side walls of the carrier, it needs to be butted flush against the BOTTOM of the carrier. This will allow the energy to be transferred directly to the center line of the carrier rather than be deflected to the side which is the weakest point. The side walls have no structural integrity and are only designed to keep the op rod in alignment. If you take the measurements of the op rod and the inside depth of a failed carrier you will find that there will be an excessive gap at the bottom. When the energy is transferred to the side walls of the carrier it is only a matter of time/cycles before metal fatigue sets in and the carrier will crack. Hotter loads/high brass will accelerate this process. If you are concerned about preventing this, then remove your op rod and check the installed length and correct it as necessary or install a new aftermarket op rod and make sure it bottoms out. There exists a slight taper at the bottom of the carrier which can prevent the op rod from bottoming out, but it needs to be installed as far as it will go till it bottoms out in the threads or taper the op rod to clear the threads and make a flush contact with the carrier. The new Tromix Op Rod for an SBS is of excellent design in the fact that the shoulder of the op rod will transfer energy directly in line with the carrier, without having to be bottomed out. Jack

 

Will shortening the overall length of the op rod to fully seat into the carrier effect the function without any changes to the gas block or gas tube?

Reason I ask, is that my 2001 built Saiga's operating rod is approx. 3.481" from the end of the carrier to the tip of the op rod with about 4 full threads showing. If I go to a heavy duty op rod and in order to screw it down flush leaves me under my factory length of 3.481" will this effect function?

[alistar 13]

Shooting a vast majority of skeet rounds through a generously gassed gun, my piston rod broke, which apparently is not so unusual. Replacing it with Mr. Cole's heavy duty rod seemed to be the best option, but it seems that there are bolt carriers that come from Izhmash a bit too brittle.

 

Unfortunately, after the first attempt, the pin loosened with shooting, after the second attempt, the bolt carrier began to show a crack. We then subsequently tig welded a new pin and all around the new piston rod and annealed the bolt carrier. But, alas, after only 192 skeet rounds, the bolt carrier is starting to crack apart, and the pin is again loose. There was absolutely no play with this (or the previous two) repairs

 

The design of the carrier results in very little metal around the threads of the piston rod, and if you happen to get a carrier that is brittle, or has a flaw, the heavy duty rod will only solve the immediate issue. A new bolt carrier is the only option for me at this point. Good luck with your repair.

 

How many gas ports do you have & how big are they?

 

3, but I don't know the size and don't have any gauges to measure. Tromix build from 2007, if that is any help.

[Paulyski 2,227]

I've not known Tony to overgas to get stuff to run so I'm sure you're good in that Dept.

Just was curious.

[jdtravers 637]

Generally the heat treating process is easy to control during the manufacture process of parts and without a Rockwell Hardness Tester you don't have a clue. The primary reason for the failure rate of the carrier is because the op rod is not bottoming out inside the carrier. The op rod should not be supported only by the side walls of the carrier, it needs to be butted flush against the BOTTOM of the carrier. This will allow the energy to be transferred directly to the center line of the carrier rather than be deflected to the side which is the weakest point. The side walls have no structural integrity and are only designed to keep the op rod in alignment. If you take the measurements of the op rod and the inside depth of a failed carrier you will find that there will be an excessive gap at the bottom. When the energy is transferred to the side walls of the carrier it is only a matter of time/cycles before metal fatigue sets in and the carrier will crack. Hotter loads/high brass will accelerate this process. If you are concerned about preventing this, then remove your op rod and check the installed length and correct it as necessary or install a new aftermarket op rod and make sure it bottoms out. There exists a slight taper at the bottom of the carrier which can prevent the op rod from bottoming out, but it needs to be installed as far as it will go till it bottoms out in the threads or taper the op rod to clear the threads and make a flush contact with the carrier. The new Tromix Op Rod for an SBS is of excellent design in the fact that the shoulder of the op rod will transfer energy directly in line with the carrier, without having to be bottomed out. Jack

 

Will shortening the overall length of the op rod to fully seat into the carrier effect the function without any changes to the gas block or gas tube?

Reason I ask, is that my 2001 built Saiga's operating rod is approx. 3.481" from the end of the carrier to the tip of the op rod with about 4 full threads showing. If I go to a heavy duty op rod and in order to screw it down flush leaves me under my factory length of 3.481" will this effect function?

 

Yes, you need to maintain the proper over all length because this will effect the travel/stroke of the op rod/carrier during cycling. I haven't used one of Tom's op rods so I am not familiar with them. Usually machine my own a little longer and then set it up to my specs with a factory piston. You can also use the CSS Performance Piston, as it is a few thousands longer and will give you the ability to adjust for the difference, if it is not too great. The relationship/measurement of the clearance between the piston, ports and the clean out plug is the main concern (volume). Not all of them are the same and this is where you can either gain or loose effectiveness of the gas system.

 

Really kinda spiting hairs here, because the failure rate really isn't that bad considering what these guns go through and how many are out there. Actually it is pretty damn incredible how durable they are!

 

Jack

[Litlratt1 3]

Generally the heat treating process is easy to control during the manufacture process of parts and without a Rockwell Hardness Tester you don't have a clue. The primary reason for the failure rate of the carrier is because the op rod is not bottoming out inside the carrier. The op rod should not be supported only by the side walls of the carrier, it needs to be butted flush against the BOTTOM of the carrier. This will allow the energy to be transferred directly to the center line of the carrier rather than be deflected to the side which is the weakest point. The side walls have no structural integrity and are only designed to keep the op rod in alignment. If you take the measurements of the op rod and the inside depth of a failed carrier you will find that there will be an excessive gap at the bottom. When the energy is transferred to the side walls of the carrier it is only a matter of time/cycles before metal fatigue sets in and the carrier will crack. Hotter loads/high brass will accelerate this process. If you are concerned about preventing this, then remove your op rod and check the installed length and correct it as necessary or install a new aftermarket op rod and make sure it bottoms out. There exists a slight taper at the bottom of the carrier which can prevent the op rod from bottoming out, but it needs to be installed as far as it will go till it bottoms out in the threads or taper the op rod to clear the threads and make a flush contact with the carrier. The new Tromix Op Rod for an SBS is of excellent design in the fact that the shoulder of the op rod will transfer energy directly in line with the carrier, without having to be bottomed out. Jack

 

Will shortening the overall length of the op rod to fully seat into the carrier effect the function without any changes to the gas block or gas tube?

Reason I ask, is that my 2001 built Saiga's operating rod is approx. 3.481" from the end of the carrier to the tip of the op rod with about 4 full threads showing. If I go to a heavy duty op rod and in order to screw it down flush leaves me under my factory length of 3.481" will this effect function?

 

Yes, you need to maintain the proper over all length because this will effect the travel/stroke of the op rod/carrier during cycling. I haven't used one of Tom's op rods so I am not familiar with them. Usually machine my own a little longer and then set it up to my specs with a factory piston. You can also use the CSS Performance Piston, as it is a few thousands longer and will give you the ability to adjust for the difference, if it is not too great. The relationship/measurement of the clearance between the piston, ports and the clean out plug is the main concern (volume). Not all of them are the same and this is where you can either gain or loose effectiveness of the gas system.

 

Really kinda spiting hairs here, because the failure rate really isn't that bad considering what these guns go through and how many are out there. Actually it is pretty damn incredible how durable they are!

 

Jack

Interesting. How exactly do you determine the OAL of the op rod/carrier?

I ask because my carrier broke near the OPs did. It was repaired and then within a couple of thousand light rounds the op rod broke. Replaced the op rod with one of Toms' to the original OAL and have been waiting for something to break ever since.

[jdtravers 637]

PM me and I will go over the specs I use tomorrow. Calling it a night. Sometimes one can over engineer and try for too much efficiency when it is not required and it can become a problem.

 

Jack

[Paulyski 2,227]

Just a general random observation, but these carriers differ greatly with regards to depth of the hole & the length of the female section that the op-rod screws into.

 

I had 10 in front of me one time & noticed that 2 sitting next to each other were way off from one & other.

The first had 5 threads showing while the second had none showing. The carrier section, minus the op-rod with no threads showing was a few millimeters longer than the one with threads showing.

Upon closer inspection the cutout on the carrier that makes it so a 12 gauge shell can eject was cut differently also.

 

Like I've said before, I'd give my left nut to tour the plant & see how these guys manage to be so inconsistent.

It's like they all are using jigs & building them by hand, or drunk on manual mills & lathes.

It's actually fascinating that such a large company can be so consistently inconsistent in this day & age.

 

I honestly wouldn't be surprised if their computers were still 286's.

[beefcakeb99 572]

Im not really up to date on all the op rod news, but reading this would it be safe to assume that the less threads showing the safer your bc will be in the long run?

[alistar 13]

JT Engineering, I think you have an excellent point with your analysis. My understanding was to install the replacement rod so that the length matched the length of the broken rod. I did not consider that the rod should be bottomed out or this area filled in, but this sounds like excellent advice for anyone replacing a broken rod.

 

It would be interesting to know how often this happens, but as Pauly indicates, there is a lot of variability in the production of carriers as well as rods. Aside from ultrasound or industrial x rays, there is probably no way to tell if there is a space between the end of the threaded rod and the carrier.

[caal 9]

I know there,s allot of debate on whether the piston rod needs to be loose or rigid.However it seems to me that it being loose the point of pressure is exerted to the outer rim of the carrier when it pivots back and forth .If it has a tighter fit it could disperse the shock over a greater area of the carrier s threaded hole. I put thread locker around mine and let it run down in it by wiggling it and let it set and cure and no wiggle at all .I've shot many rounds with no sign of loosening to my surprise .This may or may not help with the brittle carrier issues but i don't think it will hurt.

[Paulyski 2,227]

Im not really up to date on all the op rod news, but reading this would it be safe to assume that the less threads showing the safer your bc will be in the long run?

Brother, there's no rhyme or reason.

A while back forum member Cybermaniac (another member who is a Russian national) posted an explanation that an Izmash rep over on the Russian forum posted referring to possible errors in the manufacturing process. Problems with gasses rising that shouldn't be which can cause the brittle steel.

 

I've welded a couple that have held.

Another one on the other hand, ended up failing somewhere else even though I heat treated as outlined in this text; http://www.neuch.ru/referat/85117.html

I just heard about it today.

 

Sergii seems to be absolutely correct when he says;

 

 

We tried to brew bolt carrier. Does not work. It breaks down again. We need to change a new one.

 

 

It seems when it's brittle, it's just brittle.

It's defective steel & chances are, the shit's going to break again somewhere else.

 

So, try reducing resistance in the action rather than overgassing, take care of the gun & if you have a crack form, start looking for a replacement.

I have one more inbound with just a minor crack that I'm going to tack, but after that, I will only rebuild stuff that people messed up on & removed too much steel.

I've just heard too many stores of carriers breaking somewhere else after being repaired & now it's happened to me.

Before I figured they weren't being heat treated, but this just tells me it's a steel defect & it's just going to crack somewhere else..

 

 

I have no idea how many broken carriers are out there, or if it would be worth the effort to build a fixture for the lathe or mill, which would clamp the carrier on center and allow you to both weld up the broken carrier and then do the necessary drilling, re-tapping required to clean/dress it up.

 

Jack

 

I had to re-drill & tap one & I just centered the rear in a 4-jaw chuck & put the round end in a steady-rest to keep it centered.

It worked well.

 

I average about 1 request a month for cracked female ends.

Some I'd take on, some not.

I can start deferring them to you if you want.

I'd be more than happy to.

Please?

With sugar on top?

 

It's definitely a niche.