Help with Short stroking rifle

Balzer94 · Apr 4, 2020

3paul10 said:
The clown is right on with this.....and has a good point I wish I had hit on....I would definate switch of bolt CARRIER with a known good carrier (if you or a friend have one handy)....the reason I say carrier is I'm supposing the bolt is head spaced to the barrel....that is very Important....now, if you can head space other bolts and they pass....switch the bolt too and see what that does for you
there are 3 points on a bolt that could be out of spec and cause gas leakage....

I would also suggest you gage your gas tube, and your gas key on your carrier....when I inspect an AR.....I gage at least 8-10 points.....you could have 3 or 4 aspects of gas areas out of spec....and the gun may still run fine with 1 or 2 gas points out of "spec " ....and and isolated... ...but when you add them all together that's when issues begin...

Hope that makes sense.....and of course, yours may simply be the reloads....when things are back to normal I'd be glad to take a look thru her and see if we can't figure it out.

I definitely appreciate the offer. I might have to take you up on your offer. I do not have any of the gauges to check all of the specs. I’ve been interested in taking the SOTAR course but, time, money, and availability never quite lined up.

Balzer94 · Apr 4, 2020

Atlantic Guns said:
From having built a few hundred ARs over the years. I would recommend checking the alignment on that gas block. You shouldn’t be getting any carbon spitting on the barrel like that. Just my two cents

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What is going to be the best way to check the alignment?

outrider58 · Apr 4, 2020

John from MD said:
The 14.5 mid length gas barrel with welded brake operates well most of the time IF you use the proper ammo. If the OP was to use factory ammo, it would probably run fine. I say probably because there IS NO standard for port size on the 14.5 inch mid gas barrel and sometime you have to tweak them. I use 4198 in various platforms but it is not going to give the gas volume needed to run reliably unless maybe he changes the port size to .080 or even .090

You can do the research on line. I remember finding there were plenty of pages about the mid gas 14.5. Mine uses 335, CFE223, 748 for the most part and a H2 buffer. I did have to open the port a little but it was a home made job and I knew I would have to tweek it.

outrider58 · Apr 4, 2020

Balzer94 said:
What is going to be the best way to check the alignment?

It would need to be viewed trough a bore scope.

dist1646 · Apr 4, 2020

Not related to the issue you are having but, based on the primer pic, I would suggest taking a look at the tip of the firing pin and most likely replacing it. That primer looks like you are really close to having piercing issues. The secondary dimple in the center of the primer is what I am looking at.

danb · Apr 4, 2020

I had to squint to see the carbon on the barrel by the gas block. That for sure is a sign of a misaligned gas block. Who built the rifle again? Its easy enough to fix. If I saw that I am not even sure I would bore scope it, I would just re-align it.

That said, it runs fine with factory loads and many people report problems with that powder, so you may or may not fix it by re-aligning the gas block.

Assume for the sake of argument, its under gassed with this powder, even after you re-align the gas block. Lots of ways to fix this (including getting new powder).

outrider58 · Apr 4, 2020

Atlantic Guns said:
From having built a few hundred ARs over the years. I would recommend checking the alignment on that gas block. You shouldn’t be getting any carbon spitting on the barrel like that. Just my two cents

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danb said:
I had to squint to see the carbon on the barrel by the gas block. That for sure is a sign of a misaligned gas block. Who built the rifle again? Its easy enough to fix. If I saw that I am not even sure I would bore scope it, I would just re-align it...

Okay, as far as 'leaking gas blocks' go, I have not built hundreds of ARs, but the ones I have built(basically all of mine) have all had their gas blocks aligned with the use of bore scopes and excluding one clamp-on GB, they all have leaked, initially. They will eventually self seal with fouling. An expedient check would be to wipe off the fouling leaving what is between the FSB and barrel journal. If the fouling continues to re-appear, them maybe you have a misalignment. Just about any gunsmith can scope your rifle bore and make necessary adjustments.

danb · Apr 4, 2020

outrider58 said:
Okay, as far as 'leaking gas blocks' go, I have not built hundreds of ARs, but the ones I have built(basically all of mine) have all had their gas blocks aligned with the use of bore scopes and excluding one clamp-on GB, they all have leaked, initially. They will eventually self seal with fouling. An expedient check would be to wipe off the fouling leaving what is between the FSB and barrel journal. If the fouling continues to re-appear, them maybe you have a misalignment. Just about any gunsmith can scope your rifle bore and make necessary adjustments.

what, you dont use the spaghetti trick?

Balzer94 · Apr 4, 2020

dist1646 said:
Not related to the issue you are having but, based on the primer pic, I would suggest taking a look at the tip of the firing pin and most likely replacing it. That primer looks like you are really close to having piercing issues. The secondary dimple in the center of the primer is what I am looking at.

I will pull the primer and take a look at it, however I grabbed a handful of cases from yesterday and they are firing pinch dimple is smooth all the way around. I think you may be seeing a shadow/reflection that makes it look like a second dimple

Balzer94 · Apr 4, 2020

danb said:
I had to squint to see the carbon on the barrel by the gas block. That for sure is a sign of a misaligned gas block. Who built the rifle again? Its easy enough to fix. If I saw that I am not even sure I would bore scope it, I would just re-align it.

That said, it runs fine with factory loads and many people report problems with that powder, so you may or may not fix it by re-aligning the gas block.

Assume for the sake of argument, its under gassed with this powder, even after you re-align the gas block. Lots of ways to fix this (including getting new powder).

I assembled the lower. the upper was assembled by BCM.

3paul10 · Apr 4, 2020

So, you'll get a hundred suggestions, and they are all good ideas. But, that being an A2 PINNED front sight, you cant just pull it off and "reset" it....you can with a low pro type gas block but not a factory pinned, pressed on, A2 sight. That being said, in my opinion, it is highly unlikely that a factory BCM upper is not set correctly.....I would go on the assumption it is not the problem. I'm straining to look at your gas block pics too, and I'm not seeing anything that causes me alarm...carbon in the area of the gas block is not an automatic sign of a misalignment of the gas block in my opinion, most blocks have a slight leak until they seal up. I forget how many rounds are thru the gun?

Anyways, most times you can fix AR stuff starting out small, and working your way up to the "big stuff" is all else fails. Unless you are really set on running reloads thru her, I would suggest putting reloads aside and use good factory ammo , ie: Federal brass, not steel cased, etc....

Dist1646 may be on to something, do you have a pierced primer there? Was that a factory round of a reload? I know nothing about reloading,but if that is a reload that may be the cause of the primer issue....

Keep us posted, its fun to put our minds to something other than COVID shit......

danb · Apr 4, 2020

Balzer94 said:
I assembled the lower. the upper was assembled by BCM.

So I am back to: its the IMR4198. Someone up-thread suggested adding .5 gr more. Did you/can you experiment with the load?

Balzer94 said:
I’m just trying to wrap my head around why it is so sporadic. I would think if it were a volume of gas issue, which the reasoning behind makes sense, why isn’t it happening to every round, or atleast more than once or twice per magazine.

I’m also just trying to use up the rest of this ammo on this beautiful day. Haha

No, not necessarily. Reliability is not binary. There is always some margin of error. There can be variation in the powder, friction, accuracy of measurement, ... lots of things. Your load could be good "only" 9 times out of 10 and you will see sporadic failures. There are always outliers.

That's why a lot of rifles are overgassed - overcompensate for the margin of error.

Balzer94 · Apr 4, 2020

danb said:
So I am back to: its the IMR4198. Someone up-thread suggested adding .5 gr more. Did you/can you experiment with the load?

No, not necessarily. Reliability is not binary. There is always some margin of error. There can be variation in the powder, friction, accuracy of measurement, ... lots of things. Your load could be good "only" 9 times out of 10 and you will see sporadic failures. There are always outliers.

That's why a lot of rifles are overgassed - overcompensate for the margin of error.

I will check some of my other manuals to check adding more powder and see what happens

John from MD · Apr 4, 2020

Hogdon says you can go up to either 20.4 or 21 depending on the bullet used.

outrider58 · Apr 4, 2020

danb said:
So I am back to: its the IMR4198. Someone up-thread suggested adding .5 gr more. Did you/can you experiment with the load?

No, not necessarily. Reliability is not binary. There is always some margin of error. There can be variation in the powder, friction, accuracy of measurement, ... lots of things. Your load could be good "only" 9 times out of 10 and you will see sporadic failures. There are always outliers.

The ragged edge of reliability. It's like dancing along the edge of subsonic when trying to keep up velocity and maintaining subsonic speeds at the same time. Every few rounds will break the speed of sound and go bang(which is a failure).

That's why a lot of rifles are overgassed - overcompensate for the margin of error.

Military arms run on the over gassed side intentionally. They need to keep running no matter how hot or how fouled they get for obvious reasons.

3paul10 · Apr 4, 2020

outrider58 said:
The ragged edge of reliability. It's like dancing along the edge of subsonic when trying to keep up velocity and maintaining subsonic speeds at the same time. Every few rounds will break the speed of sound and go bang(which is a failure).

Military arms run on the over gassed side intentionally. They need to keep running no matter how hot or how fouled they get for obvious reasons.

danb · Apr 4, 2020

outrider58 said:
The ragged edge of reliability. It's like dancing along the edge of subsonic when trying to keep up velocity and maintaining subsonic speeds at the same time. Every few rounds will break the speed of sound and go bang(which is a failure).

Military arms run on the over gassed side intentionally. They need to keep running no matter how hot or how fouled they get for obvious reasons.

outrider58 · Apr 5, 2020

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Help with Short stroking rifle

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