AR 15 Kaboom... Sort of.

[CulpeperMM]

This is a frankengun i made with a nodak spud lower (NDS-16A1), cmmg LPK, a daniel defense BCG, tapco 6position carbine stock and a RRA HBAR 16" flat top upper, with a carry handle. the upper was filthy when i bought it. i have cleaned the barrel thoroughly before shooting it. (i will not do this again. for now on, if its dirty, i will have to walk)

I have created a doozy of a single shot 5.56MM that cuts the brass in half after every shot and leaves me with a perilous extraction to perform where the next round is crammed into the remaining half of the brass of the first shot which is stuck nicely in the chamber. (when i stripped the rifle and ran the chamber brush through at the range after extracting a partially crushed live round and the back half of the brass i found the front half of the brass on the chamber brush. yikes.)

This is what the final product looks like. Sliced Brass. I left the bent and dinged live rounds at the range, so no pictures.

The range officer suggested it may be the ammo... I changed from Remington/UMC 223 to PMC 223... same results. I dared not fire the xM855 i had in my bag.

Any suggestions on how to proceed on remedying this would be appreciated.



this is not my first build, it's my second the first one actually works fine. not a problem in nearly a year.

 

[Colt556]

Is the barrel a 5.56 or .223?

 

[thompal]

Is the barrel a 5.56 or .223?

Would that result in what this brass did? I always thought the neck was slightly longer on one or the other (don't remember which), but either could be safely shot in a rifle chambered for either one?

This looks like it was neatly sliced. There is no bulge that I can see. Maybe there's an edge of some sort around the circumference of the chamber.

I dunno. I'm far from an AR expert, I had several years ago, but haven't had one until recently, and I haven't even shot it yet (dang work schedule!).

 

[pftraining_in]

A ruptured case is the result of the action unlocking too soon or a burr in the chamber causing the hot brass to pull apart during extraction.

Check you action spring (ie: buffer spring) and buffer. You may have a weak spring, under weight buffer or both. Chamber honing should be left to a gunsmith.

I have seen the same thing occur in a brand new RRA 16" Car 15.

 

[thompal]

A ruptured case is the result of the action unlocking too soon or a burr in the chamber causing the hot brass to pull apart during extraction.

But, if it unlocked too soon, wouldn't there be noticeable bulging?

 

[CulpeperMM]

i should have mentioned that the barrel is chambered in 5.56, but i have never had any trouble shooting .223 out of any of my other 5.56 chambered rifles. i would not think that is the issue.

could it be the spring and buffer that came with the tapco stock causing this? easy enough to test this hypothesis.

how can i check for a burr in the chamber? my pinky is too big to stick in there. keep in mind this was a used upper i bought that was obviously fired a million times since the last cleaning. my point is it had been fired, a lot. wouldn't a burr be a manufacturing defect? (pardon my ignorance)

 

[451_Detonics]

My guess is an overlength chamber with your BGC. Does your 'smith have a set of go, no go gauges? If not you might want to buy a set, especially if you do many builds.

 

[Duce]

Were you firing reloads???? Duce<><

 

[pftraining_in]

But, if it unlocked too soon, wouldn't there be noticeable bulging?

Depends on the amount of time that the case is supported. This appears to be towards the end of the pressure drop as the brass is still hot.

i should have mentioned that the barrel is chambered in 5.56, but i have never had any trouble shooting .223 out of any of my other 5.56 chambered rifles. i would not think that is the issue.

could it be the spring and buffer that came with the tapco stock causing this? easy enough to test this hypothesis.

how can i check for a burr in the chamber? my pinky is too big to stick in there. keep in mind this was a used upper i bought that was obviously fired a million times since the last cleaning. my point is it had been fired, a lot. wouldn't a burr be a manufacturing defect? (pardon my ignorance)

Take a dry patch and spin it around the inside of the chamber and the throat of the barrel. Burrs will catch the cloth.

RRA does not cut a true 5.56 chamber in their new barrels as they use a Wylde which is in the middle. This can cause issues with the brass being pulled apart while still hot due to a tight chamber.

For about $20 you can get a buffer sprint from Tactical Springs. Leaps and bounds above TAPCO.

 

[CulpeperMM]

Were you firing reloads???? Duce<><

nosir, Remy UMC and PMC .223. right out of the factory box, which i took out of the factory case.

 

[CulpeperMM]

For about $20 you can get a buffer sprint from Tactical Springs. Leaps and bounds above TAPCO.

i forgot to mention that i was trying to see how little money i could put into this build.

the Tapco stock was the cheapest option i could find that included a buffer, tube, and stock! what a deal!

I'll try a spring and buffer out of another gun to test this theory. may not hurt just to have a nicer spring regardless.

 

[Gamez235]

Bring it by the shop and I'll have a look at her...

 

[loony1]

My guess is an overlength chamber with your BGC. Does your 'smith have a set of go, no go gauges? If not you might want to buy a set, especially if you do many builds.

agreed

 

[Fixer]

I have a Tapco stock and spring and have had no issues with it so far. I built my rifle from the ground up also, but with all new parts. I agree that it sounds like it may be in the BCG or the barrel chamber, or a combination of the 2. Probably why the person sold it. Bummer on the problems. Hope you can get it figured out.

 

[SharkyZiff]

Good luck getting your baby fixed!

Keep us posted on your progress!

 

[I Love Bourbon]

You have excessive headspace, most likely due to an oversize or over cut chamber. It's possible that your bolt is out of spec but since you listed the barrel used and dirty that would be my first look. You need to have the headspace checked and if it shows to loose try another bolt, outside of that you will need to replace the barrel.
I wouldn't worry about the difference between .223 & 5.56 chamber, the chamber is the same dimensions the throat is what's different.

In retrospect I guess it's possible that someone overdrilled the gas port but even then I don't believe your failure would look like it does. it looks like a headspace issue...

 

[LPMan59]

sweet thread resurrection.

 

[I Love Bourbon]

sweet thread resurrection.

No problem, happy to help.
I was led ,here by a link in another thread and I didn't look at the date.

+1

 

[sepe]

sweet thread resurrection.

That made me laugh. I was going to do the far too common "trying to get to 50, huh" but then I noticed May 2008 under their name.

 

[shooter521]

That made me laugh. I was going to do the far too common "trying to get to 50, huh" but then I noticed May 2008 under their name.

Well, he *is* trying to get to 50... he's just taking his sweet time.