Who has broken a bolt with a mid-length gas system?

**Failure2Stop** · 06-06-13, 09:32

When middies first hit the market it was widely proclaimed that the system should exhibit lower wear and reduced parts breakage.

I have personally experienced or witnessed numerous bolt failures (broken lugs, break at the cam-pin hole) with carbine gas guns.

However, while there are plenty of folks running around with middies, there hasn't really been any data collection. Carbine gas has had military scrutiny and data collection for about 20 years now.

So, there's the poll:
How much have you shot through single samples, and when did it break?

**Robb Jensen** · 06-06-13, 09:47

I've not broken one myself but replaced 3 broken midlength bbl bolts for a local LE agency.

**Traveshamockery** · 06-06-13, 09:51

Originally Posted by Robb Jensen

I've not broken one myself but replaced 3 broken midlength bbl bolts for a local LE agency.

Any idea of the round count or firing schedule of those bolts?

**Failure2Stop** · 06-06-13, 10:11

Poll up

**Zane1844** · 06-06-13, 10:18

Originally Posted by Failure2Stop

Poll up

Did you have to add the last option?

I still think Filthy 14 is telling. Broken bolt lugs at 16,400.

Though, since firing schedules of most people is less, I think the bolts will last...forever.

**ra2bach** · 06-06-13, 10:28

Originally Posted by Robb Jensen

I've not broken one myself but replaced 3 broken midlength bbl bolts for a local LE agency.

manufacturer of these bolts?..

**Robb Jensen** · 06-06-13, 10:59

Originally Posted by ra2bach

manufacturer of these bolts?..

Armalite whole guns made during the Federal AWB, clamp on FSB. All bolts failed in less than 5K rounds.

**VIP3R 237** · 06-06-13, 11:18

Ooh can I click the button?

I personally haven't broken a bolt, but my father's Colt HBAR cracked a lug at roughly the 11,000 round mark, which isnt a middy but oh well.

Jack, I've heard that KAC has never had a broken Bolt, is this true?

**Clint** · 06-06-13, 11:22

I have not emptied enough brasss to break a bolt yet.

It is my belief that:
both gas drive (gas port size / suppressor) and gas system length / barrel length play major roles in determining the level of stresses involved during unlocking and extraction that can lead to parts failures.

Buffer weights, bullet weights and pressure curves matter too.

The whole thing is a system of inter-related factors.

It's more complicated than just middie vs CAR.

**Failure2Stop** · 06-06-13, 11:26

Originally Posted by Clint

It is my belief that:
both gas drive (gas port size / suppressor) and gas system length / barrel length play major roles in determining the level of stresses involved during unlocking and extraction that can lead to parts failures.

Yup, that's the assumption, looking for the data to support.

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