PF Nickel Boron Super Match BCG worn out at 700 rounds.

[Sticks]

I decided to give my rifle a cleaning Sunday (200 rounds since last). This would be the third cleaning (barring the break in, but that was barrel only). Total of around 700 rounds fired.

This is a Precision Firearms NiB Super Match Bolt and Carrier that came with my upper.

Part of my cleaning includes the disassembly of the BCG, and scraping off the carbon cake with a brass tool from the bolt and the bore of the carrier at the back. Always very careful to stay away from the gas rings, and only hit the back wall in the carrier.

This go around I decided to try my Ultrasonic cleaner since I really hate scraping. A total of 14 minutes in a simple water/dish soap solution at 145* managed to remove all but a tiny ridge on the bolt, and left a small amount in the carrier. I was happy with the results.

Upon assembly I noticed that the bolt was moving really easy, and failed miserably with the standing of the BCG up on the extended bolt face.

I have over 8k rounds in my 16" middy 5.56, and it's only had about 6 cleanings. I just lube and go. PSA BCG, still holds the carrier up.

Now either the ultrasonic trashed the BCG, or I have phenomenal bad luck, since every thing associated with my 6.5 Grendel foray has been a freakin' nightmare hassle - especially dealing with PF.

I was so disgusted that I just put her all back together, did a quick function test and back in storage.

Next weekend I will try swapping bolts and carriers to see where exactly the failure is at. Either way this to me is unacceptable. My Google-Fu has not turned up anything showing BCG damage from Ultrasonic Cleaning.

[Lastrites]

When I reviewed how to test, it was to turn the bcg upside to see if the bolt falls out by its own weight, not by sitting it face down on a table.

*ARMY TM 9-1005-319-23&P
AIR FORCE TO 11W3-5-5-42
NAVY SW370-BU-MMI-010

Page 130

Figure 8. Checking for Fit of Bolt Assembly.
9. Check bolt assembly (4) for proper fit with bolt cam pin removed. Turn key and bolt carrier assembly
(5) and suspend so the bolt assembly is pointed down. The bolt assembly must not drop out. If weight
of bolt assembly allows it to drop out of key and bolt carrier assembly, replace bolt rings (see WP 0012)

http://www.transasianaxis.com/orig_site/content/manuals/M4_16_23Pchange8.pdf

[cb4017]

Sounds like it's just broken in. Is it functioning okay? At worst change the bolt rings.

[Sticks]

Gas rings should not wear out that fast.

I have a new BCM carrier and a group buy bolt sitting at home. I am going to try both of them to see where the issue is.

[Lastrites]

Sticks, your looking at replacing rings that likely don't need replacing as the method used to test wasn't appropriate.

[DJL2]

If it makes any difference to you, my Dad and I have a 6.8 SPC that absolutely devours gas rings. If I shot that rifle every day in a field environment, I'd have to change the gas rings more often than I change clothes. Now, my Dad is still pretty new to the AR platform. His first indication that our rifle was devouring gas rings is when little chunks of the ring fell out of the BCG during disassembly and cleaning. I don't know what to tell him on that, honestly. He is much more attentive to the issue now and replaces them with high frequency. The rifle seems to run just fine, otherwise.

[Kilco]

In all my years shooting the piss out of ARs, 5.56, 308, 260 Rem and now Grendel I've never replaced a gas ring nor saw the need to.. My old Maine made Bushmaster 5.56 had at least 10k down the barrel and my Ruger AR556 has anywhere between 5-6k.

[cb4017]

Have you contacted Mark at PF? He may have some insight.

[DeanD]

I am with Kilco, I have been shooting AR's for 50 years if you count the M-16's I poured thousands of rounds through in Vietnam and I have never changed bolt rings. I currently have six AR's including one 6.5 x 39 which is my fav. If they are breaking apart I would say they are poor quality, get some real mil-spec rings.

[Sticks]

When I get back home I will try the method described by lastrites. Honestly it felt loose enough to qualify.

[Sticks]

Gas rings are shot.

Following Lastrites test, it barely stays in. Tested a 5.56 bolt, and a group buy Monster bolt, and both were tight in the carrier, and the NiB bolt was just as loose in two other carriers.

Here is to hoping that it was just crap quality gas rings on initial install.

[cb4017]

Well that is strange. My PF bolt had a 1 piece ring and was very snug in the bolt carrier. Are the rings worn down or no tension? How is the finish inside the carrier?

[Sticks]

I would presume the finish inside the carrier is good since two other bolts went in snug, and passed my test of extending the assembled BCG, and placing it bolt down and the weight of the carrier does not force the bolt back.

I did not pull the old rings off (never heard of a once piece gas ring instead of 3). Going to wait until I have replacements.

[just_john]

Sticks - have a good friend way up north who had a problem with his MSR short-strocking - no matter what! Worked fine by hand but just would not cycle properly when fired. We looked at / discussed many things and he finally sent it off to an upstate "wizard". Turned out that the inside of the carrier was not machined properly and the gas rings were hitting and hanging and accelerating the bolt travel time. Replaced the carrier and all went well. - Just a thought.

[cb4017]

A one piece ring is spiral and does not have gaps to deal with.