.300 Blackout Hard Carbon Buildup

[arrowshooter]

Have a new build .300 blackout pistol that I ran the first 100 rounds through yesterday and other than not being able to use the Magpul MBUS (shot way too low) it ran great. When I took it down for cleaning the new NIB BCG was covered in vary hard carbon build up and the bolt was difficult to remove. Inside the carrier was coated with hard black and green carbon, like copper corrosion colored, and the bolt tail was definitely covered in copper. Also, the rings were completely shot due to the carbon I assume. The rounds were S&B 147gr and 124gr FMJ's and I'm running an 9.5" pistol length barrel. The 147's were headed out at 3:00 and the 124's were 5:00.

My first thought is very crappy ammo, but my second went to a way over gassed system throwing all kind of crap into the BCG even though the ejection patterns did not show it. I have absolutely zero knowledge about the .300 Blk, but what I have learned so far is this thing has a kick to it.

Thoughts?

Thanks

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[Member 34319]

How do the rings look? Me thinks they don't exist if after 100 rounds fired it looks like a bomb went off!

Also, suppressed?

 

[arrowshooter]

Not suppressed, but I am running a KAK Shorty Flash Can. The rings were intact but offered no resistance when I got it cleaned up and put back together.

 

[Member 34319]

Who's BCG?

 

[arrowshooter]

RTB (Right To Bear)

 

[Member 34319]

Sounds like bad rings. Did you ever take the BCG apart prior to shooting? Or just go at it after assembling?

 

[arrowshooter]

I took it all apart except for pulling the rings, and wiped down and lubed. I did not bother to "test" the rings though.

 

[Member 34319]

I took it all apart except for pulling the rings, and wiped down and lubed. I did not bother to "test" the rings though.

Test? Lol, not really something even I know how to do.

If the bolt simply just slid in without any sort of resistance though (before firing), that may have been a sign.

My conclusion, get at least 500 rounds through it. See if it gets better.

If the bolt is still fouling like crazy, which some is expected, but not crazy amounts. Problem solved.

If it gets worse. Swap rings. Go from there.

 

[arrowshooter]

Roger that. I use the "stand the BCG up on the pulled out bolt to see if it drops under its own weight" method LOL. Shud'a did it the first time.

I already swapped the rings out and will see if it repeats and will report back next week. Thanks for the brain storming.

UPDATE: The vendor said he would swap out the BCG if needed.