I have a custom built 300 PRC built by Randy Melvin of Bull Mtn Rifles. Incredibly reputable gunsmith but has since retired. Last year the carbon ring was so bad it pulled bullets from the casing when ejected prior to firing. This year I’ve cleaned with thorough clean, butch’s, Montana extreme, and boretech eliminator along with other lower end products. The gun is built on a Borden LRX action with a lilja barrel. When functioning correctly it’s a dream but honestly I’m in a love hate relationship with the thing. I bought a repaint to confirm the issue. The barrel is spotless. After scrubbing and soaking for 6 days the carbon ring was mostly removed. 7 shots later it’s back in full force. Question now is should I have it reamed out a bit more for tolerance issues or keep scrubbing. It has never seen a factory load. All loads have been with either ADG or Peterson brass, H-1000 powder, either Winchester lrm or CCI magnums. Cases were trimmed to sammi specs. Please advise!
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Relentless carbon ring
- Thread starter Kcarp
- Start date
But not together! Haha stick with nylon brush if using thorroclean.
The issue isn't removing it. It's that the carbon ring comes back almost immediately.
Might be a case trimming issue?
Carbon ring (not your normal)
This fucking barrel… TL/DR: Carbon ring every 55 rounds or so, cannot chamber, 2 times in a row, 3rd time approaching. Alright.. Proof Stainless, 6 Creed barrel, 26”. It’s been a hammer and problem free for over 800 rounds with a can. Normal cleaning reg is 200 rounds, bore tech c4, scrub...
www.snipershide.com
I would stop trimming to SAAMI specs and measure to see just how long you can leave your brass .
This simple plug is all you need to check your chamber to determine trim length.
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SINCLAIR INTERNATIONAL 30 Caliber Chamber Length Gage SKU: 749000804 | Brownells
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Yes he needs to know what / how long his chamber is to the case mouth dimension. Measure it or....
If the reamer was a Saami min spec. reamer and it cut properly... max chamber length is going to be 2.5874" from the case head to the case mouth. You even hit the 2.587" dimension and you can start pinching the bullet upon firing which will cause pressure issues extraction issues etc...
So you have to give the brass / chamber some clearance. Otherwise...You better be careful in doing things like this because if you don't... again pressure issues etc...
If I was the OP I'd ask for a copy of the reamer print from the gunsmith so he knows what was run into his barrel. That would be a nice starting point.
Please tell us your load details.
*Powder load weight.
*Bullet type & weight.
*COAL, bullet seating depth & neck tension.
*Case volume measurement would be nice also.
Thanks.
More questions than answers right now. Without knowing more details going to be hard to start suggesting things.
I've done back to back days with around 70-80 rounds being fired thru my 300PRC in a Fclass match. No issues with a carbon ring etc... My load is 76.0 of H1000 and 230gr bullets. I shoot the gun all day.... clean it that night... then put another 70-80 rounds on it the next day.
All the test barrels we've been making in 300PRC I haven't heard a complaint back from Hornady, Hodgdon, or any other place making 300PRC ammo.
Is it a powder lot issue?
Trim length/chamber issue combination?
I'm just guessing.
OP hasn't posted anything back.... so?
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Here are some interesting chamber drawings. Take particular note of G, G1, H1, H2.
The 300PRC has a much shorter leed & reduced H1 & H2 diameters in comparison to the other two chambers.
I think there are 3 possible scenarios.
1) The case is full to a crush seating with minimal neck tension & the projectiles are backing out with recoil from an already minimum distance to jam & a slight carbon ring forming at the jam point with the projectiles moved slightly forward of the COAL.
2) There is no projectile movement during recoil & the projectiles are seated out too far to avoid the slight carbon accumulation.
3) The chamber has been reamed with a worn reamer & the leed is tighter than spec, causing exaggeration of a slight
carbon build-up.
The 300PRC has a much shorter leed & reduced H1 & H2 diameters in comparison to the other two chambers.
I think there are 3 possible scenarios.
1) The case is full to a crush seating with minimal neck tension & the projectiles are backing out with recoil from an already minimum distance to jam & a slight carbon ring forming at the jam point with the projectiles moved slightly forward of the COAL.
2) There is no projectile movement during recoil & the projectiles are seated out too far to avoid the slight carbon accumulation.
3) The chamber has been reamed with a worn reamer & the leed is tighter than spec, causing exaggeration of a slight
Don't even compare it to the 300wm saami spec. That throat design is horrible from an accuracy point of view. It's cone shaped and starts out at a .315" diameter at the case mouth. That's .007" bigger than bullet diameter for the most part.
The 300RUM is +.0003" bigger on the freebore diameter but it has about a .125" shorter length in the throat than a saami min spec. 300PRC.
My .02.... the guy needs a copy of the print of the reamer that was used. Start there. Then it should be looked at/measured and see if the reamer cut the throat undersize. My last attachment is a reference with some bullets and approx where they should touch the rifling. If a sample round of his and the bullets listed are say with in .010" or so of my reference numbers... than I'll say the reamer cut to spec.... but if they are much more shorter than that.... then I'll say the reamer didn't cut to spec.
Again the reamer could be worn and not cutting to spec. or.... I've seen brand new reamers not cut to spec.
Unless the OP gives us more information.... again we are guessing.
The 300RUM is +.0003" bigger on the freebore diameter but it has about a .125" shorter length in the throat than a saami min spec. 300PRC.
My .02.... the guy needs a copy of the print of the reamer that was used. Start there. Then it should be looked at/measured and see if the reamer cut the throat undersize. My last attachment is a reference with some bullets and approx where they should touch the rifling. If a sample round of his and the bullets listed are say with in .010" or so of my reference numbers... than I'll say the reamer cut to spec.... but if they are much more shorter than that.... then I'll say the reamer didn't cut to spec.
Again the reamer could be worn and not cutting to spec. or.... I've seen brand new reamers not cut to spec.
Unless the OP gives us more information.... again we are guessing.
