Pressure Problems 6.5 PRC

[Pbark8311]

I just recently purchased a Mossberg Patriot Predator chambered in 6.5 PRC. I worked up a load for it with 54.6 Gr of H4831SC, 147 ELDM, Fed Match 210M primer and hornady brass. Shot really really well. Lights out at 1200 yards.
After about 120 rounds I started to experience pressure mostly from the ejector. Was not shooting worth anything anymore either. I thought it was just my barrel breaking in but I took 2 grains off my load to work back up and even the lighter loads were still on the hot side.
I cleaned my barrel and I shot some factory bullets through it and I had blow back from one so I stopped immediatly and sent it off to my gunsmith.
He cleaned my barrel and I had a lot of copper fouling but I wouldnt think that would cause so much pressure. Had a little bit of carbon build up around the throat. Its all cleaned out.
He said it is shooting better now with no pressure with his loads. He was shooting 150 Sierra Match King with RL-26. My reloads might be hot still.
Do you think it was just carbon build up and copper fouling? Barrel break in a part as well? Anything else I should make sure that is right so I dont experience this again?
When I get my gun back I will work up my load again but should I try a different powder? or anything else?
Thanks for you help.

 

[gman47564]

im having pretty good luck in a savage build 6.5 prc with the 156 berger eol and reloader 26 ...

 

[Rsadams]

There's a ton of variables here but I would first back off the load and work back up , all the while doing a serious cleaning for awhile.... Remember if you don't need the load to be hot there's no reason to load hot.... As a matter of fact a hot load is normally not your most accurate....

 

[R.Morehouse]

Be sure you keep an eye on your brass OAL.....

Regards
Rick

 

[shoot4fun]

I will say Hornady recommends max 54.5 H4831 (or the SC variant) with the 147 grain bullet. SO, you're about .2 over and that shouldn't be a problem unless other issues are spiking pressure. A carbon ring and/or coppered up barrel could certainly contribute to increased pressure.

 

[KMart]

The carbon build up in the throat will certainly cause high pressure and poor groups. You need to talk with your gunsmith and see if this was hard carbon that took an abrasive cleaner to remove it.
The best way to prevent the carbon build up in the throat is improve on your cleaning techniques and frequency of cleaning.

 

[Pbark8311]

Thank you for your responses.
I don’t like to have my guns hot but it has shot the best groups consistently and the lowest SD and ES by far.
I agree about improving my cleaning. He(gunsmith) just used a foam bore cleaner. Also be better with the copper fouling cleaner as well. I use Sweets. Does anyone use that?
He also mentioned after you shoot you should run a bore snake with some rem oil to get the copper and stuff out a little. But I didn’t think you wanted oil in your barrel?
Do you guys think I gained velocity too because my barrel “broke in”?

 

[FLS2885]

Barrels on average speed up during the first 50-150 rounds, all barrels are different. So yes you likely gained velocity as the barrel "broke in". That along with the carbon and copper just added even more to the issue. Sweets works. You will still need to go after it for the hard carbon from time to time. Lots of good threads here on cleaning techniques.