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Discussion Starter #1 (Edited)
This past Saturday, I went out to shoot a ladder for my 6.8 SPCII SBR yesterday. 12.5" ARP barrel, suppressed. First group, cold bore, starting load (27 gr H4198), all three rounds touching. Awesome. But with the next load (27.3 gr), I started seeing pressure signs...ejector and extractor swipes. Since it was a mild load, I initially chalked it up to a gas block/timing issue, but then I noticed primers looking a little unhealthy. For the life of me, I don't understand why I'm seeing the pressure on the mild end of this ladder. It seems I see guys routinely shooting 28-30 grs with the Gold Dots on here.

Any thoughts?

Specs:
100 yards
90 gr Speer Gold Dot
H4198
Sellier & Bellot pre-primed brass
Temp about 80 degrees
 

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When shooting my 7.5" SBR with the suppressor, I have to close the adjustable gas block considerably to offset the extra pressure it creates. Try the same load without the suppressor and check for pressure signs.
 

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Discussion Starter #3
Thanks, will do. I'm also thinking about installing a heavier buffer to slow all the violence down just a bit. I think between the two I can get the rifle tuned pretty well.

I was just concerned as I've never had issues with any factory loads or any of my own reloads with H322. Is H4198 that much more "gassy?"
 

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If the brass was brand new the volume is probably less than once-fired, may contribute to higher pressure as well.
 

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I believe most would not compare loads in a suppressed use with loads built up for a non-suppressed use as others have suggested. I also suspect that most would suggest an adjustable gas block rather than a heavier buffer-this would be particularly valid if you plan to use the gun without the suppressor at times.
 

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Discussion Starter #7 (Edited)
I have an adjustable gas block and work my loads up with the suppressor.

I just shot 2 ladders today at the range, H322 and H4198, both with S&B brass and 90 gr Gold Dots. I think I've gotten the GB adjusted and I never saw any pressure signs at the primer. I did however continue to get what I believe to be heavy ejector and extractor swipes, or scarring from the bolt picking up a round from the mag and the ejector gouging the rim as it travels over to catch it.

Then I shot the last 12 rds I had of 95gr TTSX, 28.8 gr H322, and Hornady brass (CCI 41) that I loaded a few months back. None of the Hornady brass have the type of scarring the S&B brass does, and what the Hornady shows is very light.

Both the GDs and TTSX were seated the same and both fit in the mags without issue.

So I gotta ask, is the S&B brass soft? Every single piece of S&B brass I have shot (three ladders now - 87 rounds) has been chewed up. Four boxes of factory Federal and SSA (Nosler) and 50 rds of Hornady have barely shown the lightest ejector swipe.

S&B Brass with H322:


S&B Brass with H4198:


Hornady Brass with H322:
 

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Thanks, will do. I'm also thinking about installing a heavier buffer to slow all the violence down just a bit. I think between the two I can get the rifle tuned pretty well.

I was just concerned as I've never had issues with any factory loads or any of my own reloads with H322. Is H4198 that much more "gassy?"
Adding a heavier buffer is a waste of money and time, IMO. More reciprocating mass doesn’t solve the issue, restricting gas does.


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Discussion Starter #9
Adding a heavier buffer is a waste of money and time, IMO. More reciprocating mass doesn’t solve the issue, restricting gas does.


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Noted. I think I solved the pressure issue with adjusting the gas. No cratered primers this range trip. The chewed up S&B brass is concerning, though. Especially when it's supposed to be the best we have available for the 6.8.
 

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Noted. I think I solved the pressure issue with adjusting the gas. No cratered primers this range trip. The chewed up S&B brass is concerning, though. Especially when it's supposed to be the best we have available for the 6.8.
What does the case walls look like ? The problem is very likely the chamber needs a real good scrubbing and possibly polished . ___ My self and others have experienced the same thing with those barrels . Excessive / rough Melonite in the chamber grips the case and gives the impression of overpressure . Sometimes the cases sides will be discolored also. The reason S& B shows more could be several things from case gripping chamber tighter to different shoulder distance on new cases . Give the chamber a good cleaning and possibly polish it . I have 3 of those barrels and after polising chambers there are no false pressure signs .

Sent from my moto g(7) play using Tapatalk
 

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Discussion Starter #11
What does the case walls look like ? The problem is very likely the chamber needs a real good scrubbing and possibly polished . ___ My self and others have experienced the same thing with those barrels . Excessive / rough Melonite in the chamber grips the case and gives the impression of overpressure . Sometimes the cases sides will be discolored also. The reason S& B shows more could be several things from case gripping chamber tighter to different shoulder distance on new cases . Give the chamber a good cleaning and possibly polish it . I have 3 of those barrels and after polising chambers there are no false pressure signs .

Sent from my moto g(7) play using Tapatalk
For yesterday's range session, I removed the depriming pin from my sizing die (I use Lee's Universal anyway) and ran each case through the sizer before loading. Checked each one in the case gauge as well. In fact, each spent piece of brass still fits into the case gauge after firing, but you can see the small amount of stretch.

As for the chamber, due to the suppressor use my rifle gets a good scrubbing after each range session, including chucking a chamber brush in a drill to ensure I get all the fouling and blowback cleaned out. Still, I've read about the need for chamber polishing and that may be the case here, but I know it's not from dirt. I'll do some research on chamber polishing, but again, these symptoms never showed on any of the factory or my own reloads until the last two range sessions where I've been working this Gold Dot/H4198/S&B brass and primers.

With the suppressor, it's really difficult to see any discoloration... they're all dirty. The walls of many of the cases show some gouging, potentially from the barrel extension lugs/feedramps, etc. I got the smiley face dent on some of the case walls too, but I think I tuned most of these pressure symptoms out with the gas block- except the gouged case rims. In fact, I cut so much gas off the bolt wouldn't cycle reliably, but still got the chewed up case rims.

In addition to chamber polishing, I feel my next step is to load two new Gold Dot/H4198 ladders...one with the Hornady 1x fired brass I have on hand and the other with the S&B 1x fired brass. I wet tumble and the steel media smooths out the case rims pretty well, and ensures a consistently clean case to start from.

By the way, I really appreciate all who have chimed in with advice. I'm frustrated by this puzzle, but fascinated with the problem solving involved with this. Thanks again!
 

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For yesterday's range session, I removed the depriming pin from my sizing die (I use Lee's Universal anyway) and ran each case through the sizer before loading. Checked each one in the case gauge as well. In fact, each spent piece of brass still fits into the case gauge after firing, but you can see the small amount of stretch.

As for the chamber, due to the suppressor use my rifle gets a good scrubbing after each range session, including chucking a chamber brush in a drill to ensure I get all the fouling and blowback cleaned out. Still, I've read about the need for chamber polishing and that may be the case here, but I know it's not from dirt. I'll do some research on chamber polishing, but again, these symptoms never showed on any of the factory or my own reloads until the last two range sessions where I've been working this Gold Dot/H4198/S&B brass and primers.

With the suppressor, it's really difficult to see any discoloration... they're all dirty. The walls of many of the cases show some gouging, potentially from the barrel extension lugs/feedramps, etc. I got the smiley face dent on some of the case walls too, but I think I tuned most of these pressure symptoms out with the gas block- except the gouged case rims. In fact, I cut so much gas off the bolt wouldn't cycle reliably, but still got the chewed up case rims.

In addition to chamber polishing, I feel my next step is to load two new Gold Dot/H4198 ladders...one with the Hornady 1x fired brass I have on hand and the other with the S&B 1x fired brass. I wet tumble and the steel media smooths out the case rims pretty well, and ensures a consistently clean case to start from.

By the way, I really appreciate all who have chimed in with advice. I'm frustrated by this puzzle, but fascinated with the problem solving involved with this. Thanks again!
When you say Hornady do you weight them and or look at the head stamp and separate them . Some are made by S&B and some Hornady . I think x man said the S&B made ones have a , between the 6 and 8 instead of a .

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Discussion Starter #13
When you say Hornady do you weight them and or look at the head stamp and separate them . Some are made by S&B and some Hornady . I think x man said the S&B made ones have a , between the 6 and 8 instead of a .

Sent from my moto g(7) play using Tapatalk
When I got my 6.8, a few years back, I also bought a few packs of new Hornady brass. Back in January, I ordered a pack of 250 pieces of pre-primed S&B brass from CBB. They have the European comma between the 6 and 8.
 

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When I got my 6.8, a few years back, I also bought a few packs of new Hornady brass. Back in January, I ordered a pack of 250 pieces of pre-primed S&B brass from CBB. They have the European comma between the 6 and 8.
Strange , if the Hornady you have has the , then it was made by S&B and you would think would be the same .

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Discussion Starter #15
Sorry, but I must have misunderstood you. But to clarify: the S&B have commas and the Hornady have periods. I'm certain they're different.
 
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