Reasonable price $82.95. 16" barrel is hard on brass even in 308win carbine length gas. 16" 6.5creed would undoubtably be worse at suppressed or not. Aero Precision list port size on their barrels under specs.
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If there's not enough weight and/or load pressure behind the bolt an agb can only do so much? If you're only dealing with ejection patters, then an agb can help.what will fix it?
so right now, my spring is the stiffest that jp makes. however i can increase the weight a little bit by adding another tungsten weight instead of steel.@rockwind1
Your bolt is unlocking too early. The extractor trying to rip the rim off is a good sign as well as the false pressure signs on your brass. Which buffer weight are you using? Whatever it is, it needs to be heavier. Possibly a stiffer spring as well. An adj gasblock does help but as you can see from your rifle, it isn’t a fix.
Okay these are three pieces of alpha brass I just shot the other day, what I consider almost a perfect hand load. I'll add the velocity data as well. At about 2800 mv for a 130 AR Hybrid.
View attachment 8286895
View attachment 8286897
that is some clean brass, how much does your bcg weight? how much does your weight weigh? i am curious the relationship, if there is some math that a normal person can do, like my bcg weighs this much, there fore use x oz's. but i am curious. it seems like a heavier bcg will also slow stuff down.
i know, i started one thread when the federal ammo had pressure, i started this one to see if anyone had found lighter load factory ammo and in the meantime, i fixed the problem with the hornady varmint express 95 gr amax.Between 3 threads of near same issues, I get lost on which 1 is which? Ok, I've re-read your post above and you're stated a cbi barrel. I have a 20" standard rifle gas system and it blows primers bad w/Hornady 123 amax and sst's. Accuracy is exceptional (2 shots in near same hole). Thought I missed, so I went and checked the target and the hole was barely oval. Which gas length is it? I'm sure it's short (maybe mid length, hopefully not carbine length). H3 should cover the issue. Being that short it might take H4?
That will add ~.85ozs changing from steel to tungsten. Also did see you're using a scs, but is it standard or heavy scs? SCS needs to make contact with the bcg when closing the upper to a point of almost pushing the scs back with a thin blade screwdriver. If not, you need to add the C-clip that came with unit. That extra play between the scs and the bcg can be an/the issue!so right now, my spring is the stiffest that jp makes. however i can increase the weight a little bit by adding another tungsten weight instead of steel.
Just heavier than the H2 in weight. Not sure how much difference as it changes between mfgrs by a few tenths or hundredths.i know, i started one thread when the federal ammo had pressure, i started this one to see if anyone had found lighter load factory ammo and in the meantime, i fixed the problem with the hornady varmint express 95 gr amax.
what is H3 or H4?
i don't even see the H3 or H4 on their website? i believe i have the heavy scs, because it is the ar10 version and i have the 110 red/yellow painted spring. it is the heaviest spring. thanks for tip on that washer, didn't know that was what it was for. but i checked and the scs and my bolt lightly touch as it goes together. sigh.. maybe i should add it anyway!Just heavier than the H2 in weight. Not sure how much difference as it changes between mfgrs by a few tenths or hundredths.
sent message.If you're running a JP SCS standard with a Ultra 7, you will be chasing your tail. Personally, I'd completely re-do the action/recoil system, or get a different can.
i checked my spring,, it is already the heaviest one they have. at this point i can add about .85 oz to my weights and see what happens. i may add a bigger suppressor as well, perhaps that will help. i have a couple 338 cans not doing anything. they weight twice as much as the ultra 7 thoughIncreasing spring weight will cause more issues. The JP springs won't do what you need them to.
2650 seems possible for a 16, my barrel is 22" and I'm seeing 2850-2800 ish.
what would dropping down to a weaker spring do, if the goal is to keep bolt from moving back too soon? not arguing at all, just trying to understand the physics and diagnostic process for futureIf you have the heaviest spring, you may want to drop the weight of that spring down by one, and add all the weight you have. That will be a good test.
For the first 5 shoot without the can. Then try 5 with. Save all that brass and take pics to post.
The 338 volume can may help the issue. I'm running a dominus myself and I am dealing with high back pressure as well but I think I have a good handle on it. I plan to swap to the magnus once it's freedom.
I would ditch the jp silent capture.
An AR10 shooting 260/6.5 CM or like work best with a very specific set up providing that gas is correct:
1. 7-5/8" internal length receiver extension
2. 308 standard weight rifle length spring
3. 3.250" Buffer weight between 5 and 8+ oz.
That will need to be an A5 tube for that to work with a 3.25" buffer.If you have the heaviest spring, you may want to drop the weight of that spring down by one, and add all the weight you have. That will be a good test.
For the first 5 shoot without the can. Then try 5 with. Save all that brass and take pics to post.
The 338 volume can may help the issue. I'm running a dominus myself and I am dealing with high back pressure as well but I think I have a good handle on it. I plan to swap to the magnus once it's freedom.
I would ditch the jp silent capture.
An AR10 shooting 260/6.5 CM or like work best with a very specific set up providing that gas is correct:
1. 7-5/8" internal length receiver extension
2. 308 standard weight rifle length spring
3. 3.250" Buffer weight between 5 and 8+ oz.
On a SCS it wouldn't help suppressed. What is the gas system length?what would dropping down to a weaker spring do, if the goal is to keep bolt from moving back too soon? not arguing at all, just trying to understand the physics and diagnostic process for future
it's rifle lengthOn a SCS it wouldn't help suppressed. What is the gas system length?
with the federal fgmm 130 gr berger, i have had only 1 blown primer but definite pressure signs on rest,, i did try a few shots with the suppressor off and the pressure signs still appeared on head. hard to tell if the pressure was reduced in any small amount or not by just looking at the marks.Have you tried it unsuppressed?
Are you rolling your own or buying factory? A faster powder will give you less pressure down the line and possibly less gas volume.with the federal fgmm 130 gr berger, i have had only 1 blown primer but definite pressure signs on rest,, i did try a few shots with the suppressor off and the pressure signs still appeared on head. hard to tell if the pressure was reduced in any small amount or not by just looking at the marks.
i did get the blown primer AFTER switching from 338 tbac suppressor to the ultra 7 30 cal.
I am resigned to the fact that maybe some ammo just won't work in it, like that federal. so i am now onto a different path with the new hornady 95gr and now my new goal is to lessen the amount of blowback if at all possible.
without going crazy, the 2 things i can easily and cheaply do is add the .8oz to my buffer and put the 338 can back on
i stopped reloading a few years ago,, huge time suck. the blown primer and pressure was with factory ammo,, federal gold medal match that came factory loaded with berger 130 gr hybrid OTMAre you rolling your own or buying factory? A faster powder will give you less pressure down the line and possibly less gas volume.
Probably made for BA's from test guns. Here's my cbi setup.i stopped reloading a few years ago,, huge time suck. the blown primer and pressure was with factory ammo,, federal gold medal match that came factory loaded with berger 130 gr hybrid OTM
which is why this pressure was a surprise to me in the ar10 platform, i figured it would handle sammi spec ammo.
You aren’t having pressure issues most likely. Your bolt is unlocking and trying to extract too early which is mimicking overpressure. A 16” 6.5CM may require more buffer weight than you can get with that JP stuff you are using. You will need to weight up that buffer significantly.i stopped reloading a few years ago,, huge time suck. the blown primer and pressure was with factory ammo,, federal gold medal match that came factory loaded with berger 130 gr hybrid OTM
which is why this pressure was a surprise to me in the ar10 platform, i figured it would handle sammi spec ammo.
I measured the fired brass, and it seems to have measurements consistent with a normal sized chamberYou aren’t having pressure issues most likely. Your bolt is unlocking and trying to extract too early which is mimicking overpressure. A 16” 6.5CM may require more buffer weight than you can get with that JP stuff you are using. You will need to weight up that buffer significantly.
Now is there a chance you have an out of spec chamber which is causing the false signs as well? Possibly but less likely.
That will need to be an A5 tube for that to work with a 3.25" buffer.
I'm copying from a message that I wrote to the OP as reference:
"Standard AR-10 SCS are the equivalent of 3.8oz buffer, heavy is 4.6. Not sure you can replace the bottom weight, you used to not be able to. Ultra 9 is in the top zone for back pressure, the Ultra 7 is a bit better, but still high. Your 16" RLGS barrel is ideal, but with that can, the dwell is the equivalent of a 20"+ barrel. You're unlocking under excessive pressure. the only way to delay the bolt unlocking is to increase the buffer weight, like up to 8.5oz. Or a flow through can. Lots of details if you change your action/recoil sys."
Buffers and spring have to work together, but they have different characteristics during the BCG cycle.
In regards to delaying the bolt unlocking, the buffer operates under Newton's Laws of Motion. The buffer has its greatest force opposing BCG movement at the beginning of the cycle after firing. That opposing force decreases until the buffer bottoms out in the RE. The greater the buffer weight, the more it opposes BCG movement, thus delaying the bolt unlocking, hopefully enough that chamber and bore pressure drops to acceptable levels.
Springs have the least amount of force upon the BCG at the beginning of the cycle after firing. The springs opposing force on the BCG increases until the buffer bottoms out. This is true even with flatwire springs, but to a lesser range. Delaying the bolt unlocking solely by increasing spring strength is difficult without creating other issues.
Bottom line - increase the buffer weight to delay the bolt and increase the spring strength enough (if needed) to tame the buffer from slamming into the RE. Then you get to deal with the other half of the cycle - feeding.
ETA: I believe OP already has as AGB
I measured the fired brass, and it seems to have measurements consistent with a normal sized chamber
so, it is the same otherwise than the barrel, and it is acting completely different? that is crazy. what do you think it is?I can't believe it! The cbi has the same port size as the AP barrel (.076"). With the same ammo the cbi pops primers and the ap doesn't.
I’ve been looking around for an8.5oz buffer weight. Searches have not foundI'm copying from a message that I wrote to the OP as reference:
"Standard AR-10 SCS are the equivalent of 3.8oz buffer, heavy is 4.6. Not sure you can replace the bottom weight, you used to not be able to. Ultra 9 is in the top zone for back pressure, the Ultra 7 is a bit better, but still high. Your 16" RLGS barrel is ideal, but with that can, the dwell is the equivalent of a 20"+ barrel. You're unlocking under excessive pressure. the only way to delay the bolt unlocking is to increase the buffer weight, like up to 8.5oz. Or a flow through can. Lots of details if you change your action/recoil sys."
Buffers and spring have to work together, but they have different characteristics during the BCG cycle.
In regards to delaying the bolt unlocking, the buffer operates under Newton's Laws of Motion. The buffer has its greatest force opposing BCG movement at the beginning of the cycle after firing. That opposing force decreases until the buffer bottoms out in the RE. The greater the buffer weight, the more it opposes BCG movement, thus delaying the bolt unlocking, hopefully enough that chamber and bore pressure drops to acceptable levels.
Springs have the least amount of force upon the BCG at the beginning of the cycle after firing. The springs opposing force on the BCG increases until the buffer bottoms out. This is true even with flatwire springs, but to a lesser range. Delaying the bolt unlocking solely by increasing spring strength is difficult without creating other issues.
Bottom line - increase the buffer weight to delay the bolt and increase the spring strength enough (if needed) to tame the buffer from slamming into the RE. Then you get to deal with the other half of the cycle - feeding.
ETA: I believe OP already has as AGB
what brand or shop would you recommend for an 8.5oz buffer. which spring have you used and prefer, lb wise?I'm copying from a message that I wrote to the OP as reference:
"Standard AR-10 SCS are the equivalent of 3.8oz buffer, heavy is 4.6. Not sure you can replace the bottom weight, you used to not be able to. Ultra 9 is in the top zone for back pressure, the Ultra 7 is a bit better, but still high. Your 16" RLGS barrel is ideal, but with that can, the dwell is the equivalent of a 20"+ barrel. You're unlocking under excessive pressure. the only way to delay the bolt unlocking is to increase the buffer weight, like up to 8.5oz. Or a flow through can. Lots of details if you change your action/recoil sys."
Buffers and spring have to work together, but they have different characteristics during the BCG cycle.
In regards to delaying the bolt unlocking, the buffer operates under Newton's Laws of Motion. The buffer has its greatest force opposing BCG movement at the beginning of the cycle after firing. That opposing force decreases until the buffer bottoms out in the RE. The greater the buffer weight, the more it opposes BCG movement, thus delaying the bolt unlocking, hopefully enough that chamber and bore pressure drops to acceptable levels.
Springs have the least amount of force upon the BCG at the beginning of the cycle after firing. The springs opposing force on the BCG increases until the buffer bottoms out. This is true even with flatwire springs, but to a lesser range. Delaying the bolt unlocking solely by increasing spring strength is difficult without creating other issues.
Bottom line - increase the buffer weight to delay the bolt and increase the spring strength enough (if needed) to tame the buffer from slamming into the RE. Then you get to deal with the other half of the cycle - feeding.
ETA: I believe OP already has as AGB
Which receiver extension are you using? Carbine length, vltor/Armalite length, or rifle?I’ve been looking around for an8.5oz buffer weight. Searches have not found
what brand or shop would you recommend for an 8.5oz buffer. which spring have you used and prefer, lb wise?
I’ve been looking around for an8.5oz buffer weight. Searches have not found
what brand or shop would you recommend for an 8.5oz buffer. which spring have you used and prefer, lb wise?
With a pcc buffer (which can be longer than a AR15 carbine buffer) can get you close to that weight and not sure what type of setup will be needed? KAK has a 9.3oz rifle length buffer (I bought in case for 7saum and 6.5prc builds).Which receiver extension are you using? Carbine length, vltor/Armalite length, or rifle?
my buffer tube depth is 9 5/8" ,, so i assume it is carbine lengthWhich receiver extension are you using? Carbine length, vltor/Armalite length, or rifle?
Nope that is rifle length. Your receiver extension screws directly into the back of the lower receiver with no castle nut to hold it in place. You must be using the JP buffer system with the spacer in place.my buffer tube depth is 9 5/8" ,, so i assume it is carbine length
I’ve been looking around for an8.5oz buffer weight. Searches have not found
what brand or shop would you recommend for an 8.5oz buffer. which spring have you used and prefer, lb wise?
I wouldn’t purchase any of his rifle length stuff. He can buy a LR308 rifle length buffer and tungsten weights for less than half of the cost and is user adjustable. As far as how much weight he needs, I don’t know. I’ve never had a 16” 6.5CM.You can not or should not use the rifle length buffer from slash, it's 10oz. I don't belive he makes a rifle in 8.5 oz.
You shouldn't need 10 oz.