The loaded case was a once fired, resized and loaded Starline brass.Was this new brass unfired brass? Most of my new cases run around 0.4166". Wow - 0.0085" expansion. In my experience, your getting warm when your case web expansion is over 0.0045" and hot when greater than 0.0050". Resized cases usually don't expand as much as new. ARP provided me a fired case from a 70K psi test. It's case web expansion was 0.4265"
Was it the same load also ? Or different powder measure and or bullet?The loaded case was a once fired, resized and loaded Starline brass.
I just measured fired brass from my noveske barrel and it was .4200 from the same lot of Starline brass.
The cases I measured that I referenced above were the same loads yes. 115 grain Nosler custom competition. 28 grains of 322. 2.260 COAL. once fired Starline brass that I resized with RCBS full length sizer die.Was it the same load also ? Or different powder measure and or bullet?
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I have several 18" barrels with rifle length gas and every one not made by White Oak Armament I had to open up gas port to make function properly due to such short dwell time. Do not have any 6.8 18" barrels with rifle length gas but purchased eight 5.56 Wylde barrels set up like this with 0.080" gas ports. Had to open up the five I have built to 0.125" before they were reliable with all ammo including 50/52 grain varmint ammo. If stick to 69 grain and 77 grain SMKs these barrels like an 0.090" port but are 50/50 even with 55 grain M193. Would imagine an 18" rifle length 6.8 could see dwell time issues and as bad as some bulges looked at am wondering if rifle is firing with bolt not fully in battery.
Do people not take chamber casts anymore? Every rifle I own have a chamber cast to set up,dies if want to load precision ammo for it as every chamber will have slight variations and some huge variations out of specification. If a new barrel is that bad out of specs I want to know before pull trigger on first round. I chamber cast new factory rifles as well as builds from my custom turn bolt smith and loose barrels soon as come out of box or go onto build bench. Same as measuring port size I like knowing what I have if post build trouble shooting is required.
Once you have your properly cured cast can use a myriad of tools to take all types of measurements. Using anything from a chamber checker to just check your cast fits, remember cast will be bigger than a loaded shell and likely the same dimensions as a SAAMI chamber dropping the cast in a device same sizes as cast it will be very snug to coming just shy of fully dropping in but will give a quick easy idea of how close to spec your chamber is. Allows easy measurements of neck for length, concentrity, free bore, diameter at case head, shoulder, etc.Contraction - Expansion Factor VS. Time
2 minutes -.0004"
6 minutes -.0007"
30 minutes -.0009"
1 hour +-.0000"
2 hours +.0016"
5 hours +.0018"
7 hours +.0019"
10 hours +.0019"
24 hours +.0022"
96 hours +.0025"
200 hours +.0025"
500 hours +.0025"
Most charts say rifle length gas is for 20" or longer barrels. When combine an under 20" barrel with rifle length gas then dwell time of bullet in bore once passes the gas block is very short thus not much time to feed gas up through block, down ~12" of gas tube to set the bolt carrier group in motion. Maker has to guess if user is going to lob light (85 to 90 grain) spc I spec loaded ammo or hot hand loads using heavy (115 to 120 grain) bullets. If send you an overly large port your forced to buy an adjustable gas block or really work hard to properly weld up port and redrill at proper smaller size or live with over gassed gun. (Many makers over gas most of their ARs)Thanks for the advise on chamber casting. Every 6.8 barrel I've owned has always been somewhat over gassed IMO so this one coming in vastly under gassed was a surprise. (Trim)
It's odd that a barrel manufacturer would sell a barrel like this with an improper gas port size. Makes me wonder what they were doing during development. Did they just take a shot in the dark on port size? Do they even test the barrels? I doubt it would have cycled an factory ammo at all. I ran quit a few different loads through it trying to get it to cycle but gave up because of my brass being destroyed.
ya my gas block is almost completely closed just to get it ejecting in a 3'oclock position. Also if it is opening early how do I stop that? Heavier buffer?I've not been able to run any of my 6.8s suppressed without an adjustable gas block turned down at least 1/2 closed. Otherwise the bolt is opening too early when the chamber pressure is higher.
gotcha,My 12.5-inch runs suppressed with standard components accept for the AGB so I'm not sure I can help much. It might be good to list your configuration so others can provide helpful inputs.
Never found out the issue for sure. They just refunded my money when they got the barrel back 🤷♂️ They never told me anything about what was wrong with it. I'm pretty sure there was something out of spec with that barrel though.@TrouserSnake Did you ever find out what was causing the bulges on your casings? The reason I am asking is that I have a 11.5 inch barrel from ar15perfromance and its having bulges on factory ammo and just on one side. I don't think its short stroking but when I suppress it the bulges get worse and if I don't its hardly noticeable but still there. Any info you might have would help a lot.
Wilson barrels are made by ER Shaw not BartleinI wonder about the rifle length system also. My WC 18" barrel also came with rifle length gas system. I had to open the gas port two drill sizes, to .094" The bolt would not lock back before I enlarged it. FWIW, Wilson does not make their AR barrels. I think they come from Bartlein.