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Discussion Starter · #22 ·
Did you ever measure the difference between a fired case and an unfired case as suggested?

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I did measure at the huge bulge. loaded brass before firing was .4170. Measurement after .4255

Measurement at the case web
 

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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"
 

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Discussion Starter · #24 ·
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"
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.
 

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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.
Was it the same load also ? Or different powder measure and or bullet?

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Discussion Starter · #26 ·
Was it the same load also ? Or different powder measure and or bullet?

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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.

Those loads shoot great through my 12.5 noveske barrel and 16" YHM barrel.

I tried many different loads though and they all did the same thing. 90 grain gold dots with 31 grains of h322 at 2.260 / 90 TNT 35.5 of H335 2.290 COAL. 1.800 to ogive / 110 Vmax but I dont have to load data on hand and a few others with lighter loads and had same result as all the others. Case bulge on one side and short stroking.
 

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Discussion Starter · #27 ·
Little side note, It actually grouped really well with the 90 TNT's. Brand new barrel groups under and inch running 2950 average velocity single digit SD's. Just destroyed my brass and wouldn't cycle. So I am impressed with the accuracy.
 

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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.
 
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Discussion Starter · #29 ·
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.

Thanks for the advise on chamber casting. Yeah, I haven't got that far into gunsmithing yet. I'd like to know the proper procedure of casting a chamber. I took a gamble on this barrel being rifle length gas system because I was hoping it would have a softer recoil impulse. 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.

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.
 

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Chamber casting is easier than reloading on a single stage press or bullet casting. Buy a chamber cast ingot (usuallycalled Cerrosafe but other vendors offer casting alloys) from Midway/Brownells/Mid South/etc. Push a tight fitting patch into bore from muzzle using a brass jag about 1/2" to 1" shy of rifling lands. Want cast to include beginning of chamber body, shoulder, neck, freebore area and first bullet length of rifling. Want to measure inside diameter of throat (especially match chambers so can outside turn and inside ream cases to fit neck with minimum clearance but not bind), diameter of chamber at base, where shoulder begins, throat length and distance to lands. Will allow you to examine transition from freebore area to engaging threads for burrs that may require lapping plus helps in setting up bullet seating depth for precision loads and sholder angle but most importantly measure to ensure chamber dimensions are in spec.

This is a very simple process that is almost impossible to mess up. Coat chamber with just a fine dusting of graphite, heat your Cerrosafe in a ladle of some sort like plumbers ladle, gutter installers ladle, lead dipper (I use a older cast iron bullet casting ladle for casting muzzle loader bullets over a fire with a spout) that is big enough to drop a Cerrosafe ingot broken into two pieces) using your stove, propane torch, camp stove, etc till melts the Cerrosafe to 200° F and pour into chamber holding barrel plumb with muzzle down till Cerrosafe fills chamber and mounds up just a bit so get full cast but not let overflow over sides so does not make removing as difficult. If your ladle does not allow an easy pour a prewarmed aluminum funnel can be a help.

As the Cerrosafe cools it shrinks just a tad allowing you to tap it out without undo difficulty using a wooden dowel from the muzzle or if need stiffer rod because cast cools fast an aluminum or brass rod will not damage rifling of a steel barrel unless your just stupid but be careful not to nick/damage crown. Cerrosafe is made of a nifty material which shrinks a thousandth or so as cools so easy to remove but returns to original size as cures (During the first 30 minutes of cooling cerrosafe shrinks. At the end of one hour it should be "exactly" chamber size) giving user a very accurate cast of their chamber, throat and rifling. There is slight size change with time based on brand/alloy of chamber cast material but this chart gives average expansion factor fairly accurately as it cures overy time..

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"
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.

If do not want to keep a chamber cast of your chamber can remelt and use to cast another chamber. I have some rifles such as 22 CHeetah, 22 Nosler, 22-250/22-250 A.I., 240 Weatherby Mag, 6mm-284, Lazzeroni 257 Scramjet, 7mm Rem Mag, 7mm Practical up to 300 Win Mag and 300 RUM plus other throat smoking hotrods had built over the years which take a chamber cast every 400 to 600 rounds to help determine if time to lap the throat or time to replace barrel. My 240 Weatherby is set up nothing like the factory rifles as smith who built it set it up to run with little to no free bore.

How Weatherby gets velocity without blowing up rifles is a lot more free bore than most so bullet has nearly cleared case when engages rifling and thus pressure drops much quickly plus the bit of extra gas bleeding back reduces stuck cases. My 240 after blueprinting the action lapping bolt lug engagement and cryofreezing barrel and action to relieve stress points in steel smith says to load to full 240 Weatherby specs or beyond, seat bullet where ogive engages lands when close the bolt or has minimal freebore and pretty much grantees can't blow it up unless use fast pistol powders. Have several turn bolts built by same smith that he advises what would be dangerous distances from ogive to rifling in factory rifles but his are built to take these pressures.

That said have rifles with 1,000 round to 2,000 round barrel life before see steep accuracy drop off unless they are lapped as needed. Have a bore scope that does video capture so able to compare still pics and video of throat when new against current round counts. When start to see rough areas and burrs can use Tubbs Fire Lapping Rounds or hand lap the throat thus extending the bores life. Some of these rifles may start off with 28" to 36" barrels and when throat is smoked smith cuts anywhere from 1/4" to 2" off back of barrel, recuts chamber, replaces barrel and can sometimes get three rechambers out of barrel before rifling is eroded past use.

Will take a chamber cast before fire first round if smith does not provide with a cast then take a new cast every 200 or so rounds. When see odd wear or divots/burrs will lap and then when lapping no longer brings back accuracy take to smith to decide if cutting and rechambering is needed or new barrel. Have a 22 CHeetah on its second barrel which have the casts from first barrel as souvineers and recently took second cast on new barrel. Get a really good feel for when rifles will show accuracy fall off without firing a round on paper as barrels with 1,000 round throat life other than verifying scope as needed just shooting paper to check accuracy as a habit reduces the number of varmints or long range bigger it kills before buying a new barrel.

I purchased a bunch of barrels in end of year clearance from a popular AR parts company several years back. Like eight of one, five of another, etc. They had a reputation for one particular stainless barrel having chamber issues which had purchased four of. I took a cast of all four, two of which throat was very rough and another throat was rough and lands were mangled. Sent email with photo of casts plus video captures from bore scope and they sent an RMA number same day saying that replacement barrels would be shipped next day rather than having to send back for inspection. To date have only built two of the four barrels, had I not had this habit could have built the two good ones first and not discovered the bad pair till a decade after purchase and doubt warranty would have covered them even if had just been removed from boxes and wrappers.

I can't keep casts of every chamber of every rifle along with comparisons as round count increases. As 5.56, 6.8, 458 SOCOM, etc tubetube ome in will take a cast, measure and check for concentrity, obvious issues and if passes add to parts locker. If doesn't get it replaced and check replacement. My varmint rifles and extreme hotrods will keep original, casts taken through its life then when smoke it use the old casts to make new casts for other rifles. Only AR 15 cartridge I keep original cast are 22 Noslers, AR 10s keep 6XC and 6mm Creedmoor casts.

Delved a bit deep but taking a chamber cast is the easy way to ensure there is no issue with chamber as have a barrel right now to return where reamer shattered while chamber was being cut and inside looks like bomb exploded. Find more issues than would think but I buy lots of clearance barrels at two to a dozen units per purchase if cheap enough. Purchased eight Noveske 6.8 barrels in one lot second hand but sealed in wrapper so need to know they are right before go in locker if may sit years before built. Also don't want to assemble a single unit and discover chamber is fubar after all the labor of assembly.
 

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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.
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)

Opening up a port is so easy that if a person feels challenged to do so may need to buy completed uppers. I build lots of uppers for people who feel comfortable asembling lowers but after troubleshooting their first problematic upper have no desire to do it again. All you need is a machinists wire size drill bit index where can open port one diameter at a time till rifle is tuned or open to a value you know will work then slap on an adjustable block to tune it. I have target rifles built specifically to shoot a single round have drilled port to work with either a 69 or 77 grain bullet and never tested to see if a 55 grain or lighter would operate the gun.

We are talking 6.8 but in guns where reliability is king like rifles built for USSOCM "operators" will often be gassed wide open. A Mk 12 Mod 0 (5.56) uses an 18" barrel with rifle length gas and ports are drilled at 0.125" so they will munch any ammo fed to them but have a slower cyclic rate for increased accuracy. Longer gas systems slow speed the bolt unlocks in theory so projectile has plenty of time to clear muzzle before parts begin slamming back and forth.

Can have similar issues using a 10.5" barrel with carbine length gas. Only ~3" of bullet dwell time past port can make tuning interesting but is part of the build process. I have a pair of 20" varmint weight barrels with rifle +2" gas systems. These came with ports tuned perfectly for the 62 through 69 grain bullets I use in them. Have quite a few 24" and 26" barrels with rifle +2" gas.

With your barrel first sort out if chamber dimensions are in or out of spec. If all is fine then case bulges are from gun firing before fully in battery or bolt unlocking too quickly which is least likely of the two. My favorite general purpose 6.8 barrel is an 18" mid length 5R with 1:11ish twist. My favorite general purpose 5.56 barrel is an 18" mid length 1:8 twist. From there I have barrels short as 7.5" to as long as 28" in small chassis ARs. While does not help with your bulge issue here is a great introductory article on AR 15 barrels.

The AR-15 Barrel Cheat Sheet: Everything You Need to Know

If you were near North Georgia would do a chamber cast for you. If unable to sort out and have to remove it, if ship to me will do a cast, return with cast plus my measurements and pay return shipping just to know. I enjoy troubleshooting rifles.
 
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Quote "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"

I used a Wilson Combat 18" rifle length gas system on my gun. It also had an undersized port that required opening up to function properly. It didn't take much and now it runs like a champ. Some have suggested that perhaps Wilson's supplier delivers them undersize on purpose, so the opening can be sized just right. If so, Wilson should put that in the description. All that in the past now and I have enough rounds down the pipe to say I'm satisfied with the accuracy and reliability of my rifle.

On a related note, I had and issue with a leaking gas key on my Wilson BCG. I found thier customer service to be pretty good. I spoke with live people, including a smith, and they rectified my proplem with a new key sent out in a timely fashion at no cost to me.
 

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@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.
:)
 

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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.
 

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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.
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?
 

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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.
 

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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.
gotcha,
well I am running a 11.5 inch 6.8 ARP 3R barrel with 1 in 11 twist. its a carbine length gas with a kaw valley adjustable gas block, Hailey Ordinance upper with a presuma charging handle and PSA BCG. The lower has strike industries hardware except for the trigger is a CMC 3.5 pound trigger and the buffer is a milspec buffer and the spring is a Red spring heavy spring. The suppressor is a 9 inch suppressor that I did a form 1 on.
 

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Discussion Starter · #38 ·
@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.
:)
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.
 

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I 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.
Wilson barrels are made by ER Shaw not Bartlein
A small amount of case bulge is normal. Brass is made new .415-.417 and chambers run .422. If you run a tight chamber at min spec .418 the Hornady brass will stick in the chamber because they compress the crap out of the 120 sst loads.

In addition chambers are hardly ever out of round. The reason is the barrel spins and the reamer is stationary. Even if the reamer is not aligned properly the chamber will still be round.
There is only one company I know of that uses an old WWII reamer that looks like a 3 place drill press, reamers spin barrel clamped in hyd vices. If you look very very few of those barrel have a concentric throat/freebore.
Headspace gauges do not measure diameter, only headspace.
 
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