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Case bulge near webbing

8K views 45 replies 14 participants last post by  TrouserSnake 
#1 ·
Took out my new 18" wilson combat barrel to the range today and had a few issues with it. First issue was it short stroking. It has a rifle length gas system. Im using a carbine buffer and carbine spring with 36 coils. Gas block is properly aligned. Use the dimple on the barrel to align it. Tried a few different bolts and carries and had same issue. The other issue was its causing a bulge on the case webbing. This is the first time I've ever had this happen on my reloads. Tried different ammo and brass through it and it did it to ever brand of brass from new unfired starline brass to resised Hornaday brass. I had a few different loads worked up ranging from 90 grain tnt's to 130 spear BT. Same issuse on everything I tried. Short stroking and bulging. I emailed Wilson Combat today about it. Probably hear back on Monday from them im sure. I was just wondering what would cuase the case bulging? Oversized chamber? too much headspace? All these loads run fine in my other barrels, Noveske and Yankee Hill barrel. Any input would be helpful! thanks
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#4 ·
You can check the headspace by depriming the fired brass, measuring the case base to shoulder and comparing to unfired cases.

Why would an 18" have a rifle gas system?
 
#6 ·
Good question on the gas system. I guess you'd have to ask Wilson Combat about why they made it rifle length. I have a feeling the gas port is too small for that length. I tried a few different powders including h335 being the slowest, hoping the slower burning powder would cycle the rifle. It didn't make any difference other then blowing a huge flame ball out the muzzle.
 
#5 ·
The bulging cases can cause the rifle to short stroke. There are few issues that can cause bulge cases. Other signs of overpressure on your handloads would be the first thing to check. Try lowering the powder charge or firing a couple factory loads. It could be a headspace issue. It is possible there is some blockage in the gas port or the block not being aligned.

The bulge can easily be caused by an improperly machined chamber or tight bore. It is difficult to tell from your pictures, is the bulge concentric to the case? Does it bulge evenly or to one side? If a case bulges to one side it will, effectively, wedged itself in the chamber and require more effort to eject it.

I am very curious to see how this works out for you. Please keep us updated. My wife's new Savage in 270 Win has the same issue. We just got the gun back from Savage this week. In typical Savage form, we have had no communication from Savage on what, if anything, was done.
 
#11 ·
Adam Savage voice: "Well, there's your problem!"

I'd definitely take pics and/or video and e-mail them to WC. I hope this is a one-off issue, and not a broader problem. Other folks who don't know what to look for (and, therefore, would just crank on the gas block and keep running it) could end up getting seriously injured.
 
#10 ·
first see if a round chamber and then extracts easily by hand. I had a grendel doing about the same. What i found out was i actualy had an overly tight chamber and when the bolt was sending the rounds home it would chamber them just enough to fine but not a 100 percent. The short stoking i thought i was having was because it took so much to extract them from the chamber that there wasnt enough gas left to complete the job. What cured it was just setting my press up to cam over harder on the shell plate. I mean hard enough that things on the bench jump. Might not be your problem but its easy to check. Just load about 5 rounds in your mag and run them by hand.
 
#17 ·
Old school way of checking if you had a sloppy chamber and didnt have a set of calipers was to size a case. Dont prime it charge it or seat a bullet. Then drop in in your chamber and take a wooden down and give it a good tap with a hammer. If you tilt your barrel up and it falls out its on the loose side. But thats a crude test. I dont care how hard you pound on a head space guage its going to fall out. Its made to easily drop in because its not made to measure for loose chambers. It made to check the dimension to the shoulder. You can have a head space issue on the tightest chamber or a sloppy one.
 
#18 ·
If you have a micrometer, measure the diameter of your case web. I can compare it to measurements from my rifles which I keep track. Include the brass manufacturer. Calipers can work too, just not as accurate.
 
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#20 ·
After talking with Wilson combat they had me send the barrel back for replacement. Well see it they say anything about it when the get it. I'm convinced theres a problem with the chamber. I understand the gas port being too small but I've never had case bulging issues like this before in the maybe 10 different 6.8 barrels I've owned. I used that headspace gauge on a few other barrels I have and it didn't rattle around at all like it did in the Wilson barrel. To be more specific about the rattle, what i mean is it would fall to one side like the chamber was out of round. That would explain to me the case bulge on just one side of the brass.
 
#23 ·
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"
 
#28 ·
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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#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.
 
#30 ·
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.
 
#32 ·
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.
 
#33 ·
@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.
:)
 
#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.
 
#34 ·
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.
 
#36 ·
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.
 
#37 ·
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.
 
#46 ·
Finished up the 68 this week. Went with a yhm barrel for half the cost of the wilson combat barrel. Cycles perfectly and groups good. Stretched it out to 600 yards at the range banging steel. Im really happy with the barrel overall. Its definitly heavier being a 20 fluted hbar but that actually comes at a benefit shooting off the bench. Looking for a different gas block for it now. Brass comes out perfect even with my hottest loads.
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