Case Head Separation

[Tiny Tim]

Have you checked the other cases you shot vs others that you have fire formed for a thin spot in the same area? You may notice it with a bent paper clip as you would check for case head failure. Maybe cross section one or two of each to see if all of your fire formed brass is damaged or if it is related to the reloads.

 

[just_jon]

Would a full tilt fireform load cause the brass to stretch all in the one spot when converting to AI? Maybe try fireforming with a cooler load then turn it up.

I fire formed with 36 grains of IMR 4895 which Nosler shows shows at 3,539 fps. I think I see where your going. I reviewed my notes and last batch of brass fire formed in this gun used 12.3 grains of green dot. I got 8 loadings out of that Rem brass before the necks started splitting.

 

[just_jon]

Have you checked the other cases you shot vs others that you have fire formed for a thin spot in the same area? You may notice it with a bent paper clip as you would check for case head failure. Maybe cross section one or two of each to see if all of your fire formed brass is damaged or if it is related to the reloads.

I pulled bullets on the remaining rounds last night and checked a dozen rounds with a paper clip and found no abnormalities. Not so much as a scratch. This morning, I checked several with my bore cam And didn't see any signs of a pending case separation.

 

[243winxb]

Separations in the case body are from stretching, as the head to datum gets longer.

Its possible for light loads to expand the case body diameter, outwards & make the head to datum measurement shorter, at the same time. On the next full pressure loading, the brass stretches. This can be seen when using Hodgdon reduced Youth Loads with H4895.

With only 1 case separation, i dont think i would worry about it. Where the separation is happening should seal the chamber on firing. Had many 223 separate in the middle because of .014" stretch. No gas made its way back to me shooting an M16A1 carbine.
A bright shiny line may appear-

Online, a false shoulder or lightly oiled brass has allowed brass to flow without damage on the first fire forming.

 

[parshal]

As others have said, case head separation usually happens just above the web on the case. Yours separated much higher. I'd agree it has something to do with the initial fireform.

You might also take a bunch of those cases and cut them in half lengthwise to visually inspect. I had a bunch of brass that was separating and the paperclip trick showed me nothing. Incidentally, cutting the cases showed me nothing either but they kept separating. So, about 400 cases are getting tossed.

 

[Stevenstl86]

Did anyone else see the load data was for 50 grain bullet and not 52g??

 

[Seabeeken]

Jon, As already stated, you case neck/shoulder was not supported properly when you originally fire formed the cases. I load for 250ai, 257ai, 7x57ai, 280ai, and 243ai. Only saw this once while forming 257ai and was the result of lack of support at the neck/shoulder. The damage was done on first firing and created a weak point in the case which stretched at that point on subsequent firings. You would need to check for pressure signs at the case head to see if they are over pressure. Ackley chambers today arent as tight as the ackley's of old. Ackley set his chambers back .004' to prevent this. The best way to prevent this is to form a false shoulder in the neck by running your virgin 22-250 brass over a 6mm mandrel and then back your ai size die out a half turn and size the neck back down. Try it in your chamber, if bolt wont close, turn the die down 1/8 turn, size, and try in chamber again. Continue this until the bolt closes snuggly on the round. Size the rest of the brass, load and shoot. The false shoulder will hold the case head against the bolt face and prevent this excessive case stretch. One way to check you chamber is to try to close the bolt on a standard 22-250 go gauge. It should NOT close on it. In ackley chambers properly done, the parent cartridge (in your case, 22-250) go gauge becomes the no go gauge.
Fortunately, it appears the leaked gases went forward as indicated by the soot on the shoulder and neck

 

[iunderpressure]

I have a love hate relationship with Encores because of brass stretching issues. I won't buy another barrel for a bottle necked rifle cartridge. I always have short brass life because of stretching. I don't have those issues in bolt rifles.

 

[Opa-lopa]

This separation is caused by improper case hardness profile, likely due to your annealing operation. See: https://ndiastorage.blob.core.usgovcloudapi.net/Ndia/2019/armament/Krogstad_SA3_3PM.pdf

 

[tooOld]

Yup, you're right, I missed the AI load info. My mistake.

I don't think that this is a head separation. With the powder marks down the case it looks to me like hot gasses were able to move along the case which means that the case didn't have time to expand before the bullet was out of the case.

You are loading 52 grain bullets, but attach Nosler info for a 50 grain bullet. A difference.

 

[Huntz]

This can happen because when the chamber was opened up to AI the barrel was not set back.That is why it is important that you do what was suggested above and make a false shoulder by sizing the neck up to 6MM and then neck it back down to 22 caliber.You do this in increments until you get a tight fit when you close the bolt.This guarantees proper headspacing.Also using a bullet other then what was shown in the loading manual is a bad idea as it will have a different ogive and and a lot of HP bullets have a thicker jacket so they don`t deform.BR shooters want clean holes in their targets.JMHO,Huntz

 

[just_jon]

Steven/Bill- Excellent point re bullet weight. In doing further research after the fact, I discovered that Sierra max for 52 SMK is 39.5 grains. Had no clue their manual even listed 22-250AI. Up until this point, all load development had been done with the 50 grain V-Max. After finding a wide velocity node in Satterlee testing with Varget, but unable to find acceptable accuracy in OCW testing, I made the mistake of trying an old standby bullet without rethinking charge weight.

Opa-lopa - As for annealing, I tend to agree. This was the first lot of brass I annealed with my Annealeez. I used 700 degree tempilaq on the neck and 400 mid way on the body on several test cases and everything looked normal temp wise Unit was set at 65% which is a touch over four seconds. I kept a dozen of this lot of brass for

Seebeeken - I'll try the false shoulder technique when I get my new brass. Seems like good insurance against a repeat occurrence. I load for five AIs and have always fire formed using the COW method.

Goes to show that despite loading for more than 35 years, one can still screw the pooch by not paying attention to the detail.

 

[freddiej]

Just-Jon, if you will entertain a small experiment with one piece of brass of yours. full length size, put a primer in your brass, go outside and fire the primer off in the firearm that the brass separated in. see if the primer sticks up past the head of your brass, if so, how much?
two things could have happened, the first is that your brass stretched beyond it's limits on fire forming or the problem is you have not set your dies right for a 0.002" set back of the shoulder. this test will eliminate one and prove the other depending on results of the test.

 

[Rflshootr]

Sierra lists 38.0 grains of Varget max for their 52/53 grain bullets and 39.6 grains of Varget for all of their 50 grain bullets. Back your load off!
1.6 grains is A LOT in a small case....and in your case 2.0 grains difference.
Plus, Lupus brass is thicker then the Winchester brass that Nosler lists as their test case.