Brass Case Head Separation after 6 firings

[bigngreen]

If I were to go back to a false shoulder to hold headspace I would certainly anneal after forming the shoulder and before firing, this helps.

I look at it this way though, we are careful in precision loading to minimize our sizing without getting into too tight but in general we avoid large jumps now think about punching out a 7mm case to 338 which means your working up into the shoulder then your bringing it back down to 30 and setting a shoulder in yet another place, that's a LOT of working brass in the neck and shoulder, I've always found the more brass you move the more things move inconsistent so in the end you'll see case mouths, thick and thin spots in the neck and other things that just add to the challenge.
As you do all this run the case on a runout guage, just expanding up the brass will start to move slightly of, that's why you don't want the neck or shoulder centering anything, cause it's not centered. Bullets do not leave the case before it blows out unless your obscenely low pressure so a heavy jamb puts you between centers and I get just beautiful, concentric cases with the brass pulling in shortening.
I also do my trimming at the longest neck length so that my neck shoulder junction is made up of neck thickness brass after it sucks back warding of donuts which tend to rear their ugly head the more brass you move back and forth.

 

[nksmfamjp]

I run several Win Model 70's, if you're checking you shoulder bump with the firing pin installed in the bolt STOP! Remove it and check your bump, otherwise you'll get false readings, the firing pin spring will alter where the bolt face is in regard to your measurement if using a comparator system.

Gotcha. That is my favorite part about the M70 action. Easy to remove the firing pin!

Improving Peterson brass they told me to anneal down the shoulder and case body a bit, and to lube the case a little. As mentioned make sure the action lugs are lubed, as they should be.

Actually, I think I had a couple issues. First I used 280AI brass. It is just too strong of a shape. It think it pulled instead of just blowing out. Additionally, I don't think I annealed after creating the false shoulder.

When you made your "false shoulder" how much longer was it than your normal length? Ie how much was your size die backed off (turned out) when sizing the neck back down?

I set the die to just barely close the bolt?

 

[Mike Matteson]

Case gages are available for standard cartridges, and there are headspace gages to check to see if your chamber is too long, or about right, or just right. - Is this a rare chambering? - Then you have to make DAM*N sure it is all right.
My Dad had a custom .338 WM, then later found the chamber too long. - Dangerously long!= Cases separate, and screw you and your rifle up = BAD DAY. - I caught it and nothing happened. The neck-sized rounds would not fit in a stock .338 WM. Too long! - Sold it to a gunsmith who fixed it.

To long to cycle out of the out of the magazine. Now that problem happens a lot of times, because the length of the bullet reaching out to the lands. Now I have two different M98 action rifles in 308 N.M chamber by the same reamer. The magazine were different in the rifles. One I could reach out farther with one, and the other I couldn't. Finally figure it was the magazine were different length ID.
If the head space is off. They take out the barrel and reset the chamber to correct the length. Now I never had that problem, but have come across that a couple of times with other people rifles. Belted Mag are noted for case stretch. I have a 264WM, 7mm RM, 308NM, and 2-338WM. To slow that down in case separation with belted Mag, only bump the shoulder by a couple .002" or use a neck sizing die, and not bump the shoulder. You may from time to time full length the case if the bolt won't close or hard to close. I generally didn't have to use a FL size die, because the primer pocket were toast in about 10 firing anyway. I was loosing the case in about 3 firing with case stretch at or about that at the belt area.

 

[MW204]

- Opened up to .338"
- Used .30 Gibbs sizing die to establish false neck
- 11g WSF, fill COW to the base of the shoulder, and then stuff with a cotton ball (packed)
- Shoot and clean barrel as required.

Virgin Peterson brass started with .001X" thicker than Hornady. I do not have the thickness after COW, but I can measure them for you. I do not worry about it until one full load firing off the chamber.

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1 - .35 Whelen Hornady virgin brass
2 - After running through .30 Gibbs sizing die
3 - After COW fireforming
4 - After firing off the chamber with a full load

I have done some fire forming from a 270 to a 280 but those are pretty close in size, but the 35 Whelen down to a 30 Gibbs is a dramatic change.
Do you have two sets of dies, one to get the first resize down to the 30 Gibbs and then one regular size die to finish all your reloading? If not how do you get the 35 Whelen to start in the 30 Gibbs die?

 

[FEENIX]

I have done some fire forming from a 270 to a 280 but those are pretty close in size, but the 35 Whelen down to a 30 Gibbs is a dramatic change.
Do you have two sets of dies, one to get the first resize down to the 30 Gibbs and then one regular size die to finish all your reloading? If not how do you get the 35 Whelen to start in the 30 Gibbs die?

Nope, just one set of die (sizing and seating).

 

[RidgeTop]

I was working with a .303 Lee-Enfield which are notorious for stretching cases. What I did was put an o-ring of the proper size around just next to the rim. Then proceed to fire form with Quaker Corn Meal. Worked like a charm for the .303 and increased case life many times over..

 

[jdyoung]

Is it possible/feasible to buy a hydraulic forming die setup for any caliber of rifle one has???? Conventional, wildcat, any cartridge.
For instance, I think it would really be useful in getting a magnum cartridge to headspace off the shoulder instead of the belt.

 

[MagnumManiac]

Is it possible/feasible to buy a hydraulic forming die setup for any caliber of rifle one has???? Conventional, wildcat, any cartridge.
For instance, I think it would really be useful in getting a magnum cartridge to headspace off the shoulder instead of the belt.

Of course you can.
I just find COW an easier and less expensive way of doing it.
Most issues arising with belted mags are rifle system issues, not issues with the brass design.
An unsupported case head, no matter the cartridge and it's design will eventually lead to case head separations. Why people think this is just a belted cartridge issue is beyond me.

Cheers.

 

[nksmfamjp]

I used Titegroup, COW & 1" square of TP for a cap. 11gr was about the best charge weight for 270 win case to form 300 Sherman. It didn't pull any brass out of the case head as far as I can measure….Only thing is case length is 2.475". I think the chamber can accept 2.540". Case length should be 2.525".

Where did my 0.050" go? How do I get It back? Would lubing the cases before firing improve that?

 

[dennisinaz]

You can set your caliper up to scribe a light line on the brass about ½" up. Fire form and then check the line to see if it has moved. If it has, you're stretching the brass

 

[Rflshootr]

I used Titegroup, COW & 1" square of TP for a cap. 11gr was about the best charge weight for 270 win case to form 300 Sherman. It didn't pull any brass out of the case head as far as I can measure….Only thing is case length is 2.475". I think the chamber can accept 2.540". Case length should be 2.525".

Where did my 0.050" go? How do I get It back? Would lubing the cases before firing improve that?

Anytime you blow a case out to a larger diameter, you lose length. The reason is because you are increasing the circumference. A larger circumference requires more metal. So to get that larger diameter, the extra metal needs to come from somewhere. More metal just doesn't magically appear, so the length shortens.
πD (3.1416 x Diameter) will give you the circumference. Just for math fun, take the starting diameter of the body/shoulder junction on both cartridges and figure the difference. Then do the 2 neck diameters. That will tell you how much difference in length you are changing the circumference.....next math class is "pies are square" which gives the area increase.

 

[MW204]

To get a perfect expansion on the brass is it not better to load a lower powder charge and leave the bullet touching the lands? That way the firing pin does not push the loaded round forward before expansion begins, otherwise won't most of the stretching occur in the web area.

 

[nksmfamjp]

I have fireformed 2 ways: case with false shoulder touching chamber and bullet touching lands with a light load. This method seems to thin the lower case walls, but necks were right length.

I have also now done the COW method.

COW method is giving me short necks and no base thinning.

Bullet light load method gave me base thinning. I will probably use COW method from now on.

 

[MW204]

I have fireformed 2 ways: case with false shoulder touching chamber and bullet touching lands with a light load. This method seems to thin the lower case walls, but necks were right length.

I have also now done the COW method.

COW method is giving me short necks and no base thinning.

Bullet light load method gave me base thinning. I will probably use COW method from now on.

I can see that with different calibers, but the load I was talking about was a 22-250 to a 22-250 Ackley and other calibers I made Ackley's out of. If the same caliber, I don't see how you can make a false shoulder.