Bullet Case "stretch"

[CarJunkieLS1]

I've been reloading for a little while now and I know enough to be dangerous I guess lol. I've noticed something and want to ask the experts what you think. I have some once fired (not in my rifle) Winchester nickel plated cases. I trimmed them all to the minimum length and loaded a few to test load them. I shot them yesterday and today I full length resized them and the cases stretched .004-.007 after resizing. Is this amount of stretch normal or should I worry about it. I have no high pressure indications primers look normal, bolt lifts easily, case head looks good, and cases aren't bulged. I guess my question after all this is; is there a general rule as to how much case stretch per firing is acceptable or should I even be concerned about it.

 

[243winxb]

The trim length will get longer, after full length sizing the fired brass. Use lube inside the case neck, so the expander does not pull the neck/shoulder forward.

 

[witchhunter]

Always full length size before trimming. They will stretch. Size a few that haven't been fired and measure, you will see that they stretched a little too.

 

[rcmodel]

If you trimmed them before resizing them??

That right there is your problem.

rc

 

[bob4]

Use lube inside the case neck, so the expander does not pull the neck/shoulder forward.

If you accidentally pull the shoulder forward is it possible for a round not to chamber correctly or worse yet get stuck in say a bolt action ?

 

[243winxb]

Bob4, I dont think it would be a chambering problem, as a bolt can size the brass a little on closing. A crimp that is to hard may put a bulge in the shoulder & will jam.

 

[CarJunkieLS1]

I trimmed them after I full length sized them. Before firing the were all 2.530 +.002 -.000. Now that I have fired them and sized them again they measure 2.534-2.538. I use a brush and put some RCBS case lube inside the case mouths. Is that amount of stretch normal or should I be concerned.

 

[Walkalong]

Doesn't sound like enough to worry about on the first or second firing. The first three or four firings they will stretch more than the next three or four. It should be less and less the first few firings as the cases harden up.

How much pressure and how soft the brass is determines how much it will need trimming after sizing.

 

[243winxb]

I would say, more stretch than normal, if your controling your shoulder bump when sizing. What cartridge are you loading?

 

[fguffey]

I will assume you are shooting a 270 Winchester or a 280 Remington, then, for me, it would help if I knew what rifle you are shooting.

The pulling of the neck forward is never an issue, there is a technique that can be used to determine if the case gets longer by pulling the neck. Then there is necking down, the case neck gets longer, when necking up the neck gets shorter.

F. Guffey

 

[CarJunkieLS1]

I am loading .270 Winchester. The rifle is a factory stock Tikka T3 Lite. I'm not sure if it will help but I will post my load data. Keep in mind that this load works in my rifle and may not be safe in your rifle. Use accordingly and with caution.
This load is very accurate and I have consistently shot 1/2 inch groups @ 100yds.
.270 Winchester
Winchester Nickel Plated Brass
130gr Nosler Accubond
COAL 3.300
57.0gr IMR 4831
Rem 9 1/2 primer

 

[243winxb]

Brass Stretch

Walkalong gives great info. As the brass work hardeneds. , it may flow less. From Olin-

modulus of elasticity- Cartridge Brass-
Material is 70 copper/30 zinc with trace amounts of lead & iron , called C26000. Material starts to yield at 15,000 PSI when soft (annealed), and 63,000 PSI when hard.
Material yields, but continues to get stronger up to 47,000 PSI when soft, and 76,000 PSI when work hardened.

Looks like a hot load, if you look at the 140 gr data on Noslers website. This will make brass flow, needing more trimming. The 270 does run at high pressures.

 

[CarJunkieLS1]

Thanks yall have been very helpful. I agree I have a hot load for sure and that bullet is screaming, but it does very well in my rifle and I have no pressure signs. Guess I'll just watch my brass for issues.

 

[fguffey]

Carjunkie, running high pressure/hot loads is possible, there are tight barrels and loose barrels, the difference between two new rifles can have 4 grains difference between hot and mid range loads.

A reloader was shooting max plus 2 grains and was happy with the appearance of the cases, with another rifle he had to back off 2 grains below maximum to prevent resistance to bolt opening.

F. Guffey

 

[quartermaster]

.007 seems like a lot, but .003-.004 seems normal. I wouldn't worry about it unless other signs of pressure are showing. Maybe soft brass. Shoot them all up, trim them again after sizing and see what happens. I'll bet they won't grow so much during the next shooting.