Inconsistent Brass Growth?

C

coleman1495

CGN Ultra frequent flyer
Rating - 100%
50   0   0
Location
Whitecourt
Hello,

Does anyone know what causes brass to grow inconsistently from case to case? I just finished trimming my Lapua brass and noticed that I had to trim very different amounts from each case.

This brass was trimmed,loaded,fired, FL sized, then trimmed again. On some of the cases I remove a lot of brass while others the case mouth wouldn't even contact the cutter.
 
I notice it more on lesser quality brass. Brass like Lapua's and Nosler seem to be more consistent. Why it happens I don't know, especially on brass that is loaded with the same powder, bullet, etc.
 
It deals with how much the case expanded when fired and when it is resized and "squeezed" in the die.

It should be more uniform after the second firing, but remember the amount of lube on the case will also effect how much the case is squeezed.

wm05ArY.gif
 
Yeah brass is loaded with same components. Everything was trimmed to the same setting both times. I am guessing it may be a poor quality batch of brass. We will see how more firing/loading cycles effects things.
qnhD7Gp.jpg
[/IMG]
 
It looks filthy. It doesn't look like it has been resized. Trimming should be the last step before starting reloading and definitely done after any full length resizing.
Clean, lube, full length resize with 1 to 2 thou shoulder bump for a bolt gun, 3 thou for a gas gun, clean again to get rid of lube, trim to length; or trim and then clean. Clean primer pocket and flash hole. Now it is ready to reload.
 
I've seen the same with my brass, which is Lapua for the most part. Some cases stretch more than others.
Do you measure case length before trimming, or just trim each case as a regular part of your routine?
I ask that question because I do measure the length of each case as the last step before the case is deemed "ready to load" or not.

It's not unusual for me to find once-fired resized cases ranging from 1.910" to 1.916" in length, for example. If my trimmer is set to cut to 1.911" , some cases wouldn't be touched while others would have 0.005" removed. This sounds like what you're experiencing.

Out-of-the-box new Lapua brass has varied 0.003"-0.004" over it's length in my experience.
 
Wow! pretty anal about case length I say.
I do not trim any until the longest reaches maximum length.
Then I trim all back to minimum. Trimming every firing [Except for
long range match ammo] is a waste of time that I can use far
more productively elsewhere. D.
 
It’s not dirty brass. It had Imperial Neck lube (graphite) then lanolin applied to the outside. After its sized they look like that.

I will have to measure the lengths after they are fired again.

Eagleye- Yes these are long distance shells.
 
Last edited:
My 2 cents...I have often wondered this as well. I use Lapua and PRVI.

I chalked it up to the thought that perhaps not all the original brass material in the same lot is the exactly the same metallurgically speaking, factory tooling differences creating the case thicker or thinner, and my annealing (which is subject to concerns of consistent repeatability) torch and socket/drill method (with tempilac) creates differences with case stretch as OP is experiencing.

Otherwise, for myself, I have trouble understanding the resizing process with the same tools producing different results regarding case length increase with the same lot of brass.

Above being stated, I am not experienced enough to see differences in hot loads vs. light loads results in brass length.

Regards
Ronr
 
Well - I think you are seeing the natural variation that occurs. If you trim after every firing, you are talking about a very small amount of case growth, perhaps a thou or two max. You can see in the pics that some cases go untouched, some partially etc. If you let the cases grow from two or three firings, this variation would be less noticeable as all brass would take a trim.
 
You must log in or register to reply here.
Back
Top Bottom