300 WSM Norma Brass - excessive growth!!

[Elkslayer1]

I have a 300 wsm and shooting a 190 vld. It shoots sub moa and I have no pressure signs ( no hard bolt lift, primer problems, case markings etc )

After each time I shoot, these cases expand after sizing to over the max length recommended for the cartridge. I have to resize and cut the brass back after one session of shooting.

Can anyone tell me what might be the pproblem?

I reload for many other calibers and have never seen this problem

Thanks,

 

[rscott5028]

Is your case length measurement before or after sizing?

Are you full length or neck sizing?

-- richard

 

[Lefty7mmstw]

What is your pre-fire trim (ie. .010) under?? You may have a chamber that is a bit on the long side and have to set your dies a bit long.
I get around .003" growth per firing on bigger cases.

 

[cahunter805]

Elk- If you are getting the Max length measurement from your reloading book that is just a generic number just like the OAL. Every chamber is different and you can measure yours to find out the actual lengths. That sure seems like a lot of unneeded trimming.

Also is this FL or Neck size and how are you setting up your die?

 

[Mikecr]

Can anyone tell me what might be the pproblem?

Sounds like excess FL sizing

 

[Tikkamike]

sounds like excess fl sizing

bingo!

 

[Elkslayer1]

I am using Redding dies and full length sizing. Also using 59 grains of H4350 with the 190 VLD.

These cases are long after just one shot and before I full length size. I am trimming them to the .010 under each time.

 

[Lefty7mmstw]

I am using Redding dies and full length sizing. Also using 59 grains of H4350 with the 190 VLD.

These cases are long after just one shot and before I full length size. I am trimming them to the .010 under each time.

It really sounds like a rather big chamber combined with fl sizing fully. Crank your die out to the point it just bumps the shoulder a bit and try it again. Smoke your case shoulder with a wood match after lubing to check for this. If it's anything like my my 7stw it will fix the issue. I went from .012 growth to .003 growth doing that.

 

[Elkslayer1]

Thank you....I will try that!!!!

 

[Lefty7mmstw]

Thank you....I will try that!!!!

Cool

Remember though, if you are running two or more rifles you will now need to have a set of dies just for this rifle; ammo too. The brass may not chamber in a tight chambered rifle if sized long for a looser chamber. Small price to pay for better brass life and accuracy.