New 30 BR Brass
I’m making new brass for next year (30 BR). I started with 6 BR and necked up to 30, trimmed the necks to .0085, and getting ready to fire form with 150 SPFB bullets, something I had on hand. I tried each case in my rifle before starting to load. As I started to load I found I could not seat the bullet in the case. I had to expanded the neck again before the bullets would enter to case. I had 25 cases that I had not tried in my rifle, tried one of these cases and the bullet started with no problem. I checked the length of the un-fire formed cases and it was 1.534” and the chamber is 1.520”. It looks like I’ crimping .014” of case on the bullet when I close the bolt. Should I trim the un-fire formed cases to 1.520”? I think the long cases would have a large increase in pressure when fired. I have made 30 BR cases before and never had this problem. I have a copy of the Robinette reamer and 1.520" is where it start to neck down to .3085".
L A R G E ! ! ! pressure increase!!!! I've done it, it ain't perty.
Trim your cases back.
If the length of the chamber is truly 1.520", I'd trim to 1.515" for safety sake, even though the case is going to shrink ever so slightly after fireforming, just as its length shortened when necking up. What is the diameter of the neck chamber? What is the diameter of the loaded round measured at the pressure ring if your bullet has a pressure ring? If you're using 150 grain bullets, how much freebore do you have? Will it accommodate the 150 grains' length? Try the 118 grain bullets and see what happens.
Originally Posted by Fla mac
Last edited by abintx; 12-16-2012 at 06:12 PM.
Unrelated to the length issue, what neck diameter do you have? I think .330 is pretty standard for the Robinette reamer, so .0095 to .010 wall is normally used. I'm just curious why the extra clearance.
I would suggest firing the cases with a load of pistol powder about 2/3 of a case full and a pistol primer. Use NO BULLET just a wad to hold the powder in. This will blow the shoulder out and shrink the case up. I usually do this before neck turning , but this method ends up with cases not needing so much trimmed off the necks.
I trimmed the new cases to 1.515", I think this will work. abinjtx you are right "turned" and used a new case with no bullet.
Thanks, "Merry Christmas".