View Full Version : Winchester 458 and 375 brass out of spec.

02-13-2010, 05:51 PM
I am a new guy. I thought that one of you might know the answer to a couple of questions. I bought virgin Winchester 458 brass and found that the head just above the belt measures .508 the spec. is .513 just below the mouth measures .478 and the spec. is .481 These are O.D. The problem is I cannot get 80 gr. of 4895 into the case and seat a 350 gr. Hornady to the cannulure. There is a prominent bulge behind the bullet.

I sent the batch back to Win. and they sent new cases with the same dimensions. Am I missing something that someone can educate me on. It looks like the case is reformed behind the bullet by the compression and the bullet is prominently stretching the case where it is seated.

Any ideas would be appreciated. Thanks,

Butch Lambert
02-13-2010, 06:19 PM
Most brass is a little undersized until fireformed. I think that after firing it will be fine. My load books indicate that 77grains is max load for a 350grain bullet.

02-13-2010, 06:22 PM
80 gr of 4985 is a compressed load in that case. Bullet seating is deforming the case by forcing the powder to stretch out the brass. Something's got to give. Maybe, just maybe, you would have better success using a "drop tube" that will do a better job of depositing the grains into the case in a more compact manner to start with.

Good luck.

Joe S
02-13-2010, 08:35 PM
Starting a bit low instead of at max then working up with result in fire formed brass that as already said will have a bit more capacity and should allow the charge without bulging the case when compressing the charge.

Greg Culpepper
02-14-2010, 09:42 AM

I think the specs. you list are chamber specs., not brass specs. The brass needs to be a little smaller so the chamber can except it. Production variations for chamber and cartridge size recommend clearences that handloaders will improve on. Nothing is more frustrating than when you can't get your new brass or ammo into your new rifle. I don't think anything is amiss.


David S
02-14-2010, 10:05 AM
I shoot and reload for several belted mags. .508 seems normal for new brass. I have a 375 H&H and the cases measure .509 & .510 just above the belt on once fired cases.

02-14-2010, 11:58 AM
Thanks to all for the information. They all make sense. I will try the 77 grain load with a drop tube. After I fire a few, it seems sensible, that the brass will form to the chamber. I think I mis-interpreted the chamber dimensions with the brass dimensions. When it warms up a bit I will report back.