300 Win Mag Sizing

[Daerider]

After initial fire forming, I plan on resizing the cases until they will just drop into the chamber without any friction on the bolt face with the firing pin and ejector spring removed. Typically about .001" to .0015" of bump on a fired case. If I do this, the resizing die does not bottom out on the belt leaving a small portion unsized. Do I need to be concerned with this?

 

[can1010]

keep that brass with that gun only and it will not be a problem. if you measure that area it will be still undersized and as long as you don't beat your brass it will be fine. if it does expand there is a collet die to fix that problem

 

[bigedp51]

Like any die with a non-belted case the die does not size to the base of the case. The same thing happens with a belted case just above the belt.

The problem is the diameter of the chamber above the belt and the thickness of the case and its diameter. Meaning some cases expand more above the belt and can cause problems.

In another forum rather the spending the money for the Larry Willis collet die this person used a Redding body die. He removed .025 from the base of the die so it would size down to the belt, but this gave him .005 shoulder bump.

So if the shoulder in the body die could be removed in some manor it would just size the case body above the belt and not the shoulder. And since you have the machinery to do this its food for thought. And possibly also running the chamber reamer into the body die moving the shoulder forward.

 

[Daerider]

Factory dies are a bit too hard to run a reamer into, but I have some 1" diameter O1 tool steel in the shop that i could easily make a body die out of without a shoulder. I could start with .489" bored hole and run my finish reamer in to a depth that yields maybe .511" at the base, heat treat and polish.

 

[bigedp51]

The person that had .025 taken off the bottom of Redding body in a machine shop. Could the top of the body die be removed the same way cutting off the shoulder area of the die. I'm not sure if the base of the die was ground down on a grinder or machined down on a lathe.

Larry Willis stated a small base die does not work because it plows the brass toward the belt making the problem worse. So the base diameter of the die is critical and I assume removing .025 from the bottom of the die just removed the rounded edge on the base of the die.

 

[can1010]

I also seen where the small base die will be a problem. I was testing some ADG, W-W against my Lapua 300 win mag brass this year for case life. W-W lasted 12 reloads. ADG made it to 15. Lapua made it over 20. all loads were H-1000, 208 ELD-M 215m primers all loads in the 2950 range never needed a collet or body die don't even own either one. don't beat your brass and keep it in that barrel only and the brass will work harden in that area and you wont have any problems

 

[bigedp51]

Below while not a belted case is a example of the belted case expansion. Both .303 British cases below were fired in the same Enfield rifle.

The Prvi Partizan case on the left is a larger base diameter and .010 thicker in the base web area. The HXP case is a smaller diameter and has a thinner case wall than the Prvi case.

If you would imagine the HXP case with a belt you will see why "some" cases can bulge above the belt and cause a problem. I was sizing some Lake City 7.62 cases last night and noticed the die stopped sizing 1/8 of an inch short of the base. And the same would happen on a belted case.

 

[Daerider]

I also seen where the small base die will be a problem. I was testing some ADG, W-W against my Lapua 300 win mag brass this year for case life. W-W lasted 12 reloads. ADG made it to 15. Lapua made it over 20. all loads were H-1000, 208 ELD-M 215m primers all loads in the 2950 range never needed a collet or body die don't even own either one. don't beat your brass and keep it in that barrel only and the brass will work harden in that area and you wont have any problems

I intend to bump the shoulder .001" to .0015" after fire forming, so hopefully I will have similar luck with my ADG brass. It is just nice to know that there are options available if I am not able to chamber the brass anymore after 4-5 reloads due to case expansion near the belt.

To all who have responded to my post, I really appreciate all the good info!