7mm mag case sizing
- Thread starter BW64
- Start date
AckleymanII
Gold $$ Contributor
This is the best explanation. I would say the die is way under even what would be considered a small base sizer die dimension.
I have been shooting factory 7 mag(Remington, Browning A bolt, Browning BAR, and one Savage) since 1968, I have never seen the issues that you present in your pictures. Over the years, I have used standard RCBS and Forster dies for full length sizers. I bought a special collet die for sizing at the base, never used it...sold it off to a friend that thought he had a problem.
RCBS made dies for the BAR 300 Win Mag, they also made BAR dies for the 270, 30/06 etc. Reloaders assume there is a lot of difference in the standard full length sizing die and the BAR (small base dies), I would consider the Bar dies good fitting full length sizing dies.
F. Guffey
That .512" diameter spec is SAAMI's for new, unfired case diameter 1/4th inch forward of the case head. It has a -.008" tolerance.
What does your new, unfired cases measure there? It's not unusual that new cases vary from them.
OK 67.9 - 68.5 H1000, 162 ELDX,CCI LRM primers. No hard bolt lift after firing. Pockets are tight. No pressure signs.
BW
If I have a belted magnum that bulges in front of the belt, I use the Belted Magnum Collet Resizing Die from Larry Willis (Innovative Technologies). I use this before I size in either a full length or body die. It really helps alleviate the problem that you are seeing because as the sizing die moves down, that brass has nowhere to go because of the belt.
Reset the headspace of the barrel before you get a face full of scorching gasses.
I do not use headspace gauges for my belted magnums. I get a handfull of different new factory brass from pulled cartridges and test which is the longest from base to above the belt and use it to set the headspace.
To my surprise the difference between factory brass base to above the belt is no more than 0.002". But HS gauge is a lil more generous.
I do not use headspace gauges for my belted magnums. I get a handfull of different new factory brass from pulled cartridges and test which is the longest from base to above the belt and use it to set the headspace.
To my surprise the difference between factory brass base to above the belt is no more than 0.002". But HS gauge is a lil more generous.
There is a method/technique that would allow you to use one head space gage or a case head that has been cut from a case. Problem: It is not possible to talk about things like that on this forum.
F. Guffey
Sure looks like a die problem now. Bart B. wins another one. But post #2 was first.
Shop skills, and then there are reloaders that are socially dysfunctional. There is go, no go and beyond, reloaders are stuck on go and can not get to beyond. Count on the next response having to do with shims.
F. Guffey
Years before Willis collet die, people made their own body dies to size cases all the way to the belt after bumping case shoulder back .002". Best accuracy happened and equalled that of new belted cases. 1000 yard accuracy easily less than 7 inches.
Before Larry Willis? There were a few reloaders with lathes and collets. Before that there were reloaders that measured the diameter of the case ahead of the belt and they measured the diameter of the extractor groove before and after firing.
F. Guffey
Practically what I do with belted case headspacing is the not unlike the cut off case head method.
Setting headspace with that method gives the case no chance to stretch above the belt when fired. Simple and logical.
I've heard of folks having barrels headspaced to match that of their belted cases plus .001" to minimize case head clearance when fired.
If the case dimension from belt front to shoulder is less than the chamber belt shoulder to the front shoulder by its neck (typical with new cases), won't the case shoulder get blown forward sometimes stretching the case body .001" or more? Most times, all new cases are shorter after firing with maSimi loads
That sometimes happend with rimmed cases, which are identical in this regard to belted cases.
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Well I spoke to Lee about the die being small. He asked what lube I was using. I told him Imperial Sizing Wax. He says try Lee's lube. Guess what??? The dam stuff works better!!! Unbelievable!!! Now I will reset the headspace with some new cases as Zero333 suggested & see what happens. I do think the gauge is a little generous as new cases have no resistence at
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