I was told in the commercial primers Winchester was a tougher one to use
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I don’t recommend WLR anymore. At the turn of the century Winchester changed from a nickel plated primer to a brass finish. I called Winchester, when they made the change and found that they had made their primers “more sensitive to combat off center firing pin hits” . This was not the direction one should go with primers in Garand actions and it turned out real bad in my AR15’s. The new brass finish WSR’s pierced something awful in my AR15’s and dished a handful of firing pins. I had to cut my loads back by at least 1.5 grains in 223. In the end I used CCI #41’s and life was good again.
If not being able to get Mil primers.
Of the primers I have used CCI 200 seem to have harder cups but commercial primers are always going to be more sensitive than mil spec. The primers you don’t want to use are those that are advertized as “more sensitive”. Federals are the worst in this regard and Federal match primers are the most slamfiring primer ever in the Garand mechanism. I have been using Tula7.62, they were advertized as mil spec, and they are an excellent primer. I never used Remington so I don’t know anything about them. I wish Winchester and Federal would make their mil spec large rifle primers available to the public, but, for what ever reason, they don’t.
Do you use a case gauge after resize?
Always use a case gage to set up your sizing dies, but remember, case gages only measure this distance between shoulder and base. It does not measure “fatness”. Once you get case gages you will see that different brass, sized a different amount of times, will have a different headspace and you must adjust the die to compensate.
This is a typical "Go- No Go" Case gage:
The difference between “Go” and “No Go” is around 0.006”, this picture ought to tell you that is this is barely the thickness of a line. If you are a real lucky person you may get there by sizing to the shell holder and adding a quarter turn, but I never have. I had to use gages to determine the correct headspace on every sizing die I have ever used. Sometimes I have had to grind material off on the bottom of the die as the dies were too long and would not push the shoulder back to "Go".
and after finishing loaded rounds?
Gene Barnett made me some reamer cut gages. These were gages cut from barrel stubs using an actual chamber reamer. Incidentally Frank White of Compass Lake
http://www.compasslake.com/ made me one for 223, cost about $35.00. Prices are probably more, worth a call if you want one. I found something interesting with a gage that was a correctly dimensioned rifle chamber. Cases would drop in after sizing, but seat a bullet and it turns out gravity was an insufficient force to get the loaded case to drop in flush. This lead to a test of all my sizing dies. Cases sized in my standard sizing dies and my Bonanza match die were all an interference fit after the bullet was seated. Cases sized in my small base die dropped in flush. Seating a bullet must buckle the case somewhere and it is noticeable in 30-06 cases. Not so noticeable in 308 or 223, but it was a real phenomena in 30-06. So, I think gaging after loading is a good check that everything is still OK.