I get the primer ring in two Savage Precision Actions, usually with Federal 205M primers, less with others especially the Remington 7-1/2 BR. Both the Shilen and Pac-Nor barrels are set to minimum headspace, because I set it myself and triple check it. The loads used aren't anywhere near maximum, which may be one of many causes for the ring, where the firing pin raises the initial crater with subsequent pressure insufficient to rivet it flat.
Recently I replaced the Savage OEM bolt heads with newly released replacements from Pacific Tool & Gauge. Monday February 4, I took one rifle to the range and found the ring gone! Both the Federal 205M and Remington 7-1/2 BR showed no sign of the ring. This rifle has a 1:8.5" twist barrel installed and the loads included the Berger 50 grain Varmint BT bullet and up to 25.8 grains of Varget (3295 fps, SD=23), This combination is running somewhere north of 55,000 psi.
There is a discussion of a problem with the stock Savage bolt head on the PT&G website
http://www.pacifictoolandgauge.com/sava ... rmance.htm click on the yellow banner at the bottom of the page to read Norm Darnell's article. In brief, the Savage factory bolt heads are investment cast then tumbled to deburr them. That polishing process deforms the firing pin hole allowing the primers to flow into the gap. Darnell found that he could true up the firing pin hole with a PT&G Carbide Bolt Face Truing Tool, which also flattened the bolt face. Yet several hundred shots later the Savage bolt face had become dished again, and the process needed repeating. Dished or eccentric bolt faces can wreak havoc on brass and accuracy. His discussion with Dave Kiff of PT&G resulted in PT&G developing its precision machined replacement bolt heads machined from a billet of steel.
Installing the PT&G bolt heads required that I reset the headspace, backing off a turn and adjusting back down until the bolt closed snugly on the GO gauge, with the NO GO gauge not allowing any bolt movement. This left the caliber designation on the top of the barrel, about 1/4 turn clockwise from its original position. These PT&G bolt heads are much more precise than the originals and require a bit of lug grease to smooth out (always a good idea to lube the lugs to prevent galling). I left the ejector pin out, to remove the side to side tension on the case in the chamber, which has a small negative effect on accuracy. 10 shots at 100 yards went into a little over .5" center to center, with one called mulligan discounted, 9 shots went into .296" CTC. Main difference was that the primer ring disappeared.
It would seem that bolt face geometry has a great deal of influence on the primer ring. The PT&G bolt head with its flat face and sharp edged firing pin hole eliminated the problem. For those with this problem, a firing pin bushing and bolt face truing, and headspace correction (if needed) may eliminate the primer ring problem. Interestingly, this consistent primer artifact seems a peculiarity of the .204 Ruger cartridge, as I have experienced no other cartridge that would produce it as consistently.
