Building a 358 STA to go along with my 358 Norma....wondering if there are any concerns fireforming brass from 7mmstw ammo or would I be better off selling the ammo and buying the correct cases? They ARE pricey but I have about 10 boxes of 7mm STW ammo(Win bst and Rem core-lokt,all 140gr).......I worry about the pressures as well and case corruption.......thought about buying the 7mm but always loved Craig Boddington's stories and he used to carry a 358 STA.......wish there were a better selection of soft point/ballistic tip as well as solids for this caliber......would be a true long range heavy hitter if I could get the same bullets that were available for the 338 and 375 but in a heavier form...lets say 280 to 300 grains....would have one helluvah BC.......
I have always found that the smaller jump you have to make the better. I'd start with 8mm mag and fireform. I have also found that necking down is easier than necking up--the brass sometimes gets thin.
I have one and I usually neck 8mm Rem Mag brass up or you can neck 375 H&H down and then fireform. Great caliber! I like the North Fork and Swift A-frames in mine.
I've been necking up cases for many years: .270 to .30-06, .30-06 to .35 for a fireforming shoulder to make .30 Gibbs, 7 STW to .300 Wby, and 7mm RUM and .30 RUM to .375 RUM, all in one stroke with long tapered expanders that I made, and without any problems. I didn't find it necessary to anneal any of those cases before I expanded them, but I do anneal them after every 3 times that they are fired. However I did find it necessary to anneal .257 Roberts cases before I fireformed them to Ackley Improved.
Originally Posted by 505ED
I have only necked down one case, a .375 H&H to .300 Wby. It took considerably more effort to neck down that case (in my Rockchucker press) than any of the cases that I have expanded up. I had 100 unfired .375 H&H cases that I was going to resize to .300 Wby and I decided not to after I resized that first one.
I keep the cases separated by headstamps, and usually use the changed cases for practice loads with lead bullets.
kingcorona, With 10 boxes of STW brass you should have large enough quantities of cases with the same headstamp to work loads up with.