04-11-2012, 01:53 PM
Bwild97 Wrote:The hardest part of fire forming 7.62x39 into Grendel brass for me, is the expense of the of the projectile. There just isn't a projectile under $19.00/100. And I have about 1500 7.62x39 cases to re-size and fireform. If you plan on reforming brass for your Grendel, get a set of 7.62x39 dies (or just a sizer die) as well or you will ruin alot of the brass trying to re-size it straight to the 6.5mm diameter. Use the 7.62 sizer die to deprime and bring the mouth of the case to a near perfect circumference. You will not need to full stroke with the 7.62 die so there is no need to lube the cases for either of the sizing operations; only after you have fired the 7.62 case into a Grendel case will you need to lube for full length sizing, and every time then on till you discard the case. Its not a difficult task, just time consuming, and in the end; I feel for me, that it is worth the effort! I have a batch of 7.62 cases on their 5th reload!
PS: Stay away from Winchester Large Rifle Primers, the cups are very soft! I have used S&B LR and Wolf .308 primers with good results!! Also when Fireforming 7.62 cases use a powder charge close to or just under the starting weights and seat a smidge deeper, I use 25gn of Benchmark and seat Sierra 120gn Spitzers to 2.225" COAL.
The cost of the bullets is a big advantage to using sub-sonic loads for a dual purpose fire forming and shooting load. This way nothing is wasted. Using non fire formed brass for sub-sonics also has the advantage of increasing load density and improving burn consistency. Accuracy has also been a little better for me with non-FF over FF. The one con to the load is it doesn't have enough pressure to form nice, tight corners on the shoulder. However, these square up after full length sizing to nearly the same as full pressure formed brass. I measured the water capacity of sub-sonic formed brass and compared it to full pressure formed brass and on average there was less than .1 gr difference. Not enough to make a difference in performance subsequent loadings at all.