lapua brass in a 221 fb

[foxhunter]

I don't think they are bringing it out but I did make some 221 fb and 17 mach 4 from 223 last night. the first thing I noticed was the difference between factory Remington cases and the lapua, 13.5 grains difference in weight after neck turning. it's defiantly time to extrapolate a new starting load, 13.5 grs in a case that small could be spelled (disaster) especially in the mach 4 where .2-.3 tenth of a grain can go from ok to oh my god in a heart beat.
anybody disagree with this assessment, tell me why.

bob

[WADE]

I assume the lapua was the heavier brass? Do you happen to remember what the case wall thickness was at the neck before turning?

[Dan C]

Bob, the rough rule of thumb on case weight vs. capacity is a 10 to 1 ratio. Meaning, a case weighing 13.5 grains more than another should hold roughly 1.3 grains less powder. I recall using some Lapua 222 brass for my 222 Bobcat (222 Improved) one time, and finding it held a full grain less powder than W-W brass. I don't recall weighing the brass though beforehand.

I did form a few 19 FBI's from the Lapua 222 brass and found it ridiculously thick in the 'new' shoulder area. It was difficult to form and you had to shoot top end loads in order for the case to seal the chamber at the shoulder area, even after annealing. I 'think' that the new Lapua 223 brass is not so heavy however, so it might be an apples to oranges comparison anyway. It would be interesting to cross section them and see what the internal profile looks like. The newer 223 stuff might be heavier mainly at lower half rather than all the way to the neck as on my 222 cases.

[foxhunter]

wade, yes the lapua was the heavier of the 2, neck thickness was .0225 and was turned to .014, giving .002 expantion at the neck.

Dan, the brass is about 2 years old and gives 100 fps faster loads than the same load in a rem. case, the lapua averaged 3665 with 40 v-max gr bullets loaded with 20.0 gr of aa1680 ,a 205 primer and .010 off the lands.


bob