IMR 7383 in my 8 x 57mm Mauser

[Maven]

Since I still have 7 lbs. of IMR 7383 and don't shoot many j-word bullets, I decided to try and chronograph some loads today in my Shaw rebbl.'ed 8 x 57mm Mau. The CB's were the Lee 175gr. CB and a LBT 195gr. SP, both gas check designs, and very accurate. The charge was essentially the same as the one I use in the 7.5 x 55mm Swiss (K-31) with CB's of the same weight, the only difference was that I chronographed them in the 8 x 57. Here are the particulars:

Rifle is a Shaw rebarreled 8 x 57mm Mau. (full military when I got it in 1964)
Brass was Win. 8 x 57mm; primers were CCI #34
Powder charge was 37.5gr. IMR 7383 (weighed)
CB's were the Lee 175gr. @ .3245" and 3.035" OAL; and the LBT 195gr. SP also @ .3245", but seated to 2.96" OAL. Both were lubed with Felix Lube.

Results with the Lee CB: Mean vel. for 20 shots was 1,887 fps +-45 fps; ES was 176 fps
Results with he LBT CB: Mean vel. for 20 shots was 1,882 fps +-44 fps; ES was 162 fps

Btw, there wasn't a trace of lead in the bore, no signs of pressure, and the bbl. wasn't badly fouled by powder residue either. ~1,900 fps is faster than I need to push my CB's and the high extreme spreads I recorded indicate that 7383 isn't the ideal powder to use with CB's...unless you want to push them fast. Accuracy was excellent, but I was concentrating on not shooting the chronograph and recording its readings more than I was on the target.

[felix]

I use 41 grains, Maven, in the 8mm, with the "same" boolits. 38 grains in the 308, 165-180's. Any idea of the ES's there? ... felix

[Maven]

felix, I think most users of 7383 find the extreme velocity spreads decrease when you use more of it. E.g., I somehow managed to get 50 grs. of 7383 into the 8 x 57mm case, topped off with 150 gr. Hornady, Sierra, and Speer SP bullets. The mean ES was only 60 fps; mean velocity was 2,449 fps. In my .30-06, using 125gr. Sierra SP's and 55 grs. 7383, the ES was 77 fps (vs. 64 fps for IMR 4350). Similar results in my .243Win. (with j-word bullets) suggest the same story: IMR 7383 doesn't respond well to loads that leave a bit of space in the case. Btw, 40.5 grs. 7383 (41 grs. in cool weather) is practically a caseful in my .243Win. Does it also fill the case of the .308Win.? If so, I'll bet your ES's are under 80 fps.

[felix]

I'll take any ES below 80, let's say, for 125 yards which is about my range limit using utmost safety for go-carts about the area. I am using boolits, not condoms, and I bet the ES's won't be that much different with full cases, like you say. Thanks! ... felix