Larger than expected ES's

[Travelor]

Did a search and read most of the posts with no epiphany.

I am a experienced reloader but new to the 204 Ruger cartridge.

Gun: Cooper in 204 Ruger
Scope: Zeiss 6.5-20
Load data: Winchester case; Wolf SRM, CCR-BR/Rem 7 1/2/Fed GMM primers/Have Not tried other Mag primers yet;
Powders IMR 8208 XBR and BenchMark;
Powder weight 29.3 of 8208 and 26.6 of BenchaMark
Rest: Sinclair with rear bags
Shooting table: Concrete
Using wind flags and range is 100 yards

I am getting reasonable groups (.7 and lower) but I am finding the velocity spreads to be much larger than hoped for - in the order of 70 fps.

Any experience with these ES spread and range results to verify an improvement?

[Bill K]

Are those velocity spreads between the loads and mixed primers, or the average of spread with loads and the same primer, in each group ? I have had some groups/loads show a larger velocity spread than I thought should, but that load grouped so good, I just did nto worry about it. If it shot little teeny groups, even tho one FPS was 3400 and then next 3460, I really did not care. Maybe I am not too picky. Anyway just my thought. Bill K

[FastPPC]

I'm with Bill K., I shoot a 204 Ruger in Cooper Phoenix also and I shoot 27.5 grains 8208 XBR but get well under .430 groups consistently and many 5 shot groups .315 or less. I see 40/50 FPS extreme spreads but am happy with the accuracy. I've found that unless I'm shooting 900-1000 yards I'm really not to concerned with extreme spreads , I look for consistent accuracy. I'

[Jim White]

I agree with Bill K and FastPPC; look at how it groups. I've good SD and ES and lousy groups and then; vice-versa.

HTH

[Travelor]

The large ES's were with the same load, cases, and primers. I haven't tried 27.5 of 8208 so I might give that a try. I'm looking at using the 204 for prairie dog hunting so the ES's should cause vertical dispersion at distance - at least that is my experience with shooting other guns in NRA mid and long range matches.

Groups seem better with 26.6 of Benchmark for me.

Thanks guys for the help.

[MZ5]

I don't try to shoot 'long range' with my 204, so like the others I just look for good precision. Nevertheless, maybe see if annealing the brass helps? Sometimes high ES indicates variable neck tension, or anyway it _has_ for me, on occasion.