.35 Rem Standard vs. Magnum Primer

[avogunner]

There are many good powders for the .35 Rem and one I like is IMR-4198. 22gr gives me about 1600 fps and very good accuracy so just to see any differences, I loaded up 40 identical rounds (20 ea) using the Lyman 358315 and RCBS 200. For each boolit, 10 had the CCI-200 and 10 with the CCI-250.
Using my chrony (yeah, I'd love a Labradar) I found that the MAGNUM primer averaged LESS velocity and double the ES. This was the same for both boolits:
CCI-200
358315 - Avg 1603 ES 72.53
RCBS 200 - Avg 1607 ES 45.9
CCI-250
358315 - Avg 1564 ES 133.2
RCBS 200 - Avg 1536 ES 112.1

I was expecting a modest increase in velocity with the magnum primers and wanted to see how it affected accuracy, if at all. Well due to the better ES/SD, groups were a bit tighter with the standard primer.

279566 279567

Ugh, not sure why the pics are sideways but the one on the left is the 358315 and the flyer (would be at 1 o'clock if right side up) was the 1st shot of the day (cold bbl). Oh, target was at 50yds. I would have taken them out to the 100yd sign but the dang range was too muddy and I didn't want to lose a shoe.

Anyway, should I have seen an increase in velocity, or.... are there some other factors at play here that I don't know about?

Thanks
Semper Fi.

[NSB]

I’ve gotten different results just changing brands of primers without going mag vs standard. If you really want to do it right, mix them up when you test instead of ten of one and then ten of another. The reason they have mag primers is basically some powders are harder to ignite due to grain shape and the coatings they put on the powder. Sometimes you need a mag primer to get the powder to burn correctly (pretty basic explanation). Anyway, to get a good comparison you need to randomize (mix) them up without doing all of one in a row. I think you might see different results.

[44MAG#1]

Those results don't surprise me. Many from Ballistic Labs with many, many thousands of dollars worth of equipment to individuals with a few thousand dollars of equipment to others with very little equipment will never pin down all the answers.
Ballistics is an ever changing phenomenon that will never have concrete answers.
Only answers that apply to the situation at hand at the time of the test in that equipment by that individual.
Cocktailing conversation to give impressions there are hard and fast answers is wrong to do.
You may run the test with different lots of the same primers and it may give even more results that are head scratching.
No one knows for sure.

[farmbif]

4198 doesn't need a magnum primer, wonder what results would be with ball powder like 2520 or 748

[Norske]

It's no 35 Rem, but my 22-250 and 748 is much more accurate and the velocity is higher with the hotter WLR primer than a mild CCI. Back in the days of Ramshot powder reloading pamphlets, they once used the same 22-250 load of their double-base graphite-coated powder and same bullet with both CCI and WLR primers. The WLR made higher velocity, and the measured peak pressure was 3,000 psi greater. After a hang fire with my 45-70, I only use WLR primers with double-base, graphite coated powders. Magnum primers may be as good, but WLR used to be easier to find.

[44MAG#1]

Again this is no surprise. With different primers with ALL other components the SAME and SAME lot there will be differences in pressure and velocity. Changing lots of the same primers with the other components being the SAME and SAME lots there will be differences in velocity and pressures.
There really isn't anything new here. Try changing lots of the powder, with all else being the SAME. See what that will do.