Magnum primers in Creedmoor cases

[kilotanker22]

I finally got my hands on some H-4350. Although it seems I may have gotten ahead of myself, because I have all of my cases already prepped and primed with CCI 250 primers instead of the CCI 200, because I was using that Reloder 25.

Any of you use Magnum primers in your creedmoors? I know it's safe and if anything might affect velocity spread and initial pressure.

 

[jmr40]

You don't NEED magnum primers, even with Reloder 25. But generally speaking it doesn't hurt either and some guys report a little better accuracy with magnum primers even in cartridges where they aren't needed.

Most guys start thinking about magnum primers in cases with 60 gr or more powder. Sometimes a little less with ball powder. But that isn't a hard rule. I found that standard primers did just fine in the 300 WSM that I had.

If you've got a load worked up with standard primers switching to magnum's might see a slight increase in pressure and velocity, might not. But since you're starting from scratch that won't be an issue.

 

[kilotanker22]

Jmr, the reason for the Magnum primer with the RL 25 was in an attempt to close up my velocity spread.

I also have CCI 200, but don't want to remove the hundred or so 250's that are already seated.

 

[kilotanker22]

I already have a good load with another lot of 4350, but plan to back off a little with the new lot

 

[sako2]

You should back it off with the new lot of powder anyway. Use the mag primers and work back up.

 

[kilotanker22]

Looking through my notes last night from the past couple years. I see I tested this powder and primer with the ELDX bullet last year. My notes show that the Magnum primer actually opened up my velocity spread when compared to the CCI 200.

I loaded 20 rounds last night. If time permits I will test them today.

 

[GeauxTide]

My notes show that the Magnum primer actually opened up my velocity spread when compared to the CCI 200.

Correctamundo. Creedmoor cases are available with small rifle primers from Lapua and Starline, which indicates the intended use. I shoot a 260 and 6.5-06 with 45gr of RL19 and 56gr of H4831 with CCI 200. 1/2" groups, ES under 30fps, and SD under 10. In my 280, I use RL19 and IMR4831 over 55gr. Same stats. Mag rifle primers were developed for magnum cartridges using slow powders and cases that hold 70-80gr of powder. Mag pistol primers were developed for powders slower than 2400 in Magnum cases.