300 blackout - Magnum or Standard primers?

[workingmanjeff]

Just started reloading 300 blackout subsonic, have been using standard primers, any benefits to using magnums instead 

[NOSHMJ]

Not really.  If thats all you have, go for it.  You may have to reduce your charge down a bit is all. 

[looking4reloadingdeals]

Iv always used CCI reg SRP and never had any problems

[K-Tex]

I use both type, but switched to mag only when using 296, h110 and lil gun.   It holds about the same amount of powder as 44mag which I use mag primers in it also.

[willfully armed]

There is no benefit to using magnum primers in 300blk. 

[K-Tex]

On 8/30/2023 at 10:11 AM, willfully armed said:

There is no benefit to using magnum primers in 300blk. 

I use 450's due to the powder and bullet weights used.   As far as more speed there wasn't any/enough change.   @ primers used for comparing loads I've done are 400's and 450's.   If it works for me, then I go for it.

[HesedTech]

The answer is, it really won't change your accuracy... much.

 

In high power rifle the real difference will be found in changing brands of primers. There's lots of testing of this idea on YouTube and worth a watch. 

 

Here's a great video from a reloader testing the same brand of primers, CCI.

 

Basically Magnum are harder cups and if you are pushing the max pressures you need to test your loads when changing brands or types.

[K-Tex]

Testing of 1 powder-bullet-seating depth combo can be misleading on this video and in actual.   Also in different guns even if they're the same make and model.   Still interesting on his testing.

[willfully armed]

On 9/9/2023 at 3:39 PM, K-Tex said:

I use 450's due to the powder and bullet weights used.   As far as more speed there wasn't any/enough change.   @ primers used for comparing loads I've done are 400's and 450's.   If it works for me, then I go for it.

I've loaded about every offering for the BO, subs to supers, light to heavy... and for s#!ts and grins, standard and magnum primers. I've not seen a single instance of improvement over a standard primer, when a magnum was used. Thereby, I've not seen any need to use a component not intended for the caliber.