primer 210M or215M

[mauser]

Hi
I would like a consulting
I use powder H4350 44 gr and bullets 142 gr sierra and 139 gr scennar for a 260R Between the 210M and the 215M, which is adapted best for the reloading
thank you

[Mr. 16 gauge]

I am having a little trouble following your question; all the reloading tables I have seen have given a specific primer for a specific load. You should use what the load table for that load says: NO SUBSTITUTIONS! this is one of the basic rules of handloading. Using magnum (215) primers were they are not indicated can lead to a tremedous increase in pressures.
Generally speaking, magnum primers are used for slow burning, hard to ignite powders in large cases. I assume that by .260"R" you mean the .260 Remingtion. This is not a magnum, high capacity case, so I would imagine that you should use standard primers. Again; FOLLOW THE LOAD THAT THE DATA MANUFACTURER HAS GIVEN TO YOU COMPONENT BY COMPONENT!