Originally Posted by piutemike
I shot my new Sendero SFll 300RUM for the first time today, breaking in the barrel and trying out some Nosler 180gr E Tips. Have to go unleaded this year in my area in Ca.
My starting load was 93 gr of retumbo Fed 215M primers and RP brass. Primers had small craters on everything from 93 to 95 grains. Nosler book lists Retumbo loads with 180 gr bullets from 95 to 99 grains so I didn't even come close to book max, keeping in mind Nosler told me to stay a couple grains under max. No other pressure signs, extractor marks, sticky bolt.
I'm pretty new to hand loading and have not encountered this with my other two guns I've loaded for. I used a chronograph, velocity was around 3180 to 3265 fps with the different powder charges.
My question is this, can something besides pressure cause primer cratering and how serious should this be taken? Thanks for your help.
You've gotten some good answers here. Primers vary in hardness. Cratering/flattening of primers is one of the least reliable methods for indicating excess pressures.
As for your loading, and "staying under max". I know you've read the books. You've read "never exceed max loads published". Etc, etc. Each gun is a law unto itself. Brass capacity differs brand to brand and can affect pressure. Primer "hotness" varies greatly brand to brand and can affect pressure. 95grs of Retumbo with a 180 bullet over a CCI Mag Rifle primer, wont be the same pressure as the same load over a Winchester Mag Rifle primer. You should own a chronograph to reload. It tells you much! It's a great tool IF you know how to apply the information it gives you to your loads and the data. I've seen handload that were, like yours, under book max, that were producing very high velocity, and obvious signs of pressure. However, the FIRST sign of pressure, assuming your loading techniques are sound, will almost always be velocity. If you're using proper powders for the application, you can almost always get the published velocity of most load whether it be 2 grains under the "book max" or 2 grains over. If you're running what the manual says is max velocity but you're 3 grains under the max powder charge...you can pretty well rest assured you've found YOUR GUN'S max. Don't think that because you're powder charge weights are under some arbitrary number in a manual that you're "under max".