Home Forums Reloading Big Game Rifles primer cratering question

I have a 243Ai and found my accurate load to be a 95gr NBT with 45.5 grains of H4831sc. According to the book, I am .5gr under the max load. I chrony'd today and I am sending the bullet at 3100fps. it is also shooting a very respectable 5/8in group at 100yds.

Problem is, my primers are cratering a bit. They are not being flattened.

Should I back off a bit? The bolt still opens easily, and like I said, it is shooting like a champ. The cratering is just bothering me though.

What would you all do? Advise on this would be greatly appreciated!

Thanks,
Stewart

May just be a sloppy firing pin fit in the bolt. If no other pressure signs, I would not worry. I had a couple of 700s that did the same thing.

Could be a firing pin issue, as lastround said, but could also be a primer issue. Even primers from the same maker can vary in their hardness and/or cup thickness from lot to lot. Try some different primers. I've seen some that looked funny with less than max loads before so if you're sure that load is within limits and you're not lookin at a misprint in your loading manual then I wouldn't worry too much about it either.

I'll bet a dollar to a donut that both of you are right. I have checked and re-checked the load data for this, and I am sure that I am under max load. I am currently using CCI large rifle primers and will give another brand a try, but, I built this on a 98 Turk Mauser so the sloppy FP hole would make alot of sense too. Thanks for your input!

I have a 700 that will crater almost any load. I quit worrying about it long ago.

If your bolt isnt sticky upon extraction I wouldnt worry about it.

Many years ago, I had a pre '64 Model 70 in .220 Swift. In the more than 2000 rounds I fired through that rifle, I never saw a primer of any brand that wasn't cratered. If the loads are less than max, and the cases extract easily, I wouldn't worry.

I wouldn't make any assumptions about where a published max load might be for a non-standard caliber. Once the chamber has been opened some you're going to have a rifle that is unique compared to many others by the same name. That said, even if you think you are half a grain under max, what exactly does max mean in your chamber? But assuming max in your rifle is a pressure no higher than what is the SAAMI norm for the standard chamber, there are still some things which could allow cratering. In addition to the possibilities mentioned already, a softer spring could allow cratering. So could a light striker. (Less mass means it's less likely to stay where it should until the pressure falls off. I would think this unlikely on a Mauser, but the spring might still be a factor.)

While on the subject of pressure. Here's some pics I took a few days ago of some cases fired from my new Remmy 700 .308

The top case was loaded with a 150gn Core-lokt 47gns W748 and CCI 250M primer in Win brass. This load exhibited reasonably stiff bolt lift. A faint ejector mark can also be seen on the case,but the primer isn't flat or cratered.

The bottom case was loaded with a 150gn Sierra GameKing 48gns W748 and WLRM primer in a Remington case. This load didn't exhibit stiff bolt lift despite being loaded with one grain more of the same powder.

I think Winchester and Remington brass has similiar capacity,so I'm assuming the 150gn Core-lokt was the culprit in this instance.

The R-P should have less capacity.

You're also using two different primers, so you have more variables.

Stand those two bullets up next to each other and look at the bearing surfaces. That will probably reveal most of the cause for what you've seen.

Correct. RP brass is thicker, hence less capacity so one can expect higher pressures for a given load. mathman is correct, too many variables.

"A faint ejector mark can also be seen on the case,but the primer isn't flat or cratered."

Actually, that plated primer is about as flat as they get before leaking if the cases are properly FL resized or neck sized. Any ejector mark at all is more than I'm comfortable with and I usually obtain published factory velocities better than most factory ammo does.