Load Development

[Walker1]

Trying to figure out what is the best load for my 7mm RemMag. I am using 162gr Hornady SST. I have been loading with IMR4831 and RL25. Both seem to group close to the same. I have recently been using the RL25 more and have been adding more poweder. The book says max is 69.3gr. I have moved up to 68.8gr but a couple were actually 69gr according to my RCBS digital powder dispenser. Looking at the primer after it has been shot, I do not see any signs of too much powder. Should I go up more? What other signs of too much powder should I look for?

[athompson4]

pierced primers is one good indicator. another is difficulty extracting brass. watch the shoulder area and just in from of the extraction groove for stretching too. you should be able to see bright, shiny bands or lines in the brass if the pressure becomes excessive.

[SBruce]

Might try re naming the thread something along the lines of load development pressure signs? Might get more replies.? Just a thought.

FWIW, I measure the web of the case, the portion just ahead of the extractor groove with a micrometer. Both before and after firing, and compare the two measurements.........In my experience, when that difference gets over .0003" then the loads are getting warm. When it's .0005" then it's definately warm. The ones I've chrono'd after getting over .0003" expansion have shown velocities of 100 to 300'/sec over what the books say I should be able to get.

[CRNA]

I have had really good success with my 7RM and H1000. You might give it a try and see if your accuracy improves. I also use Fed 215s to light em up.

[MagnumManiac]

Without a chronograph, you will only be guessing as to what a max/safe load is in your rifle.
I would stick to published data, by all means, work up to the max listed charge of 69.3gr if none of the signs mentioned below are observed.

Reading primer appearance is not a valid indicator of pressure, I discovered this very quickly after buying a pressure measuring device!

Sticky bolt lift, blown primers and ejector marks are all signs that a load is WAY over max.

I used to load up until I got loose primer pockets and then dropped the charge by 2-3gr's in large cases (30-06 and larger), or 1-2gr's in smaller cases.
I now realise that some of these loads were way over max pressure, even though the velocity was 'trackable' and still within published data.

[Walker1]

Thanks for the info guys. Maybe I will stay at 69gr and see what happens. I have yet to see blown primers or ejector marks and they are not hard to eject. Appearance wise the shell is clean/shiny as when I loaded them. You can see what I would call powder burn on the neck though.

[CRNA]

Originally Posted by Walker1

Thanks for the info guys. Maybe I will stay at 69gr and see what happens. I have yet to see blown primers or ejector marks and they are not hard to eject. Appearance wise the shell is clean/shiny as when I loaded them. You can see what I would call powder burn on the neck though.

I think the powder burned neck on a 7RM is pretty standard. All of mine without exception have the blackened powder burned neck. Now if you get the powder marks down the body of the case, it could be a case of LOW pressure I believe.