7mm rem. mag. Pressure ?'s

[wnc-coyote]

Ok guys. I have some questions about reading pressure signs in the belted mags. I have been reloading for many years. This is the first time reloading for a belted case. I have started working a load for the nosler 168gr ablr. , win brass, win mag primers and imr 7828ssc. I started at 62.0gr and worked to 64.0 in half gr. increments. The rifle is a ruger m77 mkii. Before I shot any hand loads I shot some win 150gr PowerPoint. My problem is every thing I shot flattened primers. I stopped at 64 because I didn't have mics with me at the rAnge. So when I got home I mics the belts and just above the belt. All were in Spec. Belts were .528-.530. Dia just above belt was .5128-.5134. So what I need to know is Should I just keep going till bolt lift started getting stiff or what else should I be looking for. Thank you

 

[KYpatriot]

I personally use ejector stamp as the first sign of pressure. I find that primers are unreliable indicators of pressure.

I assume your cases were clean and dry, free of any residual sizing lube when you fired them. If so then I think ejector stamp would be the first thing to look for, and if you get stiff bolt that is for sure into pressure.

 

[wnc-coyote]

Yes, all brass was clean and dry, so was chamber. This is the first ruger I have had. I was concerned that the tiny little rectangular extractor slot might not be a reliable sign. Maybe it will be though.

 

[LaHunter]

I get 'flattened' primers when I shoot factory ammo as well as my hand loads in my 7 mm rem mag. With my M700, my first sign of pressure is usually a sticky bolt.

Hope this helps

 

[Lefty7mmstw]

Speed limits guys... Get it over a chrono. The 7rem has been backed off a bit pressure wise since there are a lot of variances out there in chambers.... Get her to the speed she should be at without any extractor marks or ANY noticeably heavy bolt lift and you should be good to go. The 7rem isn't as fast as the 7stw or 7rum but she'll still get the job done well way out there with careful feeding.

As to primers, you'll often see a bit of extra headspace cause this, as the primer gets re-seated when the casing fills the chamber. The only time a primer is anywhere near reliable is when you are using brass formed to your chamber with a minimum resize. Even then I consider it a secondary indicator.​

 

[Garycrow]

I agree with Lefty, you need to chrono it, otherwise you're just guessing.

All that other stuff is pretty unreliable when it comes to determining pressure, although I'll concede that sticky bolt lift does get my attention.

 

[KYpatriot]

I have a load with berger 180 hybrids seated to 3.55 oal with 72.7gr of Retumbo. It is right at 3000fps. I get a slight ejector mark. Bolt lift is clean and easy. Since this has to be a maximum load, I'd think that heavy bolt lift would be a serious sign of pressure indeed, since this load doesn't have it.

 

[upacreek]

KYpatriot, do you know how much jump that col gives you? I use the same load but 3.390 col. I have .075" jump and 2960fps. Zero pressure signs.

 

[KYpatriot]

That load is .025 off the lands. I purposely avoid loads that won't shoot without a small jump. I shoot hybrids or smks that are jump tolerant. Personally I believe it is not smart to have a hunting or tactical load that is jammed, as in those situations reliability is a must.

I just edited that post- looking at my notes it is actually 72.7 and 3015fps at about 60 degrees. I stopped there because of the ejector stamp. I may go back down to 71.7 which also shot well at about 2980

 

[jrock]

I too use ejector marks and bolt lift as my 700's firing pin hole is a bit over sized from the factory and craters primers and such. I have a couple pounds of 7828scc on the shelf but am using 68.2 grains of 7828 with .02" of jump and am running 3120 with the 168's with no pressure signs and sub MOA accuracy. 7828 is supposed to be the same as the ssc but I plan to work up when switching over. Found that 0.2 grains of powder and 0.01" of jump makes a difference so fine tuning was a must with my gun.

 

[lloydsmale]

in my experience ww mag rifle primers tend to flatten before others. could be the cups are a softer alloy. Funny thing with them is I can load 10 rounds and maybe 7 will look flattened and 3 not.

 

[rsnell]

What primer are you using? Federal primers have a soft cup and tend to flatten easily. I usually use the bolt lift as my pressure indicator.

 

[wnc-coyote]

Thank you all for your advise. The biggest reason I even asked was that I was flattening primers at such a low charge. Also this is the first ruger I have loaded for. This rifle has a blade style extractor which I have never loaded for. I was wondering if I will even see an extractor mark with this type of bolt. All my other rifles have a plunger style extractor.

Thank you.

Hope yall have a very Merry CHRISTMAS