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Changing primers during load development?

 
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Old 10-28-2011, 05:24 PM
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Changing primers during load development?

Hey guys I am in the final stages of my load development for my 7mm Remington mag custom rifle. My rifle is built on a Remington 700 action that has been rebarreled with a Broughton 5.5 5C 1 in 9" twist 26" barrel. My goal was to push a Berger 180gr VLD at 3000fps. I reached that goal today with my final load. The load consisted of a 180gr Berger VLD, 72gr of H1000 and a CCI 250 primer loaded at a COAL of 3.540" .o15" off the lands. My average velocity for a 5 shot string was 3008fps with an extreme spread of 29.8fps the group measured less than .75" center to center. I would like to get the extreme spread down a little more so my question is If I were to go to a CCI 200 or Fed 210 primer and keep my load at 72gr of H1000 do you think my pressure would increase, decrease, or stay the same. I was hoping not to reduce my load and have to work up again but if you guys have experienced pressure problems by going to a cooler primer then I guess I will have to start over.
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Old 10-28-2011, 08:49 PM
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Re: Changing primers during load development?

SpotHogg32,
All the reloading instructions say anytime you change components, drop the powder chage and work up. This really applies when you near max load. Here are a couple of links, hope they help in your quest/decision.

Primer cross reference chart

Primer Testing Reference

JohnnyK.
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Old 10-28-2011, 09:23 PM
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Re: Changing primers during load development?

Sometimes going from a magnum primer to a non magnum primer will improve SDs.

Magnum primers will normally increase velocity but be more erratic, and a non magnum
primer can make for a more consistant powder burn.

Its worth a try.

J E CUSTOM
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Old 10-29-2011, 01:26 PM
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Re: Changing primers during load development?

Especially when you change primers, you need to back your powder charge down and work your way back up. I had a load for my 260 that I developed with the F210(not match) and wanted to see if the ES would reduce if I changed to the F210M. Turns out the F210M showed pressure signs with the same powder charge.
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Old 10-30-2011, 12:24 AM
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Re: Changing primers during load development?

Quote:
Originally Posted by Spothogg32 View Post
The load consisted of a 180gr Berger VLD, 72gr of H1000 and a CCI 250 primer loaded at a COAL of 3.540" .o15" off the lands. My average velocity for a 5 shot string was 3008fps . . . .
Hodgdon lists their max load for a 175 grain bullet as 64.5 grains of H1000 producing about 2700 fps in a 26 inch barrel peaking at about 50,400 CUP. If you are loading 72 grains behind a 180-gr. bullet, I believe 3000 fps is possible.

I also believe your pressure is dangerously too high.
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Old 10-30-2011, 09:42 AM
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Re: Changing primers during load development?

Quote:
Originally Posted by Bart B View Post
Hodgdon lists their max load for a 175 grain bullet as 64.5 grains of H1000 producing about 2700 fps in a 26 inch barrel peaking at about 50,400 CUP. If you are loading 72 grains behind a 180-gr. bullet, I believe 3000 fps is possible.

I also believe your pressure is dangerously too high.
They also show the maximum load for a 7mm Weatherby magnum to be 74.7 grains of H1000.
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Old 10-30-2011, 12:34 PM
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Re: Changing primers during load development?

Quote:
Originally Posted by Bart B View Post
Hodgdon lists their max load for a 175 grain bullet as 64.5 grains of H1000 producing about 2700 fps in a 26 inch barrel peaking at about 50,400 CUP. If you are loading 72 grains behind a 180-gr. bullet, I believe 3000 fps is possible.

I also believe your pressure is dangerously too high.
Man I tell you one thing this Broughton barrel is an incredibly low pressure barrel! When I started my load development with the Berger 168gr VLD I used their load information that they provided me with. the max load was supposed to be 70.5gr of Retumbo I started at 68gr and worked up to my top load in .5gr increments. When I shot my first 5 shot string with the 68gr starting load I had dangerously low pressure signs. all 5 cases had powder residue all the way to the belt. I had never experienced anything like that before. It took a few increases in powder before the residue started moving toward the sholder of the case. When I finished working up the loads with that bullet and Retumbo powder I was at 74gr of Retumbo with a little residue on the neck of the case which I am used to seeing and absolutely no sign of pressure. No sticky bolt lift, no plunger marks, and primers were not bad either. The final average velocity was 3056fps but the ES was in the 60fps range which is not good. I have since switched to H1000 and the ES is better it is in the 30fps range but I am still not happy with that so that is my reason for playing with the cooler primers I hear that sometimes that helps improve the ES. I have decided it is a good idea to reduce my load and start over with the GM210 primers and see what the results are Thanks for all of your imput everybody. I will let you know how it goes!
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