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6 1/2 or 7 1/2 remington primer?

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Lightning330 View Drop Down
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Joined: Aug 22 2018
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lightning330 Quote  Post ReplyReply Direct Link To This Post Topic: 6 1/2 or 7 1/2 remington primer?
    Posted: Dec 29 2018 at 5:27pm
Hello all: Looking for a little input on primer use.
I have 3 carbines and have been using Remington 6 1/2 primers with great success. I eventually ran out of course and need to get more.
My question is: I just purchased my first AR 300 Blackout pistol that I run subsonic with 200 grain bullets. Time to start reloading it also now that I have a collection of brass.
With the need to purchase more primers and of course would like to use one primer for both loads.
Which would be the best choice for both?
From my studies, the 6 1/2 should not be used because of the higher pressure with an AR. Yet keep in mind I am only reloading subsonic for the 300 Blackout. Pressure drop is big.
I would have no problem running the 7 1/2 but never used it with the carbines. 6 1/2 has been good to me and hate to switch up. But if it is going to be a problem with the 300 subsonic rounds I don't want that either of course, and do hate to get both if I can avoid it.
After 1,000 reloads of testing with my 3 carbines for the combo that all 3 like. Accurate No 9 at 12.5 wins hands down if that helps per info with the 6 1/2 primer. So you can kinda see why I want to stick with the 6 1/2. Hate to mess up a good thing switching primers.
What would you do is the magic question? Would love some input guys.  Forgot to mention, Accurate 1680 will be my choice of powder for the subsonic loads.
Many thanks.... 
Lightning 330
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Uncle Mike View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Uncle Mike Quote  Post ReplyReply Direct Link To This Post Posted: Dec 30 2018 at 11:50am
Hi, I don't see why you would want to change. The 7 1/2 has a thicker cup here's an article.. http://www.jamescalhoon.com/primers_and_pressure.php
I would not change.
When you change a component you have to retest your load; accuracy or pressure may or may not change. Just what I would do, YMMV, regards, Mike
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Lightning330 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lightning330 Quote  Post ReplyReply Direct Link To This Post Posted: Dec 30 2018 at 5:04pm
Thanks Mike, appreciate the link you sent. I will save that for future reference. I tend to agree, and I don't want to change. It had been voiced that the thicker cup should be used with high velocity rounds to prevent piercing, which of course would be the 7 1/2 primer. But since I'm going to be loading subsonic low velocity with my 300 Blackout I was wanting to stay with the 6 1/2 if input on the subject was good. That way I'm not messing with my sweet spot load for my 3 M1 carbines.
I can use the same primer in both, and just work towards the happy powder load for my blackout.
I read a lot on this stuff, and you get lots of mixed input. One that I saw many times was that the Remington 6 1/2 were small pistol primers. That info I guess was a misprint on Remington's behalf.
Even my boxes state small rifle primers. You are right about the thicker cup, and the 7 1/2 is also quoted as the bench rest primer. Standard small rifle is 6 1/2 the 7 1/2 is the bench rest with more time an money spent to make them match grade. My info and understanding could be off, but that's what I'm getting.
Thanks again Mike for your help and input. Love my carbines and love this site.

 
Lightning 330
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