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I chose to use cci450's because I was able to cut my group size in half over the 400. Test to see what your rifle likes.
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Just to add fuel to the fire. I have a batch of unfired PPU brass. This brass has a large primer. I thought, what the heck. I have some CCI200 and CCIBR2 primers. I loaded up a test run using the same Hodgden benchrest powder and Hornady 123g FMJ with the CCI200 primer. The only thing that I noticed different was a 45fps increase in velocity (2343). 21/2 inch group and 12.5 SD. Then I went to the CCIBR2 primers. This is where things really surprised me. Things that were the same; I got the similar velocity (2340), similar 14.2 SD. Things that were different. The accuracy greatly improved. I shot two 5 shot strings that both measured less than .5 at 100 yds! This was the most accurate round I have had so far. The only downside to this is the primers are very slightly showing signs of flattening. Put that in your pipe and smoke it!
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I've read accounts where primer matters but only with certain combinations. One was lvr and 130gr + lapua brass. Magnum was preferred because it was not showing signs of over pressure .
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To quote your OP/first line directly:
"OK, just about everything I have read is that you must use CCI450 primers for this cartridge. "
Your word "must". Not mine. I will grant that since you are posting in this forum, but you did not specifically qualify your statement to strictly this forum (saying "everything that I have read..."), maybe you were saying only about "everything I have read" as being all other places on the 'net except for here, which forum you [under this assumption] have not read nor searched on. If that's the case then you should perhaps read what actual Grendel shooters/loaders are doing before making such a universal claim on this forum, eh? Why start with a generalization that is untested/untrue of the place whereupon you make the statement. But enough of that, you said what you said/read what you read and we can certainly move on.
I will admit that I haven't found (from today's brief searching) a study of small rifle primers on their ranking by brisance, there are however, 2 or 3 on the web that I found on studies for the large rifle primers, with rankings. Even a couple with photos. The similar conclusion likely applies to the SRP's also, but of course you may have a different opinion on that ... which is fine by me.
I did my own "flame/brightness" test of the SRP's I had on hand a couple years ago, in my workshop. Flame lengths/brilliance/sound differed for all with the 41 and the 450 being the longest/biggest. Didn't have the technology or abilities to take photos of them however.
cci450, cci400, BR2, #41, federal 205's.
As I recall the Federal 205's (std not AR) were the smallest flame/weakest looking.
On LRP's I did my own tests on accuracy for a couple of rifles/loads I was working up, and for those the Fed 210GM were the best in terms of lower SD/tighter MV on cartridge loads I tested. Not that I would extrapolate that to all LRP loads but for those rifles the GMM's are what I use, and still happy with the results although I have not re-visited any testing.
Other than hardness of cup, the general statements from Remmy on their 6 1/2's, and need or beliefs regarding slamfires, primer use ought to depend on either what you have on hand (an obvious statement in today's markets) or the one that gives you the best results you're looking for.
A lot of this is becoming a bit moot since primers are nowadays coming more available than even 6 months ago. For me, in order to stretch out my 450's a bit I use 205's or even the 200's for Grendel bolt actions, but that's my choice. The work fine for the bolt action loads I do.
Stay safe in your shooting."Down the floor, out the door, Go Brandon Go!!!!!"Comment
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