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Old 05-06-2007, 03:57 AM
montdoug montdoug is offline
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Join Date: Sep 2006
Location: Bozeman Montana
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Excellent topic.
As we've talked of repeatedly but it can never be too much, not only are rifles all different but lot to lot differences even with the same brand of powder can be "significant".
As I mentioned in the 3,800fps topic which had to do not with a specifically attainable velocity in the VarTarg or any other rifle but how 4 of the small caliber rifles I'm using for gophers and p-dogs this summer are just below or just over that number. That wasn't by design, it's just where they all ended up.
I agree with ST that chasing a specific load in a rifle is big time bad news! In fact I stressed that in the sticky about rifle to rifle differences as I'm the one that started the thread. It wouldn't hurt any of us to read that whole thread from time to time cause a lot of guys posted good stuff in there.
As to my rifle with the batch of powder I'm using I'm well back from a max load but that means nothing with someone else's rifle and powder lots. I'm thinking that there is probably a fair difference between ST's Cooper Chamber and my Greg Tannel chamber as in my fired/neck sized cases 18.7 grains of my batch of H4198 is not a compressed load with where my bullets are seated and in fact comes just below the shoulder neck juncture and my SPL'd V-Max's sit a bit above that and in fact as mentioned have a bit of room left but I stopped at the accuracy point not the velocity limit. Just about perfect load density to me. Not a warm load in my rifle. In Terrific .20's there is what was obviously a safe load for Todd using a "36 grain" Berger and 20.2 grains of H4198 for 3,811fps. My working load is slower than that and use's a 3 grain lighter bullet as well as 1.5 grains less powder in it. They are all different.

I haven't tried N120 cause I have 8lbs of H4198 it's an Extreme powder and it's a bit slower burning than the N120 (cheaper too ).
This batch of cases was weight segregated in 50 round MTM box's and not only have some of them been fired 5 times in temps up to 105ish and still have tight pockets plus as little as I size them I've yet to have to trim them either. Also a 24inch barrel is probably longer than a Cooper barrel.
Larry I wondered what other indications of pressure your using beside bolt lift? My experience is that with the steep angle of the cocking ramp in a Cooper bolt lift is extremely difficult to use as an indicator. Like Kenny if your getting primers blown back in a case it pretty much has to be a headspace issue. I'd try the die set up for a solid crush fit, sure makes good cases.
Regardless of all that one of my personal crusade's is a guy hearing about a specific velocity someone gets in a particular rifle and chasing it with his rifle, it's a recipe for disaster!
An interesting aside.
Dan C. and I have .20 Killer Bee's cut with the same reamer and I believe both are Pac-Nor's as well. He tested his batch of AA1680 in his and was able to use considerably more than I was able to with my batch, he got up to 18.2 grains for 3864 and did that load 10 times in the same cases with primer pockets staying tight. The load I ended up going with was just under 3,800fps with 17.1 grains of 1680. In Dan's it took as I remember more of his lot of 1680 to get to that velocity than mine did, I obviously have a faster lot of 1680 than his.
There are very few constants in reloading.
Good reminder ST we can never be safe enough.
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montdoug

Last edited by montdoug; 05-06-2007 at 04:37 AM.