.300 SAUM - Reloading
A question for reloaders of .300 short mags: What issues have you encountered when trying to develop consistent loads for the short/fat mags and how did you overcome them?
Background: I spent the better part of 2 years trying to develop an accurate load for my 700 BDL in .300 SAUM. Different bullets, bullet weights, powders, powder weights and seating depths were tried. The bullets were what we would all recognize as "premium". The powders were all respected brands. I was just about to give up on the rifle.
Eventually, even a blind sow finds an acorn and I did too, but it was 300+ test bullets into the work. I was finally able to get a 165gn TXS seated at 0.070" off the lands to give me a sub MOA group with less than 9 fps standard deviation in velocity. The powder is IMR 4350 and the primer is a Fed 215.
I don't want to go through this again and if you have any advice / tricks specific to the short mag, I'd sure like to hear it.
PS: I also load .30-06, 7mm Rem Mag and .22-250 and have never had difficulty developing a consistently accurate round with any of them.
Browning.. I have never loaded the 300saum but from other reloading experience- some guns are just plain finicky. I always start with some Rem. core/locts to see if it's normal or not. Most of my experience shows that some guns want to be loaded way off the landssome as much as.015". I also have a hand gun in 7mm TCU that the bullet is touching the lands. As far as standard deviation goes I try to get close but I'm not for certain that means to much!! Load them same cases up tommorrow or next week & go back to the range & I'll bet you don't get the same standard deviation!! You may be surprised I've had it alredy going from 13 to 109 fps & the load still was as accurate - I was just testing group size to see that it wasn't a fluke!!!!
Calhoun - any load that shows me some "promise" for accuracy and uniform bullet speed gets made again (10 rds) and reshot to verify. If it passes again, I go to 20 rds and reshoot for group through the chronograph.
You are right, variability can be high, that's why I run statistical analyses on multiple shots.
Additional info I should have put in my first post: I purchase brass from a single lot number. I buy 2x as much as I need, deburr the flash holes, resize, trim to length and then weigh each piece. I grade out all brass that does not fall within +/- 1 std dev for weight. It helps like crazy with uniform velocity. (My experience anyway...)
Obviously, I'm anal about accuracy, but to me it's the fun part about reloading - always working to get as much accuracy as possible from a rifle and load.
Don't buy new brass from me at a gunshow - it's the heavy & light grade outs.
Since I don't have these problems with conventional-cased loads, I'm wondering if the case configuration of the short mags contributes to the issues I've had. They must burn powder very efficiently since they do get more velocity than a long-case load with the same dose of powder.
Browning.. i used to be real anal about the whole process when I was really in to the competition thing. All groups were 10 shot groups repeated & the normal new gun was around 300-500 rounds shot!! I used to weigh the cases but I never figured it did to much for me!! It seems like the short mag cases are a touch more finicky from what my buddies tell me but they burn more efficent and that 4350 seems to work real well in several calibers !!