another load question

[jeremybowlin]

Well heres what im needing advice on. I have a factory Remington sendero in 7mm rem mag. I found a load using H4831sc and 168 HPBT sierras. When i bought the powder they only had 2 1 pounders. Well i used all that up and bought a big keg of it. I know powder varies from lot to lot. so i ran a few loads threw the chrony. When i worked up the load it was cold out. when i tested the new powder lot it was fairly warm out. My VOL is all most a 100 fps slower then the old lot of powder. When you guys change lots of powder do you just adjust the charge weight to match the vol of the load that shoot lights out? Or do you do another load work up? I know the VOL that shoot extremely well for this rifle. Any help would be greatly appreciated.

 

[BuzzBoss915]

Re: another load question

If it is a different lot, to be safe, you should back off a little bit, especially if you are operating up around max.

100FPS difference seems like a lot? In fact, it would be more logical if the reverse had happened; warmer ambient, higher pressure, more velocity. This is why I develop my loads in warm weather and do not depend on temperature stable assurances on the label.

The only other thing I can think of is maybe you positioned the chronograph too close to the muzzle one of those times? BB

 

[MALLARD]

Re: another load question

yes lot to lot variations can effects your velocities by 100 fps ( though , i never seen that much of a change in standard rifle calibers, but in big magnums its more common)

you can even get those same lot to lot variations within the same jug of powder !

i would not adjust the charge weight to meet your old velocity expectations.

i would do an OCW type test and see what charge weight yields the best group

 

[RingingSteel]

Re: another load question

I would re-check the setup with your chronograph. If you are using one that folds out and you don't get it flat it will effect your measured speed drastically. If it is not folded out all of the way it places the sensors closer together and will give you a higher velocity than you actually have.