powder burn understanding

[Ghengisahn175]

Gentlemen,

Having some difficulty making a decision about powder choice. If I had quickload I probably would be able to answer my thoughts but I don't. So before I begin i will list rifle specs and current specs:

rifle: 300WM w/ 29" heavy bull barrel 1:10 twist
secondary barrel will be: proof research 28" with a 1:9.4 twist

300WM
RWS brass
hornady 208 AMAX
IMR 4831 @ 68.8 gr
fed 210 match primers
seated 30 thousandths off the lands
AVG velocity: 2942 , ES: 21, SD 7.5

300WM
remington R-P brass
hornady 208 AMAX
IMR 4831 @ 70.0 gr
fed 210 match primers
seated 30 thousandths off the lands
avg velocity: 2910 , ES: 27, SD 7.8

Currently I made the switch from remington brass to RWS. RWS has smaller case capacity and 4831 has a pretty decent burn rate (fast compared to the favorable h-1000). Although i reduced powder charge from 70.0 gr to 68.8, I increased velocity (while the remington brass didnt see pressure signs until 72ish, the RWS is seeing very very slight pressure signs at 68.8 / 69 definitely).

with either case, I'm not filling up case capacity (plenty to move around in there). My intent is to switch to a slower burning powder & switch to a magnum primer (already have CCI-250's). The powders up for consideration from fastest to slowest are:

7828 , 7977 , h-1000 , retumbo

My reasoning for wanting to go with a slower powder is to fill up a bit more case capacity which should help build slower pressure and efficiency while not reaching pressure signs like I am currently. I know all of these powders (with the exception of 7977 being it pretty new) have great loads for the 300WM with the H-1000 favored highly. I am wanting to understand how I should go about choosing powder. If its bullet weight, here is what I am considering shooting with an asterisk * next to what I will most likely be shooting:

hornady 208 AMAX * (economial & match use)
SMK 220 gr * (economical)
berger 230 OTM (match use only)

I suppose one of my main issues is the huge swing in bullet weight (208 amax to 230 berger). But I am lacking the knowledge in why or how I should be choosing ONE powder to work with. Hopefully someone can help me out here.

 

[gilcarleton]

I hope you get some good answers because I have the same problem. There are so many powders out there and if it was not for a reloading book, I would have no idea what to choose. I often feel I am missing some good powders because I just don't understand. That would be a great class at a NRA or gun show. I would certainly pay for that one.

 

[TRG300WM]

All loads were worked up shot from good rear bag and a solid front rest. and showed very good accuracy out of my TRG-42, with 28" barrel
Tested over a ced m2 chronograph

225 gr Hornady Match AMP
78.5 grs Retumbo.
FED 215
Norma brass
2914 fps
This is a maximum load in my rifle

225 gr Hornady Match AMP
78 grs H1000.
FED 215
Norma brass
2809 fps
This is a maximum load in my rife

208 gr Hornady Match
80 grs Retumbo
FED 215
Norma brass
2956 fps
This is a maximum load in my rifle, My start load was 78 grs but I found lots of soot around the neck and shoulder upon extraction until the load reached the 79 gr mark, H1000 would have been a better choice for 208gr, i might have reached 3000 fps.

 

[Sniper338]

Ive seen better accuracy with h1000 over retumbo..

 

[MagnumManiac]

Determining the best burn is rather straightforward, those powders that produce the highest velocities are the most ideal, as you go faster in burn, velocity drops, the same happens when you use a powder that is too slow, you can't get enough in the case to get the desired velocity.
The 300WM performs at it's best with powders like H1000, RL22, RL25, RETUMBO, N560 and so on.
They are all very slow powders, the heavier the bullet, the better the slower powders work due to the longer time they have in the barrel to push on the bullet. It often helps to load to the rifling, which also helps increase powder capacity and lowers pressure somewhat.

Hope this makes sense.

Cheers.