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Is there any where you can find info for bullet weight / powder combo for barrel lenght? For instance: I have a 308 win with 22 inch barrel and want to shoot 168 grain bullets, lets say Barnes, Will IMR 4064 perform better than 4320 or 3031 for this combo? Heck Barnes shows 12 different powders for the bullet weight. Or is there a rule of thumb to go by. Short barrel faster powder for heavier bullets? or the opposite? slow powder for heavy bullet in short barrel ?
4064 should perform well in a 22" barrel with a 168 gr bullet. You don't want to go with too slow powder as it will increase muzzle flash. Any of the midrange powders will perform well in the 308, it's not a finicky caliber to load for. For load development, a chronograph is really indispensible.
You can also check a manual such as Nosler's which shows the "best powder tested" for each tested bullet weight. Another option is an internal ballistics software such as Quickload.
You can also call the ballistics techs at Sierra. The guys at Sierra have been really helpful and friendly with me in the past and have probably done more testing than all the guys on this board combined. The Sierra bullets seem to be a great place to start when I'm ladder testing for an accuracy load.
800-223-8799
Almost any powder that actually works for the 165-175gr is all burned LONG before the end of the pipe.
Any fire-balls that you see at the muzzle isn't from actively burning powder. It is a combination of "glow" or re-ignition once the bullet leaves the muzzle. IF there was enough oxygen in the powder to get a 100% burn(no more fouling!) the temperature would have long melted the barrel.
I agree with Sierra's data on mine with 175 SMK's. Win 748; personally speaking.
Didn't have the chrono out with me but I had 2 different work ups and wanted to see the poi difference. I knew the 4064 and 4320 were very close in burn rates but I like the metering of the 4320 better so I thought I would check it out. what I got was very similar groups at the different weights for both powders but the 4320 was a little over 3'' lower in poi. This is what got me thinking on the subject. Was it just a quirk ? or was the 4320 that much slower that it was not burning all of it ? Then I thought that jumping way up the chart to 3031 may be to far.
Darrker wwhat lenght barrel you using and what kinda velocity with the win748?
Barrel length only determines the velocity. The powder choice is entirely determined by case capacity and its relation to bore diameter and bullet weight.
Ideally for max velocity and consistency, you want the slowest powder that will reach max allowable pressure for your given bullet. The slow powder will provide a full case which usually results in consistent performance. It will also sustain pressure the longest creating the largest "area under the curve". Area under the curve is what determines velocity so the ideal pressure curve reaches peak allowable pressure and sustains a high pressure down the length of the barrel. If the powder is too fast, it will reach peak pressure but it won't maintain that pressure and area under the curve suffers and velocity does as well. If the powder is too slow, it fills the case without reaching peak pressure and area under the curve suffers and the velocity along with it.
Notice that I didn't mention barrel length in any of this. For the several powders that suit a particular bullet weight and cartridge, barrel length determines the end result of velocity, but the same powders will perform regardless of barrel length. Notice the ammo makers don't sell loads tailored to different barrel lengths, there's a reason for this and that reason distills down to the fact that proper powder selection has nothing to do with barrel length.
Powder burn percentage isn't terribly indicative of anything either. Varget, for example, is usually at the top of the list for consistency and velocity out of the cartridges where it is suitable and it almost never burns completely in a practical length barrel. Doesn't mean anything. It is what it is.
Muzzle blast is determined by residual pressure when the bullet leaves the bore. High velocity loads will have high pressure when the bullet leaves the bore and will have muzzle blast. Unfortunately the two are part and parcel.