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Best powder for short barreled 308

 
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  #22  
Old 04-19-2013, 08:42 PM
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Re: Best powder for short barreled 308

"Generally, the faster powder, at equal charge weights, will produce faster velocities. This is because a lot of the slower powder's energy is wasted in heat transfer to the barrel and escaped gas and heat at the muzzle." Understanding Firearm Ballistics. Pg. 25 Robert A. Rinker.

So please explain how a slower burning powder "Varget, will produce better velocity in a 16.5 inch barrel than say 4895 or 3031. Both are faster burning powders.
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  #23  
Old 04-20-2013, 12:52 AM
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Re: Best powder for short barreled 308

As already mentioned, the same powder that gives highest velocity in a rifle will normally give the highest velocity in a short barrel.

I used Varget in a 15" barrel .308 Win with great success.

Without getting into a debate on fast vs slow powders in short barrels, I've shot a lot of different powders thru short barrels (currently don't own a rifle and shoot only 15" to 16.5" T/C Encore and XP100).

In my experience, the same powders listed as giving highest FPS in rifles also give the highest FPS in shorter barrels. There are some exceptions. But typically that's the case.

In my 280AI 16.5" long IMR7828ssc gave me the fastest FPS when compared to some faster burning powders. That's just one example. I've chrono'd nearly all my loads at the range, and as I've said, that's typical, though there are some exceptions.

In most cases, maximum peak pressure occurs within the first three inches of the barrel. This is why even in short barrels, the same powder type produces the highest FPS in both short and long barrels. The longer barrel simply contains the solid state matter converted to a gaseous state for a longer period allowing it to push on the base of the bullet for a longer time thus producing more FPS in the longer barrel. Short barrels do tend to display more muzzle flash due to the burning gases exiting a shorter barrel.

Check out some loading manuals that have a handgun section that includes loads for the 308, 7-08, etc.

I'd load some Varget and go have some fun.



Regards
Rog
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  #24  
Old 04-20-2013, 05:34 AM
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Re: Best powder for short barreled 308

Deleting subscription to thread; why bother.... It doesn't matter a dang bit anyway. Heck, I just deleted subscriptions to all threads!!

Last edited by Lefty7mmstw; 04-20-2013 at 06:07 AM.
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  #25  
Old 04-20-2013, 09:14 AM
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Re: Best powder for short barreled 308

"So please explain how a slower burning powder "Varget, will produce better velocity in a 16.5 inch barrel than say 4895 or 3031. Both are faster burning powders."

.Ara, I make no prediction on what powder will be ideal for your rig.

I know what I said is counter intuitive but intuitive in this case is based on incorrect "conventional wisdom". I've already explained that the powder which produces the highest speed in a 24" barrel will do so in your 16" barrel; the bullet's acceleration is solely dependent on the time:pressure curve, it matters not at what part of that curve the bullet exits, fastest in one length will be will be fastest in the other. That's all there is to it. I won't argue with your author but I will question him on this point. I'm sure Mr. Rinker is a smart and quite knowledgable man and I would love to have his book for study but he is not the first author to write something which sounds right but isn't entirely correct in application.

Think of how little heat energy can possibly be transfered to a bore surface in the 2-3 milliseconds it has to do so. Certainly heat (energy) IS transferred or the barrel wouldn't get hot but that's because the burn temp is quite high, hot enough to melt the steel if it were maintained longer. IF barrel temp mattered very much we could reasonably expect the last round fired would always be fastest but...not really! Thus, Mr. Rinker's equating a measurable velocity difference based on heat exchange to the barrel because of powder burn rate is quite a stretch of both physics and logic! The actual bore time of bullets at say 2,500 fps and 2,800 fps isn't much no matter what powder is used so the end difference in energy transfer will be infintesmal no matter the burn rate.

We reloaders make a lot of noise about "fast" and "slow" powders because it matters to us but the real world time differences are quite tiny. We're only moving the instance of peak pressure small fractions of a millisecond and changing the duration of that pressure peak just a little longer.

Last edited by boomtube; 04-20-2013 at 10:04 AM.
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  #26  
Old 04-20-2013, 05:42 PM
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Re: Best powder for short barreled 308

I agree with boomtube I have had a 26" barreled 308 that I would get 2775 with varget and 175 smk I now have a scapel with a 22" barrel that is running 2730 with varget. I also have a 19" 308 that will shoot 2700 with the same load 45fps is not going to make that much differance. The barrels are in order a Shilen,Krieger and Broughton. It does not matter how fast it is going as long as you do your part. Good luck and if you have 4895 try it and see what you think. I am always trying something different but always end up with Varget for my 308s.
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  #27  
Old 04-21-2013, 05:30 AM
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Re: Best powder for short barreled 308

Quote:
Originally Posted by Lefty7mmstw View Post
Deleting subscription to thread; why bother.... It doesn't matter a dang bit anyway. Heck, I just deleted subscriptions to all threads!!
I've gotta stop playing around here half asleep...I suppose apologies to the o.p are in order....

Boomtube has valid point. I have seen plenty of short barrels that can be made to shoot at almost the same speed as a longer barrel with the right powder and primer choice. Most of these loads would be screamers in a longer barrel too though.
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  #28  
Old 04-24-2014, 10:41 PM
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Re: Best powder for short barreled 308

Digging up an old thread. I have a savage 10fp xplea chambered in 308. It came with a 25" barrel. I reload on a dillon 550 with dillon digital scales. I use 7.62 nato brass. Hornady sst 180gr. And h380 powder with Winchester large rifle magnum primers.
My experience
With the 25" barrel I got 2780-2800 fps
I cut the barrel down to 18.5" and turned in a lathe to a buttoned 11degree crown
And now I get 2675-2700fps and typically shoot .200-.250 groups at 100yds
The load is 48grs of h380 compressed with Winchester magnum primers. Brass trimmed to 2.05 and a coal of 2.80.
This is a compressed load. I worked up to this load in half grain increments and it shows no over pressure signs. The magnum primers help with the ball powder.
This year during deer season I shot a doe at 775yds. With a balistic calculator I'm not a mathematician lol. Perfect heart shot and bullet still passed completely through. That's good enough for me.
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