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Discussion Starter #1
Can not find any info on the effect of a 16 inch barrel v/s a 24 inch barrel in the new winchester super short magnums. In the WSSM do you need a full 24 inch barrel to burn all of the powder? If I use a 16" or 18" barrel what will I lose? Any body have any ideas? :?: (looking at the .243 WSSM)
 

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well accuracy should be the same with differnt barrel lengths
what you will notice is an increace of velocity with a longer barrel like 24" while a shorter barrel like 16-18" will loose a good deal of velocity
im not sure how much faster a 24" barrel will push a .243 WSSM than a 16" barrel would but im sure that it would help considerably at long distances to have a 24" barrel
 

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re

I have always understood that barrels can be too long velocity wise, although I do not know for sure.

On paper the LSW has a slightly lower muzzle velocity than an SA-80, this is while an SA-80 has a barrel length of 518mm's, while the LSW has a barrel length of 646mm's.

I understand this to be due to the exploding gasses of the shot accelerating for only a limited distance; ie while the gasses are accelerating the round constantly in 518mm's of barrel, before the round reaches 640mm's of barrel the gasses have expanded to the extent that they no longer accelerate the round, leaving the extra length of barrel to cause added friction to the bullet without any gain from the powder, and so slightly decelerating the round when compared to an optimal length barrel.

If this is true, and I am not completely mistaken, what is the ideal barrel length of a 556 rifle where velocity is concerned?
 

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Yimmy good question
i dont know, it all depends on velocity wise all i acn go by is what is on Bushmaster's site for various barrel lengths

barrel length and velocity with M193 (55 gr) and M855 (62 gr) and energy
Bushmaster XM15 E2S (Bushmaster's AR-15) Series:
10" 2739/2627 918/950
11.6" 2872/2738 1007/1032
14.5" 3064/2907 1146/1163
16" 3132/2989 1198/1230
20" 3259/3095 1297/1318
24" 3315/3158 1342/1373
26" 3391/3231 1404/1437

for velocity it seems that the ideal barrel length is going to be byond the practical length you will want

a side note the Bushmaster M17 Bullpup's barrel is 21.5" long and gets better velcoities with M193 and M855 than the 24" barrel on thier XM15 series does, and almost as much velocity as the 26" barrel
it depends on the tollerances of the barrels
 

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Yes. A shorter barrel means the gasses still have yet to expand, and, as such, you lose quite a bit of velocity. With a .308, I believe, every inch of extra barrel after 26 will only get you an extra 5 fps, up to 40 inches (I recall reading an article on Lilja about them toying around with giant barrels like a 40 inch one. They complained about the fact that there is quite a bit of visible barrel whip, and, of course, the weight, and unweildy size of the thing).

I'd just live with the extra 8 or 6 inches on my barrel, really. At the very least, i'd live with 20 inches.
 

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With a WSSM you will experience a great loss because it has more powder and gases that will be wasted with the shorter barrel. I would guess that you will lose at LEAST 200fps over a 24" barrel, and I would venture to say it will probably be more than that.

Auto vs. Bolt gun also effects velocities, especially in gas operated semi-autos, the gases that it takes to operate the bolt could have been used to accelerate the bullet, though its not a huge difference.

CM2k - I also read an article where a group of experimenters ran super long barrels, and it was over 40 inches before velocity began to fall.

MEL
 

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Discussion Starter #7
Thanks guys for the input!!

I guess what I am looking for is the specific about of loss of energy and velocity per inch of barrel loss starting at 24 inches. I know that there are several ballistics programs on the market but I am not sure if someone has access to such a program and if it would output that information. I am only looking for good clean kills on southern whitetails out to about 200-300 yds. max for this rifle

CM2k – You are probably right, a 20” barrel is probably the way to go. Thanks!

Jeff_850, speaking of bushmaster, I do not see near the amount of adds for them is I have in years past. Everything going good for them? Thanks!
 

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There is no EXACT amount that is lost per inch, because every inch will be different (more or less usable gas the longer/shorter you go). Plus barrel tolerances, gas used to operate the bolt, etc etc etc.

For a ball park on the .308 I use 25 fps per inch... but that is just a number, sometimes more accurate than others....

MEL
 

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Discussion Starter #9
Thanks Mele. What about "ballpark" insead of exact :D

Still think 20 inches looks the best so far.
 

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I'll give you the snipercentral forums guarantee:

Once you leave the forum, there is no guarantee!! :wink:

MEL
 

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The effect of barrel length

I've done a few experiments on the effect of barrel length re: velocity.

With IMR-4350 powder, in a 7mm Mauser it seems that one gains about 25 fps for each one inch increase in barrel length.

The identical load was fired in a 29" long Mauser rifle made by Deutsche Waffen und Munitionfabriken and a 17 inch long Ludwig Loewe & Co. carbine.

The load was 43 grains of IMR-4350 powder with the 160 grain Sierra boat-tail. Average velocity from the DWM was 2302 fps and average velocity from the carbine was 2054 fps.

With other powders having different burn rates perhaps my results would vary a great deal. But then again, maybe not.

However in high intensity magnum cases, I suspect that muzzle velocity will increase at a higher rate. I would not be surprised to see an increase of about 40 fps for each addtional inch of barrel.

But I have not done the chronography. But then again, I don't know anyone with a short barrelled magnum rifle. The two don't usually go together....

I would expect to lose about 300 fps when reducing barrel length from 24" to 16" in the .243WSSM.

Perhaps you should phone Accurate Arms at (800) 416-3006 or the folks at Sierra. Perhaps one of their technicians has already done the chronography.

Mad.
 

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Discussion Starter #15
The 243 WSSM has been put on hold for now, found a deal on another AR. Maybe later. Thanks for all the help!! Will post a review after this weekend (I hope).
 
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