Barrel length vs 308 Ballistics

janesy

janesy

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Hi guys, I've done a couple searches with no results, so I thought I'd throw this out to the Ballistics guru's on here.

What would the difference be between a 308Win fired from a @4" barrel as the tests are done vs. a 16.5" barrel.

I'm not really looking for a specific bullet analysis, but I'm going to be test firing some 180Grn core-lokt as well as some 150Grn Harnady interbonds.

This is a 7600Police to be used as a dogging/tight bush gun, so MOA is not really the issue, I'm just looking to find out what the difference would be between the two barrel lengths.
 
I've had outstanding results with 165's with my 1-10 twist 20" savage. YMMV.

Short range I'd go heavy as the gun is happy with. Start in the 160's and try 180's.
 
Never heard of or seen a 4" .308win, but I chronyed my 308 win with 18" barrel absolute max load of Varget and 150gr Speer HC 2615 fps and tested the Winchester Power Maxes 150gr just a few FPS slower
good luck trying to find Ballistic's on a 4" barrel
manitou
 
There will be a difference but it will not be as dramatic as you expect, and it will be more apparent with light bullets than with heavy. Chances are that in the field it would be impossible to make any practical use of the difference. That 7600 Police should be a capable hunting rifle for any North American game.
 
maynard said:
I'm thinking the @4" barrel is a upper case error and should be 24"?
Click to expand...

Thanks, It should read 24" as the ballistics are typically tested. Compared to my 16.5" barrel?

Is it going to create significantly less velocity, will the drop be greater. Does it matter...Probably not as I'm going to zero it tonight anyway, but I'm curious how the math work.
 
If you do a Google search, you will find a lengthy article published in one of the magazines a few years ago which tested exactly what you're asking about.

IIRC, there were only significant velocity drops once the barrel got shorter than 16" or so.
 
Depending on the rifle, it will vary. 25 to 30 fps loss per inch is common. My 308 bolt shoots rem corelokt 150s at 2720 fps v 2820 in the ballistic chart. 20 inch tube on the bolt action. My 7600 carbine with a 19 in tube shoots these same bullets at 2600 fps. I would be surprized if you could not easily get over 2500 fps with your 16.5 inch 7600.
 
so marginal at best.

The gun was shooting about 2" groups, however, the front police bead covers14-16" of target at 50 yards, so where those groups actually hit...well lets just say I bought a smaller bead on my way home today
 
I think lots of guys underestimate the velocity loss with a shorter barrel.

I have chronied my .308 load (165gr SST, IMR 4895 Powder, all rounds chronied from the same batch of reloads, shot on the same day) in M14's and found this -

2760fps with 22" bbl
2590 fps in 18.5" bbl

That's 170 fps loss between a 22" and 18.5" bbls. And that's with 4895 powder, which is not a slow powder. If shooting a slower powder you'd lose more. If you went with a fast powder like 3031, you could likely shave off some velocity loss, but not that much. If you go from a 24" to a 16.5" barrel you'd surely lose well over 200 fps according to my readings. I'd bet closer to 300 fps actually.

I've chronied my Lee Enfields also, and found well over 200 fps difference between long barrelled No1's/No4's and the shorter No5's (about six inches of barrel difference.)

I have a couple of short barrelled rifles, and I like them, and I've killed lots of game with them, but I honestly feel that the guys talking about you losing only a little velocity are wishful thinkers. If they actually measured their loads their comments would be changing from "..you don't lose that much.." to something like "...velocity isn't that important..."

200 fps is the difference between a 223 and a 22-250, or a 25-06 and a 257 Weatherby, or a 30-06 and a 300 win mag - basically it's a whole other level of cartridge. Do you need that whole other level? Only you can say, really. I'd bet you can still hunt just fine with a shorter barrel, but you should be honestly aware of what you're shooting, particularly if trying to calculate your long range ballistics.
 
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Comparing two rifles with dffernt length barrels does not tell you much because the difference between individal rifles can easily be 100 fps or more.

I once cut a barrel off in 1" increments, and chronied it each time. I was converting a 30" target barrel to a 20" short hunting barrel. It dropped about 25 fps per inch. Don't recall what ammi I was using.

The biggest difference is in the noise. Some powders make such a terrific muzzle balst that the rifle cannot be shot without ear protection.
 
I've read anywhere between 20-60 FPS all over the net. Taking a round number such as 50fps, we are talking a difference of ~400fps. Huge difference.

I did learn over the last week, In my hunting ground, if I'm taking a 200 yard shot, it's rare and most likely max I'll ever see. All three Moose we got this week past were between 60 and 100 yards. Most Deer shots will be the same, altho the possibility of a longer shot is there as the trees are thinner in the next couple weeks.
 
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