MV for 20" 308 Barrel

[ned kelly]

G'Day all,
I'm looking at buying a left hand Rem700 SPS varminter (26" barrel) and lopping 4"-6" off the barrel to make it a handy hunting rifle.

I'm trying to work out what the MV would be for handloads out of a 20" (or 22") 308 barrel with the usual 150gn to 180gn bullets and if the heavier bullets will still stabilise in the shorter barrel.

Anyone out there with experience in short 308 barrels who can help me please?

Cheerio Ned

[stu_bear2002]

G'day Geoff,
From memory you will loose approx 100-150fps for every inch you lop off.
i did a similar thing with a .243 i had and lost about 230fps, it made the rifle very easy to handle but also increased the recoil somewhat.
cheers Stuart

[johnk]

Velocity loss probably isn't linear, but rather gets more sudden the closer you approach the chamber, based on what I've seen with target rifles across chronographs. I suspect that it relates to the residual pressue remaining in a barrel at any given point, which equally must relate to the burning characteristics of the powder used. In an extreme case I recall from way back, a BR shooter using a .222R ringed his barrel at about 11" by leaving a chux patch in the bore. He had his gunsmith back bore & recrown the barrel past the bulge & lost only a handful of fps with his usual load.

On the other side of the coin, match rifle shooters like myself have concluded that it's not cost effective to fit 34" barrels over the cheaper & more readily available 32" tubes.

You'll find that one of the reasons that .22 target rifles have relatively long barrels (apart from the sight radius) is that the get more consistent subsonic velocities that way, albeit at slightly lower velocities than might be achieved in a shorter barrel. When Anschitz built a model with a minimum length barrel & a bloop tube, shooters in warmer places like my home state found velocities & accuracy went out the door. In fact, the Federal ammo being launched at that time would go supersonic about 1 in 2-3 shots, which didn't please the users at all & buggered sales of Federal fodder in Queensland.

If you must lop the barrel, I would suggest that 22' is a reasonable compromise length. However, you mightn't get a rifle that's all that handy if it has a varminter barrel profile. There's going to be a fair amount of weight there still.

I can understand a LH rifle being desirable to mollydukers, but I would suggest that you invstigate hanging onto the varmint barrel for future possibilities & rebarreling with a sporter profile barrel of your chosen length.

John

[ned kelly]

G'Day All,
thanks for the replies. The big problem I'm faced with is a number of LH 308's is manufacturer's is to reduce cost on making LH actions is by only making a LH long action for all chamberings. And to the mix I have a maddco 1:14" 7.62mm tube I probably will fit to one of my target rifles for FS or 500m Fly so it makes sense to stick to the 308 chambering.

I could simply get a long action 30-06 and go from there, but I have a lot of tooling for remingtons and the idea of a carbine length heavy barrel seems to make sense. especially if the catalogued weights for various 30 cal sporters compared to 20inch "tactical/varmint" rifles are approx the same, I should end up with a 20"-22" LH 308 around 7.5lb bare weight (then add scope, rings, bases & ammo)

Docking the barrel is a heck of a lot cheaper than a new tube especially when it it to be used for goats/pigs/deer. (John, I do appreciate the weight implications of a lighter fluted barrel) This is why i'm interested in the MV's of a 20-22" 308 barrel. If I'm not losing much MV, then it may be the way forward for me.

hope this clarifies my question.

Cheerio Ned

[bruce moulds]

i believe you will lose about 25 to 30 fps per inch in very rough terms.
the 308 can work moderately well with 20 to 22 inch barrels, and will certainly forgive docking more than a 243 will.
bruce.