Velocity, barrel length, and actual consequences

Grizzlypeg

Grizzlypeg

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I was looking at some data on cutting down a 308 barrel, and while a reloading manual suggested to expect 20 fps difference per inch, someone's real world test measured 22 fps.

So I started thinking, ok, if you cut down a barrel to 19" from 24", what is the practical impact on hunting? That 5" cut would translate to an approx 110 fps loss in velocity.

Now, looking at ballistic charts, it seems a 150 grain 308 bullet losses that amount of velocity in 25-50 yards, depending on closer or further from the muzzle. Makes me think, that barrel shortening would not have a great difference in performance at most reasonable hunting range.

Anyone care to chime in with their real world experience?
 
May be more portable with short barrel, velocity will drop, the shorter you go the more obnoxious will be its report, and the rifle may become unbalanced if you lop 5" off.

Think practical short barrel would be 20" for a big game rifle, considering the above, my experience only.
 
Agree. Short barrels don't lose enough to matter in every situation I've ever found myself. I just moved an XPR with a 16.5" barrel, but only because I have a Sig Cross which is also short barreled. So nice in the field. I would consider a short barrel (18" and under IMO) for anything shy of an '06 case or magnum (once they get overbore like that the velocity goes nuts along with consistency).

Good article here for some additional reading: https://bulletin.accurateshooter.com/2015/06/308-win-barrel-cut-down-test-velocity-vs-barrel-length

He cuts a .308 down from 28" to 16.5" and posts his data points along the way. Lots of cartridges in and around the .308 power level that are useful, efficient hunting cartridges.

Some of this has to do with powder burn rate though - consider the new hybrid case designs (with stainless steel case heads) intended for 80k PSI. They are being loaded up with a fast burning powder with a lot of volume and crank the pressure through the roof and you can get these things cooking out of a short barrel. The "target" ballistics for the .277 Sig Fury are now somewhere between the .270 Winchester and .270 WSM (as fired from a 24" barrel). Closer to the former, but that is as fired out of a 6.5 pound, 16" barreled folding rifle with lots of modularity and flexibility.

You just can't get away with those burn rates out of larger cases, not in enough volume to fill it. Not unless you want an immediate, strongly unwanted disassembly of your rifle. But for those cases, we have long barrels which allow them to build to maximum pressure much more slowly.
 
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The reason i won't shoot a .308 shorter than 20" is extreme muzzle blast and crappy balance / handling characteristics. Turning a .308 into the performance of a .300 savage would not bother me at all. Loud, muzzle light, unbalanced rifles do not appeal to me, even though they're nice to get into a blind or a vehicle with.
 
A longer barrel with give you more velocity, which means you will retain the velocity required for the bullet to open properly at longer ranges.

My opinion is chopping a barrel only makes a significant difference if you are already on the edge of the performance you want/need. Lets use 308win with a 165gr GMX bullet - minimum velocity for proper expansion is 2000fps. Muzzle velocity for the factory ammo from Hornady is 2610fps from a 24" barrel, which gives you 2051@300yds and 1881@400... Interpolate a bit, and lets say its at 330 yds your velocity drops to 2000fps. If you chop 5" off that barrel and lose 110fps, you're now looking at something more like 1900+fps @300 and 2100fps @ 200. You are now hitting that 2000fps minimum at something more like 260 yards.

Now, I'd say shooting a monometal at 2610fps is silly (Either go down in weight to get more velocity for your monometal bullet or pick a bullet that is more forgiving at lower velocities), but thats a different discussion all together...
 
Modern reloading powders can help offset the slight loss in velocity by loading a bit faster powder for a shorter rifle, and slower powder in a long rifle. Using loads with long cut extruded powders that work well in a 26" barrel will result in unburned powder being blown out of a 17" barrel. That unburned powder=lower pressure=lower velocity. A slightly faster burning powder may get you the same pressure, and almost the same velocity. However, the quicker pressure rise may affect accuracy.

One can also compensate using slightly lighter bullets, as they accelerate faster.

Bottom line is you can taylor a load to optimize your rifle, what ever it is, and however long it is.
 
Meroh said:
Modern reloading powders can help offset the slight loss in velocity by loading a bit faster powder for a shorter rifle, and slower powder in a long rifle. Using loads with long cut extruded powders that work well in a 26" barrel will result in unburned powder being blown out of a 17" barrel. That unburned powder=lower pressure=lower velocity. A slightly faster burning powder may get you the same pressure, and almost the same velocity. However, the quicker pressure rise may affect accuracy.

One can also compensate using slightly lighter bullets, as they accelerate faster.

Bottom line is you can taylor a load to optimize your rifle, what ever it is, and however long it is.
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Nope. That idea gets thrown out a bunch, but its not correct at all.

Peak pressure is reached within the first few inches of barrel length, regardless of powder used. A slower powder will create that peak farther down the barrel, but both are going to reach peak pressure within a few inches; Nothing is reaching peak pressure at 20". That unburnt powder means just that, unburnt powder. Peak pressure is achieved long before all the powder is burned.

A lot of people seem to misunderstand how the burning of powder works. Peak pressure is reached in the first few inches, but the powder still burns after reaching peak pressure, creating expanding gases that push on the bullet. The bullet continues to accelerate after peak pressure is reached, pressure only needs to be high enough to overcome the resistances (friction mainly, also air resistance in the bore) present to accelerate the bullet. For a 308win, the bullet will keep accelerating through more than 40" of barrel.

Think of it this way: You want to match your powder to the case capacity and bore diameter. A 300mag can use a slower powder than 308win effectively, because the 308 case can't hold enough of that slower powder to create 60k+ PSI. Meanwhile, a full 300wm case of a powder suitable for a case like 308 would put you WAY over 60k PSI.
 
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I chopped my 24 inch barrel down to 19, Only thing I noticed was the weight loss .

I lost 117 FPS ,

Savage 10 TR .308
 
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Suther do you find any difference in your short barreled guns on big game?

100 FPS could be the difference in loads and powders, you can accommodate with powder and bullet choice.

I like 20 inch barrels “ I just think they’re neat”. Short barreled magnums really seem to offend people; maybe someone can quote some stuff from the internet to explain why

Handiness in thick bush gets thrown around a lot but I find myself avoiding the kind of stuff I get paid to walk through sometimes while actually hunting. Even if you insisted on hunting in thick alder and blowdown for some reason I don’t know why you would walk a straight line through the worst of it and not follow a game trail while hunting.

Changing from a bolt to a single shot will change your oal more in some cases. 20 inch single shot: perfection. Practicality, probably overstated but again “ I just think they’re neat”.


I found 16 and 18 inch barrels very loud even in smaller calibers. Kind of cool though, something about a short barreled lever gun. I have had a few really short shotguns and they never appealed to me anywhere but on paper; short sight radius and weird handling characteristics imo.
 
All my rifles are 22” and shorter in barrels except for an old Mauser 98 in 8x57 that has a 23+” one, some are 20” and I don’t see the difference on game compote to others with 23-24” barrels in the same calibers no differences at all! That said I try hard to keep my shots inside 200m, maybe past 400m it would make a bigger difference? I don’t know I hope to never have to know!! I really like the look, handiness and handling/balance of a short barrelled rifle!
 
Many hunters here in NZ shorten their 308 barrels, and a whole lot of other calibres too, 14-16" barrels is not uncommon. And many of those hunters are using those shortened rifles to take deer ethically at beyond 500 metres. Just like any rifle and any calibre, you just have to do the research and load development to get the type of projectile you want to use, doing the speed you would like. After that its simply comes down to the ballistic's, your data, and your ability to use that data. Shorter barrels usually require a different powder choice, but not always. And possibly a different projectile choice.
The down side of a shorter barrel is that they are not as user friendly and hearing protection is definitely recommended. But hearing protection should always be used regardless of the barrel length cos 6" of extra barrel doesnt make that much of a difference to the ability to damage your hearing. Then if you want to attach one of them bloody loudener brake thingy's, thats when it gets really bloody obnoxious!
We are legally allowed to use suppressor's and a short barreled 308, with an over barrel suppressor, is an excellent rifle in the bush.
 
First choose the barrel length that works for you where and how you hunt.

If for example, you like the 308, but your chosen 20" barrel doesn't offer quite enough muzzle velocity and energy, move to a 30-06 or even a 300 Win Mag with a 20" barrel.
 
To get any velocity out of a 308, your pushing light projectile. Larger projectile and your 308 is a modern 303. Shorten the barrel too much its pushing light projectile at 303 velocity.

Another poster mentioned the 277 sig (277x51), a hybrid case, pushing 80k pressure. During these impossible times, made worse by LGRv2.0, how are you to get a rifle/ammo/components. It's not like your going to take a used rifle, proofed typically for 55-63k and just rebarrel it. Realize that people in the US can easily pay a $200 tax and suppress short barreled firearms.
 
Velocity will be the least practically noticeable change. You will only notice a change there if you're using long range trajectory data. For hunting ranges, no.

The most noticeable thing will be handling. The gun will point very quickly, but settle down less. If you're hunting in the woods, it might be ideal. If you're shooting farther in open country, you might miss that steady hold in field positions. If you're somewhere in between, a compromise barrel length might seem more optimized.

The other thing you will notice is blast. This will be more notable at a range with baffles or overhead shelter than out in the open.
 
I cut a 6.5x55 barrel from 22 inches to 19 and lost an average of 45fps on a 140 gr. bullet. I have a preference to carbines for the handling but cutting the barrel back too far will cause balance issues. Velocity has never been a problem for hunting and my 6.5x55 shoots better with the shorter barrel. I have several 18 1/2" barreled carbines that are delightful to carry and very quick handling but the muzzle blast is quite a bit louder. Not a big deal for hunting but can annoy others at the range. Almost as bad as installing a brake.
 
The downfall I experienced with a short barrel (Remington 740 Carbine 18" barrel 30-06) is high muzzle jump, intense muzzle flash, most of all, increase muzzle blast. I have four built rifles which all have 27" barrels. I try to squeeze out as much velocity I can from the cartridge. If I didn't live in wide-open country, I would hunt with a shorter barrel.
 
BCBRAD said:
May be more portable with short barrel, velocity will drop, the shorter you go the more obnoxious will be its report, and the rifle may become unbalanced if you lop 5" off.

Think practical short barrel would be 20" for a big game rifle, considering the above, my experience only.
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Not argueing Brad - just saying but it depends on the barrels weight about UNBALANCING - I have a M600 in 308 with a 18.5 " and its a GREAT balance - my M7 308 with a skinny 308 barrel is Unbalanced - I do Like 20 " TOO ! jmo RJ
 
I started going short 25ish years ago, lots of criticism at the time. Nothing in the safe over 19”.
No less moose in the freezer.
 
Im now a recent Fan of 20 inchers.............
the downfall may of been the cartridge choice of barrel that was chopped...... i had a lefty 30-06 that i plan on keeping forever, an it was this i went for a 20 and had it fluted to lose some weight...minimal i know.

anyway, The 20 inch Barrel suits what im doing very well- i bush stalk alot and often shoot game as im stalking an seldom with a good rest, need a fast acquisition and often less than 100m but my average is 250 point and shoot.

So i played with 130gr Bonded to get Velocity back an settled on 150gr bonded to compromise Velocity and Trajectory with Penetration in close.... its a perfect fit so far, looking at 180gr cup an core for cheaper game getters.


im yet to chrono, but im also loading a too fast of a powder-- So my numbers would be around 2450fps for 180gr hornady il. sloww.

slower than a 308 win with most powders but i know the 308 is more than capable so im not toooo phased with it.... altho eventually il put slower powder an get faster velocity
 
nowarningshot said:
To get any velocity out of a 308, your pushing light projectile. Larger projectile and your 308 is a modern 303. Shorten the barrel too much its pushing light projectile at 303 velocity.

Another poster mentioned the 277 sig (277x51), a hybrid case, pushing 80k pressure. During these impossible times, made worse by LGRv2.0, how are you to get a rifle/ammo/components. It's not like your going to take a used rifle, proofed typically for 55-63k and just rebarrel it. Realize that people in the US can easily pay a $200 tax and suppress short barreled firearms.
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I don't even know anyone in the US who has received a Cross chambered in .277 Fury, I believe Sig is prioritizing the military contract first (actually, that's what they told me directly) and there's just a slow trickle of components to come over the next 3 years or so. But you are correct, if you want to fire off an 80k psi cartridge, it'll need to be in a Cross for now (with the hybrid design). In the States, MCXs (also proofed for the next generation cartridge design) are pretty hot for obvious reasons so I expect that shortage to last longer than 3 years.

That said, the design is rad.
 
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