Bullet Weight vs Barrel Length??

jt_trouble

jt_trouble

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I recently purchased a new Savage FCXP3 in .308 from Wolverine. It came with a 22" barrel and 1 in 10 twist from what I read on the Savage website. I want to turn this into my boat gun and when I am bombing around in the winter by skidoo. And need something a bit more compact, so I was thinking of chopping the barrel and installing a muzzle brake. I've read that chopping the barrel can affect the performance of heavier bullets. And/or can also improve the accuracy of some seeing that you now have a thicker barrel to shoot out of.

So IF I was to do this, what would that mean for the types of bullets I can reliably use once the barrel is shortened?

Would I have to start using lighter bullet (145-168g) ?

Has anyone else done this to the average hunting rifle? I know that it's a common thing with the m1/m14/m305 crowd, with good and bad results.

Opinions?

My shots are usually under 200yds and typically chasing moose :D
 
Why would you chop the barrel and add a brake?? The brake will kill your hearing real quick, and you won't gain anything in worthwhile shootability with it on a 308. Chopping the barrel won't make any difference to what bullets you can use. It will make a bit of difference in velocity, a bit slower.
 
well the brake is optional ... I just threw that out into the mix.

How bad would chopping the barrel affect the velocity? I guess a good question would be is .. when does the powder stop burning in the barrel to produce the pressure to propel the bullet? Would using a lighter bullet counteract the affect of a short barrel on velocity?
 
jt_trouble said:
well the brake is optional ... I just threw that out into the mix.

How bad would chopping the barrel affect the velocity? I guess a good question would be is .. when does the powder stop burning in the barrel to produce the pressure to propel the bullet? Would using a lighter bullet counteract the affect of a short barrel on velocity?
Click to expand...

i was watching a clip of the gunsite scout on youtube, and the ruger rep said they found that in reguards to the 308, you lose about 30 fps for every inch you remove from the barrel. i'm no expert though, so take that with a grain of salt.
 
Your burn is normally finished in the first 12" of barrel travel. That is the opinion of many good gun men who have persued the science like, Seyfreid, Barsness, Waters, Sisk, etc.

The pressure continued to build as the gases expand, and resistance (friction) is a constributor to the velocity created by the expansion's progress being retarded by the resisitance. The resistance stops when the barrel does, and then you get a ultra fast completion of the gases expanding at the end of the barrel. Shorter the barrel, the less velocity you get, the more muzzle blast you recieve.
Simplest way to explain it I can think of.
18" barreled .308 I played with maxed out at 2560fps with a 165gr bullet and Varget.
It pushed 150's to 2700fps with RL15.
I would expect the 180's to do 2350 in the same rifle.
 
22" is pretty short already. Most bolt guns stop around the 20" length.

The velocity won't matter in 200 yds and unless the accuracy goes so bad when you shorten it that it will barely shoot inside 10"@ 200 yds you can still hit a moose with that.
 
rem338win said:
Simplest way to explain it I can think of.
18" barreled .308 I played with maxed out at 2560fps with a 165gr bullet and Varget.
It pushed 150's to 2700fps with RL15.
I would expect the 180's to do 2350 in the same rifle.
Click to expand...

thanks ..

My thinking was 18.5 with optional muzzle device or no muzzle device for 20" over all, knocking 2" off the barrel is plenty short for me.

My original concern came from a magazine I read, shooter had a 18.5" barrel and was using 180's and was constantly keyholing. he dropped the bullet down to 150-165 and started shooting tighter groups with the same twist that my barrel currently has (1-10). I've used Win Silvertips 180's before and they have still carry a good punch and take down power on moose up to 200yds. Anything further than that and I think I'd let them live another day :D
 
I have a 308 20" Savage. Makes quite a bit of muzzle blast. OK for hunting, when you only fire one shot. I would not cut any more. I have a 18" Mauser carbibe in 308 and it is painful to shoot, noise wise.
 
Lots of variables here. The only definative arcticle that I have read wa years ago in the american rifle man using a 270 and H4831 with 130 gr bullets They started with a 26" barrel and shortened the same barrel by 1" at a time to 20" . The average over the 6 ' shortening wa 25fps per in . Of course the difference for inch between 24 and 26" was less tha 20-22".
I believe useing Varget , IMR 4064 or a similar burning rate you willbe losin in the 15-20 fps velocity range with the same barrel.
Ther are other factors suh as bore dia and quality of the bore. A friend and I checked 2 of his 30-06's One was a earlier push feed #0-06 with 22 barrell as compres to an A bolt wit the boss. The Boss shortens effictive barrel lenght by 2 "
Results werte that the 20 A bolt was almost 100fps faster than the 22 winchester with the same . He was using Imr 4831 and thae results would have been different with a faster burning bowder. The rule is check diifferent loads and with shorter barrel use th efaster powders and with those long tubes use a slower powder. There are a lot of variables with bore diameter and the smoothnest of the bore .
With the 308 if you used 3031 or something clode you would see a negliable loss in velocity
Neil
 
This is going to sound harsh cause, well, it is.
Nothin in Neilm's post makes sense, from the English to the context. You don't save anything on burn rate between 3031 to 4831. We are talking the burn is done well before 18".
Neilm said:
Lots of variables here. The only definative arcticle that I have read wa years ago in the american rifle man using a 270 and H4831 with 130 gr bullets They started with a 26" barrel and shortened the same barrel by 1" at a time to 20" . The average over the 6 ' shortening wa 25fps per in . Of course the difference for inch between 24 and 26" was less tha 20-22".
I believe useing Varget , IMR 4064 or a similar burning rate you willbe losin in the 15-20 fps velocity range with the same barrel.
Ther are other factors suh as bore dia and quality of the bore. A friend and I checked 2 of his 30-06's One was a earlier push feed #0-06 with 22 barrell as compres to an A bolt wit the boss. The Boss shortens effictive barrel lenght by 2 "
Results werte that the 20 A bolt was almost 100fps faster than the 22 winchester with the same . He was using Imr 4831 and thae results would have been different with a faster burning bowder. The rule is check diifferent loads and with shorter barrel use th efaster powders and with those long tubes use a slower powder. There are a lot of variables with bore diameter and the smoothnest of the bore .
With the 308 if you used 3031 or something clode you would see a negliable loss in velocity
Neil
Click to expand...
 
In a nutshell, the load that produces the highest velocity in a long barrel also produces the highest velocity in a short barrel. But a heavy bullet tends to loose less velocity than a light bullet as barrel length is reduced. It requires a greater volume of slower burning powder to produce the same velocity as fast burning powder, and a larger volume of powder makes more noise than a smaller volume of powder. A break takes that noise and throws it back at the shooter. Sooner or later you will need to make a snap shot with that rifle, you will not have your hearing protection on, and the phone will be ringing for a couple of days. But worse than that, it will hurt and you might well develop a flinch from it.

If you have trouble dealing with the recoil of a .308, either handload and shoot enough to develop a tolerance for the blast and recoil, or purchase reduced recoil factory ammo and shoot enough to overcome the issues you have with blast and recoil.

With a barrel shorter than 20" you run into issues related to muzzle blast and to the balance and handling characteristics of the rifle. Another consideration is to the aesthetics of the rifle. A rifle that appeals to your eye with a 22" barrel might look like a club with an 19" barrel. Be sure you'll appreciate the change before you get busy with that hacksaw.
 
Thanks for the replies ..

Not to concerned about the recoil and blast of the rifle, I've fired a few rounds before ;) I was just looking for something a bit shorter. The idea of a muzzlebrake has been put on the back burner. But I still am thinking of sending my rifle out to get it chopped to 20" for a slightly compact build, we'll see. I know it's not going to be a target rifle, so my concern for any adverse affects on performance have been addressed I believe, it'll mean some range time with a few factory choices will be needed to see what it likes should I decide to get it done. And unfortunately I don't handload myself, it's been a thing I have been thinking about trying one of these days.
 
jt_trouble said:
:cool:

That was one of the questions I forgot to ask .. thanks!
Click to expand...

If you are not shooting heavy bullets and hot loads with slower burn powder, the shorter barrel length won't make much real difference in 200 yds.

The difference in noise and blast from an 18" vs 20" .308 barrel is substantial though, and there is a huge difference from 22" to 18."

I don't know your planned shooting positions but I can tell you from a prone position a normal 18" barreled .308 is going to "disturb" some ground.
So if you shoot propped over a truck hood or ATV you will be in for a surprise.
All our agencies tactical .308s with a barrel of 20" or less were surpressed for the obvious reason and also for reduced blast signature.

Hope it works out for you.
 
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