.300 Magnum and 20-Inch Barrel?

Sir Isaac Brock

Sir Isaac Brock

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Hi,

What issues would there be firing a .300 Magnum round with a 20-inch barrel?

Will all the powder burn?

Will there be extreme muzzle flash and sound issues?

Velocity and Force issues?

What rifle manufacturers sell this type of cartridge and barrel combination?

Here is an old but interesting article on the subject:

SWAT: BARREL LENGTH AND THE PRECISION RIFLE

Thank you,

SIB
 
I can imagine accuracy to be as good or better, as shorter barrels tend to be stiffer, but , I would imagine, you'd need different powders which burn slightly quicker? Muzzle blast would certainly not be pleasant. I'm interested to hear about this also.
 
Efficiency would be down, with increased muzzle blast for sure. For the difference between a magnum/vs non magnum in a 20" bbl rig I'd go for a more efficient cartridge powder column (short and fat) 300 wsm or saum being the largest I'd go. In my mind they would offer great potential in a smaller action. That being said, Hornady's new superformance powder is shortening the gap between say a 308 and 300 wsm. Cut the difference and work a superformance load with a 155-190 gr 30/284. There could be real potential there.
 
What issues would there be firing a .300 Magnum round with a 20-inch barrel? Blast and velocity loss. I can do a magnum with a 22" barrel, but 20" is getting a little excessive...

Will all the powder burn? Yes, almost. In modern rifle loads 95% of the powder is consumed within the first few inches of barrel. Whatever powder yields the greatest velocity in longer barrels will also produce the greatest velocity in your 20" barrel.

Will there be extreme muzzle flash and sound issues? Most likely. This depends somewhat on the load you use.

Velocity and Force issues? You'll lose ~25fps for every inch of barrel on average.

What rifle manufacturers sell this type of cartridge and barrel combination? I'm not aware of any.
 
Johnny_Canuck said:
Efficiency would be down, with increased muzzle blast for sure. For the difference between a magnum/vs non magnum in a 20" bbl rig I'd go for a more efficient cartridge powder column (short and fat) 300 wsm or saum being the largest I'd go. In my mind they would offer great potential in a smaller action. That being said, Hornady's new superformance powder is shortening the gap between say a 308 and 300 wsm. Cut the difference and work a superformance load with a 155-190 gr 30/284. There could be real potential there.
Click to expand...

Hi, thanks for the tip. The 300wsm seems to be the correct maximum cartridge for a 20-inch barrel fitting between the .308/7.62 and the 300magnum.

What manufacturers are producing 20-inch barrelled rifles for the 300wsm?

Thanks,

SIB
 
Accuracy international had a model for 338lapua in 20" for short range, I am sure remington does have ONE also for their New sniper rifle. is a matter of picking the right powder(burn rate).
 
"...extreme muzzle flash and sound issues?..." Yep. Serious muzzle blast as well. Mind you, the muzzle flash will only matter a half hour before and after sun up and sun down. Significant velocity loss too. Magnums tend to work best with 24" or 26" barrels.
 
Infractions: 0/1 (1)

Hey, I just noticed they put "Infractions: 0/1 (1)" under my name because I used the term "Vest Busters" in the subject header of another that was completely deleted, I bet you guys are jealous! :p
 
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Hi, there does not seem to be many manufacturers producing 20-inch barrelled rifles for the 300wsm. I suspect there is a reason for that; however, I do not know what is the reason.

The 300wsm seems to match up with a 20-inch barrel perfectly, the epitome of getting maximum function out of a rifle!!

Strange.

SIB
 
Jordan Smith said:
What issues would there be firing a .300 Magnum round with a 20-inch barrel? Blast and velocity loss. I can do a magnum with a 22" barrel, but 20" is getting a little excessive...

Will all the powder burn? Yes, almost. In modern rifle loads 95% of the powder is consumed within the first few inches of barrel. Whatever powder yields the greatest velocity in longer barrels will also produce the greatest velocity in your 20" barrel.

Will there be extreme muzzle flash and sound issues? Most likely. This depends somewhat on the load you use.

Velocity and Force issues? You'll lose ~25fps for every inch of barrel on average.

What rifle manufacturers sell this type of cartridge and barrel combination? I'm not aware of any.
Click to expand...

All true and proven many times, but contrary to popular "logic".

A 20" barrelled 300 RUM does not "become a 308", as the story goes.

The "logic" seems to come from the fact that almost all magnums come from the factory with long (24"+) barrels, therefore it goes, magnums "need" long barrels. The reason for the long factory barrels is because people buying magnums tend to buy them to shoot at long ranges, and therefore, they value the extra MV, and are not bothered by the long barrel's weight, nor its handling ability, i.e. getting caught on branches.

Still, the myth will never die.......
 
Sako had/has a carbine in 338win. Kicks like a mule! Good for in the thick for moose hunting. Doesn't have too much for weight saving as the barrel seems pretty thick.
 
BigUglyMan said:
Loss of velocity, increase in noise...ranks up there with "Dion for PM" in the Stupid Ideas Department.
Click to expand...

How much velocity do you feel would be lost when a .300 WSM is fired from a 20-inch barrel as opposed to a 22 or 24-inch barrel?

Another poster mentioned 95% of the powder burns in the first 3-inches.

Cordially,

SIB
 
It's been tried before and failed miserably: Winchester doomed the 264 Win Mag by producing in short barrel, light weight rifles. They learned their lesson well: overbore magnums need long (24in or more) barrels to be viable or you might as well produce a 308Win case based caliber like 338 Federal.

On the plus side, a short barrellled overbore rifle:
  1. kicks like a mule,
  2. produces a blast that will make you deaf,
  3. and generate non-magnum performance!
Alex
 
even 300winmag or 338lapua in 20" , you don't lose as much Velocity. that what every one though on 308 with 20" barrel in the pass, but even at 18", with an accurate action, barrel, one can shoot out to 1000yard, a 100fps is would be the max that you loose, but for long range work 24 or 26" would be the norm.
 
if i can i ll find what a barrel maker and a well known gunsmith Charlie Sisks (SP ?) made and published some researches on shortening barrel and you ll decide.

im using a magnum in 20" : this is the 375 ruger and that s great but that s me.
 
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