Talk me out of a 20 inch 300 Winchester magnum… or not.

[ButtersDad]

I suppose if you're willing to turn a .300WM into a very loud 30-06 ballistically you're also willing to live with the reduced performance. You can't cheat physics. A common caliber exists that will perform happily in a 20" barrel: .308 Win. A Very Merry Christmas and a Happy, Prosperous New Year to All!

Well, you have to remember, in my original post I stated I'm shooting exclusively suppressed. So there is no "loud" anything . No cheating physics either, show me a 20 inch 308 that sends 178gr projectiles @2880fps in a factory ammo offering. The goal was meeting a specific set of needs with the best caliber for those needs. I got lucky as well with Hornady 178gr eldm TAP ammo, my rifle seems to love it.

 

[Shane Lindsey]

Sweet rig! You are stacking too...I would be interested to see how this does with say a 220 grainer. Your velocity isn't terrible.

I did similar to your 308. 20" sends 215s at 2495 FPS, but your parameters don't work for what I did.

 

[ButtersDad]

Very nice! I run another short setup with a 16" 308. Still my favorite rifle…

 

[wrightjr]

I like how you followed your own goals / vision and built what you wanted. I did the same to a 26" Remington 700 LR in 7mm Rem mag. I liked the rifle and the accuracy, but grew tired of the long barrel quickly and chopped off 4" of barrel. The rifle felt more balanced and I was pleased all around the board. No chrono numbers to verify the exact velocity loss, but it was still bugholing groups so I was pleased... Enjoy your new rig and keep thinking outside of the box.

 

[Calvin45]

I suppose if you're willing to turn a .300WM into a very loud 30-06 ballistically you're also willing to live with the reduced performance. You can't cheat physics. A common caliber exists that will perform happily in a 20" barrel: .308 Win. A Very Merry Christmas and a Happy, Prosperous New Year to All!

.30-06 out of a 20 inch barrel will still be well behind a 20 inch 300 win mag at equal chamber pressure. Like you yourself say here, no cheating physics. Of course you're right…she's gonna be LOUD! Unless suppressed. The .308 certainly makes sense in a 20 inch pipe but chopping a .300 Winnie to 20 inches doesn't turn it into a .30-06 or .308…even with a 26 inch pipe I doubt the .30-06 would exceed the horsepower of a 20 inch .300 magnum, and while being much more inconveniently long at the same time.

It would be interesting tho to know where the line of diminishing returns lies…anyone on here with money to waste, er, spend, feel like making a 16 inch .30-378 carbine?

 

[Montucky Roamer]

Nice build! That's how you do it ! Pick the bullet and velocity you want or need , then your rifle length, weight etc that you can live with and suits your purpose, and then the case to hit that velocity.
I'm in a similar boat...I want a 215 Berger at killing velocity at 800 yards. I can drop to a 20 inch barrel if I choose to, and retain that ability. This is a rifle that gets packed up 3000feet before breakfast and get dragged thru alder choked hell holes, yew brush and other crap and then I pop out in open alpine, extra length and weight is not a benefit in these hills.
That's true efficiency. Guys do 338 edge specialty pistols for crying out loud and they are far faster than a 338 federal of the same length, I'll tell ya that for free. It's all about reaching the goals YOU need. Nice work. That'll hunt.

 

[Ken61]

My 20 inch 30-06 comes close. It is loud.

 

[yorke-1]

.30-06 out of a 20 inch barrel will still be well behind a 20 inch 300 win mag at equal chamber pressure. Like you yourself say here, no cheating physics. Of course you're right…she's gonna be LOUD! Unless suppressed. The .308 certainly makes sense in a 20 inch pipe but chopping a .300 Winnie to 20 inches doesn't turn it into a .30-06 or .308…even with a 26 inch pipe I doubt the .30-06 would exceed the horsepower of a 20 inch .300 magnum, and while being much more inconveniently long at the same time.

It would be interesting tho to know where the line of diminishing returns lies…anyone on here with money to waste, er, spend, feel like making a 16 inch .30-378 carbine?

I had a 16" 300 RUM specialty pistol that was getting 2980 FPS with a 180gr accubond with H4831sc. The same load gave 3130fps from a 26" rifle.

It's not a 30 caliber, but I went to the extreme with a 338 SnipeTac in a 20" barrel on a specialty pistol. I actually had a 30" rifle barrel cut with the same reamer, so I did a lot of direct comparisons between the two. Dropping 10" of barrel length cost me less than 250fps of velocity when the same load was fired in both guns. A 300gr OTM over 140gr if h50bmg gave 3120 fps in the 30" barrel, and 2890 fps in the 20" barrel.

If I dig through my notes, I have a lot of data on different chamberings in both short and long barrels shooting the same load.

 

[hicountry1]

Be a loud 30/06.....

 

[Calvin45]

I had a 16" 300 RUM specialty pistol that was getting 2980 FPS with a 180gr accubond with H4831sc. The same load gave 3130fps from a 26" rifle.

It's not a 30 caliber, but I went to the extreme with a 338 SnipeTac in a 20" barrel on a specialty pistol. I actually had a 30" rifle barrel cut with the same reamer, so I did a lot of direct comparisons between the two. Dropping 10" of barrel length cost me less than 250fps of velocity when the same load was fired in both guns. A 300gr OTM over 140gr if h50bmg gave 3120 fps in the 30" barrel, and 2890 fps in the 20" barrel.

If I dig through my notes, I have a lot of data on different chamberings in both short and long barrels shooting the same load.

Awesome!

 

[whitetail regulator]

Hey I hope your 20" 300wm came out good...I have 24" rem 5r700 that I am seriously considering cutting and threading at 19.5-20.5" ish what do you think? Any thing not mentioned here that you would suggest? Thanks

 

[Hugnot]

Great Balls of Fire!

 

[ButtersDad]

Hey I hope your 20" 300wm came out good...I have 24" rem 5r700 that I am seriously considering cutting and threading at 19.5-20.5" ish what do you think? Any thing not mentioned here that you would suggest? Thanks

Do it! I have zero regrets, and my barrel now has about 120rds through it and is only 80fps slower than an advertised 26inch test barrel with Hornady ammo. I haven't had any negatives with my setup.

 

[jlarose85]

I love this! This would be right up my ally if I ever decide to put something together in a magnum caliber. I also only hunt suppressed so the shorter the better as far as I'm concerned.