Cutting down barrel to 18 myth?

[bvmoney]

So ive been reading more and more about GPS Defense cutting down their 308 rifles to 18. So my ques is: what other calibers can you cut the barrel down to 18 without considerable lose in accuracy or FPS. Also are they cutting down factory barrels or aftermarket?

Also i found a website the other day that started at 24 and ended at 10 barrel length. It also showed the FPS table for every inch cut off. But i dont rem the caliber.

 

[Ernie]

So ive been reading more and more about GPS Defense cutting down their 308 rifles to 18. So my ques is: what other calibers can you cut the barrel down to 18 without considerable lose in accuracy or FPS. Also are they cutting down factory barrels or aftermarket?

Also i found a website the other day that started at 24 and ended at 10 barrel length. It also showed the FPS table for every inch cut off. But i dont rem the caliber.

First, Welcome to LRH!
I hunt and shoot almost exclusively with specialty pistols-Primarily single-shot handguns chambered in rifle cartridges.
250 Sav AI, 6mm-6.5x47Lapua, 6-284, 6.5-284, 284 Win, 7mm Rem Mag Imp, & 7mm Dakota.
My barrel lengths will run from 14"-18"
With my 17-18 inch barrels I will see about 200-300 fps difference (depends on cartridge for one) compared to typical rifle lengths (whatever that is)
For instance with two different 17" 6.5-284's using 140's MV's run from 2700-2775. An 18" (140 grain A-Max) runs @ 2725. I go for the accurate load, not the fastest load.
Accuracy is not an issue for these short barrel rigs if you use quality, prepare everything correctly, and as long as what is going on between yours ears is good you will hit your target

 

[bvmoney]

Thanks for the welcome.

Learn me on this 7mm mag imp please. Ive never heard of that before.

Also if what your telling me is correct, id like to use a 7mm mag but with a shorter barrel. Im not worried about loosing FPS as much as i am knock down energy. But my research has shown that anything in a magnum under 24 barrel burns/wastes to much powder. So how could you shoot a mag out of a 17-18 barrel? Isnt it a waste?

Thanks for the knowledge.

 

[Ernie]

Thanks for the welcome.

Learn me on this 7mm mag imp please. Ive never heard of that before.

Also if what your telling me is correct, id like to use a 7mm mag but with a shorter barrel. Im not worried about loosing FPS as much as i am knock down energy. But my research has shown that anything in a magnum under 24 barrel burns/wastes to much powder. So how could you shoot a mag out of a 17-18 barrel? Isnt it a waste?

Thanks for the knowledge.

The 7mm Rem Mag Imp., is simply an improved 7mm Rem Mag.
The 7mm Dakota is a larger case than the improved 7mm Mag.
Next barrel (18") I will be getting on my center-grip Rem XP-100--It will use upward of 100 grains of powder.
I don't care about wasting powder.
What I do care about is performance and accuracy. With those two things in mind, if I want the performance of the 260 Rem in a regular rifle lengths then I will have to step up to a 6.5-284. Some of my 6.5-284 handgun MV's may be at the max or slightly over what the a 260 rifle gets.

I pretty much look at rifle performance with a given cartridge/bullet in a rifle and then subtract 300 fps and that is pretty close to what I get in one of my SP's.

 

[bvmoney]

So you could shoot a regular 7mag (not improved) out of a 18 rifle barrel?

Any downside besides loose of FPS?

 

[Ernie]

Thanks for the welcome.

Learn me on this 7mm mag imp please. Ive never heard of that before.

Also if what your telling me is correct, id like to use a 7mm mag but with a shorter barrel. Im not worried about loosing FPS as much as i am knock down energy.

What do you mean by knock-down energy?
What kind/weight of bullet are you looking at using?
What would you consider your maximum hunting distance in ideal conditions?

 

[bvmoney]

Knock down energy- enough energy to drop a deer.

Bullet weight- 140

300 yards max

Living in GA we dont see much beyond that. Most of the time it wont be close to that far. But i wanna be able to reach that far if i have to. I hate limiting myself.

 

[Ernie]

So you could shoot a regular 7mag (not improved) out of a 18 rifle barrel?

Any downside besides loose of FPS?

Easily!
Nothing else but your MV.
You would have the rifle performance/velocity of the 284 Win or the 280 Rem would be my guess or close to it.

My old 15.75" 284 Win XP-100 had a MV of 2750 fps with either a 140 NBT or 140 grain Partition=about what one could get out of a 7mm-08 in a rifle.

My original 7mm Dakota Barrel (18") had a MV of 2706 fps with a 200 grain Wildcat bullet.
Using 180's (76.5 grains of Retumbo) would get MV's from 2850-2900 fps.

 

[bvmoney]

So then y is everything that i read about barrel length so negative about short barrels if your only loosing 200-300fps? In the grand scheme of things thats nothin!

 

[Ernie]

Knock down energy- enough energy to drop a deer.

Bullet weight- 140

300 yards max

Living in GA we dont see much beyond that. Most of the time it wont be close to that far. But i wanna be able to reach that far if i have to. I hate limiting myself.

If you only need 300 yards, you might consider a lesser cartridge, and save yourself some recoil.
In the past, with a 140 NBT in a 14" 7mm-08 center-grip XP-100 I have taken mule deer and antelope past a quarter mile.
If you had an 18" barrel in either a 7-08, 284 Win, or the 280 Rem, it would more than fulfill 300 yard deer IMO.
I am partial to the 284 Win case myself, but that is personal prejudice.

 

[bvmoney]

Thats the conclusion that ive come to. Less recoil same ballistics coefficient.

 

[Ernie]

The other reason I personally like the 06 level capacity is that is gives you a little more umph if you ever decide, to start stretching things out-It tends to happen when you start hanging out with this group

The 7-08 will do the job for your current set-up
You should be around 2700 fps or a bit more with a 140 grain bullet.

 

[bvmoney]

Thank you for your time and knowledge. Exactly what i needed to know. Now gotta find me a good 7mm-08 to cut up

 

[Ernie]

You are welcome.
Make sure you share your new rig once you get it up and running.