18" or 20" barrel for .308?

**1911-A1** · 09-09-12, 15:36

I'm looking at a. 308 precision bolt gun build, and I would like to see how much capability I lose going from 20" to 18". I'd like to keep it short, but not if it hurts its ability to perform well at long ranges. The idea is to put a can on it and possibly a folding stock for transportation.

**orkan** · 09-09-12, 15:58

Been there done that.

Basically, compute for 15-25fps per inch of barrel loss. Yet some barrels shoot fast, others slow.

Expect 2500-2575fps from an 18"
Expect 2525-2600fps from a 20"

This, given a stout load of varget and a 175SMK.

**jpipes** · 09-09-12, 16:01

You'll likely lose approximately 10fps per inch removed, but you'll only know for sure when you test it. A good barrel, with a good chamber, coupled with good handloads and good bullets and I bet you won't have any problems to 1k. For reference, my 20" Brux sends sierra 2156 palma bullets at 2890 via 8208 xbr. Im at 2650 with 175 smk's and Varget. Both are using Winchester brass.

**rundm** · 09-09-12, 16:23

I am guessing that the 2800+ speed is with the 155 gr palma bullets? I am able to get there with my 20 in AI with the 155gr lapua but the accuracy is not the same as with the 168's or 175 sierras. Does the xbr powder meter well? I havn't tried anything except for varget.

**jpipes** · 09-09-12, 16:25

Yes sir, this are the 155 bullets with a "palma" designation. Higher BC than the original 155 smk. I love them, and found them to shoot slightly better than 155 Scenars in my rifle.

XBR meters very well, and has shown to be very temperature stable in my testing. I use two chargemesters to dispense powder, so I can't speak to how it meters out of a standard powder measure. It's more ball like, so it should be fine. In my opinion, it's THE powder for heavy bullets in .223 and 155 class bullets in .308. I've been extremely pleased with it.

**1911-A1** · 09-09-12, 17:00

Is there any difference in accuracy between the two lengths?

**Iraqgunz** · 09-09-12, 17:52

Barrel length does not = accuracy. There are many past threads that covert this topic.

Originally Posted by 1911-A1

Is there any difference in accuracy between the two lengths?

**orkan** · 09-09-12, 18:33

Originally Posted by Iraqgunz

Barrel length does not = accuracy. There are many past threads that covert this topic.

Actually, it does... to a degree.

The shorter, thicker the barrel... the less drastic the harmonic vibration... the more forgiving it is in regard to ammo selection/load development.

**a0cake** · 09-09-12, 19:31

At some point this "longer barrels aren't more accurate" thing is going to have to die. Accuracy = the ability to place rounds on target. Precision = group size. Each word has different implications.

High Accuracy / Low Precision

Low Accuracy / High Precision

While longer barrels are not more inherently precise before transonic range, and in fact short barrels often have this advantage due to rigidity - go shoot a 16'' .308 at long range with 10-20 MPH variable winds, and then shoot a 24'' gun, and tell me the 24'' doesn't produce a higher level of accuracy. And actually, longer barrels ARE also more precise starting at the transonic range of the round from the shorter barrel.

Longer barrels allow you to fudge the wind call and fudge the range estimation. Longer barrels are more accurate in the real-world, and regardless of inherent / mechanical differences, also tend to allow greater levels of demonstrated precision in the real world.