Optimal long range 308 load 20"

[jonnefudge]

Hi!
I would like some advice on developing a load for long range shooting that is optimal for my rifle: 308, 20 inch barrel (lothar walter), 1/11 twist. I know this setup is far from ideal for long range. But the rifle is what i have, custom built, very accurate and i want to reach out as far as possible. My goal is 1100yards.

My first question is about powder: does the 20 inch barrel require a faster burning powder than normal for long range 308 shooting?

I have seen different data on this. From what i have been reading I might consider normal to be Vithavoui n140, Varget, RL15 and faster being H4895, Norma 202.

My second question is about bullet weight: does the 20 inch barrel require a specific bullet weight?

I have seen different data on this. From what i have been reading I would argue that it stands between 155gr and 175gr but any input would be greaty appriciated.

Third i would like some input on a load that i think would be great for my intended purpose. It is based on what I have read so far and calculated in JBM ballistics calculator.

Bullet: Alco 175 gr rebated boat tail
Powder: H4895 (maximum load without pressure signs)
Brass: lapua
Primer: CCI br2

Lastly I wish for any tips for the optimal for my setup.

 

[Slamfire]

I would like some advice on developing a load for long range shooting that is optimal for my rifle: 308, 20 inch barrel (lothar walter), 1/11 twist. I know this setup is far from ideal for long range. But the rifle is what i have, custom built, very accurate and i want to reach out as far as possible. My goal is 1100yards.

A long range 308 rifle with a 20" barrel is an oxymoron. I have talked to my Army Reserve buds who are firing their 20" 308 AR10 rifles at 600 and 1000 yards. They are shooting 185 Bergers with beyond maximum charges of Varget. Expect the lugs to crack within 5000 rounds with their loads. A 20" barrel really cuts into your velocity and the further you go out, the slower the bullet arrives on target, and that means, good luck hitting anything in a fish tail wind, or any wind at all.

 

[jmr40]

The 20" barrel won't hurt nearly as much as most people think. I'm about 50 fps slower than a 24" barrel with my 18" Ruger Predator. There is a guy over at 24hourcampfire shooting 215 gr Bergers and getting good accuracy out to 1800 yards with a 20" 308.

Your 11 twist should be fine with high BC bullets up to 215 gr or so, maybe even even heavier. Barrel length isn't really a factor. Heavier bullets start slower, but retain speed longer. I'm not really into true long range shooting. But 178 gr bullets fired from my 308 start out 200 fps slower than 150's. But at the 300 yard mark the 178's are faster and the farther down range you go the farther the gap widens.

The same powder that gives the best speeds from a long barrel will also be the powder that will give the best speeds from a short barrel. At least with rifles. All powders burn completely long before you run out of even the shortest rifle barrel no matter how slow. In handguns with 4" or shorter barrels it can be a factor.

 

[RC20]

You might look into R17, its got a longer pressure plateau, it does tend to like heavier bullets (175 and up)

You get more velocity with safe pressures (generally)

 

[Zen Archery]

You ask Al at Alco? He will get you where you need. Only he understand those bullets more than anyone else. He helped me out.

 

[disseminator]

Powders can most definitely make a difference.

Generally, going from a 24" to a 20" barrel will cost you around 100 fps. This will vary some but is a good general rule. 308 is very capable in short barrels as you already know being very happy with your rifle as you are.

If you have a good load already, I say shoot it and don't worry about your short barrel.

 

[hagar]

175 Sierra or 178 Amax with 43.5 - 45(max) grains of RL15. Only use Winchester or Lapua cases with this load.

 

[AllenJ]

If the BC on the bullet you've picked is correct you should not have any problems getting to 1100 yards. I shoot the 178 Hornady Match bullets in my Savage (20", 11.25 twist) and the calculators say I won't be subsonic until after 1200 yards.

You are not going to need a faster burning powder in your 20" barrel, I'm using Varget and have also had good results with 4064. What you should be looking for is the fastest load in your rifle that still shoots sub MOA.

 

[jonnefudge]

Ok thanks very much!

 

[Unclenick]

The 20" barrel won't hurt nearly as much as most people think. I'm about 50 fps slower than a 24" barrel with my 18" Ruger Predator.

If the difference is that small, then there is some other factor than barrel length involved. Experiments cutting down barrels (so you always have the same chamber and barrel friction) show the difference should be about 150 fps. I'm guessing that if the two guns you have had the same barrel length, then there would still be 100 fps difference between them for reasons of chamber and barrel dimensional differences and bore smoothness differences.

This chart is typical:

Jonnefudge,

Choice of powder burn rate does not reflect a difference in velocity ranking in the .308 until you get down below a foot in length. In other words, a load that is fastest with a 24" barrel will also be fastest with your 20" barrel. So you are really looking to maximize velocity with your bullet of choice with the same powder you might use elsewhere. The only obstacle will be if it proves to be a combination that just doesn't have a good accuracy sweet spot in your gun, as occasionally happens. The RL-17 suggestion is a good one. Unlike your H4895, it is not a temperature stabilized powder, however.

 

[Don Fischer]

That load may or may not be a good load. The best for that rifle you'll have to find. And that best is going to be whatever makes you happy. If it were me, I'd go with a match bullet for sure. I don't think the brass or primer is that important but certainly may be better. There are several different powder's I like for the 243, IMR 3031, H335, BLC/2. IMR4063, W748. Those with a 165 gr bullet have always served me well with hunting bullet's at both 165gr and 180 gr.

I've never heard of that bullet your using but there's lot's of things I never heard of. My absolutey favorite match bullet is the Sierra Match King. Everything I read, those Burger's match bullet's work well. And I think Sierra and Burger may be easier to find. I didn't mention the Hornady match bullet as I've never used one and haven't heard much about them, I am a Hornady freak for hunting bullet's!

I believe more important than the bullet or rifle you have will be range time at the distance's you want to shoot. You probably have stepped into the world of high dollat speciality scope's also.