powder burn vs barrel length.

[xdeano]

I would like to know what the minimum length of barrel that all the powder would be burned in a 308win, using 155g Lapua Scenar's, Fed 210Match primers, and 46.0g Hodgdon Varget, with approx. 2900fps velocity.

Is there a way to find this out?

I'm questioning because I had though about purchasing a rifle that has a 20 inch barrel for F class shooting at 1K. Will this work?

If anyone has any suggestions please let me know.

Thanks for your time.
Deano

 

[xdeano]

twist is a canted land 11.25.

thanks.

 

[JERRYHM]

Most f class rifles in 308 have barrels that are 30 to 34 inches.
I would be surprised if you get 2900 fps with 46 grains of Varget in a 20' barrel even with a 298/3065 barrel.

 

[xdeano]

Well it wouldn't exactly be F class, it would be F/TR class.
Would the powder be completely burned in a 20' barrel?

xdeano

 

[cliffy]

Burning ALL the powder within 90-95 percent of barrel length is the real 'trick' we all strive for. Powder burn speed is the key. This is why powders have published burn rates. cliffy

 

[canderson]

I had a remington LTR that would shoot Black Hill 168 smk's @ 2550 with a 20' barrel. I do not think that the 168 will stay supersonic @ 1000K. If you get the short barrel gun, be kind to the other shooters and try to edge forward on the firing line so that your muzzle blast does not rattle the other shooters as bad.

 

[xdeano]

I realize this canderson, That is why I will also be running a AAC suppressor. Now I know it isn't in the NRA rules, but we are also non-sanctioned so the rules don't apply. So i'll actually be the nicest guy to shoot next to on the line.

So with the stated powder and projectile, would it completely burn in a 21.5' barrel or not?

xdeano

 

[canderson]

Can I shoot beside you? I guess that I am not qualified to answer the question about the varget. If you know someone that has quickload, they may be able to help you.
Chris

 

[xdeano]

If you come to ND, you can shoot beside me. It's a lot better than shooting next to a guy shooting a 300 RUM. I've done that and it isn't fun, even with ear plugs made for you.

Thanks Chris, I'll give a buddy a call.
deano

 

[cliffy]

Within 6mm accuracy loads, Hodgdon H4350 will reach out and touch the target with aplumb, sidewise headaches aside. Don't shoot on-line if you can't abide modest muzzle blast. H4350 is the powder that all others should be judged by . . . 300 WSM ALWAYS give me headaches when fired too close to my noggin! cliffy

 

[Obtunded]

You will be at your functional max at 1000 but you can do it. You may need to use more powder. There is less velocity drop per inch in a 308 than you might think. 10 fps or less.

The whole 34 inch barrel thing is about being steadier in the aim when fired off your elbows or your toes,Creedmore style), and about keeping iron sights as far away from each other as possible,Ever seen a 'bloop tube'?). Velocity gains are secondary. Besides, faster does not mean more accurate. Likewise, subsonic does not mean unstable. 11.25 is way more twist than you need, so your bullets will stay stable at slower speeds.

 

[spclark]

Yes, your propellant should have burned completely by the time your bullet's half-way down a 20' barrel.

We use longer tubes to gain velocity,and sight radius, as stated in other posts); hot combustion gasses are still expanding even though the propellant's burned 100%.

,Muzzle-flash isn't unburned powder, but the secondary combustion of propellant gasses once they meet available oxygen outside your bore. Some propellants are better than others because of flash-inhibiting agents their manufacturers include.)

20' may be a bit short for throwing 155's out to 1,000 yards. 46 grains of Varget in a 30' barrel ought to give you 3000+ fps,stout - but not unusual - charge in some brands of 308 brass but probably too much in Lapua or Lake City) but you'll lose perhaps 100-200 fps from the missing 10'.

With that twist you might consider a heavier bullet,175-185) which ought to work fine at the 1k distance in a shorter-than-30' barrel.

 

[xdeano]

Well I figured out that my barrel is actually 22', It's a GAP rifle.

spclark,
With my 26' 700P, the 155's did very well at 1K, and beyond, furthest I've ever dropped them on target is 1300yds. But that is a good stretch, I was pushing them at 2925 during the summer.

I've heard of many people shooting 1K with a 20' barrel, with no problem, I figured I could do the same with a 22'.

Thanks obtunded for the suggestion.

Cliffy,
I've only shot once with a guy next to me with the 300 RUM, after 5 or 6 rounds down range, I stuck my flag in, got up and talked to the range master, I ended up moving down to an empty target way on the end. It sucks to put it lightly.

Thanks guys.

Deano