Home Forums Hunting & Shooting Custom Rifles & Wildcats Question for barrel speed?

The last custom I had was a 257 ackley on a 700 sa and a 24" lilja barrel. At the time we were told lilja makes some "fast barrels" and with the hornady 120 HP and 205 SG powder we got a max load of 3150 fps.

Who has the reputation for "fast barrels' now, is it still lilja or some other customs barrel makers?

Tracy

Broughton 5c are known to be fast barrels.

Yes, fewer lands and grooves can make for a faster barrel. With everything being the same (fewer lands and grooves/the same teist) what other barrels are fast?

There is an ongoing thread about this subject. Frank Green from Bartlein has some good info on the various types of rifling - not specific barrels but rifling/grooves and so on and how they perform and pros/cons of each. Its a pretty good read IMHO.

http://www.scout.com/military/snipe...3-curious-about-different-rifling-styles

Fewer lands and grooves make a faster barrel? Wow!

I read somewhere that Jarrett makes barrels that are "tight" as he believes that contributes to accuracy. Consequently they are slower. Perhaps "looser" barrels are faster....?

From 6mmbr.com: Tests show that, with the 80-90gr bullets, a 1:10 or 1:12 barrel will give you as much as 80fps more velocity than a 1:8 barrel, shooting the exact same loads. Fast twist (1:8) barrels have more drag and friction, which can slow the bullet down. Ideally you want to use the slowest twist rate possible that will stabilize the bullet you choose to shoot.

A old friend that did custom loads for a living told me that tighter twist increases pressure and you would get more velocity. and when you reduce the twist you get less velocity when using the same load. He used two oehler 33 chronograph together for years.

But you would also think if you had a max load then reducing the twist would mean you could increasing the powder load and then get more velocity?

Now you are attributing it to twist. I thought this thread was about lands and grooves? You can take 2 barrels from the same barrelmaker, same lot, same lands and grooves, and the velocity will be different.

Speed is irrelevant.

dave

Dave,
You are pretty much correct.

The post is about "fast barrels" I think its ok to talk about twist sence it does and can afect velocity, no big deal

Tracy

So we should all shoot 30/30's? I for one like everyone elce will always try to safley get the most speed along with all the accuaracy that I can. And in long range varment hunting it can make a drifrence

One time I sat down and did the calculation for how much energy was tied up in the angular velocity of a bullet compared to the linear velocity component. To facilitate things I used an idealized shape whose angular moment of inertia wasn't too hard to calculate, and the shape would actually overestimate the spin component of the energy compared to that of a regular bullet.

Nevertheless, the angular velocity component was a quite small percentage of the kinetic energy, and the difference because of different twists was not nearly enough to explain the velocity claims of slow twist proponents.

mathman,

You know math is science and science is fact and facts don't do well here. Most of us use ignorant prejudice for our decisions.

Speed differences depends on the individual barrel.....

My 6 groove 8" twist 7mm-08AI shoots the same 7mm-08 load ~160fps faster than the previous barrel shot the identical load. New barrel is 1" longer than the old barrel.

David

Yes that goes without saying, and my question is pertaining to coustom barrel builders, but if twists and number of lands and groves has some efect then that is good also

What was the twist of the old barrel and was it 7mm-08 or AI chamber?

I don't want to bring up any statistical burden of proof, but I would have to see a statistical difference between barrels when using the exact same components. I'm sure there's some difference, but I would guess the difference is less when using the same components.

I've only had 3 30-06 barrels so far (one more on the way) and they've all been pretty darn similar, but I'm using the same reamer and components. And if they are 20 fps different, it doesn't matter.

And when it comes down to it, less velocity means less pressure. I almost don't load to powder weight anymore, I load to a velocity. I've never had pressure problems unless my chrono says I'm over a velocity max. A slow barrel is slow, until you put more powder in the case.

Was the 7-08 barrel a factory barrel, and the 7-08 AI barrel an aftermarket barrel?