308 Barrel twist...

[Idaho Sharpshooter]

Ever have one of those itches you can only scratch one way?

For twenty-plus years I have wanted a rail gun. Mostly just to experiment with cast bullets. A 308 Winchester. Might shoot a CBA match every now and then.

What twist would you specify if your plans centered around the 175gr and heavier boolits? I am thinking 1:10", but I have always been intrigued by the notion of a gain twist barrel.
Bartlein Barrels offers them, and they are cut rifled as well.
1:11" to 1:10", or perhaps 1:10.5 to 1"9.5"?
:castmine:

thanks,

Rich

[Scharfschuetze]

Cast or jacketed bullets?


Mostly just to experiment with cast bullets.

Might shoot a CBA match every now and then.

If you are thinking cast boolits, I think that you are thinking too fast.

My good friend Larry Gibson uses very slow twist barrels for cast boolits with excellent results. I know, I've shot them out to 300 yards with almost Sierra Match King accuracy and velocity, but with cast boolits.

Knowing that, I'd really consider a 1 in 14" twist. I might add that many 30 calibre Palma Match from back in the day used a 1 in 14" twist and they easily held the the X and 10 rings at 1,000 yards with 150 or 155 grain bullets.

While the 308 will suffice for cast boolits, there are a couple cast boolit specific cases that handle cast better. The 30 CBC comes to mind.

Now for jacketed bullets of 175 grains, then I believe that a 1 in 11" or 1 in 12" twist will be the best for you, especially at the longer ranges. I've used both of those twists in the M21 and the M24 rifles 7.62 NATO and both rifles excelled through 800 yards and were usable to a thousand with 168 or 175 grain bullets.

[Yodogsandman]

I'd take a look at the CBA match results to see what rifle twist was used to win with that boolit.

[Outpost75]

John Ardito set all of his heavy bench CBA records driving 190-200 grain bullets at high velocity in 14" twist Hart barrels, mostly in. 308x1.5" using RL7 powder

[Bama]

What velocities are you aiming for. A 1 in 10 handles 165 through 200 gr PC bullets real well with sub min of angle at velocities equal to or higher than jacked in the bore rider type bullets.

[runfiverun]

1-12 is real flexible.
most 30-30's use this twist and have no issues getting a 170-180gr bullet/boolit stabilized, or up to about 2400 fps.
going to a slower twist is the easy way out, but teaches you nothing.

[Scharfschuetze]

going to a slower twist is the easy way out, but teaches you nothing.

It doesn't need to teach you anything. It's good advice and you get small groups doing that. Wasn't that the OP's intent with building a rail gun?


John Ardito set all of his heavy bench CBA records driving 190-200 grain bullets at high velocity in 14" twist Hart barrels, mostly in. 308x1.5" using RL7 powder

[Ken in Iowa]

Back in my varmint hunting days, I built a 6mm Remington Improved in a Hart heavy varmint 1-13. My goal was to shoot 75-80 SP bullets at Pdogs in the wind and 85-87 BTHP at 600 yard targets and varmints.

I never regretted going with that odd slow twist.

[Scharfschuetze]

I never regretted going with that odd slow twist.

Thanks for the reminder Ken.

I should have added to my previous post that many of the top shooters in the bench rest game, Palma and long range matches like to use a rifling twist that just stabilizes their projectile at the furthest distance that they are shooting. I have spent hours talking with the best shots at US state and national matches as well as at international matches on this very subject. Virtually all of them are of this opinion.

We are indeed lucky that our faster twist barrels are flexible enough that they will handle a wide variety of weights. Still, if a rifle is built for one purpose, then the slowest practical twist for the calibre, velocity and the bullet weight is the proven formula.

[Love Life]

Going with a slower twist is a proven method (very well documented and proven, not just word of mouth) to get accuracy with speed with cast bullets.

[runfiverun]

no you don't need to learn anything unless your writing an article for a magazine.
or are just in the habit from writing for a precision reloading type magazine for years.

heck if you want easy get a 1-16 twist 4" diameter barrel and weld some legs on it, and 2 thin pieces of wire to sight with, then bolt it all down on a 6" slab of concrete and haul it around.
you won't even need a scope, or to spend any more than 200 bucks on an action, just point it at the paper and pull the trigger.
the groups will still be measurable.

[M-Tecs]

Someone having a bad day?

[runfiverun]

it's Christmas that's always a bad time of year.

[Scharfschuetze]

Well, I hope it gets better for you in the coming year 5Run5. Have a beer and chill. :drinks:

[Hannibal]

Some things never change.

[tomme boy]

:Fire::Fire::drinks: Here we go again!

[B. Lumpkin]

I don't know if this helps because I mainly shoot jacketed bullets in my match rifles. I have used 1 in 12 twist 30 cal barrels to stabilize 175gr SMK bullets out to 1,000 yards. I have also used 1 in 10, and 1 in 11 twist. I can't help with the gain twist as I have no personal experience with them with either cast or jacketed. I can see the slower start being easier on the cast bullet. Whatever you decide on, I can't wait to read the results!

[oldblinddog]

Whatever you decide on, I can't wait to read the results!

:drinks:

[swheeler]

no you don't need to learn anything unless your writing an article for a magazine.
or are just in the habit from writing for a precision reloading type magazine for years.

heck if you want easy get a 1-16 twist 4" diameter barrel and weld some legs on it, and 2 thin pieces of wire to sight with, then bolt it all down on a 6" slab of concrete and haul it around.
you won't even need a scope, or to spend any more than 200 bucks on an action, just point it at the paper and pull the trigger.
the groups will still be measurable.

I didn't know you were a writer, what kind of articles, fiction?:kidding:

[runfiverun]

most of them seem like it, from what I'm told.

[swheeler]

most of them seem like it, from what I'm told.

Just kiddin' Have a Happy New Year!:drinks:

[runfiverun]

just poking back at you a little bit Scott.
not mad.

[cainttype]

I love "easy", if it works.
I'm not terribly fond of working with problem guns that require lots of work and tinkering to get anything useable, although I will when the mood strikes me... I enjoy rifles and hanguns that co-operate more easily a lot more than the problem examples, though.
The same can be said for moulds and alloys. Those that deliver the best results with minimal fuss are the ones that will be used the most... I'm funny that way.

When a firearm delivers outstanding performance with little to no issues it moves way up my "Favorites" list quickly. It will definitely see more use, more often, than it's stable mates.
Did I mention that I love easy?

The consensus appears to be that a slower twist than the OP was entertaining would deliver the goods "easier"... I'd give that serious consideration if I were building a special-purpose rifle from scratch.