Best twist for 6mm cast shooter?

[madsenshooter]

What do you all think would be the best twist barrel for making a 6mm target rifle? I have everything I need to make a 6mm-30/40 Krag AI, dies, reamer, Krag action, and a target stock. All I need is to do is find some folks with some experience with this caliber. I made the mistake of having an AR built in 6x45 with a 1/8 Obermeyer, it won't shoot over 1500-1600fps with any degree of accuracy, so I'll probably go with 1/12 or 1/14, just need to know which would be best. The capacity of the wildcat would be about the same as a 6mm Remington, and it would be a cast only shooter.

[ktw]

I have a VV contender carbine barrel in 6x45 with a 1 in 12 twist. I have shot it some but not extensively. I have been getting reasonably good results with the Eagan you had made up into the 2400 fps range. I plan to do some work this summer with the BRP 245-77-GC

I was looking for something with a 1 in 10 twist to handle jacketed bullets up to 100 gr but ended up running across a deal on the used CC barrel. I noticed recently that Cooper's 6x45 offerings are in a 1 in 14 twist rate.

-ktw

[madsenshooter]

I should've made a poll of this. Thanks ktw, the Eagan is what's not working in my Obermeyer, but it works better than the Lyman 245498. I think that's just the difference in basing and/or the Lyman's wholly unsupported nose. 1.4" at 100yds isn't bad, it just isn't good enough when you're shooting against CBA benchrest shooters, and I have been. The 10 ring is only .75", and they can really put em in there. Heavy 30 caliber bullets at 2000fps and a bit beyond. I could compete with them, if they'd let me use 87-105 jacketed bullets!

[felix]

I predict you will run into powder selection problems. I have found the 6s to be finicky, in general. With all the powders available in the proper speed range, I am sure you can find at least one, and hopefully more that will not exhibit obnoxious peaks in the acceleration arena. Use the powder that gives "equal" accuracy with the projectile of choice by altering the powder back and forth a half-grain minimum around the most accurate point. I would make the gun a condom gun first and foremost with 12 twist using 90 grainers max. 14 twist would allow a good distance with 75 grainers max. ... felix

[Bullshop]

For cast only I would go 1/14". I once had a 6mm Rem with a 1/14" twist and it didnt want to shoot anything over 85gn with a jacketed bullet. A 100gn cast boolit will be about the same length or shorter than an 85gn spitzer jacketed bullet so should shoot well. The 1/14" would limit your weight range with jacketed bullets but I dont think so with cast. It will also allow you to shoot cast at a higher velocity with good accuracy.
If I were going to limit my cast boolits to not over 85gn and the nose profile rather blunt as in RN I would consider even slower twist like a 1/15".

[madsenshooter]

Thanks folks, I think the 1/14 is what it'll be, not having something made like the 1/15, going with the easily obtainable. If I do shoot any jacketed, it'll be some little 55gr flat base j-words I got from Nosler for like 10 cents each. They were an over run for an Australian order. Felix, it seems to me WC860 ought to be a good powder for boolits in the wildcat, seems to work good in the 6.5x55 which has about the same capacity, though I'd be using lighter bullets.

[felix]

Madsenshooter, good idea! Do a PM to Maven (Paul) who has experience using 860, 872, etc. in the 243. With a little more capacity within your 30-40 you might be able to better tune a "charge" for boolits. ... felix

[Larry Gibson]

14" twist and use a suitable cast bullet for it.

Larry Gibson

[45 2.1]

I made the mistake of having an AR built in 6x45 with a 1/8 Obermeyer, it won't shoot over 1500-1600fps with any degree of accuracy, so I'll probably go with 1/12 or 1/14, just need to know which would be best.

Several in my little group have the 6x45 in the AR....... wonderfull shooters with jacketed. The boolits built to fit the AR mag and seat at the base of the neck don't have enough weight for the increased bore size and less resistance to efficiently burn the powders normally associated with this cartridge. To get them to burn right....... try magnum small rifle primers and see the difference. A 77 gr. BRP boolit user that has a 9 twist and gets sub MOA groups at around 2400 fps....................:bigsmyl2:

[felix]

In addendum to what Maven says, you might get better control of the acceleration pattern with duplex loads. If the gun has a strong firing pin imprint on rifle primers, I would start with the Federal 150 pistol primer when dealing with boolit loads. Then use an appropriate faster powder than the 860s to alter the ignition characteristics of that primer. Adjust the kicker powder by speed and amount to make the 860s produce 2400 fps with the 14 twister. Select a kicker powder with the same dimensions as the 860s or close to it. The 335s come to mind, as well as AA9 for a faster jump start than the 335s. The 860s typically do not like to be compressed, so it's best to compress the whole shootin' match with plastic balls just enough to keep everything in place. If a faster jump looks inviting, use a flake pistol powder rather than one with a tube configuration. Helps consistency down in that important area. ... felix

[madsenshooter]

Several in my little group have the 6x45 in the AR....... wonderfull shooters with jacketed. The boolits built to fit the AR mag and seat at the base of the neck don't have enough weight for the increased bore size and less resistance to efficiently burn the powders normally associated with this cartridge. To get them to burn right....... try magnum small rifle primers and see the difference. A 77 gr. BRP boolit user that has a 9 twist and gets sub MOA groups at around 2400 fps....................:bigsmyl2:

45 2.1, I've been talking with Joe, sharing my failures with the AR so far. He's going to send me some boolits, which I'll try but I think it's either just too fast a twist, or the 5R rifling form isn't exactly cast friendly. I even hardened the Eagan up over 30bhn to no avail, and I don't think Don Eagan made any boolits that didn't work. Though I suppose it possible I got a cherry that should have been in the scrap pile. Has a very small lube groove compared to what you designed. I'm using CCI #41 primers and have tried all the powders I have from Blue Dot to, yes, even 860.

Since I have everything I need, I'll be building the Krag anyway. I'm glad I didn't use the Obermeyer to do it.

[Doc Highwall]

My vote is also for a 1:14" twist. If you look in the third edition of Lyman's cast boolit book the 6mm PPC has a 1:14" and they have loads for SAECO #243 85 grain bullet at 2200 fps. I just ordered this mould in a four cavity for a 6mm BR with a 1:14" twist I just bought.

[45 2.1]

45 2.1, I've been talking with Joe, sharing my failures with the AR so far. He's going to send me some boolits, which I'll try but I think it's either just too fast a twist No, I don't believe it is considering what i've done with a 8 twist in the 5.56 or Joe's 7 twist in the same. Alloy, it's toughness and hardness makes all the difference here. Harder is not better in this case., or the 5R rifling form isn't exactly cast friendly Try much softer with very low antimony content and you'll do better. The 5R rifling will help with what your doing.. I even hardened the Eagan up over 30bhn to no avail You really are much too hard there., and I don't think Don Eagan made any boolits that didn't work. Though I suppose it possible I got a cherry that should have been in the scrap pile. Has a very small lube groove compared to what you designed. I'm using CCI #41 primers I haven't tried those, i'm useing CCI small rifle magnum. and have tried all the powders I have from Blue Dot to, yes, even 860.

[madsenshooter]

I've been the softer route too, that's where I started, I'm through with it. I'm went to the range today, 1600 is tops. 9 of 13 you could cover with a postage stamp, but the other 4 were out enough to spread the group to that same 1.4". Down another 50fps, and they might all be covered by a postage stamp, but it isn't going any faster with better accuracy, no way, no how. I'm going to build my Krag and I'm going with a slower twist. All the guys above, along with last year's Cast Bullet Association, benchrest national champion, aren't full of it and they've all said slower is better. I've had enough of doing it the hard way, but glad it works for some people. This little experiment will be shooting jacketed from now on, unless I decide to shoot some suitably sized vermin at the speed it will accurately shoot a cast boolit.

[Doc Highwall]

madsenshooter, are you sure that your bench technique did not cause the fliers?
I did some studying last year over on the 6mmbr.com web site on anything I could read about the causes of fliers like too hard of a front bag or one that is too tight causing them, even resting the forend in the wrong place.
The rear bag can cause errors because the ears have too much sand in the making them live causing vertical or the rear bag not being aligned with the front rest causing horizontal fliers among other things. It helped me out a lot.

[madsenshooter]

Sure Doc, we're not all perfect, so I might take the blame for some of those, or a fractional part of that 1" out. But 8 of those 9 you can cover with a postage stamp are touching with the 9th less than 1/4" away, so my technique must be pretty good, perhaps not the same on each shot though. Sure wasn't recoil shyness, at 1600fps there isn't a whole lot. Down .2gr more on the powder, should give me 1550 or so. I don't care how fast it's going as long as it hits where I'm aiming. Minute of squirrel noggin would suit me. Let's hope the Krag is less of a problem child. The Eagan may not even fit it, seems to have been made for an Obermeyer, they're the only barrel I know of with a .233 bore. ktw has to make the nose bigger on his.

[Doc Highwall]

Last year I was shooting my Remington 40X with the Kevlar stock and if I rested it in the wrong place on the forend it would jump up off the rest so I did a series of test to see where was the best place to rest it.
I ended up making a stop for my front rest to have repeatability.

[madsenshooter]

I must be pretty good at trigger control. I've shot one inch groups with my Krag, using the banister of my porch as a rest with me crouched behind it. Only one out of the group that day, and I called it. I felt the rifle slip just a bit as the striker fell.

[Doc Highwall]

I am looking to eliminate fliers for bench-rest shooting and rereading and looking for anything that might help make the groups smaller.
Here are two groups, one shot at 100 yards and one shot at 300 yards with my 40X in 308 Win. I am going to try my 40X in 6mm BR for even less recoil and it has a 2oz trigger so maybe I will get lucky and shoot some good groups with it.

[firefly1957]

What are you using it for? target only 1-14 is for lighter bullets 1-10 or even 1-9 would be for heavier bullets. With Boolits you do have a velocity limit with that much case capacity you can get more energy only by going to heavier bullets. If you are hunting you may need extra bullet weight but paper and plinking a light bullet should fill your needs well. Meaning that 1-14 twist would be fine.

[madsenshooter]

I am looking to eliminate fliers for bench-rest shooting and rereading and looking for anything that might help make the groups smaller.
Here are two groups, one shot at 100 yards and one shot at 300 yards with my 40X in 308 Win. I am going to try my 40X in 6mm BR for even less recoil and it has a 2oz trigger so maybe I will get lucky and shoot some good groups with it.

So where's the fliers? Oh ok, I see what you're referring to. Looks as good as the guys at the CBA benchrest club I shoot at do, and one of them is the national champ! These little boolits are cantankerous, that much I know, be prepared to be effected by the wind a lot more, unless you can get higher velocity than what the CBA shooters are getting with their 30BRs shooting 220gr boolits. They tell me they're shooting around 2000fps.

[Doc Highwall]

You should have seen the vertical stringing before I did testing for where to rest the forend on the front rest.

[madsenshooter]

I could see that being a problem with my Krag, but not with my heavy barreled AR that has a full float tube. A straight line stock like an AR has helps eliminate the vertical stuff too. With my Krag faster bullets hit lower because of lower barrel dwell time during recoil. Recoil initiated even before the bullet leaves the muzzle. But with the AR, faster hits higher it seems.