6mm re-barrel brand,length and barrel twist

[mcseal2]

I have a custom rifle in 243 win built on a Ruger M77 short action with a thumbhole stock. I am considering rebarreling the rifle to a 6mm rem set up for 105gr Berger or A-max bullets. I am thinking of going with a 23" Mcgowan #4 fluted barrel with a 1 in 8 twist and having it cryoaccurized. I want to be able to get 3000fps with these bullets to shoot long range varmints and possibly antelope.

Any recommendations if I'm on the right track as to twist, barrel length, or barrel brand? I will be very particular about the accuracy of this rifle.

Also will the short action Ruger be able to handle the long bullets with adequate seating depth? I've shot 95gr Bergers in the 243 and had no trouble with adequate magazine length.

Thanks for your advice, Heath

 

[Gene]

If you want to shoot 105 gr. bullets in an 8 twist, the first thing that comes to my mind would be the 6BR for which factory ammo is now available, or the 6mmXC, or any of the many other derivatives, which you can find here:

AccurateShooter.com 6mmBR.com -- Best Guide to Precision Shooting and Precision Rifle Accuracy

I don't know anything about the McGowen barrel, but you can't go wrong with a Shilen. Cost would be about the same. Tell your gunsmith what bullet you want to shoot and how deep you want to seat the bullets and he will be able to chamber it to fit your specs.

I have a custom rifle in 243 win built on a Ruger M77 short action with a thumbhole stock. I am considering rebarreling the rifle to a 6mm rem set up for 105gr Berger or A-max bullets. I am thinking of going with a 23" Mcgowan #4 fluted barrel with a 1 in 8 twist and having it cryoaccurized. I want to be able to get 3000fps with these bullets to shoot long range varmints and possibly antelope.

Any recommendations if I'm on the right track as to twist, barrel length, or barrel brand? I will be very particular about the accuracy of this rifle.

Also will the short action Ruger be able to handle the long bullets with adequate seating depth? I've shot 95gr Bergers in the 243 and had no trouble with adequate magazine length.

Thanks for your advice, Heath

 

[shortgrass]

Main issue will be the magazine. You have the rifle , so you can measure that mag length yourself. With a ruler is good enough as if you fill a mag to max length it , most likely, won't feed. Why limit yourself to a 23" long barrel if you're looking for max velocities?

 

[Trickymissfit]

first I'd get a better barrel blank. I'd just order in a good Shilen or Pacnor and be done with that part. Secondly don't hooked into the 26" and longer tuning forks when using smaller capacity cases. A 6BR is just fine with a 22" or 23" barrel. Another one that fits right into your action length is the 6XC and of course the 6/250AI. The 6BR is the most efficent of the three, and will have a greater throat and barrel life. But they also have some feeding problems out of some rifles (can't say much about the Ruger). Now if you just gotta shoot those 105 grain bullets in any of these rounds your gonna want a 1:8 twist barrel. But if it were me I'd either go with a 6BRX or better yet a 6HLS.
gary

 

[Firecat]

I own a 6mm Rem and couldn't be more happy with it. However, If I were building a new .243 caliber I would also consider a 243 Ackley Improved. You can shoot the factory ammunition and then you will have fire formed cases to reload with. This has to be one of the best small bore options available in my humble opinion. Like I said. I do really enjoy my 6mm and you can find brass for it pretty easily. The choice is yours. I would check into the availability of brass and the reloading tooling to make it happen. the 6mm rem Ackley is a neat little cartridge also. Good Luck and have fun. Most of the bullet manufacturers will have a recommended twist rate for their bullets. If its not listed don't hesitate to call them. Also I would not recommend that you build a rifle to one specific bullet. If for some reason you gun doesn't like it you are dead in the water. Just something to keep in mind.

 

[Outlaw6.0]

+1 for the 6mm ackley, I re-barreled my .243 to .243 ackley then to 6mm ackle & I would do it again without hesitation. I find myself shooting it more than my 6mm-284 while not quite as fast, it's every bit as accurate at the ranges i've played with.

 

[Trickymissfit]

I own a 6mm Rem and couldn't be more happy with it. However, If I were building a new .243 caliber I would also consider a 243 Ackley Improved. You can shoot the factory ammunition and then you will have fire formed cases to reload with. This has to be one of the best small bore options available in my humble opinion. Like I said. I do really enjoy my 6mm and you can find brass for it pretty easily. The choice is yours. I would check into the availability of brass and the reloading tooling to make it happen. the 6mm rem Ackley is a neat little cartridge also. Good Luck and have fun. Most of the bullet manufacturers will have a recommended twist rate for their bullets. If its not listed don't hesitate to call them. Also I would not recommend that you build a rifle to one specific bullet. If for some reason you gun doesn't like it you are dead in the water. Just something to keep in mind.

the .243 has a poor neck design, and this causes problems with very light bullets as well as very long bullets. As long as you stay in the 80 to 95 grain range your fine. A 6mm Ackley will also allow you to use factory ammo. You can also ream the chamber a little short (with a 6mm Rem. reamer), and get several wildcats that really shoot well. I like the 6mm HLS, and the 6/250AI, but the HLS is the better of the two.

If you going to shoot big long VLD's, then you need at least a 1:8 twist barrel with a one & one half degree throat that's very short. I shoot VLD's and Amax bullets out of my 6/250ai at about 3000 fps for .270" groups
gary

 

[Trickymissfit]

+1 for the 6mm ackley, I re-barreled my .243 to .243 ackley then to 6mm ackle & I would do it again without hesitation. I find myself shooting it more than my 6mm-284 while not quite as fast, it's every bit as accurate at the ranges i've played with.

I have some buddies that have been doing 6/.284's for about 12 years now, and the original rifles in 6/.284 went thru a barrel about every 800 rounds or less. Then somebody had one reamed short (.100"), but kept the case pretty close to the same length. Never lost much if any velocity, but they were seeing close to a 1200 round shot count with the barrels still shooting well. Later another builds a 6/.284 that's .150" short, and says he might have loast 50 to 75 fps from the full length .284 case. Finds the groups to be tighter. These guys may have found a near perfect combo
gary

 

[mcseal2]

My thinking of the 6mm is that it would be a good balance of velocity and barrel life. I already have the short action Ruger with a Timney trigger installed and good stock, so I wanted to build on it. What wildcats would give me 3000fps with a 105gr bullet?

The 23" barrel is just to keep the length down for hunting and calling predators. 24" would be ok, but I'd hate to go longer.

I wanted to shoot the heavy bullets because high winds are very common where I live. Today is 30mph gusts, and I want the high BC.

I'll measure my magazine length and post it.

 

[6ppcfan]

Feeding problems with the BR and length to get in magazine . 1 in 8 is good for that 103-108 VLD's i have not tried the 115's. I choose the 6 x 47 Lapua very very accurate . I believe you can push the Lapua close to the 243 A speeds . Barrel length on the Lapua is 24. for sale too i guarantee 1/2" or under at 100 meter under right conditions.

 

[shortgrass]

A quick look at my Sierra load data says the 6mm Ackley, I didn't check the others, as your OP stated 6mm Rem. I'm a big fan. Have built quit a few over the past few years, their owners a very satified. Most run 107MK at 2950-3000. They shoot 6mm Rem almost as good as a fire formed re-load. Given good care, I'm seeing 1300-1400+ rounds, and then , not so bad they can't be 'set back' and re-chambered.. Start at 25" and work your way back with barrel length. It's always windy where I live, too. The 6 Rem. or the Ackley make good coyote 'medicine' with those heavy for caliber bullets. The .243 A.I. ranks right up there, too. It'll work in that S.A. mag. with a little 'fidiling'and maybe a Wyatts mag . Don't let the 'poor neck design' fool ya, the .243 A.I. has racked up some pretty good long range scores over the years.

 

[mcseal2]

I did some looking at my Sierra book also, the 6mm Ackley looks like it offers exactly what I've been looking for with the exception of fireforming cases which isn't to much of a step. I have a Wyatt magazine on my 264, and can see the advantage there. Thanks for the tip.

Anyone have any experience with how the 105 A-max will expand on a coyote size critter?

 

[ubettcha13]

Here's a great article for your quest from the 6mm br site. I feel your 23" barrel will have to be a hot load even with these wildcats. If you go to 25" you'd be better suited. Also consider having your firing pin bushed because to get there your pressures will be high might as well do it right.
Hot Rod Versions of the .243 Winchester — BR-K and Super X

Gunsmith Mike Sosenko and long-time 6mmBR.com supporter John Adams have been using a modified .243 Winchester case with great success in Varmint Silhouette matches at the Pala Range in Southern California. Officially called the "243 BR-K" (and informally dubbed the "6BR Long"), the wildcat is basically a .243 Winchester with less body taper and a 30-degree shoulder. The design essentially grafts a 6mmBR Norma "top end" to the .243 Winchester case. After fire-forming, Mike and John can reload this case using normal, unmodified 6BR neck-sizing and seater dies.
Compared to a .243 Winchester, the 243 BR-K's body length is about .006″ longer, and the shoulder is about .0055″ wider. The main difference is the shoulder angle (30° vs. 20°), and the location of the neck-shoulder junction ("NSJ"). Based on reamer prints, the base to NSJ dimension is 1.718″ on the 6BR Long, compared to 1.804″ for the .243 Winchester. Neck length is a bit shorter because "the neck shrinks a little when the shoulder blows out" according to Sosenko. We've provided a mock-up diagram of the 243 BR-K, but you should check with Dave Kiff of Pacific Tool & Gauge for exact dimensions. Dave created the reamers for both the 6mm and 22-caliber versions of this wildcat. Ask for the "22 BR-K" or "243 BR-K" reamer designs.

Wicked Velocity with Stable Brass
The main advantage of the 243 BR-K is serious velocity in a case that is very stable. Mike's favorite load is the 95gr Berger VLD pushed by Reloader 22. With a stout load of RL22 and Federal 210m Primers, Sosenko is getting 3450 fps with the 95-grainer, with no bullet blow-ups. This is with a 1:8.5″ twist Broughton 5R barrel finished at 28.5″. The cases are holding up very well. Mike has a half-dozen loads on his brass and he hasn't had to full-length size yet. Mike runs a .262″ tight neck, but there is also a no-turn version of the case (see illustration). Accuracy is excellent. Mike says the round delivers repeatable 1/4 MOA groups at 100 yards in testing. He has also experimented with N160, but, thus far, Reloader 22 has delivered smaller groups with better ES and SD.
VIEW 243 BR-K REAMER PRINT (No-Turn Neck)
John Adams shoots a no-turn (.274″) neck 243 BR-K with 105gr Berger VLDs. He's getting about 3230 fps using Reloader 22. John says he can push the 105s faster, but 3220-3240 fps "seems to be the sweet spot." John notes that "after about five reloadings on a case, it gets a little tight". John then full-length sizes with a custom Hornady FL bushing die. "The Hornady custom shop dies work great" according to John. Adams also shoots a version of this wildcat necked down to 22-caliber. It has demonstrated outstanding velocity and good accuracy in initial testing with a 9-twist barrel. Using the 80gr Amax bullets, John is getting 3570+ fps speeds. John feels that his 22 BR-K needs some more development work. "The 243 BR-K is proven. We know what works. With the 22 I want to try different seating depths, experiment with a few different bullets, and fine-tune the velocity."
Whitley's 6mm Super X
Robert Whitley shoots a variant of the .243 Winchester he calls the 6mm Super X. This features a 30° shoulder, and slightly less body taper. He gains a little case capacity over the standard .243 Win, and he says the cartridge is extremely accurate with both 105-108 grain pills and the heavier 115s: "Here's a picture of a .243 Win (left), a 6mm Super X (center), and a 6XC (right). All I can say is the 6mm Super X has been good to me and I have shot many a clean in 600-yard High Power matches with it with either DTAC 115s or Berger 115s."

While Mike Sosenko and John Adams use their BR-Ks to push 95s and 105s at high velocities, Robert takes a different approach with his Super X. He shoots the high-BC 115s and keeps velocities under 3000 fps. A long-range High Power shooter, Robert demands consistency during long shot strings. That means backing off from max attainable speeds, at least with the 115s. Robert writes:
"You can get 3050 fps with H4831SC and the 115s with no problem, I did it in testing multiple times, but to me that also does not mean anything because I shoot loads where they are the most consistent and accurate over a 22+ shot string. I have never found that any of the 6mm cartridges I have used with 115s will stay consistent, tight and accurate the whole way at 3050 fps for 22+ shots straight. I have tried 115s in the .243 Win, the 6CM, the 6mm Super X, the 6XC, the 6-6.5 x 47 Lapua and none of them ever stayed consistent and tight for 22 shots straight with the 115s at that speed. Most of the time with all the 6mm cartridges, if you get the 115s much over 2975 fps, they won't hold tight for 22+ shots straight. Now if you're a bench rest shooter and you only need to do a few sighters then 5 or 10 shots for record, you can run 3050 fps or more and the groups will likely hold tight during your string, but not when you need to go 22+ shots straight with no break. I have shot many different 6mm cartridges and done a lot of testing with many different powders, moly and non-moly bullets. I don't find the 'consistent accuracy' (for 22+ shots straight) at those higher velocities."