I am putting the pieces togeter for another Martini cadet, this one in .218 Mashburn Bee. I plan to shoot bullets in the 45- to 55-grain weight range and assume the velocities will run in the 3,000 to 3,400 fps range out of a 26-inch barrel at moderate pressures. I am thinking that a rifling twist of around 1:12 would be about right, but am open to suggestions.

Dave

quote:

I am thinking that a rifling twist of around 1:12 would be about right,

The .222 Rem was 1-14" and no one ever complained about accuracy with that combination....

I'd say your dead on the money with the 1-12"

Either a 1/12" or 1/14" would be fine for those bullets.

You might get to 3,000 on a Martini action with 40's or 45's. 1 in 14 twist will do it for you.

my martini 218 mashburn is 14" and my load is 16.2 gr of 4227 and a 40 gr nosler bt. it is my most accurate martini

If you are planning on trying polymer tipped bullets up to 55 grains like the V-max, Blitzking, and Ballistic tip, go for the 1-12".

I've got a standard Bee with the original rf 16:1 barrel. It runs at about 3,100ft/sec with IMR4198, 45grain Sierra 'Hornet' bullets and a 26" barrel. Any more and the case heads start to separate - I'm getting 20 shots/case - very difficult brass to buy. I find that the shorter 50grain bullets shoot accurately at 100metres - under an inch for 5 shots. I tried the wonder child, Lil Gun, but it was not a happy combination - lower velocities and moves towards head separation vs. 4198. I had put aside a 12:1 barrel if the 16:1 did not work with 50 grain bullets. I'd go with the 12:1.

quote:

Originally posted by loud-n-boomer:
I am putting the pieces togeter for another Martini cadet, this one in .218 Mashburn Bee. I plan to shoot bullets in the 45- to 55-grain weight range and assume the velocities will run in the 3,000 to 3,400 fps range out of a 26-inch barrel at moderate pressures. I am thinking that a rifling twist of around 1:12 would be about right, but am open to suggestions.

Dave

I agree with 1/12"......

The 1:14 twist on my deuce will not stabilize 55 gr polymer tipped bullets-go with a 1:12 to be safe.

A 1-in-12" twist would be fine, as then you can use boattail 55 grainers.

I do believe your anticipated velocity for you cartridge/firearm combo is a bit optimistic.

As to twist rates, a 1:12 would be perfectly fine, but a 1:10 would be my choice. Within reason, you can't overstabilize a bullet, but you can certainly understabilize one. The 1:10 would also give you the option of reduced turkey-pelt loads with 55 grain bullets at modest velocities.

The only bullets showing objectionable performance to quicker twists (and at higher attendant velocities) are the old-style Hornady SXs, but the speed your Mashburn Bee will operate at shouldn't even cause problems with those projectiles.

I've had a couple 1:18 Contender barrels in .223, and both digested everything from stubby 40 grainers up through the streamlined 75 grain A-Max with aplomb, affording me excellent accuracy with virtually any bullet weight I fed them.

14" twist would be perfect. BTW; you can indeed "over stabilize" a bullet.

Larry Gibson

Larry Gibson wrote: "14" twist would be perfect. BTW; you can indeed "over stabilize" a bullet"

Larry-

The original post by Dave mentioned 45-55 grain bullets, and it is common knowledge that at Mashburn Bee speeds, some of the longer (boat-tailed) 55 grainers may not be fully stabilized with a 1:14 twist as you recommend.

As to "overstablizing," the 1:8 .223s I've had consistently printed tiny, bug-hole groups with even the stubby little 40 grain pills.

Not specific to the Bee, but in regard to twist and speed; i have seen jacket separations of 40,50 and 55 gr bullets in a 1:7 barrelled 220 Ackley Swift.
I would not call the effect over-stabilization as two projectiles come from the previous one!

In 1:9 and faster, the Hornady SX does come apart rather routinely. But beyond 3400 fps, it may come apart no matter what twist it is fired in.

Other lightly-constructed bullets may do the same in the 1:7 you mention, particularly at Swift speeds. Some bullets, such as the aforementioned SX and the medium-velocity Sierra blitz, have velocity guideline restrictions for good reason.

I've built up three .218 Mashburns over the years. Have always done 14" twist barrels. 40gr through 55gr bullets all shot well. It could well be the plastic tipped 55gr bullets may be too long. I suppose 12" twist could be better for them.

quote:

Originally posted by Bobby Tomek:
Larry-

The original post by Dave mentioned 45-55 grain bullets, and it is common knowledge that at Mashburn Bee speeds, some of the longer (boat-tailed) 55 grainers may not be fully stabilized with a 1:14 twist as you recommend.

As to "overstablizing," the 1:8 .223s I've had consistently printed tiny, bug-hole groups with even the stubby little 40 grain pills.

Bobby Tomek

The quoted velocities were; "the velocities will run in the 3,000 to 3,400 fps range out of a 26-inch barrel at moderate pressures"

The 14" twist will handle those weight bullets at those velocities quite nicely. After all the .222 does with the same bullets at the same velocities, even the BT 55 gr bullets. However if in sub freezing temperatures the longer BT'd 55 gr bullets at 3000 fps might not stabilize (ala the 5.56 NATO when first adopted with 14' twist ARs shooting M193 ammo)

"As to "overstablizing," the 1:8 .223s I've had consistently printed tiny, bug-hole groups with even the stubby little 40 grain pills." Bet you haven't with the thin skinned varmint type bullets such as SXs or Blitz's. Yes you can indeed shoot some nice groups with light weight bullets at 100 yards when those bullets are intended to withstand the stress of much higher velocities. However those lighter weight bullets at longer range from your faster twist will not be as accurate. Overstabilization does not mean inaccuracy. What it means is the radial accelleration from the intended flight path is greater at longer ranges for the faster twists when light for caliber/twist bullets are used.

Larry Gibson

PS; I see in later posts you are aware of the bullets coming apart. They spin apart based on RPM not just velocity alone. Both velocity and twist (rate of spin) are part of the equation. This is why your 8" twist will probably spin the SXs and Blitz bullets apart at a much lower velocity. They should do very well in a 14" twist .218 Mashburn at 2400-3500 fps without spinning apart around 30-40 yards from the muzzle as they will with a 8" twist at that velocity.

Larry Gibson wrote:

quote:

However those lighter weight bullets at longer range from your faster twist will not be as accurate.

Larry, in this instance, you are indeed off base. In my custom barrels, most of my load development work is done at 300 yards and not at the customary 100. The longer range quickly separates the wheat from the chaffe, amd the 40 grainers from the 1:8s had no problems at extended ranges.

Also, if your assessment held water, my 1:8 6.5 Bullberry Imp (26" Contender barrel by MGM) wouldn't do well with the stubby 85 grain Sierra HPs.

But that bullet is amazingly accurate at any range I've used it at.

If you don't believe me, you are welcome on my range at any time to witness how these barrels with faster twists do at any range you want to try them at.