While everything I've fed this thing shoots .5" or better @ 100 yds, 85 gr of Retumbo under the 240 SMK loaded .010" off the lands averages .25". It's not a hot load by any means. I'm only getting 2850 fps but I can shoot the wings off a gnat @ 100yds w/it!!
Heh, I guess that's one disadvantage to longer barrels. [img]/ubbthreads/images/graemlins/wink.gif[/img] With this round, the longer the better ballistically until you're well beyond the 30" mark I believe. Of course then you have to live with it. Where you draw the line is up to you and your needs. Don't believe those who say you need a super long barrel to justify the RUM or all you're doing is wasting powder. A 26" RUM still blows a 26" Win Mag out of the water by a huge margin (I've actually had both in the same 26" barrel). Of course longer is better for ballistics so get as long as you think you can live with but don't feel bad if you decide not to go super long (especially for a carry rifle).
I went 27" with the new barrel. That's all I want to have to deal with in and out of scabbards, vehicles, crawling through thick brush, etc. My goals for handiness as well as weight (#5 fluted) might be much different than yours of course.
I'd say 1:10 is obviously the most versitile twist for this round. Many shoot fairly light bullets very well and while not optimum for 240's, mine did very well with them. And it's very good for the range of weights people are mentioning.
I got a 1:9. One of these days, Richard is going to start kicking out some seriously big heavy nasties in 30 cal. Once he does, I believe they will finally offer enough of a BC gain over the various 210's to provide a significant advantage at extreme ranges (which I don't believe the 240 SMK does). Now when this happens, you just might really want to try them--and be kicking yourself for getting a 1:10. If that's something you don't think you'd ever be interested in, nevermind then--go 1:10. If it does interest you some, you might contemplate a 1:9 for a while before you order the barrel.
The other thing I think that pushed me to 1:9 is that with the vastly improve quality (better concentricity, balance, etc) of today's bullets you aren't shooting yourself in the foot by spinning a bullet a little faster than it needs to be spun accuracy-wise the way you were in years past. I fully expect it to shoot 200's and even 180's pretty darn well (but obviously my focus is on heavier bullets). And you ensure you're getting all the available BC from your bullets (I don't think the 1:10 does that with the 240's). Spinning a bullet too fast won't hurt BC unless you ridiculously overdo it. But marginally stabilizing it will.
I also believe there are some terminal performance advantages to be had, especially with long bullets on the edge of expanding/not expanding.
Anyway, just some points for you to ponder before you lay down the cash. I know there are probably more than a few big-cased 7mm shooters who, upon seeing pictures of those big long beautiful super high BC 200 Wildcats, wish they had enough twist to use them.
Get a 31 inch barrel. When its worn out, cut off 3 inches from its hind end, rechamber and thread that same hind end and you've got a virtual brand new 28-inch barrel for only the cost of those two tasks.
Barrel length typically has little to do with accuracy but will effect muzzle velocity. I doubt you would notice any significant change with a 3-inch difference in length from 31 back to 28 inches.
BJ has had great luck with the 240gr SMK in his rum with a 1-10 twist. Shoots .5 or better everytime. Only problem with it is that once you get to 1600yds the bullet has heart attack. I believe that BJ is only marginally stabilizing this bullet and once it hits the subsonic transition it destabilizes.
It is a amazing thing to see, the gun will shot moa to 1/2 moa out to 1500yds and then within 100yds it will group in a 10ft circle.
It think a 1-9 twist would be ideal. BJ's bbl is also a tighter bore than normal. I dont fully understand this so maybe he can ellaborate more.
I also hear that Hornady is coming out with something pretty sweet here soon. Will have to get back with you all on it when I get some more info
take it easy
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I've got it at 28". It is a Lilja 1 in 10 with a brake.
I went over today and looked at it again. It amazes me watching a piece of steel become a working piece of art! He is going to start fluting monday. the action is square. The bolt face and lugs are tight. As soon as it is finished, I will ship it to Black Ice for a coat of teflon.