80 grain SMK in .224 changed?

[Texas10]

Was browsing the Berger Twist Rate calculator to find a bullet that would perhaps shoot better from my 8 twist 22-250 than the 80 gr A-Max I've been using. The A-Max is not well stabilized at the velocities and altitude I'm shooting, but does seem to shoot well with the exception of very annoying and frequent flyers. Not sure if it's me, the gun, or the bullet but decided to try the 80 grain Sierra Match King based upon it's predicted stability.

When I opened up the new box and measured a few, they were all about .040 longer than the JBM or Litz data base listed.

They also seem to be factory "pointed", as the hollow point tip is for the most part completely closed.

Listed length is 1.066, but my box varies from 1.094 to 1.109

Based upon these measurements, the local range temperature will have to be 95 or higher to attain a twist rate stability index of 1.5 or greater, and although better than the 80 grain A-Max, is not what I thought I was bargaining for.

Any similar observations or comments from those who have shot, or are shooting the 80 SMK?

[sharpshooter]

It's not uncommon for the lengths to vary about .015", but the ogive lengths run very consistent. I've never had any stabilization problems with a 1-8 twist in any temperature or altitude. I've run them anywhere between 3000 and 3600+ fps.
The batch I have is probably 10-12 years old, and the lengths run 1.070-1.080". I had the same trouble with 80 gr A-Max's, unexplained flyers, but the 75 A-Max seemed to be alright. I've also shot 80 Bergers, which shot just as good as the SMK, but since it was a wash, the SMK's were cheaper.
80 gr JLK's had a small edge on the other 2, but it took about .3 grs more powder to get the same speed. I attributed that to the difference in bearing surface.

I wouldn't put too much faith in those twist calculators, as every barrel is different and there are too many other factors to figure into a real world scenario. The best way is to shoot them and find out first hand.
I remember when Sierra came out with the 90 gr SMK's, they recommended a 1-6.5 twist. I got about 35 bullets from Carrol Pilant, plant manager, from the initial pilot run. Of coarse I shot them from a 8" twist just to see if they would stabilize. They stabilized from my starting load @ 3000 fps, and shot good all the way up to 3550 fps. Once I figured out the powder that gave the best velocity, the first group on paper was less than 1" @ 300 yds. I was impressed, but also out of bullets at this point. So I got a 500 ct box and started over. That's when I noticed that something had changed. The accuracy was not that good, and in hot weather, some bullets never made the target.
Upon more investigation, I found out that the pilot run was made from different jackets than the first production run. Some were complaining about losing bullets @ 2550 fps with a 1-6.5 twist. After I spoke with Rich Macholts, we determined one of the common denominators was a 3 groove barrel coupled with that 6.5 twist. He said they never actually tried that combo.

[Texas10]

I agree, the best thing to do is shoot them, so yesterday I loaded up for an OCW test starting at 35.0 grains of IMR 4451 and working up to 38 grains in half grain increments, 3 rounds each, bullets seated .015 short of the lands, plus an additional 7 rounds for sighting and chronograph, loaded at the middle charge wt. of 36.5 grains.

Shooting at 200 yds. in fairly windy conditions, sighter rounds 1 & 2 formed a perfect figure 8 measuring .036 MOA, so I mounted the MagnetoSpeed to the barrel and shot 5 more. Average speed 3250 fps, SD 16, ES 39

I then began shooting 3 rounds each of the 7 different loads, at separate targets, starting at the lower end and progressing towards max load. When I shot the three rounds loaded with 36.5 grains, total groups size was .224 moa. most of which was vertical. With the wind blowing from 210 relative, that strikes me as about as good as I can expect. 3 shots is not much of a test, actually 2 in one target and 3 in another, but I see this as worth further testing.

I paid just under $125 for 500 rounds of 80 grain SMK's from Grafs, including shipping, or about 25 cents each, not much more than the 22 cent a pop Hornaday that don't shoot quite as well out of MY barrel. YMMV.

For those who might care; 28 inch X-Caiber, match grade, 8 twist, 22-250 barrel purchased off this site, 80 grain Sierra Match King, IMR 4451, CCI200 primer, Lapua brass, 8th cycle, neck sized only.