Cimarron2011 said:
Laurie,
Thanks for the detail on the 175 Tactical. Will the tactical bullet still work well at the higher MV's that can be attained in a 2.800 COAL from some of the newer high energy powders like Reloader 17 and CFE 223?
How will it perform in a barrel with a faster twist...say 1:10?
Ah Ha! Now you're asking! I've wondered the same thing myself. From what Bryan L. has released, the key thing appears to be the rate of spin given to it by the 1-11.25" twist rate allied to a c. 2,600 fps MV. That works out at 166,400 rpm give or take a few tens. The MVs to give that rotational rate run at a low 2,310 fps in a 1-10" rate, and 2,775 fps in 1-12".
If I read the way this bullet works right ...... a BIG IF ..... it would still work as designed, but the entry to transonic / subsonic flight levels would occur at different distances from the design one. That is of course to give the soldier with a 20-24" barrel rifle and a bit less than full-pressure round a truly 900-1,000yd capable cartridge. (Which the US Army claims the M118LR is, but USMC snipers apparently say isn't!)
Assuming our M118LR has a 2,600 fps MV (I think it's nominally a little less), it'll start to go transonic on the firer's side of the 800yd marker and passes through the sound barrier at 960yd or thereabouts when loaded with its current bullet, the 175gn Sierra MK and average G7 BC of 0.243.
The OTM Tactical at 2,600 fps is still above the nasties at 800 and is still supersonic, just, at 1,000yd. If it works as designed, there is of course a much better chance of that prediction actually happening as it won't start to slow more than the average BC says it will during the transonic phase. It's predicted to go through the sound barrier at 1,030 yd or thereabouts under standard ballistic air conditions.
Run it in your 1-10" twist barrel with MV reduced to 2,310 fps to keep the rotational speed right, and the transonic / subsonic boundaries move back significantly towards the muzzle - about 675 and 850 yd respectively, but if it does its work well it'll remain truly stable and hence continue to group well. (I think !!)
Run it in the 1-12" barrel at 2,775 fps to get us the same rotational speed from the other end so to speak and it moves back from the firer, 925 and 1,125 yd or so. If this all works in this way (another IF again that only Bryan Litz could comment on) that could be quite attractive to the 1-12" twist rate user that needs magazine COALs for whatever reason, but has a barrel length and can run pressures that gets his bullet up there.
There is quite a difference in long-range wind effect between these two extremes - 2-MOA at 1,000 between 2,310 and 2,775 fps MV in the classic 10 mph cross-wind, so they're not comparable there either.
However, this is all of interest to the professional user / tactical rifle competitor rather than the F/TR shooter say. I'd rather use the 185gn BTLR, or depending on just how well it performs the 168 (or 185 Hybrid if 1-12" twist stabilises it) in single-shot mode in a barrel whose throat allows a good OAL. I understand that Berger Bullets didn't intend to release the OTM Tactical originally to the handloading market, but were persuaded due to the demand that arose after word got out.
Ironically, I don't believe that providing a new bullet that allows a truly 1,000yd capable .308 Win sniper cartridge really counts for much in the military / FBI HRT roles in a practical sense. I don't speak from personal experience but I've read several evaluations over the years by those who do have it and they say that one very rarely gets a clear sight-line to a target that is truly that far away (as opposed to 1,000 'short steps' in which what is still a very long shot becomes a 'thousand-yard hit'). Unless you have perfect range-finding and amazingly good / very lucky wind-reading, a .308W hit on a man-size target is a real achievement too at that range when done without the benefits of sighting shots, wind flags etc, etc. (In that scenario a bullet which remains supersonic at 950yd plus might actually be a DISADVANTAGE! That is, a close miss with a subsonic bullet might not cause the target to take cover, but a supersonic 'crack' surely will unless he's drunk or very dozy.)
The people I see as benefiting are those with custom-built sniper/tactical rigs who want to play with the F/TR guys at long range. It could make rifles like the out of the box Remy PSS and their 26" 1-12" barrels a lot more attractive in club level shoots at beyond 800yd.
I've just picked a couple of hundred up from our importer from the first delivery to the UK. They are VERY expensive bullets - dearer than the BTLRs and Hybrids, and Bergers are very expensive bullets in the UK compared to those from Sierra and Hornady. I plan to give them a whirl in my 1-10" twist F/TR rifle at the low MV in due course and see how they group in a 900yd competition. If they hold elevation at this distance at such a low MV, they truly will be delivering on the promise!
Anyway, I have the nasty feeling that I've oversimplified this. If Bryan Litz does read this, he'll no doubt comment on the soundness of my reasoning, or otherwise and also maybe comment on how much latitude there is in variations from the 166,400 rpm rotational speed optimum before the long-range stability benefits start to degrade.
