I have a factory 7mm stw 24" (I wish it was 26") barrel with 1-9.5 twist. My question is what is the heaviest bullet this will stabilize?
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I have a factory 7mm stw 24" (I wish it was 26") barrel with 1-9.5 twist. My question is what is the heaviest bullet this will stabilize?
Have built two of these. In testing and load development, the Berger 180g Hunting/VLD was stable in that twist rate. Berger recommends a 1-9 twist rate for that bullet. At .659 BC and moving at 2800fps the Berger delivers very impressive ballistics at 1000. The first STW I had was from Devin Sinner and was a Savage 114 Ultra with a magnum contour 24" barrel. Shot extremely well with the Berger. The others used barrels from the Savage custom shop and were 26" varmint contour 1-9 twist. The STW excels over the 7MM Magnum with heavier bullet weights. IMHO it is easier to obtain great accuracy out of the STW than the 7MM Mag. Sure does burn a bunch of powder!
I thought I read somewhere that you sacrifice some velocity with a faster twist. Is this true? At present I am working a 175 BTSP load but am thinking of going heavier, which brings the questions; should I get a 26" barrel and what twist is optimal for hunting bullets 168-175gr 1-9 or 1-9.5 ?
You give up some velocity in a faster twist but I doubt between a 1-9 and 1-9.5 there is much difference.
The best way to find out if the faster twist will stabilize a given bullet is to shoot it at 300 yards or more...more is better. Also the brand of bullet will make a difference. As far as going from a 24 to 26 inch
it depends on whether you want or need the extra velocity. Personally I don't think the 7MM Magnum or STW should come in less than 26. Why pay for the extra boom if you don't get more zoom. (Damm that was bad)
I agree you won't see any difference. The downside with a too fast twist is with "over stabilizing" light bullets so, unless you expect to use varmint weight bullets in your STW, the 9 or 9.5" twist will be fine.Quote:
Originally Posted by wbm
In fact, most .243 Win barrels have a 10" or 9.5" twist which will stabilize 100 to 105 grain bullets but seem to do fine with even 55 gr bullets so overstabilization isn't that much of an issue.
Yes and no on the velocity. If you are shooting 140 grn bullets through a 1:12 and a 1:9 then yep the faster twist will be a little slower. On the other hand a 1:12 won't stabilize the heavy bullets you want to use, so velocity loss is not an issue.Quote:
Originally Posted by 78stw
I (personal preference) do think it should be a 26" barrel. Why have a 7mm Mag recoil and noise and only get .280 Rem performance?
Berger bullets are usually very long and they advise 1:10 for the 162s and 1:9 for their 180 VLDs. Your 1:9.5 should stabilize most, if not all, 175s and possibly even the Berger 180s.
You can't overstabilize a bullet. It is either stable or not. If you use too thin of jackets on really light for caliber and spin them like crazy then they can come apart but that is not a every day thing. I had to build a 22-243 Middlestead and push some Blitzkings like crazy to see it happen. You are not going to see it in a 7MM caliber easily.