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Posted: 9/11/2008 1:39:35 PM EDT
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I have a Savage 10 FP and am undecided on whether I should use 150 SMK's or 168's the barrel has a 1 and 10 twist, I have heard that the twist rate will shoot the heavier bullet better ? also does a BTHP really out perform a FMJ BT I have been using H3037's from Wideners and have not had the best accuracy, I currently am using that bullet along with a Fed 210, 43.8 IMR 4895 and a OAL 2.770" Thanks |
I don't have a bolt gun so, FWIW........... With my Match M1A......I've found that the 168 gr. BTHP to be way better than the average military 150 gr. FMJ bullets. Note that I didn't say 150 SMK's. Quality of the bullets have a lot to say about your group size. Though, I'll note that Match Bullets are usually BTHPs and not FMJs. You figure, maybe there is something to that? Also, a BTHP is more difficult to make and their price reflects it. Every rifle is a world onto itself. You need to test them with YOUR rifle. Aloha, Mark |
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For a bolt action.......the choices for a powder is almost endless. Gas guns on the other hand, are picky in comparison. Again, each individual's rifle is a world onto itself, as to what it likes. Not to mention, the world of variables that exists with a load. Buy a single pound of powder and do some testing. Then, IF you like it........buy the 8 lb. jug. Aloha, Mark |
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Back to the twist rate........... Story time: The standard M14 in 7.62 NATO used a 1/12 twist rate and standard ball ammo was using 147-150 gr. bullets. The M1 Garand used a 1/10 twist. OK......so, then I remember reading an article that said that the heavier bullets liked the faster twist. I figured that in a rifle match I'd be needing at least a 168 gr. bullet out of my M1A. I combined that thought with the "talk" from other competitors using both the M1 Garand and M1A. Most of them had a 1/10 twist. Some were using a 1/11 twist compromise. Back then, .30 caliber Service Match Rifles were cool (to me anyway). And the ammo was issued on the line, M118 (173 gr.) or M852 (168 gr.) for certain competitions. Yup, FREE AMMO and I got to keep the brass. Anyway, I ended up picking a 1/10 twist barrel for my Match M1A and shooting 168 gr. BTHP bullets. I figure, that there isn't a particular twist rate that is excellent for every bullet weight. Perhaps, it's more like there is a "range." So, pick the twist rate that'll match the range of bullet weights that you plan on using the most (keeping the purpose in mind). For instance: I'd doubt that a serious varmint shooter with a bolt action in .223 Rem. would be picking a 1/7 twist for use w/ 35-40 gr. bullets. Aloha, Mark PS........I figure with a 150 gr. or 168 gr. bullet........you're still in that range with the 1/10 twist. |
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I guess there is a certain amount of experimentation that goes with reloading, I need to drill that into my small brain Thanks for the info, I guess I will try the following 150 and 168 SMK's RE-15, Viht N140 and IMR 4895 WLR primers OAL 2.775-2.800" And the quest begins Thanks Again 
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You got me thinking (dangerous) that somewhere out there .........there must be a recommended list of what barrel twist is optimum for what gr. bullets weights. I found this...........
Taken From……… www.eabco.com/TwistRate.htm Also, checkout "Greenhill Formula." YMWV. Aloha, Mark |
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If I figured out this right ( don't have a windows PC ) I am off on the twist rate for my Savage 10 (1 in 10" twist) The Greenhill Formula says 150xD2/L 150x (.308x.308) /Length 150x.094864/1.124 = 12.65 ( This is on the H3037 I have been using ) I have seen some SMK's and they look longer than what I currently use so I can assume until I measure they were designed for a 1 in 10 twist, I looked for the length on the 150's and 168's but could not find the info I also found this on twist rates: .308 0.695 to 0.729 1 in 20 0.730 to 0.769 1 in 19 0.780 to 0.813 1 in 18 0.814 to 0.862 1 in 17 0.863 to 0.918 1 in 16 0.919 to 0.981 1 in 15 0.982 to 1.054 1 in 14 1.055 to 1.138 1 in 13 (This is where the Hornady's fall I currently use) 1.139 to 1.237 1 in 12 1.238 to 1.355 1 in 11 1.356 to 1.497 1 in 10 ( This is where I need to be) 1.498 to 1.674 1 in 9 1.675 to 1.897 1 in 8 1.898 to 2.189 1 in 7 2.190 to 2.587 1 in 6 |
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My LTR has a 1-12" twist rate. It loves BH 175gr ammo. It loves a 175 SMK on top of 45 grains of RE-15 in a Winchester case primed by FC or CCI primers, 2.810" OAL. (too hot for non-Winchester brass) 1-12" twist is great for bullets up to 180 grains. 1-10" handles up to 210 grain bullets. 1-8" handles up to 240 grain bullets. Go with a 1-12". The faster twists will cost you some velocity and increase your pressures. Since the 308 is marginal at 1000 yards, you need all the BC and velocity you can get. |
Taken from......... www.6mmbr.com/308Win.html And you might want to see the chart from Lilja Barrels. www.riflebarrels.com/products/caliber_twist_rates.htm There is a range of bullet weights that is usable with differing twists. So, don't loose too much sleep over the twist question. Aloha, Mark |
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The problem with too fast a twist is the BC will be much less at longer ranges because the bullet remains nose-up in attitude, Accuracy? All depends on the quality of the bullet. My .308 has a 1:10". Cannot tell the difference in accuracy with 155, 168 and 190 Matchkings. |
| Well I would hope just by switching from this to either this or this would help, but I guess it all depends on the shooter, also is it okay to develope a load off the bench, I mean by shooting prone off of a bipod with no rear support, or should the load be developed with the rifle all locked up on the bench ? |
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The Greenhill formula is not sufficiently accurate for high BC bullets at high speed. Just about every barrel maker has a list of recommended twist rates to use. In .30's, unless you're going to shoot bullets on the heavy end of the range, stick with the standard recommended twists. Most reloading manuals also contain a list of recommended twist rates. By the time you shoot the bore out, you'll have better understanding about whether you need a faster twist. If you're a hard core competitor that will try everything to get the edge to win, you'll either build other rifles or change the barrels. You're shooting a Savage. Buy the tools for rebarreling and buy a couple of chambered Pac-Nor barrels. You can have it all then. |
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I would shoot in whatever position is the closest to what you will be doing for most of your shooting but is still relatively stable. I used to test loads with a rest from a bench but I typically shoot using a bipod on a bench or prone. When doing ladder tests I noticed that the barrel vibrated slightly different depending on the rests. If I were you I would shoot prone and use a rear support such as a dedicated rest or a sock with beads or such which is what I use. You can buy a bag of stuffed animal beads whatever they are at a hobby store for pretty cheap. |
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