If i was going to shoot ELR i would opt for a 338. Those big 300 grain bullets are great. They hit hard and reach way out there. Big difference in longrange hits. They are easier to see go and hit and I'd way better in conditions. Look at the 2 Mile shoots and see what they are using. Most are 338 and up and there is a reason for that. Matt
Anyone else wonder why custom/factory rifle makers are still using a 1-10 twist for the 300 WM?
- Thread starter Mr.Knowit all
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Ok, barrel length effects velocity. If your going to use a shorter barrel of 24"-26", then you might consider a faster twist barrel. If your long range target shooting, then your most likely going to use a 30"-32" custom barrel with a chamber cut for the bullet of your choice. This is where you can get by with a slower twist. In 54 years, I've never been to sea level much less tried shooting at that elevation. I'm not sure where people try what they consider ELR, but I would think that it would involve wide open country at higher elevations. This will also work with a slower twist. Now to what Brian Litz reports also has to play with all of these variables. After several years of hauling barrels to sell at the Berger match, he made a comment to everyone at the wind clinic. He was getting better accuracy with the 10 twist over the 9 twist with the heavy bullets in a 308. When the clinic ended, all of the 10 twist barrels that we had along were selling quick.
All that I know is that ALL of the 6mm VMAX bullets I tried in 8 twist tubes went about 25 yards and exploded in joy.The 55, 65, 75, and 87's....NONE of them made the trip!! 2 different dasher tubes and a 6-47L. I did manage to get the some of the Nostler Balistic Tips down range, but with poor accuracy.
I get fast twist tubes....I truly do. I must, because I own a pile of them. I am into LR shooting. But the medium and slow twist tubes surly have their place. How many ZILLIONS of Remington and brand "X" 22 caliber rifles have been sold and shot with 14 twist tubes? Same with 9.5 twist 7's. My thoughts are that the main population of average Joe's out there don't have any need for fast/ultra fast twist tubes....and, that, my friends , is where the money is at!!
As far as the 10 twist 30 cal tubes. I shoot 230's and 240's with no problems in my 10 twist's. I run the 215's in my 11 twist tubes with no issues. Average Joe won't have any problems either!!
Just my .02,
Tod
Smoothness of the bore and rifling have a lot to do with it.
I have a Shilen 8" twist 243win and it's never blown any bullets. And I've fed it 55gr, 75, 87, 105 and 107 grainers. They all reached their targets.
For the sake of argument...and maybe somebody might just learn something...I would like somebody to explain exactly how twist increases, decreases or otherwise "affects" a bullets ballistic coefficient???? By this reasoning, does a slower twist also detract from the given BC of a bullet as well??? and if not, then why not???? What happens to the BC of a bullet fired out of a smooth bore and thus receiving no twist????
The ballistic coefficient of a given bullet seems pretty static to me, but then again, this is rocket science we are talking about here!!! I always believed BC was a matter of cross sectional density and weight...sending it fasterslower or against a head/tail/cross wind doesn't change BC, how can the dynamic of spinning it change the BC?????
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I am not jumping onto any ones band wagon here, but I've got a question for you. Why does Sierra break down the BC of their bullets into velocity groups. It will show the BC of bullets at something like 2800+, 2200, 1800, 1600, etc..... I can't rmember the exact numbers. Speed must have something to do with it. Spin....I can't say as I don't have the data. And if it does, to what extent? I am pretty sure the shooting world in general doesn't care about a couple of tenth's of a %. But, I guess some on the fringes do!!
Tod
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dcali
Bullet Maker
BC is *mostly* constant with respect to spin. It turns out that when gyroscopic stability is near the edge, bullet yaw increases slightly - but we're talking about very small changes in drag at low stability. Bryan Litz was the first one that I'm aware of to quantify this, and it looks as if you get a maximum BC at a factor of approximately 1.5 (Sg). If memory serves, you lose a couple precent closer to 1.0. (Below, 1.0, bullets tumble, so that's the theoretical minimum).
Practically, nobody shoots at even 1.0 Sg, as the bullet will be on the verge of dynamic instability right out of the barrel. Generally, people shoot for 1.3 or so, but Bryan showed that we give up a little ballistic performance there, and suggests a minimum of 1.5ish for long range work. It's a significant, but very small difference.
On the other hand, a bullet's dispersion due to imbalance is inversely proportional to the twist rate in calibers/turn. Therefore at short range, where ballistics do not matter much, you want to use the slowest twist possible to shoot tiny groups. At long range, when ballistics dominate, the small loss in group size is a good thing to trade for a couple percent of BC.
But we need perspective here. This is edge of the envelope performance we're talking about here, and is way down on the list of things that matter.
dcali
Bullet Maker
Sierra has done this as long as I've been shooting (since they had paper ballistics tables in the back of the manual). The reason is that the G1 drag function is not a perfect fit for bullets. So rather than adjust the drag function, they choose to adjust the BC. It's very practical mathematical kludge to make the results match up to a drag function that isn't terribly well suited to sporting bullets.
A better solution is to use a better drag function, such as a G7 (usually), or better yet, use a bullet's specific drag function, which can be gathered from Doppler radar, for example.
The upside to Sierra's approach is that it's simple for them to test and it gives good trajectories. The downside is that it makes it hard to compare bullets. (You have the same problem with specific drag curves, which is one reason that Lapua publishes BC's in addition to drag curves). I don't think anyone else does it the way Lapua does, which is a shame.
Well...Brian must have it figured pretty good, because my "shooter" app is pretty spot on using his bullet library. What I haven't done yet is play with the twist calculator on the app....see if changing the twist will affect projected downrange ballistsics. Leave EVERYTHING the same except for twist. That will give me something to play with the next time I am board.
Tod
It's custom(slash)factory. Are you just being an asshole or do you need an English lesson?
All that I know is that ALL of the 6mm VMAX bullets I tried in 8 twist tubes went about 25 yards and exploded in joy.
I get fast twist tubes....I truly do. I must, because I own a pile of them. I am into LR shooting. But the medium and slow twist tubes surly have their place. How many ZILLIONS of Remington and brand "X" 22 caliber rifles have been sold and shot with 14 twist tubes? Same with 9.5 twist 7's. My thoughts are that the main population of average Joe's out there don't have any need for fast/ultra fast twist tubes....and, that, my friends , is where the money is at!!
As far as the 10 twist 30 cal tubes. I shoot 230's and 240's with no problems in my 10 twist's. I run the 215's in my 11 twist tubes with no issues. Average Joe won't have any problems either!!
Just my .02,
Tod
Yes but how far? I can group 230's with 1-11 twist well under .5 min at a 100 meters. The fliers past 1500 meters are just ridiculous. I spoke with Todd Hodnett and we recommended I shoot the 230s with an 8 twist. He says he does in his 300 NM.
I have read several books with out dated information written by people like my father (from the old school). Bryan Litz and Todd Hodnett seem to have much more contemporary and up to date data and thinking. Remember if you don't shoot ELR than this wasn't for you. Your slower twist may give you world records inside 1k yards but how does it hold up at 1500 and beyond?
I beg to differ, a 10 twist 338-416 has many kills over 2200 yards. One was 2880. That is with a 300 grain which is alot bigger and longer them any 30 bullet. The same guy shot 5 shots under 5.5 inches at a mile in competition with a 240 in a 308 Baer which is bigger then your bullets and should take more twist to stabilize. If you are getting fliers it's not the twist, probably conditions. 1500 yards and beyond is really hard with a 30 cal, period. We shot them all from 6.5 up to 50 IMP. On a bad day you can't hardly see the wash or impacts of a 30 cal, especially if it's deep snow or leaves. Matt
I (used to) shoot the 215's at IBS 1000 yard matches at Harris in 11 twists. I (used to) shoot the 230 in the same matches out of 10 twists. I have shot the 240's out of 10 twists at steel out to 1500. I (used to) shoot the 200 Hybrid out of a 12 twist at the same Harris matches.
Now I just shoot steel (or rocks) out to a mile with pretty much EVERYTHING I OWN.
The (used to) thing refers to the fact that I don't shoot many matches any more.
Tod
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dcali
Bullet Maker
Slower is relative. It's not like 10 is a slow 30 caliber twist. If you are at 1.5 Sg, you're good. A 200 grain Hybrid is at roughly 1.6-1.7 in a 10 twist. A 9 twist is not likely to do anything but open up your groups a little - which is why factory guns use a 10 or even 11 (again, most factory ammo in .300 WM is 180 grains). ELR or not, you need to be using very specialized bullets to make use of a 9 or faster twist. Which many folks do, but it's a niche, not something factory gunmakers or their customers care about. If you build a custom, want to shoot 230s or some crazy long solid, and put a 10 twist on, then you've got a point. That would be a mistake.
I wouldn't know Todd Hodnett if I walked into him on the street, but I can tell you that Bryan Litz's approach is straight out of the "old school" methods that were developed by the military engineers over the last 100 years. Nothing new about that. Just good application of proven engineering practices to sporting arms. Essentially, he's the guy who put in the effort, and had the communication skills to tell everyone about it. Kudos to him for kicking the industry in the pants. It was long overdue.
This is only one of my redneck observations but I do know that if you throw a football with a really tight, fast spiral, it will not be affected as much by the wind as one thrown with a slower turning spiral.
I know thats far from scientific but I have often wondered at what speed, if any, is the same true with a bullet.
I agree, and although the poster didn't come right out and say faster twist equals higher coefficient that was what it seemed like he was implying. Otherwise what's his argument??? He contends that faster twist is the end all/be all of stabilizing a bullet...light years ahead of the rest of us, yada yada yada...maybe he's right, but it seems that the BC can only be decreased by dynamics such as yawl and pitch, et al.
I just always thought BC was a static thing based on shape, weight and cross section. Make a bullet and assign a BC based on the bullets static properties...said bullet has a BC of 600. Does that mean when it is fired it is 600 or less??? Or can it jump to 620 because the barrel twist is faster???.....if it can be variable, how can a BC be assigned until the bullet is fired in a given rifle????
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What I picked up from reading the last Bryan Litz book I bought was to use the slowest twist possible to stabilize (the 1.5 Sg) the heaviest bullet you plan on shooting. At least that's the way I understood it.
Not the heaviest, but the longest bullet.
I would agree with that. They seem to go one after the other though I'm sure there are likely exceptions. I will modify my understanding.
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