Twist rate too fast?

[charles p]

I know the problem of having a bbl twist rate that is too slow (will not stabilize long bullets) but what are the consequences of have a twist that is too fast?
I suspect a rate that is overly fast will reduces velocity and create more bbl heat.  Am I overlooking something even more basic?  I've also read that fast rates  can cause fragile varmint bullets to come apart.

[trotterlg]

A too fast twist is not good at all.  In fast flat shooters it can turn the light weight bullets to dust, this usually occurs about 40 yards out for some reason.  A too fast twist barrel also results in a bullet flying nose high at long ranges due to it being over stabalized.  This creates a BC for the bullet that is far worse than what you would expect from it.  It does also take energy to spin up the bullet which reduces velocity, I don't know the amount, some say it is a lot and some say you cannot measure it.  The fast spun bullet will also be stressed a lot more when it hits it's target, could be a good thing if you are shooting PD's but a bad thing if you are shooting an Elk.  There are different spin rate barrels for a really good reason, just pick the one that is suited for the task you have in mind, faster is not always better.  Larry

[gunnut69]

An overly fast twist rate is detrimental but not excessively. All bullets fly with the nose slightly high and above the flight path. some velocity is likely lost but the real damage is in the alteration to the bullets performance. An excellent example is the 7x57. Originally designed with a 175 bullet it has a twist rate faster than 1 in 8(7 1/2 perhaps,, memory fades). It has developed a reputation for killing much better than it's modest paper ballistics would indicate. Likely due to several factors but the faster twist with a long bullet provides better penetration than a less stable bullet and in thing skinned game the lighter 140-150 grain bullets at modest velocity expand well and still tend to stay point on. Some say this is because the expansion is aided by the stress of this over stabilized bullets, thus allowing the bullets forward motion energy to be delivered to the animal a bit more efficiently. While neither over stabilization or under stabilization is good under is by far the worst..

[Luckyducker]

In my very limited experience with a 243 Win. with a 1/10" twist barrel and hand loads trying to shoot 55 grain Nosler BT's it seemed that the accuracy suffered until I was pushing the pressure above recommended max load according to the Nosler reloading manual.  I honestly believe with a slower twist barrel the accuracy would have been easier to attain without stress testing the equipment.  What kind of chaffs my hide is the fact that the only way to get the rate of twist needed for certain applications is to rebarrel with a custom tube (read =expensive).  I think the 243 is better suited for a varmint caliber than a big game caliber, but guess what, it isn't offered by any of the major rifle makers with slower twist such a 1/12" which I think would be the cat's meow for prairie dogs through coyotes.  And while I am on a rant, try to find an over the counter rifle in any .224" bore diameter with a fast enough twist to stabilize heavy for caliber slugs, unh unh, ain't gonna happen.   I don't know if anybody else get frustrated with this but it sure annoys me beyond my frustration limit at times.

[trotterlg]

An over stabalized bullet can hide a lot of other problems with a rifle.  One of the main ones is a bad crown.  With a bullet that is just normally stabalized or one that is marginally stable, a bad crown can "blow over" the bullet on the way out of the muzzel.  This was one of my main discoveries when I had a custon 1 in 17 twist 22-250 barrel.  Even at this slow twist, when the crown was perfectly cut, 55 gr bullets would be stable in it to at least 100 yards.  This probably explains why some rifles seem to have accuracy problems with bullets that should be quite stable in their twist rates.  Boat tail bullets also have more trouble with a bad crown, the bullet is in the transition from barrel to free fligh longer while the boat tail part of the bullet passes the muzzel.  Larry

[gunnut69]

Bullet stability is directly related to the RPM the bullet has at the muzzle. Now forward motion rapidly decelerates after the bullet leaves the barrel but the rotation slows but very little. This is likely the reason for cartridges such as the 7x57 performing better than the numbers way they should. I wonder why the bullets you described lost stability after only 100 yards.. Since bullet RPM has a mafor effect on stability bullet weight and velocity also affect the stability of the bullet in flight.. I'm sure there is a lot of physics here but I am not up to that!! Another thing about crowns that I've noticed is that they cam change.. Remington rifles are all that I've noticed the effect on but I'm sure it is a universal cause..after some shooting(variable) the ctown will develope what appear as flaking at the very edge of the bore terminus. Under magnification these flakes. These rifle usually came to my attention for their loss of accuracy.. Lightly recutting the crown usually solves the problem at least to some degree..

[Fat NDN]

I am a 22-250 shooter and I am curious about this subject.  I know that my 1:12 twist barrels good for up to 63 grain bullets.
 If I had a 1:9 twist to shoot 70 grain bullets, how would that effect 50 or 55 grain bullets ?

[torpedoman]

they would be spun up a bit but i don't think you would have any problems

[IOWA DON]

My experience shows a bullet performance difference depending on twist rate. I had a 7MM Weatherby which had a 1-in12 twist. It was re-barreled three times, once with a 1-in10, once with a 1-in-9, and finally again with a 1-in-12 twist. The last time it was chambered for 7MM STW. The faster twists made the bullets blow up and cause very large (4-inch) exit holes in coyotes. The slower twist resulted in 2-inch or smaller exit holes on coyotes. ---- I was convinced that twists should be as slow as possible for the bullet one wants to shoot, but recently changed my mind. I read a magazine article which discussed advertised versus actual ballistic coeficients of bullets. The article stated that not only did ballistic coeficients based on measured remaining downrange velocities vary from advertised ballistic coeficients, but actual ballistic coefficients varied from rifle to rifle. Generally, rifles with faster twist rates show better ballistic coeficients for the same bullet than do rifles with slower twist rates. Apparently faster twist rates do a better job of keeping bullets pointed in the forward direction. ---- Long time ago I read that faster twist rates result in higher muzzle velocities for the same load (just like less freebore). Faster twists raise pressure and more pressure results in higher velocity. Therefore (everything else being equal)a rifle with a faster twist would require a lower powder charge to get the same velocity as a slower twist rifle. However, given the same pressure, velocity would be equal for the two rifles. --- I think I had a problem with rifle with a twist rate barely stabilizing a paticular bullet. I worked up a load for some 63-grain Sierra semi-pointd bullets in my .22 CCM (a very small capacity cartridge). At a velocity of about 1,650 fps the load was very accurate at 50 yards. The load was developed at the range on a hot day. I shot some a couple days ago when the temperature was about 45 deg F. I suspect the velocity was lower because of the cooler temperature. Also, I shot them at 113 yards so the velocity probably dropped quite a bit at that range. Anyway, accuracy was terrible and it appeared the bullet holes in the target were slightly oblong. Another guy at the range told me about someone he knew who had a varmint rifle with a very slow twist. It shot accurately at 100 yards but very poorly at long ranges.

[gunnut69]

I bought a 244 M722 Remington a few years ago and the seller made sure I knew the barrel had a slow twist. He was being honest and didn't want me upset when the gun failed to stabilize 100 grain bullets. I bought the rifle and it shoots the 75 grain Sierra HP flat base bullets under 1/2 inch! Rifle makers must make what will sell. When Remington brought out the 244(6mm Rem) soon after the introduction of the 243, they too saw the cartridge as a varmit shooter. The winchester folks disagreed. Today the 244/6mm is dead as a duck...the 243 just cruiises along.. I have several of both and the 75 grain cullets shoot very well in all(except a VERY long throated Ruger No.1) but the 244 slow twist is a really great coyote shooter...  there are very faster twist rifle available for the heavy 224 caliber match bullets but most are the AR type rifles. I've seen twist rates of 1/7!

[deltecs]

I bought a 244 M722 Remington a few years ago and the seller made sure I knew the barrel had a slow twist. He was being honest and didn't want me upset when the gun failed to stabilize 100 grain bullets. I bought the rifle and it shoots the 75 grain Sierra HP flat base bullets under 1/2 inch! Rifle makers must make what will sell. When Remington brought out the 244(6mm Rem) soon after the introduction of the 243, they too saw the cartridge as a varmit shooter. The winchester folks disagreed. Today the 244/6mm is dead as a duck...the 243 just cruiises along.. I have several of both and the 75 grain cullets shoot very well in all(except a VERY long throated Ruger No.1) but the 244 slow twist is a really great coyote shooter...  there are very faster twist rifle available for the heavy 224 caliber match bullets but most are the AR type rifles. I've seen twist rates of 1/7!

The .244 Remington had a nominal twist rate of 1:12" and will stabilize SOME 100 gr bullets, but accuracy is not as good as when using lighter bullets.  Remington attempted to correct this for big game hunters by renaming the cartridge to 6 mm Remington.  All 6 mm Remingtons so named, have a twist rate of 1:9".  These will stabilize the heaviest offerings in .243 bore bullets.

[gunnut69]

The 244's slow twist as you stated was set at 1/12 but the 243's 1/10 twist became such a thorn in Remington's side that they changed the 244's spin rate to 1/9 within a very few months. I've checked several dozen 244's and very few were cursed with the slow twist.. Some books state the 244 slow twist barrel may be one of the rarest Remington variations! A neighbor has a 244 in beautiful shape. Dealer told him the same thing and he'd been using 100 grain bullets for years with no problems. We checked the twist rate and sure enough 1/9.. I haven't tried mine with heavier bullets but the guy I bought it from swore it would make oblong holes with 100 grain ammo.. The 6mm was an attempt to ditch the reputation of the 244. It seems to have failed.. the round is at best moribund and will likely become obsolete.