1 in 12 twist rate question

[tigmaned]

i have a Howa varminter heavy barrel in 223rem. i wondering which grain i should start with? i see alot of 55gr and 62gr. which would be better for a 1 in 12 twist rate barrel.
Thanks!

[Questor]

Start with the 55 grainers but try both. The heavier bullets may work, but you may find that they are not stable and keyhole. If you want to shoot the heaviest possible bullet in your rifle, just try them. I don't think bullets heavier than 62 grains will fly right, though.  One thing you may find is that plastic tipped (relatively long) 62 grainers don't work, but somewhat shorter soft points do work fine.

I think that barrel was made for 50 to 55 grainers.

[LaOtto222]

I would think that the 1 -12 inch twist would stabilize a "blunt" 62 grain bullet but like tigmaned said you will have to try it to be sure. It is the length of the bullet and velocity of the bullet that effects stability, not weight. the only effect weight has to do with it is that a heavier bullet travels slower than a lighter one does. A 223 may not stabilize a certain bullet where a 22-250 will with an identical twist rate due to the extra velocity the 22-250 will generate. Stability equates to spin rate. the longer the bullet the faster it must spin to stabilize. This can be accomplished two ways, faster twist rate or higher velocity. A heavy bullet limits velocity, so the only way to make it up is to increase the twist rate. two bullets that weigh the same can take a different twist rates to stabilize. A longer (a spitzer shaped boat tail) bullet will need a faster spin rate to stabilize that short (blunt) bullet.

[tutti confuso]

 twist charte information below will help you select the best barrel twist for your specific needs, providing of course there are multiple choices. If you’ll be shooting one bullet weight, choose a twist from the chart just fast enough to stabilize it. Too fast a twist simply overspins the bullet and may result in reduced accuracy. On the other hand, a twist too slow for any bullet will likely produce instability, keyholing and rotten accuracy. So if you’re going to be using several bullet weights, be sure to select a twist that will stabilize the heaviest one, since lighter bullets will also be stabilized.

By way of explanation, the numbers in the "Twist" column indicate how far the bullet must travel through the bore to make one full revolution. This is determined by the rate of rotation of the rifling. For example, a 9"-twist barrel spins the bullet one full turn when it passes 9 inches through the bore. In a 16"-twist barrel, the bullet makes one revolution in 16 inches. So at the same bullet velocity, the 9" twist is faster (spins the bullet faster) than the 16" twist. Consequently, as the chart reflects in the .224 CF section, the 9" twist is necessary for stabilizing heavier bullet weights.

Again looking at the .224 CF section, if you’re planning to shoot 55-grain bullets, the 14" twist is ideal. This twist is also the best choice for 52- and 53-grain match bullets driven at moderate velocities. But if you’re also contemplating shooting a 60-grainer, go with the 12" twist, since it will stabilize all the bullets you’ll be using. As you can see from the 15" and 16" twists, higher velocities also spin the bullet faster and may enable a slower-than-recommended twist to stabilize a marginally overweight bullet. However, this is tricky stuff best left to those who are highly experienced in operating at the ragged edge of stability and sanity.

The basic principles just outlined apply to all the calibers below. But, if you have questions or need a  recommendation, let us know.

                  Caliber Twist     .224 CF                           
8"        For bullets heavier than 70 gr.

                                                                9" For bullets up to 70 gr.

                                                             12" For bullets up to 63 gr.

                                                             14" For bullets up to 55 gr.

                                                             15"*    For bullets up to 55 gr. driven 4,100 fps or more

                                                             16"*    For bullets up to 55 gr. driven 4,300 fps or more


 

                   

[Grumulkin]

I use Speer 70 gr. Semi-Spitzers in a 222, 223 & 22-250 with 1:12 twist barrels with excellent results.

[LaOtto222]

I bet you do. The 70 grain Speer semi-points are pretty blunt compared to spitzers. It all comes down to bullet length and velocity. Did you have the 222 special made, just about all of them have a 1 - 14" twist rate. They made it standard to shoot 52 grain bullets best.

[303Guy]

For what it is worth, I am shooting 55gr Hornady spire points in my 1 in 16 twist hornet.  So you never know.  Spire points may just stabilize at lower spin rates.

[LaOtto222]

Bullet length has more to do with it than weight. A flat base bullet may stabilize and a boat tail may not in the same weight. Barnes has a new bullet - a 36 grain no lead hollow point. It is very long for a 36 grain bullet. Reportedly does not stabilize in some rifles. It is about the same length as a Speer 55 grain spitzer. Of course velocity has something to with it too. It is the spin rate that stabilizes a bullet. As has been pointed out , you just have to try it to be sure.

[tutti confuso]

if you have ever thrown a foot ball you can imagine what a bullet does .... you can stabilize a heavy bullet in a slow twist barrel by increasing the the powder charge or using a faster burn rate powder to drive the bullet faster down the tube, it has to do with the rpm's of the bullet knowing the twist will give the bullet the same rmps say from your 1 -12 , but it depends on fast you get the bullet to said rpms, consider the distance an path somewhere along the line it will spril an somewhere it will start a yore down range same as that football it could start with the yore an end up in a spril as well .. a bullet that has a dead center poi at 100 may not have it at 400yrds an visa versa... ask any bench rest shooter  some bullets don't fly well yet another brand same weight will

as LaOtto222 has explained the bearing surface of the bullet will help stabilize it. its not the oal length, its suface that touches the lands which is from the start of the ogive to the base [if flatbase] of the bullet, boattails have a little difference in measurement .. in most cases longer is better

with that said... it doesn't work 100% of time another factor that comes into play [heavier bullet slow twist] may depending on the caliber and the length of barrel in some cases a shorter barrel helps an other case a longer barrel will work better, you'll need to experiment in your particular rifle an bullet

[Lloyd Smale]

Ive shot lots of 60 to even 70 grain bullets in my old 1-12 ar. Try a few differnt ones and id bet you can get them to shoot. Same goes the other way as my 1-7 twist ar does fine with some 52 grain bullets. It does help to keep in mind if your shooting heavys in a slow twist get them out as fast as possible and if your using light in a fast twist you may need to back the load off a touch.