What is the full range of bullet weights that I can use for these two calibers with the accompanying twist rates?

22-250 with a 1-12 twist

and

243 with a 1-9.25 twist

I am trying to decide on the caliber for my varmint rig so I need as much info as possable so I can make the best infomred decision.

Thanks in advance for the help

The .22-250 is most often found with a 1-14" twist. That twist will allow it to handle bullets from 45 to 60 grains in weight. Hornady and Speer are the two brands that come to mind, and I'm talking varmint bullets here, not match bullets. A twist of 1-12" is not a significant change, and I don't think it will make that much difference. You might get away with the 69 grain bullet, maybe. Believe it or not, a change in velocity would probably make more difference in regards to bullet stabilization.

In order to handle the heavier .22 calibre bullets, like the 77 and 80 grain match bullets, a much faster twist will be required, like 1-8" for example.

With some of the newer models out now, I don't know if different twist rates are available.
All of the above, is based on stock over the counter guns, with anything custom all bets are off.

Regarding the .243, for the most part they come with a 1-10" twist. Some older Remingtons had a faster rate of 1-9", and M600's had a 1-91/8" twist. All will easily handle bullets ranging from 70 to 100 grains in weight.

One caveat here, don't get caught up in "the heavier is better" trap. Trajectory must be factored in. If you can't shoot down the pipe, like with a 31/2" mid-range trajectory for example, you can't reliably hit the small critters. This is roughly equal to a 300 yard zero with 55 grain bullets traveling at 3600fps in the .22-250.

packrat

I previously owned a 22/250 some 30 years ago, which had a 1in 14 twist and that would shoot the stubby 70 grain Speer, but was best with bullets in the 55 - 60 grain range with that twist.

I have since owned a 22/284, 22/250 imp, and 220 Swift imp that had a 1 in 12 twist and while they would stabilise the stubby 70 grain Speer, they would not stabilise either the 68 grain Hornady and 69 grain Sierra.

In 224 Calibre, if you exclude short stubby semi spitzers, I agree with the generally held view that a 1 in 14 twist stabilises up to 60 grains, the 1 in 12 up to about 65 grains, the 1 in 10 twist up to about 70 grains, the 1 in 9 twist up to about 75 grains, and the 1 in 8 twist up to about 85 grains.

In 243 Calibre, again if you exclude short stubby semi spitzers a 1 in 9.25 twist will stabilize bullets up to 100 grains. A 1 in 8 twist is required to stabise the low drag style bullets of 105 - 115 grains.

Bullet weight is NOT the determining factor regarding twist requirement for stabilization. It is commonly used as a guideline but such input is a bit fuzzy insofar as what will or will not work. Bullet LENGTH is the issue.

Factories generally set twist in production barrels that will accomodate a wide range of bullet lengths then blythly leave the buyer in ignorance and sell bullet weights that fall within parameters for that twist. As an example, most 30-06 barrels will stabilize WEIGHTS of 110-200 or maybe 220 grains depending on length. Round nose bullets are shorter for weight than spitzer boat tail designs or those with high proportions of copper alloy in their construction. 1:10 and 1:12 twists are common for this chambering.

I don't want to start a fire here but the comment above regarding the significance of different twists(1:12 v. 1:14) as being of small import, and being able to accomplish as much or more with velocity increase is incorrect. Quite the contrary, the twist rate change has a much greater effect on bullet stability than velocity change. Do the math. It's all about angular momentum.

On a different note, what do you want to do with the gun? You will not suffer greatly by "overstabilizing" the bullet and using perhaps a 1:10 in the 22-250 and a 1.9 in the 6mm IF shooting a broad array of bullets. As is nearly always the case however, you will find that it prefers a particular "weight" which will coincide with the proper length for the twist you have selected. Bench competitiors are known to build guns around bullets, and this is the reason. Match your twist to the bullet you expect to use, and select the bullet for the purpose at hand.

There are several web sites that have twist calculators available for use online, try this one www.eskimo.com/~jbm/ . In any case, you must know the bullet length to make them work. The comments made by Brian Winzor may serve as useful guidance barring that. Perhaps someone else can post a link to one of the other ballistic calculators that does this trick. Best of luck.

DigitalDan, I agree with you completely. My above mentioned comments were a not very good attempt to compare the standard twist to others of a much faster rate. A 1-12" spin is good, but one that is still using most of the usual suspects as far as bullets are concerned. I had the heavies in mind, but failed to make the comparison.

Based on that, I made the comment that it (the twist) wasn't much of a change. Never should have mentioned the 69 grainer, it just muddied the waters.

Regarding the velocity comment, I had long bullets in mind, like the 70 grain Speer, not target types. Some guns will shoot 'em, others won't. I have seen a 100fps(+/-)change make the difference between success and keyholes.

packrat

You know everyone is ignoring the bullet lenght/twist to stabalize factor. It's not weight so much as twist to stabalize at a specific bullet length, thereafter excessive twist/spin is counter productive...IMHO

10-4 Packrat

Theory is a wonderful thing and can be argued forever.

I have rifles in the exact twists and chambering that you mention and for the 22-250 with the 1:12" twist I've found that 50-55gr V-Max's perform wonderfully.

In the 243 I have two rifles with 1:9.25 twist and had great luck with ALL bullets and can't figure out why. My personal favorites and most accurate by a slight margin are the 87gr V-Max for long shots and the 105gr A-Max (500BC) for AT&T shots.

Hope this helps.

$bob$