Best Twist for 62gr. .243Win

[warf73]

I'm looking at buying a M77 Mark II  Target Grey Target in 243. The rifle has a 1:9RH twist barrel on it, will the twist stabilize a 62gr pill.

I've never loaded down a 243 for anyone (lightest bullet was 80grs) so this is uncharted territory for me so let me know if this will work for or not.

If not who makes a rifle with the proper twist to spit out these pills.

Thanks Warf

[Luckyducker]

I was helping my S-I-L with some load development for a M77 Mark II All-weather in 243Win with a 1/10" rate of twist.  We tried 55 grain Nosler BT and Hornady 58 V-Max, and the accuracy did not come together with the Noslers until we were showing a little excess pressure, and that was with a load that was 2 full grains over listed max load but the 58 grain Hornadys showed fair accuracy at more reasonable pressure.  I don't consider either bullet/load acceptable for small varmint shooting.  I forgot to mention this was my rifle before I sold it to Heath and I could shoot one hole groups at 100 yds shooting 100 grain Core-lokts.  I believe the rate of twist to be too fast for these light bullets, but I am probably in minority thinking.  I think the 6mm bore rifles would be great variminters if they could be bought with a 1/12 or at most a 1/11" twist.  The .22 center fire rifles have various twist rates for shooting different bullet weights I don't understand why the 243 varmint rigs don't have a slower twist for varmint appropriate bullets.  Well, didn't mean to turn your thread into a rant.  This is just my $.02 on the subject. 

[mjbgalt]

try the sierra 60 grain hollowpoint. just about every reloading place has them, they have been made for years and have been VERY accurate in my .243 and others i know of.

the design of that bullet is such that it is a bit longer than other 6mm bullets of the same weight and as such, does not need a slow twist. this is just how it was explained to me. all i know is that it's the most accurate bullet i used when working up 5 loads for my .243.

-Matt

[hunt127588]

The determine proper twist for a bullet weight, use the Greenhill Forumla:

Twist = 150 X (DxD)/L

Where: D = bullet diameter in inches L= bullet length in inches

[Lone Star]

The Greenhill formula calculates the minimum twist rate for lead bullets, not the optimum twist for jacketed ones.  It was developed in the 19th century for non-pointed lead bullets.

My M77VT in .243 shoots the 55 Noslers better than it does heavier bullets - well under 1 moa agregates at over 4000 fps.  In theory a slower twist should work better....but my rifle doesn't care about theory.  The 55s turn the .243 into an outstanding varmintier, out to 500 yards the 55s shoot flatter and drift the same in the wind.  They do lack the energy of the heavier bullets but their lighter construction still allows expansion.

.

[PaulS]

It has been my experience that too much twist is just fine. It is very hard to "over stabilize" a bullet that is made properly. I sometimes shoot pistol bullets from my 358 Winchester at speeds of rifle bullets and with a 1:12 twist. Everybody will tell you that a 1:10 twist is too fast for a short 158 grain JHC bullet but it prints groups that are commonly sub caliber - the norm is .33 inch at 100 yards. I also shoot half jacket 30 caliber bullets from mt 1:10 twist 3006 at nearly 3000 fps without any problem. If the bullet is balanced and runs down the rifling I believe that you can't "over stabilize" a bullet. You can strip lead bullets by firing them too fast and you can make them tumble all the way to your target but that is not because of over spinning. Try the bullet and see if it does OK. That is the only way you will be sure whether you can shoot them accurately or not.

[warf73]

The reason I was asking is this would be my intended bullet for the rifle.

Barnes Varmint Grenade Bullets 243 Caliber and 6mm (243 Diameter) 62 Grain Hollow Point Box of 100


Varmint Grenade bullets feature a frangible copper/tin composite core. These accurate bullets can be driven at the highest velocities without coming apart, yet fragments explosively upon impact. Perfect for varmint hunting.

Sectional Density: .150
Ballistic Coefficient: Not listed by Barnes

Notes:
•  Bullet has a copper-tin composite core and is highly frangible
•  Flat base, hollow cavity
•  Explosive fragmentation at impact

Warf

[PaulS]

Warf73,

The Barnes bullet is longer than a lead bullet of the same weight. You will need to get the bullet length to calculate the "minimum" twist with the Greenhill formula. If it is faster than your twist rate then you are OK. If it is the same or close then it may be questionable. The best way to see if a bullet will stabilize in your gun is to shoot it. I know the bullets are expensive but if you are going to shoot them you are going to have to work up your load with them.

[warf73]

The best way to see if a bullet will stabilize in your gun is to shoot it. I know the bullets are expensive but if you are going to shoot them you are going to have to work up your load with them.

  I haven't bought the rifle yet; this is the reason for the question about a light bullet being able to stabilize in a 243Win.

All my dealings with 243's have been with 90~100gr bullets.

That’s the reason for the post to ask folks that might have experience with such a rig.

Thanks Warf

[victorcharlie]

I've had .243's all my life and have reloaded for them many years.  In my experience, I haven't been able to make the lighter bullets shoot as well as the heavier bullets.  IMO, the 85 to 100 grain bullets are what the .243 shoots best.

I will admit, I haven't tried the lighter bullets in several years and I'm delighted that others fine them accurate.  I plan to experiment with the lighter bullets again soon.

[PaulS]

You are going to have to find out from someone who uses that bullet. It is longer than jacketed lead bullets and will need faster twist to stabilize.