Is riffling twist to bullet weight the same for cast and jacket bullets?
If I have a Remington 700 in 223 rem with a 1-12 twist what weight cast bullets can I reasonable expect to shot out of it compared to what weight jacket bullets can I reasonable expect to shot out of it?
Thank you for any replies in this matter. I hope that I will be able to get my confusion straightened out.
No.
Stabilization is mostly dependent of bullet length and velocity, not weight, given a specific caliber and twist. The velocity in effect, with a given twist rate, determines the rotational velocity of the the bullet......RPM if you will.
The length of a 55 gr Hornady SX is .693" and a Speer 52 gr HP is .704". Both stabilize quite nicely in 12" twist barrels at around 2100 fps +/-. My 225462 cast of COWW + 2% tin weighs 59 gr bully dressed and stabilizes at 900 fps +/- given its shorter .630 length. Even though heavier the shorter cast bullet stabilizes at a much lower velocity.
In my own 12" twist 223 Rems (M700 and M70) I get very good accuracy [1 1/2 moa with 10 shot groups at 100 yards] w/o tooo much difficulty with medium burning powders like H4895 using a dacron filler in the 21-2300 fps range. With the 225415 for squirrel shooting the best accuracy comes a bit slower in the 1900 - 2000 fps range.
Note; the above is with regular GC'd and lubed cast bullets. If you PC or HT coat them then it can be different as far as the velocity goes.
Greenhill's formula still applies. Speed caliber and bullet length help determine twist rate. 1-12 in a 223 would work best with 50-55 grain bullets at over 3000 fps or so. This can also change depending on type and depth of rifling but the final proof will be in shooting. This should get you started.
The reason for my question is I really like the MP .227 65 gr NATO mould that I see in the group buy. I had at first thought of getting it to shot out of our AR-15 rifles since the heavier weight. But was told a 1-12 twist would be needed in a AR-15 rifle. So I am wondering if that cast bullet would work in our Remington 700's and 7's 1-12 twist and our Encore 1-10 twist barrels chambered in 223 rem? My wife is also interested in this MP for her Ruger M77 in 22-250 rem no idea on twist
I had also thought originally to buy the mould as plain base for two reasons, one the difficulty in putting the Hornady gas checks on the RCBS and Lyman cast bullets. Also plain base for when we do not have gas checks. But I have come to the realization that I will have to get a GC design and I will not be able to shot the MP .227 65 gr NATO out of our Ar-15 rifles.
The MP .227 65 gr GC'd cast bullet will work okay in 9" twist ARs or slower w/o modification to the guns. Just have to load them correctly and to realize that the velocity will be much less than standard 5.56 NATO ammunition and accuracy not as good as with jacketed match quality bullets.
Also, the Hornady GCs can easily be seated on my 22 cal cast bullets including the MP 65 gr bullet, just have to use the Lyman GC seater tool on the 450/4500 is all. Other GC seater tools will work as well. My MP 27-65 runs right at .700" in length fully dressed.
My experience with,quite a few 22's is;
They seem to be really picky on not only length/weight but on shape and drive band location. Pretty much everything. Meaning,two R700 12T 223's..... one will show a distinct advantage over the other with a certain bullet profile. The RCBS 225-55(mine is 60g) is nearly identical to the Lee 55g. But are miles apart when testing.
The other thing is;
The faster a cast bullet goes,irrespective of twist,the more imbalance issues,rears it's ugly head. So,if the bullet isn't deadnuts round,as it drops from the mould, pushing it through a sizer or a barrel (unsized) isn't making it any better. Personally,I think mr Gibson's RPM "theory" misses the mark on this,not so unimportant point. It's easy to give folks a "reason" why they can't get cast to fly straight.
It shows up in smaller sizes because;
Take 3 bullets,a 22,a 30,and a 35. The processes for making the moulds are essentially the same. Parting lines,finish,and general +- tolerance is all about the same. Which size bullet is this going to effect more? Yes,the smaller it is,the more problem it is. There's a bunch more to really running the snot outta 22's but like so many things cast,you have to sorta stop looking for quick answers(not directed twds OP)..... it ain't that easy. It takes some real patience,a goodly amt of resources(equipment moreso than money),and some faith. Try right around 19g of H4198 with a Lee 55g,seated to a med-hard jam in your 223 700. Only lube the tiny area above the GC. Too much lube is just making a mess,and complicates the whole process. Remember,less is more(less lube for HV).