30-30 twist question

[lreed]

HELLO, I am wanting to put togeather a bolt action rifle in 30-30 cal as cast bullet frendly as I possibly can. I have two barrel blanks, one with 10-1 and another 12-1 twist,everything else being equal which of these twists is favored for 170-200+ gr cast, at 15-1800 fps[target vel]? The question of throating for cast bullets arises, anything better than gascheck at bottom of neck and bullet nose engraved in the rifleing? Thanks L Reed

[Marlin Junky]

For 200+ grain boolits I'd go with the 10" twist under certain conditions. For 170 or less grain boolits, the 12", no matter what. I am very happy with my old 10" twist Marlins with 200 grain boolits in the BHN 13 to 14 range at 1600 to 2100 fps but they have deep grooves (.004" to .005") so your mileage may vary... as they say. HOWEVER, if I were to build a hunting 30-30, I'd want a twist that would work well with the softest boolits possible so a 10" twist might be pushing it. I've been meaning to try RCBS 30-180FN in the 10 to 12 BHN range in my Pre-Microgroove 336 but I can't provide input at this time... sorry. I suppose when all is said and done the 12" twist may be more versatile.

MJ

[PPpastordon]

I know a little about what is supposed to work with the twist - and what is not supposed to work. But there is nothing like a little surprise every now and then.
I have a .458X1.5" with a 1-10 twist for 350 to 500 grain j-word bullets at subsonic speeds (1000 - 1050 fps). Imagine my surprise when it printed a .69" and other less than 1" 100 yard groups with Lyman 535 Postnell (hope I spelled that right) boolits. It also shoots well with Lee's 340 grain WW boolits.

[Larry Gibson]

lreed

Either twist will do int 15-1800 fps range you are talking about. HOWEVER, it is my opinion bases on tests in .30 cal with 10, 12 and 14" twists that for cast bullets or 150-200 gr the 10" twist spins them to fast, the 12" twist spins them ok and the 14" twist spins then just right. Keep in mind that the 32-40 is very accurate at 1400 fps or so with it's 14" twist (sometimes 16") and the 32 Special with the 16" twist does very well. Bullet ranges for both are 170 gr or so. If you ever want to drive a cast bullet faster, say 2000+ fps the 12" twist will give you better accuracy. I know there are exceptions to this with special bullets and loading techniques but with regular off the shelf moulds and loading techniques that is the case. So.... my advise is to use the 12" twist barrel.

Larry Gibson

[Frank46]

Since your talking about a bolt gun for the 30-30 you might want to have a throat of .310 x 1.5 with maybe 3/16" freebore. Sounds wierd but think on it. Most if not all 30-30's just have the lands and grooves start where the chamber ends. Trying to seat out lets say a 200 grain boolit may or may not work to your advantage. having the freebore and .310 throat gives you the option of seating boolits out for better guidance and also gives you more powder room. The 1.5 degree slope on the rifling eases the boolit into the rifling. If you ever get a copy of the "fouling shot" the cba newsletter check down at the bottom of some of their reports. They normally list their throatings. For a .310 throat load them sized to .311 and shoot them. Just my two cents worth. Frank