1:16 twist in 30 cal.

[RU shooter]

I was looking at some barrels for a project rifle and came across a very slow 1:16 rate in 308 Win ,Would something that slow stabilize Cast boolits in the 180-190 gr. range at medium speeds IE,1800 fps. Now on the jacketed side would a 150 or 168 MK be do able at normal jacketed speeds?

Thanks,Tim

[Leftoverdj]

I was looking at some barrels for a project rifle and came across a very slow 1:16 rate in 308 Win ,Would something that slow stabilize Cast boolits in the 180-190 gr. range at medium speeds IE,1800 fps. Now on the jacketed side would a 150 or 168 MK be do able at normal jacketed speeds?

Thanks,Tim

Should be superb with cast bullets. The match shooters of yesteryear used slow twist barrels on their .32-40s for 40 rod shooting. I have my doubts about using the 168 MK, but if I had such a barrel it would never see a jacketed bullet.

[felix]

14 twist is standard for the 168MK. Twist is based upon wind friction, and only wind friction. So, a fat 168 grainer would be shorter which would make for less wind friction at 90 degrees, even though more friction on axis because of the fatter nose. In other words, a typical profile 170 grainer boolit would be fine without doubt. 16 twist should be fine for 150 grainer boolits. ... felix

[Shiloh]

I would think you could drive them at faster velocities with the slower twist.

Shiloh

[mainiac]

16 to 17 twist is the darling with the benchrest crowd in the 30 br with 110-120 bullets.

[Larry Gibson]

I was looking at some barrels for a project rifle and came across a very slow 1:16 rate in 308 Win ,Would something that slow stabilize Cast boolits in the 180-190 gr. range at medium speeds IE,1800 fps. Now on the jacketed side would a 150 or 168 MK be do able at normal jacketed speeds?

Thanks,Tim

The .32 Special, albiet with a .321 bullet, does very well with 170-180 gr cast at those velocities. I shoot a lot of .308W with a 14" twist and mine handles 180 gr cast quite well from 1800 fps on up through 2500+ fps. Actually I think the 16" twist would be perfect for 160 gr cast bullets up through 2600+ fps in the .308W which would be my bullet weight of interest. It might stabilize heavier cast bullets as well. As to the jacketed bullets the 150s driven fast would be fine but the 168 might be borderline. I find the 174 M118 and 168/175 MKs to not give as high BCs in my 14" twist as the BCs in a 12" twist. The 10 and 14" twist BCs are comparable. The 12" twist BCs are very good. That indicates over, under and juat right stabilization. However groups with all 3 barrels are still sub moa to 300 yards so they are still "stabile". Remains to be seen what a 16" twist can do.

Only one way to find out.

Larry Gibson

[runfiverun]

bet it would do 2500 with a 150 and cast.
i get stoked over 14 twist but 16 would be some serious cast fun.
especially with a good design and the name of a gunsmith that knows how to cut a cast throat.
i would bet sundog could recommend one.

[RU shooter]

Thanks All, Sounds like it may work out as a dual purpose rifle as thats what I have in mind for it for my reduce course match shooting with cast with the RCBS 165 and or the lee 155,and on the copper side the Speer 125 TNT which always shot well in everything for me.I still wanted the ability of using a heavier bullet such as the 150 or 168 MK for the 3 or so full course (500 yds in my area)matches I shoot .

One last thing would there be a velocity threshold on the lower side even with the mid weight cast bullets like the rcbs165 that I would need to stay above for proper boolit flight? My 32 spl shoots well below 1000fps would the same apply in this case.

Thanks for the help, Tim

[runfiverun]

a shorter boolit might be better suited to slower vel's
but the only way to find out is to try it. i know guys do under 1000 with a 12 twist 30-30.