rifle twist question

twist basics
Pretty informational stuff. A lot of the twist comes down to bullet weight and length.

It all has to do with bullet stabilization. A heavier bullet or longer like the links says needs a faster twist to help it stabilize when it leaves the barrel. Having to slow of twist can cause keyholing or bad groups. Although to slow of a twist can cause I'll effects, I've rarely rarely seen to fast of twist cause bad accuracy. Normally people claim that the bullet "over revs" essentially and explodes. I've never seen this, but I don't shoot magnums or crazy calibers.

A higher velocity may help a bullet stabilize, but according to Bryan litz's book its effect isn't that great or hardly noticeable.

Think of it like rear end gears in a car. To low of a gear and you'll be at 8000rpms at 30mph. To high of a gear and you'll just stall because you don't have enough power to move the car. It needs to be just right so the car performs perfectly.

What you need to decide is what the end use of the gun is and what bullet you want to shoot. Then you can determine twist rate. A good standard twist for 30 cal is 1:11.75 for 308 or 1:10 for 300 win mag. These are just norms, other twist rates may work.

understood. however, clarify this: yrs ago me and a buddy reloaded 44mag rounds in wadcutter w/o copper jackets and had nothing but keyholing (we <17 yrs old at the time). if the barrel we used had a slower rate of twist would we had been able to stabilize the projectile?
ps: the rifiling in my super redhawk was some kinda messed up after that

A slower twist could have helped because a wadcutter is a short bullet design. It requires less twist to stabilize and almost certainly this was a case of to fast of twist for that bullet. This is why if you are building a gun for accuracy and precision its almost backwards. Decide the end use and bullet and then build the gun.

It's not complicated. Decide the end use of the gun w/ particular bullet(s) you want to use and run the calculations to determine the appropriate twist for the barrel.

Sometimes folks will choose a rapid twist barrel to handle a broader range of bullet weights. There's nothing wrong w/ that, but by doing so one may loose velocity when shooting lighter bullets. I had a 6mm Rem BR XlP-100 handgun built for prairie dog hunting. I used a slow twist (1:14") barrel that had been taken off a benchrest gun. I wanted to use lighter bullets (75 grains and less) and wasn't concerned that it probably wouldn't shoot bullets 80 grains and heavier. Indeed, it shoots many loads using bullets weighing 75 gr and less in an avg group <1/2" at 100 yds. Just out of curiosity, I shot some 80 gr bullets.......4" group at 100 yds. W/ the slow twist barrel I get a slightly higher muzzle velocity w/ the light bullets than what's reported by do folks using the same bullets w/ a fast twist barrel.

LINK

On my phone but look at the link if the barrel isn't marked.

Jag is a piece that fits on the end of the cleaning rod, it's what holds the patch.

The crown is where the bullet exits, most have an angled edge. Just don't want to scratch or damage it.

The tape is to see when the rifling makes one full revolution and the distance the rod traveled. You could use a sharpie and just make a mark.

Most good cleaning rods have ball bearings in the handle so they spin freely. This keeps people from jacking up their barrels. If you don't have like this just let the rod turn in your fingers as you pull. You need it to spin so you can see one revolution. I'll see if I can find a YouTube video. Its easier than it sounds.


ETA: Larry Potterfield to the rescue.

MidwayUSA video