Understanding twist rate and barrel length

[SmokeNFeathers]

Does anyone have any suggestions on where to start when it comes to understanding the effect twist rate has on a specific projectile on a specific barrel length? I'll give an example starting point:

I recently purchased a Tikka T3xLite (stainless) in 7mm-08 and am planning to shoot 140(ish) grain projectiles out of it. No heavier. I understand it has a 1:9 twist rate, and it comes factory with a 22.4" barrel. Will cutting the barrel down (and threading) a few inches, say to 20", or even 19" have an effect on the stability of that projectile? Surely it will effect the muzzle velocity here, and I understand that... but if I'm looking to use this as a 500 and in rifle on elk, mule deer and other similar/smaller game, am I barking up the wrong tree by wanting to cut the barrel down? Or use that weight projectile? I know there are a lot of die hard '08 shooters out there who could probably help me with this- oh, and I don't reload. And I refuse to start! I have too many other niche hobbies! Plus, with the advent of companies advertising for custom handloads, the extra cost is worth the time saved- to me, that is. For now...

I want to cut it for 2 reasons, 1) in the future, I'd like to get a suppressor and introduce my kids to shooting with one and 2) I just want a shorter barrel to carry through the woods. Shortening the barrel seems like a good way to go about accomplishing both of those things. While the suppressor may be a long ways in the future (and obviously have some influence on POI/velocity) let's just assume I'll be shooting it primarily unsuppressed.

This is my first dive EVER into "customizing" a rifle. When funds allow, I may replace the stock and turn it into a backcountry folding chassis rifle. That all seems way off in the future. For now it will continue to wear the factory stock, guts and barrel. This is a big step for me, as I have basically only ever hunted with a 1970's era 30-06, WHICH I LOVE. But it's time to make a change.

Focusing on what I have and what I want to do, am I on the right track? I've read a few different threads and it seems like I am, but I really am just looking to open another 7mm-08 can of worms for folks to chime in on.

Thanks!

 

[DB29]

JBM - Calculations - Stability

www.jbmballistics.com

 

[fuzzymarindave]

Does anyone have any suggestions on where to start when it comes to understanding the effect twist rate has on a specific projectile on a specific barrel length? I'll give an example starting point:

I've not seen barrel length as a variable involved in stability calculations. Probably only need 1" or 2" of barrel length to get a jacketed bullet to spin at the specified rate. You should be good to go on shortening the barrel to any desired length.

 

[SmokeNFeathers]

I didn't know it was such a small variable in the overall picture. I knew I was overthinking it.

Thanks

 

[whitefalcon]

I hunt with the same rifle. I've taken 2 cow elk and a mule deer buck with it. The farthest shot was on the buck at 350 yards. I was sitting against a rock and shooting off a tripod. I'm probably an average shooter at best, but I think 400 is getting to about the max range for the gun, especially when you start shooting at bigger frame animals like elk. If you cut it down, you'll lose velocity as you mentioned, which shortens your overall distance. I'm moving up to a 300 WSM and cutting that down to 18" or 20" so that I can still have the small package and get out to 500 or 600 yards if conditions allow for it.

Have you looked into much of the ballistics of what you're shooting? As an example, at 400 yards on 150gr ELDX, you're already below 1400 ft lb of energy and velocity is around the 2000 fps mark. Stretch to 500 yards and you're sub 1200 ft lb energy and 1870s for velocity. This doesn't factor in the velocity loss from your shorter barrel. ELDX needs about 1600 fps to reliably expand. IMHO, 7mm-08 isn't meant to shoot that far. Yes, accuracy is always the most important, but it leaves you with almost no room for error. Just my $0.02. Feel free to disregard.