can someone help...balastics and barrels

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brybenn

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Looking for help in twist and estimated velocity. Some will wonder why I'm sure. I'm planning to re barrel my 25/06 and use it for bigger game and long range coyote and wolf strictly. This leaves me lacking my favorite dual use rifle so I'd like to add another 25 cal for close to mid range varmints up to coyotes and for this I'd like a 250 savage. With a twist of course
I'd like a 16" stiff barrel. Which is fine for varmint bullets at whatever velocity I can get but I am curious as to which twist I should use if I were to use the odd 100-117 gr bullets with a lighter diet mainly.
I was thinking 1-10 but with such a short barrel should I go tighter?
Anyone have a program that can predict how fast a 16" barrel can push a 117 gr sst? I'd like 2200 fps if possible and 25-2600 fps with 75-87gr bullets is just fine for my application
 
A rule of thumb that works pretty well is 25 fps per inch with a bit more for "overbore" cartridges. This means you can expect about a 200 fps loss from a 24" barrel which is what most reloading manuals use. I was reading an old magazine where the author cut a 270 win barrel from 27" to 21" and the velocity drop was 114 fps which translates to less than 20 fps per inch.
 
The 117 SST is quite long for diameter, and you might be safer with a 1-9" twist in that short barrel for that bullet.
I have run 1-10" twist in 25-06 and 257 Bob rifles, and have had success stabilizing any hunting bullet up to 120 grains
but that has always been in 24" tubes, and most "hunting" bullets are shorter for weight than is the SST.
D.
 
Run your velocity and bullet in Bergers twist calculator...takes all the guess work out of it. You'll also see that velocity has a smaller impact on twist/stability than you'd think.
 
What cdn shooter said: http://www.bergerbullets.com/twist-rate-calculator/

2500fps is within max pressure for 120gr bullets in 250 Savage, 24" barrel. Load data says 1:10 twist but Berger's calculator for their 117gr VLD says that particular bullet would be marginally stable: The SST should be quite close to that.

Such an underrated and ignored caliber... I have plans for building two on Remington 7 actions in the hopes that some day I'll have a couple of sons. :) Perfect for any game animal around here, and as you already realize, doubles for varmints. With the 16" barrel you want, I expect Eagleye's mention of a 1:9 twist would be necessary for the big bullet at the reduced velocity from a 16" barrel.
 
Thanks for the link. My 25/06 is 1-10 twist and does just fine. It's 22". It's also burnt out. Chasing the lands my interlocks are barely in the neck. Weird thing is it still shoots my vmax load well. My 117 gr interlock load has opened back up to 2". It will sport a 26" varmint barrel this summer. It's little brother will take up the varmint role leaving my 25/06 set up for heavier loads. I doubt I'd get lucky enough to have two different loads hit same poi again
The 250 savage is a great varmint round and hits a lot harder than a 223 and has about the same trajectory with the added bonus of throwing heavier bullets for up to deer size game. The sst works great in non magnums an should work great on wolves or deer should I need to push it into that role. For most part it will shoot 75-87 gr bullets
I just wanted to make sure I'd have enough twist to stabilize a heavier bullet from the shorter barrel

It will sit in a mdt LSS chassis and wear a 1-6 or 2-7 scope and be used in hardwood stands and around field edges and fence rows with the occasional poke at a crow across a field out 400 yards
Could also see use as a back up wolf hunting rifle hence the want to stabilize heavy bullets as well
 
When you commit to a 16" barrel, you stop talking about velocity... clearly there are other factors that are higher on your priority list... if you are concerned about velocity, then you don't plan a 16" barrel. I have had many short barrelled hunting rifles, and I like them alot, but these are hunting guns, not performance rigs, so a loss of 200 fps is virtually meaningless on target.

Edit; ... or give up some handling and maneuverability for a slightly longer barrel... I can't see where a 20" barrel will handicap you, unless you are inside a tight box blind... even there, point the muzzle up, turn, point the muzzle out.
 
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I know for the light weight bullets a 16" barrel will be fine. For the odd time I'd use heavier bullets I was curious to know if the common 1-10 twist in such a short barrel would stabilize a 117 sst. I know I can push them fast enough to be useful as a good expanding bullet what I wasn't sure of is if they'd fly straight. Finding a 257 caliber barrel other than 1-10 twist would have to be special ordered as I haven't seen any listed
I've used a 99 with a 24" barrel and a 1-12 or 1-14 twist and it wouldn't stabilize 110 gr accubond bullets
Since it will be a custom barrel I'd like to make sure it will suit my needs
 
This will be a hunting gun. I realize I'm giving up velocity and my intended prey won't notice. If velocity was my main goal I'd build a 257 wby to go with my 25/06.
I'm just looking for enough velocity to spin a 117 gr sst straight. From the few calculators I've checked out I should be well above my 2200 fps goal
The short barrel is for handling in the chassis I wish to use should I use it for offhand shooting

A coyote hit with 75 gr Vmax at 3300 fps equals a pelt with a perfect place for that 8x7 photo of you with it lol. I'm hoping this little savage will save some pelts by hitting them coyotes at 2400 fps which works beautifully from my 25/06 at longer ranges. It should still give me explosive results on ground hogs and crows as well as more hitting power than smaller bores


The berger site is saying a 1-9 is much better for their bullet. I can't find one for the sst in particular but I may see about going 1-9 just to be sure anyway
 
Aside from the greater versatility a fast twist barrel provides due to its ability to stabilize longer bullets, terminal performance improves due to the higher rotational velocity. A bullet has two velocities, linear and rotational, and both have an affect on terminal performance. Most hunters accept the precept that the faster a bullet flies downrange, the faster it expands at impact, and the greater the degree expansion, and the more damage that will be sustained by the target. But rotational velocity also plays an important role in terminal performance.

Bullets precess (yaw) twice during flight; first when the exit the bore, and again when the bullet impacts a denser than air medium. The time it takes for the bullet to recover from precession is determined in large part by its rotational velocity, the faster the bullet spins, the quicker it's axis aligns with its direction of flight. In the case of a game bullet, the result is deeper penetration. In the case of a varmint bullet, the result is explosive expansion, due to the high centrifugal forces that rip the bullet apart.

I like fast twist barrels. I have a 1:10 twist .25/06 that I'm considering rebarreling, the holdup is trying to decide between another quarter bore and a 6.5, but either way it'll have a 1:8 twist. In your case, the terminal performance of varmint bullets resulting from impacts at modest velocities, can be boosted by choosing a faster twist like a 1:8 or even a 1:7, resulting in red mist and a carpet of feathers. Likewise, no game bullet will be too long to stabilize, and terminal performance, particularly on larger species, is enhanced from deeper penetration. Good luck with your project.
 
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