Different Results With Same Barrel Twist


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BigN
November 16, 2012, 07:15 PM
I've got a Rem 700 SPS Varmint in 22-250. Barrel twist is 1-14. Both 50gr and 55 grain hit the target at 50 yards sideways. Can't even hit a 3 x 3 foot board at 100 yards. Obviously those bullet weights are not being handled correctly by that twist. 40 grainers shoot like a laser, can't miss the bullseye at 100 yards and beyond. I see some of you here have great luck with 50 and over weights even though you have the same barrel twist. Why would there be a difference among guns with the same twist?

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Certaindeaf
November 16, 2012, 07:39 PM
Are the 50 & 55's flat base? Try one with a long boat tail/short bearing surface?

creeper1956
November 16, 2012, 07:41 PM
Theoretically, and usually in actual practice, 1:14 is the correct twist for 50 through 55 grain bullets, and 1:15 is correct for 40 grain. So... either your rifle isn't 1:14 or... to be honest, I don't know.

Keyholing is usually an indication of a twist rate that is too slow for a given bullet, produce instability, said keyholing and miserable accuracy. Hence the question about your actual twist.
Over-stabilization... meaning a twist rate too fast for the bullet generally will not dramatically damage accuracy, unless the bullet has a very thin jacket and/or an physical imbalance... in which case the bullet will attempt to come apart, or disintegrate.

You probably already know all that, so just to make sure, measure your actual twist... then you'll at least know you have something else (as weird as it might be) going on.

C

BigN
November 17, 2012, 04:19 AM
The 50's are ballistic tips and are boat tail, the 55's are varmageddon and flat base. The 40's that shoot great are Sierra HP, flat base. I'll have to measure the twist myself I guess. I just assumed since it says "1 in 14" twist" on the label on the end of the box, it was 1-14.

hentown
November 17, 2012, 08:51 AM
I'd be really surprised if it's slower than 1/14.

creeper1956
November 17, 2012, 11:16 AM
I'd be really surprised if it's slower than 1/14.
Me too... but stranger things have happened. The bullets used aren't weird or exotic or VLD, so I can't figure out why it would be soooooo far off with the bullet the twist is intended for, but work well with a 10 gr. lighter bullet.
I mean, if this was a deal where the bullet was too heavy for the twist, like a 75 gr. in a 1:14, that I get... but we're not only going in the opposite direction, we are in theoretically correct twist/bullet territory as well.

I'm sure there's a ballistically sound explanation... but I can't think of it. :banghead:

mavracer
November 17, 2012, 12:20 PM
I'm reminded of a Yogi Berra quote
"in theory, theory and practice are the same. in practice they ain't"

creeper1956
November 17, 2012, 12:31 PM
Yep. The minute you chisel something in stone... you get the :neener:

Blue68f100
November 17, 2012, 02:45 PM
How is the crown on the barrel? Or maybe some weird harmonics going on with the barrel. By chance how does factory ammo shoot. And have you fired it at a further range?

rcmodel
November 17, 2012, 04:11 PM
It has to be something besides the twist rate, if it is in fact 1/14.

1/14 has been the standard twist for the 22-250 since it was invented in the 1930's.

They will shoot any bullet weight from 35 grain up to a 63 grain Sierra semi-pointed really well.
Flat base or BT doesn't matter.

I'd look at severe copper jacket fouling, or a damaged muzzle crown.

rc

creeper1956
November 17, 2012, 04:38 PM
They will shoot any bullet weight from 35 grain up to a 63 grain Sierra semi-pointed really well. Flat base or BT doesn't matter.
Or so you'd think, huh RC. That's what's odd... shoots 40s fine, 50-55... keyhole. Assuming "BigN" knows what he's about on the reloading front... and hasn't done something odd that he's not shared, what else is there but twist?

BigN
November 17, 2012, 05:52 PM
I've measured the twist 4 times. Once it measured 15 3/4, once closer to 16 and twice dead at 16. The crown is perfect. Is this even possible? I don't have a problem with a 1-16 twist, I'll just shoot 40's and under with it, coyote soup, but it just seems odd to me. I have a 220 Swift with 1/14 and a 223 with 1/12 so I can use the heavier bullets in them. Apparently the package was just mismarked, doesn't really matter to me. Now I know. If it makes any difference, I picked this gun up new in box at a severe discount at Dicks 2 years ago, $365.00 including a Bushnell scope. Maybe that's why it was discounted, no one wanted a twist that slow in that gun. I saw what it said on the box and took it. It has less than 100 rounds through it. Seems like they called it a Rem 700 ADL Varmint. Maybe a precursor to the SPS Varmint? At any rate, just seems odd having a 22/250 with a twist that slow. I'll use the 40's and be happy about it :)

creeper1956
November 17, 2012, 06:03 PM
I don't recall ever seeing a 1:16 twist, but I have seen 1:15. Yes, I guess it's miss marked. I think I'll do a bit of research on that to see what's up.

Anyway... glad it's sorted out and you know what you have. Enjoy spitting out those 40 grain pills at 4K fps! :D

C

addendum: Was looking at the Shilen catalog and found their comments as to weight/twist and velocity. Just for a point of reference. Nothing yet on a Remington factory 15 or 16 twist.

.224 CF
- 7" for bullets heavier than 70 gr.
- 8" for bullets heavier than 70 gr.
- 8" * Ratchet rifled 4 groove
- 9" for bullets up to 70 gr.
- 10" for bullets up to 65 gr.
- 12" for bullets up to 63 gr.
- 14" for bullets up to 55 gr.
- 14" * Ratchet rifled 4 groove
- 15" * for bullets up to 55 gr. driven 4,100 pfs or more
- 16" * for bullets up to 55 gr. driven 4,300 fps or more

creeper1956
November 17, 2012, 06:31 PM
More on Remington twist. These below are all I can find that reference a twist slower than 1:14 in a Remington factory barreled rifle.

http://www.thehighroad.org/showpost.php?p=8207245&postcount=23

http://castboolits.gunloads.com/showthread.php?t=68586

http://www.go2gbo.com/forums/index.php?topic=252050.0

One wonders if, with your rifle, Remington (somehow) grabbed a barrel intended for a .22 Hornet, 218 Bee or .222 with a 1:15 or 16 twist and chambered it for 22.250.

I'm done... onward. ;)

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