220 Swift v. 22-250

Sounds like the Powder's temp sensitivity is eating your velocity (which is borderline across the divide).
What powder/have you chrono'd the hot/cold difference (?)
And pressurewise, what dare you load for cold and still shoot in hot?

BTW: I find that in cold weather, ammunition that I stick in an inside pocket stabilitizes at a 65-70° temp.
For field use w/ a small handful of cartridges at a time, that works really well.
 
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There are a bunch of good varmint rounds out there, I have really started to like the 204, but I have been a 22-250 guy for a long time... I have 222 which is nice, tac 20 which is very similar to 204 and I only bought it because it was an absolute steal, all the varmint calibers are awesome in their own way...
I am addicted to Cooper rifles, if you want the best varmint guns made, I have to say they sell them, I own a sako and a Blazer and the Coopers are hands down the best, varmint guns made...

My next endeavor will be 20 vartarg, 20 ppc, or 20 br, I shot a ppc at the range a while back it was nice and a short bolt throw, Ill probably go with the vartarg in a cooper montana varminter, I have been looking out on gunbroker so I dont have to special order one, but they are not popular calibers...
 
So it's a temp sensitive powder/velocity drop issue ?
(And it stabilitizes OK in summer temps?)
Click to expand...

Not necessarily. Even at an equal velocity, a given bullet is usually less stable in cooler air, and lower altitudes, due to increased air density.
 
True, true...

In fact I just ran rough stability calc's on the BSB at 3,800fps/14 twist/90°Temp /Sea-level and got a stability factor of 1.04 (marginal)
http://www.bergerbullets.com/twist-rate-calculator/

Then I dropped it to 30° (no change in velocity) and stability went to 0.923 (unstable).

.... no practical amout of velocity growth would bring it back up. (Well, a mile/second got me 1.04 again) :rolleyes:

Live and learn stuff..... (including that fact if you went UP a kilometer, you were back in stable territory even while still freezing) :eek:
 
Like the 223 Rem, the Swift needs a faster twist for medium weight bullets. It's more important in cold weather. Run your software again but use a 1:12 twist then again with 1:11.

The 5.56 NATO first used 1:14 twists for its 50-gr bullets and had the same cold weather problems until 1:12 twists were used.
 
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interesting my swift with 1:14 and 52gr or 55gr’s is still ok at sub -15 and -20 below. though I’ve had some wild shots at those temps i attributed to me pulling it. usually i shoot varmints at those temps and not paper ...... interesting point i bet a 1:12 barrel would keep her even tighter. next time she’s down at those temps i might have to hit the range with a few rifles.


my .204 has always been temperamental below 30 degrees, but the .223’s with 50 gr vmax’s and 1:9 barrels are as consistent if not more so than my .220 swift. when temps get really cold in the winter. she’s still a tack driver but your point is
interesting i wrote a lot of that off to various factors, powder, ME and Me again , then omitted never considering the twist relative to temp....

reality is at those temps i call em in to 100-150 yards rarely have i had an issue but now you have me wondering just for curiosities sake
 
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Normally I'd say to not worry about 52 and 55 grainers as to whether or not they stabilize in a 1 in 14 twist 220, but you did say 20 below zero. Brrrrrrr. I will never know how any of my rifles act at 20 below. No sireeeee.
 
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