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Old September 9, 2012, 08:05 PM   #1
1stmar
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Group spread from temperature...

For the last couple of months been fine tuning a load for 22-250, this morning went to the range with some loads with a variety of oval changes. Typically groups have been .3-.6, this morning I couldn't get anything less then 1" most were 1.25 and larger. Previous range days had all been in the mid to upper 80's, this morning it was 64. Would the temperature have that much effect?
Velocitys seemed higher, but was having a problem getting readings on the chrono, it was either too close or to overcast.
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Old September 9, 2012, 08:12 PM   #2
Sport45
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Quote:
For the last couple of months been fine tuning a load for 22-250, this morning went to the range with some loads with a variety of oval changes.
Switch back to round bullets and your problem may go away.

Does your rifle have a wood stock and does it touch the barrel anywhere? If so the temperature / humidity may have had an effect of the wood. What powder are you using? Some are less temperature sensitive, but I don't think 65° to 85° is enough range to make much difference.

Or you may have just had a bad day shooting...
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Old September 9, 2012, 08:20 PM   #3
1stmar
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Using varget, barrel is free floated, stock is laminated
it could have been me, I never rule that out, though i felt comfortable.
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Old September 9, 2012, 08:22 PM   #4
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Something to consider...

The Effects of Altitude and Temperature on Rifling Twist... by Dan Lilja.

C
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Old September 9, 2012, 09:43 PM   #5
RaySendero
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Creeper,

Those numbers in the examples are all from a stability factor model.
I'm not buying it - I would need to see it!

I've never seen a stable bullet at one temp/humidity go unstable with a change in temperature, humidity or air density!

Anyone else have this reaction to that article or anyone have actually had this to happen?
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Old September 10, 2012, 04:18 PM   #6
Bart B.
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When the M852 7.62 NATO match ammo with Sierra 168's came out, folks with barrels that barely shot them fast enough from 22 inch 1:12 twist barrels with tight bores in warm, thin-air weather at high elevations did OK at 1000 yards. They stayed supersonic all the way from muzzle to paper.

Same rifle and ammo lot in temperatures in the 30's at low elevations created a situation where the thick air slowed bullets down enough to go subsonic around 800 yards. Accuracy beyond that range was measured in feet, not inches. Been at the Nationals when folks unaware of this happening on cold mornings listening to them say four-letter words about the accuracy of that ammo; 'twasn't "nice," "good" or words of that ilk. I've heard that some folks had 1:10 twists in their M1A's 22 inch barrels and they had better luck with the same ammo in the same conditions; bullets were spun about 20% faster in RPM's.
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Old September 10, 2012, 04:42 PM   #7
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Need to read this

http://www.exteriorballistics.com/eb...ned/5th/31.cfm

http://www.accurateshooter.com/techn...-air-pressure/

http://www.hornady.com/ballistics-resource/external
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Old September 10, 2012, 05:00 PM   #8
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With Varget you should'nt be seeing those kinds of changes with that small of a temperature spread. I love and Shoot plenty of Varget. Everyone has good and bad days. Just think you maybe not of shoot you A game that particular time. I shoot tons. Sometimes after drinking coffee or a monster drink you can feel a jittering going on, sometimes not. Sometimes I can shoot perfect three or four days in a row and for whatever reason things just dont come together. Try again the next day. Hopefully youll be tearing up the bullseye again!
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Old September 10, 2012, 06:16 PM   #9
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Farmerboy I agree hole heartedly, the last trip to my range I only had a breakfast of pancakes, maybe had too much syrup cause I had those sugar jitters and I grouped poorly, with a rifle that puts 'em in the same hole, and I knew about four rounds in that I was moving, and coudn't steady properly.
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Old September 10, 2012, 06:52 PM   #10
1stmar
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You guys are probably right, feel like I wasted a bunch of time and resources in load development. My eyes have good days and bad, sometimes it's hard to stay in focus. I felt steady, but I was fighting blurred vision, I guess unsuccessfully. Any tips or drills for scoping?
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Old September 10, 2012, 07:31 PM   #11
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Anything different in the barrel cleaning routine...as in not cleaning it, or copper removal, etc.?

Given that you're using a temp stable powder, and minor temp changes you describe would have no noticeable effect at such short range (100), that might be your culprit?
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Old September 10, 2012, 07:39 PM   #12
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I pretty much do the same thing, hopes powder solvent, brush, carb cleaner till clean then shooters choice copper solvent for 10 min followed by carb cleaner, dry patch then oil. I rarely shoot over 30 rounds in one shooting and I clean after every outing. I did push shoulders back, i usually neck size. I checked every case with an rcbs mic, nothing seemed excessive, push back averaged .002 with variations of up to +-.002.
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Old September 10, 2012, 08:16 PM   #13
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When you know right from start you're not on your A game. (can't keep bullets shooting tight groups or you see cross hairs floating alittle and can't keep em still) put rifle away and don't shoot for groups. Instead either get rifle or pistol and concentrate on what you can get benefits from. Like polishing trigger control or speed drills or come back to why we all really starting shooting in the first place. (it's just really fun). Ever like to watch young kids shoot? Some don't do so well but they have a smile from one side to another. Sometimes just have fun for no other reason than that!!!!
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Old September 11, 2012, 07:01 PM   #14
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Never rule out shooter error. But...

It's quite possible that the Varget was showing some temperature sensitivity.
The best load my .270 Win has ever seen was something like 52 gr RamShot Hunter, under a 140 gr Partition. It provided the proverbial "one-hole groups".
But... it would only do that around 40-50 degrees F. Once the temperature came up to even the mid-60s, the groups opened.

And... don't buy manufacturer's claims of powders not being temperature sensitive. I've seen the same sensitivity with some of Hodgdon's "Extreme" powders.

Yet... one of the most temperature insensitive powders I've encountered is RL-19. ....something that most reloaders, ballisticians, and gun writers constantly flaunt as very temperature sensitive, due to its "primitive" double-base chemistry and extruded shape.

Just like charge weights and accuracy... you never know how a powder will react at any given temperature, until you try it. (Getting data for RL-19's temperature tolerance took me nearly 2 years, because I had to wait on the weather. (I tested a few others, as well.))
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Old September 12, 2012, 05:42 AM   #15
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Seems like writers and columnist say things of temperture problems with IMR 4350, I just don't see the problem, as we shoot that stuff all year round with great performance.
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