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gamma
Reply with quote  #1 
Hi,Im trying to help a friend out here,his problem is he has a brand new CZ 452 .22 rimfire,his grouping is fine out at 50 yrds but at 100 yrds,its all over the place.I know hes asking for a lot to get a .22 rimfire to tight group at 100 yrds but this thing is really bad at 100. I find it hard to work out why its fairly ok at 50 then completely scatters after that,hes tried all sorts of ammo but still seems the same.Any help would be great.
Travelor
Reply with quote  #2 
My guess given the limited information is that it is the ammo.

What are you shooting?
BikeEffects
Reply with quote  #3 
Try sub-sonic ammo.
RichinKansas
Reply with quote  #4 
I agree with the subsonic ammo. If you are using various high speed stuff it might stay supersonic at 50 yards, but drop through the sound barrier past that. As a bullet drops through the sound barrier it is buffeted and can take off. I believe the long rang Palma shooters try to keep their bullets supersonic for that reason, using long barrels and hot loads. Rich
JoeM57
Reply with quote  #5 
Another plug for the subsonic ammo. It does make a difference.
rayjay
Reply with quote  #6 
Windflags ???
22Leadlobber
Reply with quote  #7 
I play the silhouette game. Suggest trying 4 different brands of sub sonic ammo, it usually takes 5 shots to season the barrel to a new ammo brand before groups settle in.

I consider 1- 1 1/2 groups good out of my Sako Finnfire trigger set to 2 lbs. using Leupold 6.5 X 20 efr.

Eley, Rws , Wolf are my favorites.
Goofycat
Reply with quote  #8 
Here is something I picked up from I-forget-where. It was the conclusion of a study done having to do with inaccuracy due to bullet velocity. They too concluded that subsonic fodder is more accurate. I shoot Winchester Power Point (made in Australia) for good kills on ground squirrels out to 125 yards on a windless day. I chronoed it at about 1,250 fps, but it is still quite accurate. Most of my shots are 100 yards or less, however. You can buy rimfire ammo at Graf & Sons...it's in the midwest, but check Google. I personally don't shoot the match stuff because it is so expensive. I am a bottom-feeder and try to buy the cheapest ammunition that the rifles like. T-22 is another Winchester choice you might want to consider. Unlike the Power Point, it features more of a rounded nose lead bullet, versus the flatter-nosed Power Point. The Power Point bullet are hollow-pointed, but still ricochet like crazy, so if you are in an area with houses around, keep that in mind.





VI. Conclusions
1. Spark-photography range firings were conducted with Eley Tenex and UWS R-5O
ammunition, fired from Olympic-grade competition rifles, The measuerements made
led to an accurate assessment of the effects of wind on the trajectory of caliber .22
Long Rifle match ammunition used in Olympic competition.
2. No significant difference in drag was observed between Eley Tenex and RWS f-50
ammunition fired from the Anschutz rifle. No significant difference in drag was ob-
served between the Anschutz rifle and the Remington 40-X rifle, firing the same lot
of Eley Tenex ammunition. These results suggest that the choice of rifle or brand of
match ammunition used has an insignificant effect on the wind sensitivity of caliber
.22 Long Rifle bullets used in Olympic competition.
3. The round-to-round standard deviation in drag for Olympic-grade caliber .22 match
ammunition is about 2 percent. The effect of 2 percent drag standard deviation on
wind sensitivity is negligible at ranges of 50 and 100 metres.
4. The launch gyroscopic stability factor of caliber .22 match bullets, fired from rifles
with a standard rifling twist rate of 16 inches/turn and at standard ICAO sea-level
atmospheric conditions, is 1.5, which is sufficient to provide stable flight under all
weather conditions, including-cold (high density) air.
5. The nonlinear Magnus moment acting on caliber .22 match bullets at transonic and
subsonic speeds causes a slow-arm limit cycle yaw of approximately 1.8 degrees. The
slow arm grows to the limit cycle value at about 50 metres range, and the limit cycle
persists out to 100 metres range. The limit cycle yaw adds approximately 2 percent
to the zero-yaw drag, but has an insignificant effect on accuracy, retained velocity and
wind sensitivity.
6. The effect of wind on the trajectory of caliber .22 match ammunition at 50 metres
range is to cause bullet impacts distributed along a 9:31/3:30 slant line. The left/right
deflection is accurately predicted by the classical wind drift formula, and the vertical
deflection is accurately predicted by the ballistic formula for aerodynamic jump. The
rifleman needs to make one click adjustment in elevation for every four clicks made
on windage.
7. A muzzle velocity of approximately 950 fps would minimize the wind sensitivity of
Eley Tenex and '.WS R4-0 bullets. The wind sensitivity at a muzzle velocity of 950
fps would be approximately 20 percent less than that experienced at the standard
velocity of 1090 fps.
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