10/22 - groups now opening up drastically between 90 and 95 yards?

[penguinofsleep]

Groups are now opening up by a lot more than expected between 90 and 95 yards right now on a 10/22. Anyone have any ideas?

As of right now, it shoots 5rd groups at about 0.3" - 0.35" average at 50yd right now - nothing spectacular, but fine for me with a semi auto, this level of ammo, and ~1rd per second. Groups open up slowly but linearly every 5 yards up to 90yd - about .5 around 60, about .6 around 70, about 0.8-0.9 at 90yd. However, at 95 and 100, groups will suddenly open up to between 2-3 inches.

Rifle is a Kidd 10/22 with rear tang, Kidd 20" tapered supergrade bull barrel, no muzzle device/threads. Eley Club, SK Std+, and SK Rifle Match - same lots/batches as before, all coming out at different subsonic velocities, yet all opening up around 95. Accurate Rifle Systems Chassis, rifle has been torque tuned, etc. Was already taken apart and checked for any loose parts or anything wrong between sessions and didn't notice anything wrong. Have another 10/22 where this doesn't happen to hopefully rule me out as a factor. Have also moved the paper target in increments out to 100, back in to 75 or 90, and back out to 100 to make sure it wasn't something that happens over time like a dirty chamber or the barrel getting too hot. Tried shooting indoors at various distances twice since this has happened to rule out something like wind - but I get similar results outdoors as well anyways. Contacted Kidd and so far they don't know either.

I didn't check group sizes at so many intervals before this happened, but it did shoot the same 0.3-0.35" at 50 before and I could 80-90% of the time hit a golf ball (1.68") or 1.5" foam cube between 100-150 yd. Noticed that one day shooting golf balls starting at about 50 and letting them roll out as they were shot that I was missing way more than normal right around 100 but was still shooting fine under 90 or so which led to the above testing in 5yd increments.

 

[justin amateur]

Basic rule of thumb for rimfire...

Double the distance and you triple the spread.

Or:

Half the distance you get one-third the spread.

The causes of the spread are muzzle velocity differences, variations in bullet shape,
differences in bullet balance and wind drift all accruing as time of flight increases.

Try one dot-one shot targets at distance intervals and measure from center to impact
then compare the results. The double-triple rule works.

 

[penguinofsleep]

This most likely wasn't happening before though given the golf ball / foam cube - it's a recent occurrence. Also groups are what I expect around 90 - not sure why it suddenly opens up drastically at 95.

With that being said, yes, double distance triple spread does seem to play out at longer ranges with rimfire... but in this case it's more than triple.

 

[justin amateur]

Things that have caused problems for me....

Wind change next to berm and target backer.
Localized turbulence or wind shift not found at shorter distances.
Scope parallax problem, not properly focused
Shift eye left/right, viewed image moves also.
Ammunition is incapable of accuracy at extended distances.
Too much velocity shift or cartridges have component/assembly issues.
Shooter anxiety due to distance being attempted.
It is a mental game as well as physical.

 

[grauhanen]

Groups are now opening up by a lot more than expected between 90 and 95 yards right now on a 10/22. Anyone have any ideas?

As of right now, it shoots 5rd groups at about 0.3" - 0.35" average at 50yd right now - nothing spectacular, but fine for me with a semi auto, this level of ammo, and ~1rd per second. Groups open up slowly but linearly every 5 yards up to 90yd - about .5 around 60, about .6 around 70, about 0.8-0.9 at 90yd. However, at 95 and 100, groups will suddenly open up to between 2-3 inches. ...

... testing in 5yd increments.

There may be a couple things that can be helpful to keep in mind as this problem is considered.

First, no one can shoot or test the same rounds of ammo in five yard increments. That is to say, each test uses different rounds. Different rounds may give different results than previous ones, even from the same lot.

This is more likely with ammo that's not consistently consistent, a characteristic of many entry level .22LR match ammos and even some lots of top tier match ammos. (At testing facilities the performance of the same rounds can be compared at both 50 and 100 meters because are recorded electronically at both distances without disturbing the bullets' flight.)

Second, it's not possible for even the same rounds that give consistently satisisfactory performance (about 0.8" - 0.9") up to 90 yards to suddenly open up to 2" - 3" at 95 or 100 yards. In other words, the group dispersion can't change so dramatically within a distance of five to ten yards.

 

[penguinofsleep]

Things that have caused problems for me....

Wind change next to berm and target backer.
Localized turbulence or wind shift not found at shorter distances.
Scope parallax problem, not properly focused
Shift eye left/right, viewed image moves also.
Ammunition is incapable of accuracy at extended distances.
Too much velocity shift or cartridges have component/assembly issues.
Shooter anxiety due to distance being attempted.
It is a mental game as well as physical.

I agree with all of the above, but those factors are why I checked with another rifle, using the same boxes of ammo, back to back - five shots with 1 rifle A, then 5 with rifle B right away, then 5 more with A, so on. I imagine I would have also made the same mistakes in the past if this were the case.

However, I thought more about the localized turbulence - I haven't walked down the range at this particular indoor range, but I do know that indoor ranges need to be well ventilated, and it would make sense to put this ventilation near the backstop as that's where most of the impacts and hence lead accumulation will be. For those of you who have worked at indoor ranges - is it possible that the ventilation system at the indoor range is causing some sort of odd localized turbulence? I can see this getting past A/B testing if the ventilation system isn't running at a steady pace 100% of the time. For example, it runs 1 minute on and one off, which coincides with the amount of time it takes me to switch between rifles. Shooting outdoors in the CA desert where it can get windy I can also see that maybe coincidentally it was windy the last two times I shot outdoors around the 100 yd line.

Second, it's not possible for even the same rounds that give consistently satisisfactory performance (about 0.8" - 0.9") up to 90 yards to suddenly open up to 2" - 3" at 95 or 100 yards. In other words, the group dispersion can't change so dramatically within a distance of five to ten yards.

That's what I assumed and that's why I'm confused about this too.