Some time ago, I purchased an after-market bbl for my Ruger 10/22. This barrel made by Volquartsen has a faster-than-normal twist of 1:10 (normal twist for .22 RF is 1:16). I got the bbl so that I could shoot Aguila's 60 grain SSS ammo.
 
I shot a group at 25 yards, and another at 100. Here are the results.
 
Average velocity=825 f/s. St. Dev.=8.4 f/s
 
This is a real "thumper" of a bullet, and I'm happy to see the bbl produce good accuracy and no key-holing. I bought this rifle about 30 years ago, and this new bbl is the only modification I have made other than adding a 'scope. If you look at the groups, you will notice that there is a distinct lateral (windage) spread. I attribute this to either me 'pulling' the trigger, or just simply a tough 'factory' trigger. I wasn't 'pulling' the trigger. :D At any rate, this level of precision is satisfactory for my purposes.
 
Paul

I'm not sure about right now Paul, but last year Brownells was really carrying aftermarket products for the 10-22.  It was THE race gun for competition.  

One of the reasons I remember this was because a couple of fellas had me put in high grade trigger assemblys for their rifles.  I have to admit it sure made a difference.

Thanks for the heads up Jay. I've been looking at 10/22 aftermarket products for years, and trigger assemblies seem to be the very first thing people talk about when talking about "upgrading" the 10/22.
 
I can be a real stick in the mud when it comes to modifying firarms - especially "old" ones. Remember that it took me 30 years to change bbls, and I only did that because I really wanted to shoot that 60 grain .22 RF bullet. If I put a new trigger assembly on it the only thing left of the original would be the stock and the shell of the receiver. For me, that would make it... well I don't know what that would make it, but it wouldn't be a "real" 10/22. If it shot abysmally with the factory trigger, I guess I'd have to do something, but my first choice wouldn't be replacing the original trigger assembly. I like this rifle, and being somewhat 'attached' to it emotionally, I don't really want to change it any more than I have to. I didn't really want to put that new bbl on it, but I couldn't get any one to make a liner with a 1:10 twist.
 
Ol' stick in the mud,
Paul

Hello gitano. I enjoyed all your formulas and didn't understand a one of them! I sure understand the pictures, however. I shoot Aguila hyper velocity in my 10/22 and the groups I'm getting at 60 yards are astounding. I had a trigger put in, but can't remember the maker....only that it was titanium or whatever. The trigger was 50 bucks and it cost me another 65 to have it installed. I tried doing it myself but had no idea how complex the 10/22 is and soon had a pile of springs and parts and a bad headache! What is the SSS ammo? The ones I shoot are are 30 grainers at 1500? FPS. I haven't cronied them. They sure are messy, but anything within 60 yards is in big trouble! My 10/22 is a SS Walmart special that has a longer barrel than the standard model. I strippped off the original finish on the stock and there was nice suprise under there. I'll send you some pics when I get a chance. Regards, Rick.

Rick;
The Aquila SSS[ sub sonic sniper] is a 60 gr lead bullet in a .22 short case, velocity about 800-900fps.
Some guns shoot it fairly well, some very poorly.
Most of the problem seems to be from the long bullet, slow twist  and low velocity not stabilizing the bullet, a lot of targets show keyholes.
Don