Old Gunner, Yes, barrel choke would seem to be a major contribution to accuracy, Anschutz certainly seems to believe this and the few modern high quality guns that I've slugged the barrels all seem to be choked in the last couple inches at the muzzle end. Even the Chinese QB78 gun that I started pellet gun shooting has a choked barrel. However your comment about having rounded edges to the rifling lands is a new concept to me and it makes sense, can you provide barrel manufacturer names that supply barrels with this feature? I'd like to follow up on it...
Thanks...
Happy Shooting...
Mitch & Shadow...
I don't know of any production barrels other than the barrels made specifically for the lastest US Military sniper rifles that use the Rounded edge lands and grooves.
The concept was mentioned in an article on Long Range match rifles that I found on the net several months ago and I then ran across this principle being incorporated in the new Sniper rifle barrels only recently.
The principle is that rounding the edges reduces blowby by leaving no sharp angles that would prevent jackets from filling out the grooves completely.
The only other rounded land and groove system I know of off hand is the Metford pattern rifling used when the .303 British still used compressed balck powder pellets before Cordite was invented. Ultra high temperatures of cordite rapidly burned out bores regardless so its not a cure all, but so long as only lower temperature propellants or air or CO2 were used the principle should be effective.
The Lancaster "Oval Bore" is another BP era idea that might serve well for air rifles. There being no distinct lands and grooves, only a slight egg shap in cross section that has the same spiral as rifling.
Bullets fired from an oval bore look about the same as those rifled from a smooth bore. Only direct measurement would reveal the oval'ed shape.
Choked rifle bores are another BP era technique that has made the leap to airguns.
I'm not sure but I think progressive rifling has been tried in the past as well.
The lands increse in width and the spiral cut tightens as the bullet travels up the bore. Some Remington revolvers used this pattern, and some custom target rifles also used it. Sometimes the groove depth is lessened as well.
Needless to say its not that easy to manufacture.
Probably hammer forged rifling would be the best method to achieve this.
PS
I would expect that lead lapping a bore would tend to give a slight rounding of land and groove edges no matter how carefully done.
PPS
I just remembered an old crosman rifle belonging to a neighbor.
It was a long dicontinued magazine fed CO2 that was designed to use a steel BB surrounded by a thick plastic coating, perhaps nylon. Bore size was a nominal .22 but standard .22 pellets would not fit the magazine.
No round shot of the type was available so I filed the tips off some field pellets to fit the short chambers of the revolver type magazine.
The rifle was very accurate though there was no visible rifling. Apparently these rifles had bores similar to the Metford type though there was so little difference in groove and land height that it was not visible to the naked eye.
Also the S&W 78g has adjustable striker spring tension, you can dial in the best velocity for whatever pellet you are using.
some practice on your part will help. and keep an eye on that wind and there is a few other things, but others will tell you i'm sure..