My .17 Mach2 will not shoot consistant 2" groups at 100 yds with no wind.
If that is true, you have built one stupendously poor HM2! Here is what mine does at 50:
Here is the carbine that shot it:
And you darned right you can shoot and shoot well at 200 yards! You are never going to do it with a plastic stock, period. "Is that bull barrel any good" shows that you need a HUGE amount of information to even be able to know what questions to ask.
Go to Rimfirecentral.com, get registered and start reading. Don't buy any plastic stocks, don't buy any barrels that you don't know in advance are worth the money and don't shoot Stingers in anything with a Bentz chamber. If you don't know what a bentz chamber is, you just confirmed the last statement of the previous paragraph.
But what do I know? I've only built 8 or 9 of them and the WORST one shoots sub 1/2" groups at 50 yards. Here are just a few:
Apache:
Barracuda:
How about a Model 96 in 17HMR?
Tucks Tundra (note the ghost flames)
And finally... my Safari Grade: