Good evening: I just want to see if anyone out theremay be trying what I am attempting. I just purchased a TNW Aero Survival Rifle in 9mm. I've only had a chance to try it out at my indoor range, so haven't had a chance to chrono it yet; But I have some good data on several loads for 125 gn TCN coated; I want to try and see how much additional velocity I get out of the 16.25" barrel as opposed to a standard (Springfield XD 4" barrel). I also have some fair ideas of the difference between a 3" barrel and 4" (my LC9s against the XD); a fair estimate of the relative velocities seems to indicate that the added inch yields about 70-80 FPS, obviously depending on how 'hot' the load is. What I want to do is run all 3 weapons, getting a good number of rounds (10-15 per load per gun) in order to increase the pool of data and minimize the effects of outliers. I would like to try and determine if a slower burning powder performs better in the longer barrel of the carbine. A website I stumbled across, ballisticsbytheinch.com, has some very interesting stuff done that seems to indicate that (so far), at least in 9mm, the length that velocity seems to drop off is actually right around 15-17 inches (at least in 9mm). I don't think that I'll check other cartridges until I purchase the conversion kit to .45; currently those are the only two calibers I own and load. Any insights offered will be appreciated.