Thanks for the post.I have rubbed my chin over the tac 4.5 several times.It looks like bb fun, except for the trigger you mentioned.I have been shooting my daisy 74 co2 bb carbine this summer and it is wonderfully fun except for the same long, heavy trigger.It is also a co2 sipper with lower velocity and high shot count, but it doesn't look nearly as nice as the tac 4.5. FYC, the Umarex Hornaday Black Diamond bb's are giving me excellent accuracy (for bb's) out of the 74.
As best I can tell with my cheap digital caliper, it's 0.235 diameter. I dropped a brass rod down the shot tube and got a measurement of 12 5/16 inches. There is definitely room for big improvements in my opinion. The shot tune is only supported by the rear of the shroud and wobbles around when the shroud is removed.I bought mine for my daughter to use as a long range fox popper, and it works great for that as a semi auto.