The Gamo R77 certainly used to be made with a 2.5" barrel (and also 4" and 6" I think), there were also different grip styles as well - very slim plastic or a more contoured finger-grip style.

I suspect the quality wasn't as good as Umarex, but unlike the Umarex S&W it had a full length cylinder which swung out for loading - obviously the pellets went in right at the back and, on firing, travelled down an inch or so of "chamber" before entering the barrel proper.

It was, of course, only .177".

Iain