I have no shop to go to that has FX. would like to hold one. but this should be good enough. if someone could measure from the but to front bottom of grip and give me the length. thanks
11 3/4" on M3 Impact .25 Sniper. (Rear edge of butt to front, bottom of grip.)
If your worried about the fit of the Impact. Try looking at the Kraford and Lypt butt stock. https://krafordandlypt.com/products/kls-2-pre-order It will allow you adjust the cast, cant and pull length of your gun. I too prefer a longer gun. I find myself sensitive of the pull length and cant. I fixed my problems with the K&L kls2.
Mont
If you haven't seen already, there are now more options for the KLS FX platform with the KLS-3.Thanks. I like those better than the saber tactical. ones i looked at. I would like to add 2" to it. and i think it will fit me good.