"Go ahead and laugh & tell me haw stupid I am. I am considering making a .25 ACP rifle. would I gain anything over a .22lr besides bullet diameter. I would think I could make a more accurate rifle than your average .22, if, for no other reason than case and bullet uniformity. If I did attempt this, how would you go about it? i'm thinking take a single shot .22 and modify the bolt head. maybe a handi-rifle? Let the laughter begin."
I highly doubt you can make a more accurate rifle with a .25ACP than you could obtain with a premium quality (Kimber, Cooper, Anschutz, Weatherby) .22LR. I also highly doubt that you can obtain components to reload this cartridge that will display as much uniformity as good quality .22LR match ammo like Eley, Lapua, RWS, or even CCI Green Tag. Your proposition is an excellent way to waste money on a rifle and ammo to achieve sub-par results.
Have fun.