I have a complete lower reciever and its from palmetto state armory. I want to build it into a pistol. Want to get an upper which is 7.5 and i want to know what twist should i get?
well there is a brief discussion on short barrel ballistics on barfcom and the happy medium, as far as the TAC bullets go, is around the 60 gr mark. But that is from a barrel that is an inch and a half longer than the OP intends to use, so his results are gong to be different. Whatever he uses the bullets have to be designed to fragment or expand at low speeds or they'll cruise right through. Many say not to use a FMJ in pistol length rifles as it does not carry the speed to fragment at all and cruise right through, like the steel core does in m855.will a light round at low speeds really be so effective in a home defense situation?
that sounds more like a low cost plinking formula to me.
but then. what do i know
I think it was more about the suppressor talk than SBR, since you stated early on that your intention was a pistol build.Yes i hear you. Thats SBR. but i heard you can use a pistol buffer tube instead of using an adjustable stock and it will be legit without tax stamps. So is that possible?
but remember, you need reliability in expansion or fragmentation. a slower bullet is not going to do it's job if it's not going fast enough.I'd go with 1:7 twist (and a 10.5" barrel honestly). 1:9 is [best?] for 55gr, but almost no one, especially for 5.56, uses the 45gr. I'd go 1:7 so that the heavier stuff shoots better. Being unable to properly stabilize the bullet will open groups up a bit.