I knew the 5.56 and 7.62x45 was the same and the 308 was longer. Just wondered if it had been done. I do see some benefits to it but not much outside of ammo cost. No i got little interest in a special converted ar10.
I like the excuse of i need another one cause ammos cheaper lmao
I figured the mag would be the easy part since they have 22 mags for them. Unless im mistaken cause arent there 22 kits to make a ar15 22cal
Originally Posted by
homers brother
NO!
The upper for a .308 AR is LONGER than the upper for a 5.56 AR. Say you were able to pin the two together at the forward pin:
1. How is a 5.56mm magazine going to stay inside a .308 magazine well?
2. What are you going to do to plug that gap between the rear of the 5.56mm upper and the buffer of the .308 lower? All those important parts like the hammer won't line up, either.
3. And worse, the bolt won't be under the influence of the buffer spring - therefore, will not properly return to battery even if you were able to get it to fire once. But with no pin to line up at the rear of the .5.56 upper and the .308 lower, that bolt will probably just fly out and into your eye on the first shot anyway.
Edit: Maybe you don't realize this, but the 5.56 AR can handle most cartridges up to the same length as a 5.56x45mm round (which is indicated by the LAST number: 45mm). That's why the 7.62x39 is offered in a 5.56mm-length rifle. Maybe you need to convince one of the many manufacturers that there's a market for a custom (longer) upper in 5.56mm for a .308 lower? Until then, the 5.56mm upper will always be too short to fit to a .308 lower.