I feel I should respond to the LaRue comment above, that they will come up short, and some of the fan boys wi be unhappy.
I have a LaRue OBR in 7.62, one of the earlier ones with a Walter-Lothar barrel. It’s a tack driver, and a 1/4-1/2 MOA rifle all day with FGGM ammo.
I live in Marylandistan, the communist republic, potentially Soviet Republic, and didn’t want to deal with picking up another lower.
LaRue is making 65CM uppers with +2 gas systems, and it was a pretty cool idea to just slap on another upper on my lower, and work up a decent load for some distance shooting.
Unfortunately, while the original 7.62 upper was very well mated to the lower, the LaRue Ultimate Upper 65CM did not lockup well on the lower. In fact, there is so much slop in the lower, you can actually see daylight between the upper and lower with an Accuwedge installed.
This does not happen with the original 762 upper.
When I called LaRue yesterday, I got a bit of double talk and talk around. A lot of “this is what you can see with MilSpec,” and how different receivers fit together. I responded by saying: does LaRue make to milspec or used old CNC bits? I thought they made precision equipment... I can see how if it was not going on a LaRue lower, it would be a different story. LaRue told me to use an Accuwedge...
Anyway, what I’m seeing with the Ultimate Upper on a LaRue lower:
- Taken down pin has about .75-1mm of travel (you can see daylight)
- Pivot pin has good lockup compared to take down pin, but still has about 1/4mm of travel; allows side to side movement
- Pins are proprietary, so you can not use slightly larger pins from JP or others
I did take calipers to everything, and the 7.62 upper was a little tighter.
Honestly, for the money, I think there are better options. I’ve no idea if they make their 556 rifles differently. I’d probably consider a JP before I bought the LaRue IF you are looking for a 1/4 MOA rifle.
LaRue does make a VERY good rifle. That’s not in question.
I won’t lie to you, I can shoot that 65CM upper with the take down pin shimmed under 1/2 MOA. However, it would be a 1/4 MOA rifle all day without the slop... for that kind of cash, we shouldn’t be shimming or using an Accuwedge.