There are a number of lowers out there that come with tension adjustment screws. I’m particularly interested in the Mega Forged Lower or maybe the new Aero Precision Gen 2 for my BCM upper. Do these adjustment screws work well for dialing in the upper to lower fit or are they just a gimmick? Any downsides?
And yes, I know that a little wobble between the upper and lower is no big deal, just wondering if the screws are a useful feature. All thing being equal, I generally think a solid feeling AR is preferable to a rattly one.
I have two ARs with the set screw and I’ve played with it and it does work. That said, I’m not sure it makes a huge difference. Also, depending how tight you set the screw, takedown pins may be difficult or impossible to move. Set it with loctite and carefully adjust it so that it takes out play but allows for takedown pin movement and it’ll work.
I’m sure this does what it says…but…don’t things like this cause takedown pin to receiver lug wear by putting pressure on the two parts (more friction?).
Yeah they work. It’s more of a OCD kind of thing. I pretty much just buy MEGA lowers for my stripped lowers and they all have them. My last build I completed my lower and looked in the bag and there was the set screw. I wiggled the receiver and it was solid so I threw it in the bag o’ spare parts. For all I know it could be a spare but I didn’t feel like taking the grip off to check.
My M6IC lower came with one, first time I had ever used one. Tighten too much, and pins are hard/impossible to move. Too loose and it becomes irreverent. I spent some time getting it set just right and used blue locktite on the threads, but the first range session it loosened back up again - so I’m not to impressed with them. I’ve read you can adjust easily with a MOE grip using the 2nd hole (thus not having to remove the grip every time you need to adjust it back up), but I don’t see how that would work as the allen wrench to hex head angle is pretty severe - not enough clearance. I may tighten it back up and try again, or maybe not
I think they’re silly and remove the thing from any lower I have that comes with them. AGP arms (here in Tempe) makes nice lowers, but they come with this thing. I just ditch it.
I fooled around with one that came on a lower I bought but it forced a gap between the receivers to take the play out. And it made the pin require a tool to push out. Back out the set screw the slightest amount and the play was back. Not sure if that’s common or just that particular upper and lower but I don’t mind the play between receivers that much.
I’ve found the o-ring trick to be a little superior. (just place a small rubber o-ring around the front takedown post). Because it’s rubber, it will let you compress it to get the takedown pins in and out with ease but then when it’s on the fit couldn’t be better. The set screws seem problematic since they’re a solid material you’d have to have the fit exactly perfect where you could still get the pins in and out but not have any wobble.
Plus o-rings work on any lower and they’re 3 cents at Ace
You could always do a trick I’ve seen and that is to take a piece of metal from your favorite beverage can and cut it to fit around the back of the upper/lower so it sandwiches the rear takedown lug. A few of the guys on the Navy Team did it for NM guns. I never let it bother me though.
I cut four strips of 3M Super 33+ and place it as pictured. It doesn’t make it any harder to push the pins but takes away almost all of the rattle/wobble. YMMV but post here if it works or not.
None of our NM guns on the USMC Rifle team had accu wedges or tension screws (2003) and those things were the most accurate AR’s I’ve shot to this day. I asked Praslic on the AMU team what he thought of accu wedges he said they made no diference from their testing. Not sure if things have changed since.
Neither did the Navy Team. Zerb was the one that had the beer can wedge on his gun but it was more he didn’t like the slop between the upper and lower.
And there is your answer. Emil has forgotten more about shooting than most even know. He is a wealth of knowledge and is willing to help you out. He has helped me on more than one occasion at matches.
