I like my PSA 6.5 Creedmoor. It shoots better than either of my .308 AR-10's, and after some tuning, works reliably.

Once obvious gripe is there's a lot of slop between the upper & lower, at the takedown pins. Has anyone ever identified accuracy improvement, by reducing this play?

If worthwhile, does someone make oversized pins, that could tighten up the fit?

That slop is a relatively easy thing to fix, so i do it on any of my ARs that need it. Don't know if it really improves accuracy much but it sure doesn't hurt.

I bed the upper and lower together with "ultra black" RTV from the auto parts store. I use that stuff instead of hard epoxy because I get better results removing all of the rattle. Use release agent on the upper, and apply the RTV to the lower in the curve at the rear and at the front between the magwell and front pin.

Using some method of forcing the upper and lower apart while the rtv cures is important to a tight fit. I use an O-ring around the front lug of the upper. This results in a rock solid fit after the RTV cures, and the RTV has just enough compliance that you can still get the takedown pins in and out easily.

Why not just use an acu wedge?

If you're asking me, that's an option too but I like the feel of a bedded receiver set better. It's only a couple minutes of work, not like it's a big deal to do.

Any pics?

I was just asking as a general question. I don't hear a lot about them here. However, I use them and they work great. I've seen groups shrink a little by using the accu wedge. Their main purpose is to fix upper to lower slop though..

I have a few of the Accuwedges and they take out the slop fine, I wonder if a few layers of electrical tape betweent he upper and lower would do the same as bedding.

okay, had not heard of an accu wedge before; need to try one

Some of the SME's on another forum talked about them breaking down an having the potential to come apart and get in the trigger.

I have had one in a particular gun for over 10 years now. I call BS on them breaking down but I don't use them in any of my other guns. The sloppy fit is no problem except in your mind. If it bothers you then use one or bed it. Or slide an O ring over the front lug on the upper.

I think rost495 said bedding a gun only showed slightly better accuracy at 300 yards.

National Match Shim

http://www.wheeldiamond.com/nationalmatchshim.htm


Takes 15 minutes or so to fit to your upper and lower for a fit as tight as you want.

Clarence

If I feel the need, I bed ours with Steel Bed or JB.

They feel better.

I've done quite a bit of shooting, as did John Feamster in the 90s.

My take, that at 300 yards, you got about a bit better group size overall, IIRC, 10 shot groups shrunk maybe 1/4 inch or a bit more. They did become much rounder though and shot dispersion was much more centered rather than who knows how far each shot might stray from the very middle so to speak. Hard to really describe and I dont' have any of the photos anymore of all the testing.

That said, I would only do it on a "match" gun, not a hunting gun, 3 gun gun etc... just strictly were the most accuracy mattered.

This one looks uglier in the pic than in person. You can't tell it's bedded when the receivers are pinned together.
rost495, why are you saying to only do this to a "match" gun? I've never found a reason not to do it to all of them, if only because I prefer my guns not rattle.

It makes such little difference and I could care less about the fit of the gun, looks of the gun or some minor slop in the gun. Thats the only reason, well that and you have mated it permanently basically, ( until removing the bedding) to whatever lower you have it on. Not that I have a shortage of lowers, but I don't always have as many lowers running as I have uppers.

It takes a bit of work granted, not much, but enough such that the results to me aren't worth the effort.

Thats about it.

How you run yours are cool with me too!

That makes sense rost. This quoted bit though reminded me of another reason for using RTV instead of hard epoxy - there's still some interchangeability with different uppers. Not all will fit or be tight of course, but some of them will. Several of mine bedded this way get swapped around.

An O-ring over the front lug and an accuwedge beats not having to smell RTV and put up with the mess.

Oh please. If a dab of RTV bothers you that much, stay in the kitchen. Are we talking about working on guns here, or having a tea party?

RTV does wonders as a gas seal on the charging handle though...

Calm down there Fluffy, I deal with the crap everyday and I can't find any reason to use it on my guns.

I'd like to know more about this...assuming you're serious, of course.

release agent on upper where charging handle locks in place, RTV on charging handle, close handle barely, with backward tension on it, let cure. Trim as need be. Does a good job if you have a wind blowing in your face for sure...

I'm sure someone will have pictures to post.

Found a youtube video on it. Thanks for mentioning it...I'm obviously not up on all the latest AR tricks!

Yep that is a good one too. Especially for shooting suppressed.

Aero Precision's new lowers have a screw with a rubber tip on them that is moved so it touches the rear lug. The screw is under the pistol grip so you have to adjust it first them add the pistol grip. No more bedding or accu wedge required.

kwg

I've used those, and modified other receiver brands to do the same thing. It never makes the upper/lower fit really solid though, unless you actually tighten the screw with the upper/lower together; then you can't remove the upper without backing out the screw. You can set the screw "just right" so the rear pin can still be removed, as intended, but that still end up with some movement between upper and lower. It's an interesting idea, but never gave the solid feel I look for. Some people are happy with it though.

I never said it was perfect but I don't shoot suppressed so gas leaking out was never an issue. Your RTV idea has some merit for the long distance or suppressor shooter who want no wiggle or gas coming out the charging handle. For what I do the Aero lower fits my needs.

kwg

You must be confusing bedding the receiver vs sealing the charge handle with RTV? Two different things, bedding or the screw in the Aero receivers have nothing to do with shooting suppressed or not, zero affect on that either way.