AR fit question

Easy Fix. Take out the accu-wedge and shoot the gun as is. The M16/M4/AR15 has this wiggle by nature of its design. It does not impeed function and all of the "fixes" have been known to cause failures or damage to the gun.

+100 with what Azizza has stated, part of the charm of the platform

What most people don't realize is that the upper/lower fit has to do with more than just the upper and lower. I have test fit receivers before in the shop with pins and they were REALLY tight. But when I built them using a high quality LPK they were loose. The wiggle is a partially due to the size of the holes in the upper and lower and partially the pins that hold them together. I have never seen a gun with enough wiggle to cause a functioning problem. However I have seen a gun with a wallowed out hole due to upwards pressure on the rear pin in an attempt to fix it. In all fairness however this lower was of questionable pedigree to begin with.

I glass bed my uppers to lowers using Brownells Acra-Glas gel for a rock solid fit. I put release agent on the lower, so the upper retains the epoxy. It works great. I dislike immensely the play between the receivers, and this eliminates it.

I'd actually be more "worried" about the fit if there were no play after a few hundred rounds. There is supposed to be some play. A brand new gun may be a little tight, but it should loosen up after just a few hundred rounds.

I also would not install any devices that change forces between the receivers; such as the accuwedge.

Well now I'm confused. I've long read that the tight tolerances of the AR was a major reason for it's superior accuracy over the AK's loose tolerances.
I stuck an accu-wedge in my recently purchased Spikes middy,mostly 'cause I had one lying around. You guys saying I should yank it outa there?
Is it somehow a detriment, or just an un-necessary accessory?

The accuracy potential of the rifle is entirely in the upper half. So long as the sights stay aligned, and the barrel stays in it's same position relative to the upper receiver, the gun will continue to shoot to the same POI.

I do use an accuwedge in my target setup, just because I like the tight feeling when I snug up on it. If the slight side to side shifting bothers you, you can try putting a thin o-ring on the front lug of the upper. When you close it, the o-ring will keep it from shifting. I think I keep no. 14 o-ring for that.

In any case, the play between the upper and lower isn't a cause for concern. It's normal and won't affect the reliability or accuracy. One thing that you don't want to do is get a fit so tight that you need tools to drive the pins out. I would consider that to be undue upward force on the upper and sooner or later something is going to wear. If you are going to use an accuwedge, it shouldn't be so tight that you have to pound the pin in. The pin should go in while slightly squeezing the upper and lower together. If you have to do more than slightly squeeze, you should trim the accuwedge.

I've long read that the tight tolerances of the AR was a major reason for it's superior accuracy

Click to expand...

This is true.
But, it does not apply to the fit between the upper & lower.

A loose joint there has no effect on accuracy, as everything in the accuracy department is firmly attached to the upper receiver.

The lower is just something to hold onto and put the trigger group & magazine in.

Look at the close tolerance fit of the rotery bolt locking into the barrel extension, which is tightly attached to the upper, on which the sights are firmly mounted.

All that added together is why the AR is way more accurate then the AK.
The loose fit of the lower has no effect at all.

rc

But, but, but....Why do they call it an Accuwedge?

It's a catchy name. I get mine for like $2 at cdnninvestments. They're cheap enough and I just trim them to a size that tightens things up just a bit. The "accuwedge" thing is a misnomer. It doesn't NOTHING for accuracy and if it does for you, it's all in your head.

Goes with the "SPROING!"

Just part of the gun.

You can put an o-ring on the forward pin lug.

I don't. I don't notice the rattle between the upper and lower much from my Colt 6920 when bullets are zinging over my head.

How is a loose fit between an AR upper and lower OK but a loose fitting bolt action in it's stock needs to be bedded?
If only the upper was held while shot I might agree it makes no difference but half of the grip of the rifle is on the lower.
If fit between the grip and business end of a gun didn't matter we wouldn't bother to bed actions to stocks, fit slides to frames or uppers to lowers.
Every AR found on the line in high power competition in capable hands is fitted as tightly together as possible, be it a wedge (which sucks), leather under the rear lug, bedded or screwed together.

Every rifle I qualified with had some play. It never kept me from shooting expert. Most shooter's can't do even that - and shooting a 2" group at 100" is even harder, regardless of how good the rifle is.

There is a huge difference between shooting a 2MOA combat rifle and someone tuning his personal long distance precision rifle for 1" groups at 500m. I suspect they run 20+ bull barrels, weigh over 12 pounds, and have 1 1/2 pound triggers, too. What they do has about as much application to a military or three gun competition gun as a NASCAR race car to a street and strip daily driver. Those same precision shooters replace barrels annually regardless - they know a season of competition will use up the critical first 1/4 MOA barrel life. That's something most shooters can't even attempt.

Whatever race guns do is like a race car, fine on a closed course, in public, a finicky nightmare. Most of the technology is useless in a daily driver and overall performance suffers. The ones who don't learn that quickly run out of money and regret paying for the experience. There is always more to it than buying a whiz bang part - if the truth will really be known.

JP Tension Pin...

http://www.jprifles.com/1.5.1.7_small_tp.php

How is a loose fit between an AR upper and lower OK but a loose fitting bolt action in it's stock needs to be bedded?

Click to expand...

Because on a Bolt Gun Both points of contact are on the stock which if it is loose means the reciever will wobble. On an AR one point of contact is on the grip on the other on the Handguard. Since the handguards are attacked to the receiver and the barrel in some cases this means that play has no impact on shooting accuracy.

Different platforms react in different ways. that is just the way it is.