AR-15 Gap between upper and lower?

[MudPuppy]

How much gap is acceptable between an AR's upper and lower?

I've been sitting on a DPMS lower for a while, just got a new (to me) upper that has a wider gap than I'm used to between the lower and upper. (It's about half the width of a dime's thickness. I don't have feeler gauges, but am going to try and get by the auto parts store this afternoon.)

At what point is gap "too much"? And what issues would too much cause? Jamming? Dirt Entering? Sear not tripping if the bolt is riding high?

Thanks in advance,

 

[techmike]

Shouldn't hurt a thing...as long as the bolt carrier group can travel freely into the receiver extension you shouldn't have any problem. I don't find 1/2 a dime's widthg gap to be excessive. (I don't recall the spec, but I BELIEVE THAT IS WELL INSIDE IT) I've seen m-16's run flawlessly with more gap that that.

As long as the rifle is running well I woudn't sweat it. Looking at my AR's at least 2 of the 6 have that much gap. I don't think you could get it out us spec enough to matter in that direction and still be able to chamber a round.

ymmv...I am NOT a professional gunsmith...just a regular shooter who loves EBR's.

 

[jacketch]

Go to http://www.jprifles.com/buy.php?item=JPTP-1 and get one of these and your loose receiver problem will be solved.

 

[Zeke Menuar]

A little slop is fine. Stay away from the products like the accuwedge and other gimmicks that claim to eliminate the play. Most of them will damage the lower over time by elongating the pin holes.

They are a solution to a non-problem.

If you really need to tighten things up use an old earplug down inside the lower towards the rear behind the pin.

But it really isn't needed. My new AR has some slop in it and it is much more accurate then I am.

ZM

 

[Zak Smith]

At the EAG Carbine class I'm in the middle of, an Accu-Wedge wedged itself into the trigger group of one of the rifles rendering it inoperable until broken down and the pieces removed.

 

[Mr White]

Slop between the upper and lower will have ZERO effect on accuracy. I've read this in books and articles by top high power shooters and AR-15 builders.

The slop is annoying, though. I made an improvised accu-wedge from some rubber I had onhand. It eliminated the slop and has not given me any problems. It fits under and behind the rear pin and tightens the fit just enough to keep it from being annoying. I don't see any difference in accuracy when the wedge is in place or removed.

 

[MudPuppy]

Just to clarify, there is ZERO slop--it fits very tight.

The rear of the upper fits in tight (the part were the lower comes up to the buffer housing--that is the part that is vertical). The horizontal has a decent gap.

I generally don't use buffers and wedges and such unless I've seen them used by the troops for a long while and they're widely adopted. Milspec stuff is expected to work out of the box, if it don't, I'll use combloc.

 

[Thin Black Line]

The JP pin is more expensive/time-consuming compared to the accuwedge.
Some lowers will require that you trim the accuwedge and as Zak pointed
out they may not hold up. Full size/uncut accuwedges have held up for me
for thousands of rds.

Slop between the upper and lower will have ZERO effect on accuracy. I've read this in books and articles by top high power shooters and AR-15 builders.

How many of them are using sloppy rifles where upper and lower are literally
wiggling a few degrees left and right and taking them to competition?

Run for accuracy with and without the wedge and a good shooter will see a
difference. Someone shooting pie-plate size groups at 100 yds probably won't.
It won't hurt --or really help-- them.

 

[Joe Demko]

Stay away from the products like the accuwedge and other gimmicks that claim to eliminate the play. Most of them will damage the lower over time by elongating the pin holes.

They are a solution to a non-problem.

If you really need to tighten things up use an old earplug down inside the lower towards the rear behind the pin.

How is what you do with an earplug any different from what the accuwedge does?

 

[Noban]

An accuwedge will not hasten the elongation of the receiver holes. In fact, a sloppy fit will due to abrasion. I put a wedge in my AR 20,000 rounds ago and there isn't a hint of hole wear.