My AR15 started out as a Bushmaster A2 20" with a compensator and mid-length handguard.  

Since then I've replaced the upper with a Fulton Armory 16" A3, the stock has been replaced with a CAR collapsible stock.  I've added a ARMS Mount riser with an integrated rear sight and on top of that is an Aimpoint red-dot scope.  And I just replaced the standard handguards with a YHM two-piece handguard which has a vertical forearm grip on it.  

However, now the rifle twists and rattles quite a bit.  There is a small twist between the upper and lower.  And the collapsible stock twists from side to side slightly around the buffer tube.  

What are my options to tighten up the fit and feel on my rifle?  I'm sure the easiest solution to fixing the stock would be to replace it with something that has tighter tolerances.  

The YHM handguards don't have any movement to them which is good.  And the vertical forearm grip is on tight enough that it does not move either.

But, what about the upper and lower fit?  

What in an AR15 would impact the accuracy the most if it wasn't tight and to spec?

Accuwedge will tighten the upper/lower fit.  Does it shoot good?  If so, then don't worry about it unless you want to make it a little less clunky.  If it shoots badly then an accuwedge will not help and there is probably another issue.  MJD

The rattle and twist have nothing to do with accuracy.

Quoted: The rattle and twist have nothing to do with accuracy.

I don't understand how that can be.  I mean, I believe you.  But, why then, do people glass bed their rifles into the stocks?

Quoted: Quoted: The rattle and twist have nothing to do with accuracy. I don't understand how that can be.  I mean, I believe you.  But, why then, do people glass bed their rifles into the stocks?

The front and rear sights are mounted on the same plane, which of course is the upper receiver. Movement between the upper and lower receivers can not change the accuracy of the rifle. As long as you do your part i.e. proper stock weld, nose to charging handle, correct sight picture, trigger pull and breathing, the rifle will do it’s part.

Have you ever served in the military? Some of those M16’s in basic training were so loose you’d think you could fold that weapon in half and stick it in your cargo pocket! But qualifying expert was still possible.

As far as glass bedding goes, I can’t answer that. I’m not a bolt action guy.

Get a new RRA lower receiver.

But seriously,

An accuwedge will tighten it up.  An O-ring will do the same.

Here's a cheap source for Accuwedges: Accuwedges 12 for $17

Quoted: Quoted: Quoted: The rattle and twist have nothing to do with accuracy. I don't understand how that can be.  I mean, I believe you.  But, why then, do people glass bed their rifles into the stocks? The front and rear sights are mounted on the same plane, which of course is the upper receiver. Movement between the upper and lower receivers can not change the accuracy of the rifle. As long as you do your part i.e. proper stock weld, nose to charging handle, correct sight picture, trigger pull and breathing, the rifle will do it’s part. Have you ever served in the military? Some of those M16’s in basic training were so loose you’d think you could fold that weapon in half and stick it in your cargo pocket! But qualifying expert was still possible. As far as glass bedding goes, I can’t answer that. I’m not a bolt action guy.

+1



and with glass bedding some rifles take to it and some dont.

This is what I have come up with for the M4 stock havn't tried a reg car stock , but if it's polymer it should work .

This is for M4 or other stocks with the nylon type plastic ( not the alum. stocks) that are loose on the buffer tube .  
Take the stock off the tube and put it in a vise with a rag around it to keep from marring it up . Squeese it  in the vise but don't go crazy , while it is in the vise take a hair dryer and blow through the stock heating it up , do both ends , this only takes about  1min all together , then ck it for fit on the tube , repeat if nessesary to get desired fit .
You then have a stock that fits nice and tight no rattling !

Hope this helps .

Put a strip of ductape where the upper and lower meet on both sides of the pins.  Hard to explain, easy to do.  A rattly upper and lower interface hurts accuracy in two ways:  First, as the bullet travels down the barrel, the barrel will move in unpredictable ways.  Second, the rattly interface will cause bad harmonics.  The upper needs to be "welded" to the lower, and the lower needs to be welded to the stock, the stock needs to be welded to your shoulder, and your body needs to be "locked up" in a good shooting position.

Just because your sights stay aligned relative to the bore of the weapon, doesn't make it accurate.

Not a bolt action expert either, but I think it has to do with how temperature changes & stock movement/shape change can torque the barrel or move things around.

Quoted: First, as the bullet travels down the barrel, the barrel will move in unpredictable ways.

Say what? Please explain just where you think my barrel is going because I have some play between my upper and lower receivers!

Actually a loose upper will make a rifle shoot worse since it allows for too much vibration.  When the trigger is pulled and the hammer falls and the bolt starts moving etc all that is creating vibratory rotation in a counterclockwise patern while the barrel is moving in a clockwise patern and the twist is backwards.  Anyways this comes out to lead on to having bad timing.

Oh yeah  lol I have no clue what all that jumbo means but the easter bunny and myself were discussing this last night over some fried unicorn.

I have a very little play between my upper and lower and I can still shoot excelent groups. AFAIK this small play should not harm you accuracy. At least it never has for me.  

If it's just a *little* play, just cut a chunk of matchbook cover to fit, stick it in the lower right where the takedown pin tang on the upper would hit it, and close the upper/lower...you can even try folding it over.  With any luck, it's now tight.  That's worked fine on a couple of my rifles.  

I call it the "VA Po'boy Accu Wedge"®.

The only accu wedge I ever had was so tight there was NO way to close the upper and lower w/o an elephent standing on it.  

holy cow!
getting deep here boys...
explain what you guys just wrote about how a loose AR is not accurate to all the guys/gals who qualified expert in the service..
My basic training M16 shook, rattled and rolled and I still got expert with it.

glass bedding is for bolt action rifles.  A basic stock AR don't need no stinkin accuwedge.

now if you want to knock the ass out of a rat at 300 yards, that is a totally different story and then your talking accuracy improvements that a accuwedge ain't gonna give you.

Quoted: holy cow! getting deep here boys... explain what you guys just wrote about how a loose AR is not accurate to all the guys/gals who qualified expert in the service.. My basic training M16 shook, rattled and rolled and I still got expert with it. glass bedding is for bolt action rifles.  A basic stock AR don't need no stinkin accuwedge. now if you want to knock the ass out of a rat at 300 yards, that is a totally different story and then your talking accuracy improvements that a accuwedge ain't gonna give you.

It's hard to tell who you are talking to here.  Are you talking about the feel good guys that don't shoot for gnat's ass accuracy but don't want a rattling rifle.  If so, the Accuwedge is perfect, easy and cheap.

If you want gnat's ass accuracy, then you may pursue other avenues.

JB Weld and wedge.
Email me when you get tired reading the others for a how to.

As for the stock, I have removed the stock on a couple from the buffer tube and placed a piece of electrical tape on the tube. You can trim it to length so it doesn't show when the stock is extended or collapsed. That tightens them right up.

As for the receiver, use a wedge, start buying receivers until you get the fit you want or live with it.

Mike

One of my uppers included an Accuwedge with it when I bought it and I'm using it.

Even if I have the same brand upper and lower there is still a very very slight play but the Accuwedge takes care of that real well.

My Springfield M1A NM was glass bedded in the receiver area only, the barrel is free floating and there's a small gap between the barrel and the wood stock.

My former SP1 have a small play and they didn't have the Accuwedge back then but it doesn't affect the accuracy of it.

Every once in a while back then I get lucky and get a 1 inch 3 shot group at 100 yards with my SP1.

Ok, let’s use this picture of “Doc” the SF soldier as an example. The yellow line represents the bore centerline and the path the bullet will travel. The red line represents “Doc’s” Point of Aim. For all practical purposes “Doc” has zeroed his weapon using the 50m Santose IBSZ recommended to him by the fine members here at ARFCOM. Now, at 50m “Doc’s” POA and the bullet’s path of travel will intersect at 50m. So if “Doc” puts to use all he learned 30+ years ago in basic training regarding basic rifle marksmanship,  when he squeezes the trigger the bullet will impact where he had the sights at the moment the trigger released the hammer.

So any amount of play below, but not including the yellow line (bullet path), will have such a minimal effect on “Doc’s” grouping that you can consider it nil. You could rock the lower receiver in a side to side motion if you wish, as long as the upper receivers (yellow) bore centerline and “Doc’s” (red) Point of Aim remain steady the lower receiver’s movement makes no difference.

Don’t you think that if this was such a critical problem that it would have been addressed years ago! If this play was so critical to accuracy why would the Army use old M16A1 receivers as a base to build upon for the SPR rifles in use today!

I know I'm wasting my breath, but...

When you shoot a rifle, the barrel flexes.  If you have a stable shooting platform, the barrel flexes the same way each time.  If you do NOT have a stable shooting platform, it flexes in random ways.  While the barrel is flexing, the bullet happens to be travelling down it.  The amount of rattle between the lower and the upper, as well as your bench, or body anchor, affects your shooting platform.

Now, we are not talking about "not hitting the barn from the inside" kind of inaccuracy, but it is one of those variables that accuracy nuts try to eliminate in their shooting.  If we are discussing "minute of man" at 300 yds or less, don't worry about your rattle.  If you are curious in inexpensive ways to improve your rifle's accuracy, there are a few things you can do that won't cost you big bucks to improve your rifle.

1.  Eliminate play between upper and lower, as well as buttstock and pistol grip.  All this can be done with a strip of duct tape or electrical tape.  Remember that the tighter you get it, the harder it will be to take it down.

2.  Free float the barrel (I think the AR is the easiest and cheapest rifle to free-float, with a free-floated forearm to be had for under $50 and can be just screwed on)

3.  Post-ban barrels with unthreaded muzzles shoot better.  The threading can actually cause the muzzle to bell out by a small amount, which won't be noticed by anyone except for accuracy nuts.

4.  The pins that hold your front sight on should be removed, and set screws installed (4 each) to de-stress the barrel at that point.

5.  Tighten up your sights.  Whether optic or iron, accuracy lives in your sighting system.  Most would be shocked to learn how much "rack grade" M16A2 rear sights move around.

Oh, well.  I tried.