Hello, I just purchased my first AR-15, first rifle period. There is space between the upper and lower assembly. I have read that some "slop" is normal. I am just curious how much is normal and when it can become a problem. The AR-15 that i bought is the DPMS Oracle, california legal model. The rifle has enough slop that it will rattle if i shake it by the handguard. It has up and down play, and if you grab the upper and lower, can be rocked left and right slightly. Is this amount of slop normal? It is about a half millimeter serparation between top and bottom.
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Too Much "Slop"?
- Thread starter microtech
- Start date
LJ-MosinFreak-Buck
New member
The barrel,lockup,sight relationship is all in the upper.The lower holds the mag,swings the hammer,and gives the boltcarrier a place to go.If it works,it works.
It is highly likely the parts are made to the design blue prints.It is also highly likely,with modern CNC equiptment,that all the surfaces, and hole locations are within .002 or so,and maybe .001.Diameters are likely within .001.Seat of the pants guesses on the numbers,but close.
Realize design intent is not making everything a line to line fit.I suspect if you plug gage the holes for the hinge and takedown pins,they will probably be within .2501 and .2505(I do not have a dwg,this is a guess,I'm making a point).The hole will likely be within 1/2 thousandth on diameter.Now,if you go over to a whole bucketfull of hinge and takedown pins,they will likely be within a few tenths of one thousandth to .245.Precisely made to give .005 slop.I suggest,don't worry about it.
It is highly likely the parts are made to the design blue prints.It is also highly likely,with modern CNC equiptment,that all the surfaces, and hole locations are within .002 or so,and maybe .001.Diameters are likely within .001.Seat of the pants guesses on the numbers,but close.
Realize design intent is not making everything a line to line fit.I suspect if you plug gage the holes for the hinge and takedown pins,they will probably be within .2501 and .2505(I do not have a dwg,this is a guess,I'm making a point).The hole will likely be within 1/2 thousandth on diameter.Now,if you go over to a whole bucketfull of hinge and takedown pins,they will likely be within a few tenths of one thousandth to .245.Precisely made to give .005 slop.I suggest,don't worry about it.
It's purely cosmetic and won't affect accuracy. Some guys put an O-ring around the front upper receiver lug. Others put use the Accuwedge, but do you really want to put a piece of foreign materiel inside your rifle? There are plenty of stories of the Accuwedge being exposed to cleaning solvents and then breaking into pieces that get dispersed into the rifles internals.
madcratebuilder
New member
Some slop is normal, it does not effect accuracy. You can use a accuwedge, o-ring, foam ear plug as others have recommended. A select few manufacturers add a setscrew to the lower that has a nylon tip and you can screw it in until it takes up all the movement between the upper and lower.
This is the military way, from the 23&P.
This is the military way, from the 23&P.
1. With the upper receiver attached to the lower receiver, and the pivot pin and takedown pins in place, perform the
following test:
(a) Apply hand pressure to push the upper receiver as far to one side as possible.
(b) Attempt to insert a 0.020 inch thickness gage between the pivot pin lugs of the upper and lower
receivers.
(c) If the thickness gage penetrates to the pivot pin at all accessible locations, repair by replacement of the
upper receiver (see (b) below) or replacement of rifle is required.
2. If the rifle fails the above test, remove the upper receiver and install a "NEW" upper receiver and perform the
test again.
3. If the rifle now passes the above test, it shall be considered serviceable and continue in use.
4. If the rifle falls the test with a new upper receiver, this failure shall be considered a shortcoming. This
shortcoming requires action to obtain a replacement rifle. Once a replacement has been received, evacuate the
original rifle to depot for overhaul