Its a DPMS LR 308, think the slop started after a barrel change, I see the expanding pin they have at brownells but wondering if there is a way a gunsmith could press the upper and lower to make it tighter again? Any other options?
Slop between upper and lower
- Thread starter ArmyJerry
- Start date
My dpms has some slack but it doesn't affect accuracy. Since your sights/scope is attached to the upper not sure it matters too much about the slop. I wouldn't go putting crap in my lower that may cause a malfunction.
I'm not sure HOW a barrel change could possible cause or even really contribute to "slop" between your upper and lower receivers (aside from the fact that is just when you happened to notice slop that's been there for some time). However, 95% of the time or more that I see people bring this issue up, it is a non-issue and will have zero impact on accuracy/reliability of your rifle.
All of the gimmicky BS products like the accu-wedges, etc. aren't worth a flying @#$% so don't go there. They do the OPPOSITE of what you want in pushing the upper/lower apart on a soft/flexible surface. Also, good luck when they start to break down and fall apart (which they will) and pieces work their way into your FCG.
If you simply MUST try the JP rear tension pin, then just be advised that you have to be very careful with them as there is the potential to cause harm to your lower receiver with use (or at least with improper use/overtightening). They are also a certified PITA if you need to get into the rifle in a hurry for whatever reason, but they do work to eliminate upper/lower receiver play as advertised.
Furthermore, before you go spending money on new gadgetry, take some measurements and see if your takedown and pivot pins (and the holes in your receivers too) are in spec and/or haven't worn/wobbled out/etc./etc.
All of the gimmicky BS products like the accu-wedges, etc. aren't worth a flying @#$% so don't go there. They do the OPPOSITE of what you want in pushing the upper/lower apart on a soft/flexible surface. Also, good luck when they start to break down and fall apart (which they will) and pieces work their way into your FCG.
I have had an AccuWedge in my first AR since the first day it was assembled in 2008 and it's still tight as the day it went in with no signs of breaking down. It's a chemical resistant polymer and mines gotten hoppes and sweets both on it with no ill effects. After going on 6 years now, you still need to slightly squeeze the upper/lower together to actually release some tension before you can even get the rear pin loose, it's still that snug.
Now...regardless, this debate has gone on all over the net and the general consensus is that the "slop" has no effect on accuracy because the upper, barrel and optic are all one part and that's where the accuracy comes from.
However, I see no reason why slop between the upper and lower would be any different than slop between a stock and an action and it would take real scientific data to convince me otherwise.
I currently have an accuwedge in mine...but am considering a more permanent "bedding" option that others have done.
Accuwedge should fix it. But play isn't necessarily a bad thing.
But play between the receivers is usually a sign of the rest of the rifles fit and finish. But again slop doesn't make it a bad rifle if its just in the receivers.
But play between the receivers is usually a sign of the rest of the rifles fit and finish. But again slop doesn't make it a bad rifle if its just in the receivers.
Slop between receivers should have NO effect on the accuracy of the weapon--however it CAN have an effect on the accuracy of the shooter.
I have accuwedges in a couple of my AR's with no ill effects. One of these has been in my Colt for almost 20 years with no evidence of deterioration. I did have to trim some off the bottom of the wedges so they would take the slack out without affecting my ability to easily push my pins out.
A foam earplug does just as good a job IMO, and it's available NOW, cheap, and provides a good test to see if you really even want/need a wedge or some of the more expensive routes. I personally would never go to any length beyond this expedient measure unless the takedown pin holes are worn out for some reason.
I have accuwedges in a couple of my AR's with no ill effects. One of these has been in my Colt for almost 20 years with no evidence of deterioration. I did have to trim some off the bottom of the wedges so they would take the slack out without affecting my ability to easily push my pins out.
A foam earplug does just as good a job IMO, and it's available NOW, cheap, and provides a good test to see if you really even want/need a wedge or some of the more expensive routes. I personally would never go to any length beyond this expedient measure unless the takedown pin holes are worn out for some reason.
JP makes a more permanent solution. May cost a little more but it puts the stress in the right spot.
JP - Tension Pin
JP - Tension Pin
Bingo!
I have read several articles on precision shooting with the AR and all call for a tight upper and lower fit. Every time the hammer falls on a firing pin, it will move the upper if it does not have the slop taken out. The upper still maintains its accuracy. But the upper moves off POA and will effect the POI when the gun is fired.
Yes. An earplug will also.
Push out the rear takedown pin. Hinge open the AR. In the extreme rear of the lower receiver, behind where the takedown pin is located, place a foam earplug in the recess. Hinge the upper back down, compressing the earplug. Push the pin back in. Slop should be gone.
If you use an accuwedge, you may have to trim some off the bottom in order to get the rear pin back in.
Push out the rear takedown pin. Hinge open the AR. In the extreme rear of the lower receiver, behind where the takedown pin is located, place a foam earplug in the recess. Hinge the upper back down, compressing the earplug. Push the pin back in. Slop should be gone.
If you use an accuwedge, you may have to trim some off the bottom in order to get the rear pin back in.
Last edited:
Yup, proper handling will cure that issue. My handful of M16s from my military days were as sloppy as they get....maybe a few too many bayonet courses, broke too many falls, or a few too many jumps...but they would still shoot expert when operated correctly.
I run accuwedges in most of my guns as well. I don't buy the whole "slop doesn't affect accuracy" argument. Slop between upper and lower 100% has an effect on accuracy. The myth that it doesn't stems from a military test using light weight barrels, ball ammo, and open sights. When you start hanloading, using a good barrel, and magnified optics, a 1/2 moa change in accuracy is more noticable.
The other trick I learned about is to go to the local hardware store and pick up an assortment of o-rings. Find one with the right diameter and thickness to go around the front "leg" of the upper. This trick works great, but I have to replace that o-ring prettty often (like every 4th time I clean the gun).
Lately, all the ar type guns I've been building have been on Mega lowers, which have a set screw to adjust the tension. You can get it set tight enough that there is no noticable play, but you can still get into the gun. I thought long and hard about the JP tension screw, but I don't want to have to get to an allen wrench every time I need to get into my gun.
OK, just to clarify my post, I agree with this guy. The problem with slop is that when the hammer falls, it moves the upper, this movement is not necessarily predicable or consistent.
The only AR I have with the slack in it is ironically my most expensive one. Complete correct KAC lower and HCS Mk12Mod1 upper.
Figure that out.
Figure that out.
If they ever come back in stock, an armalite national match pivot pin usually works as well.
They havent been in stock for a while though. Should have bought ten of em with my last order.
They havent been in stock for a while though. Should have bought ten of em with my last order.
So, what is the fundamentally correct way to hold an AR that has slop between the receivers?
Maybe he was referring to the fundamentals of marksmanship that help contribute to a solid foundation and keeping the gun from moving when pulling the trigger?
How do you stop a gun from moving when you are holding two separate loosely attached pieces with one hand on each?
All I am saying is you will have a more accurate AR rifle with a properly fitted upper and lower receiver. If you dont have a properly fitting upper and lower, there is nothing wrong with using proven methods to tighten the fit, which will improve your accuracy.
If you can shoot great scores with a sloppy fitted receiver set, then that's great! Maybe you can add a few more points or X's by tightening the fit. It never hurts to try.
lol I thought the same thing. So, with a proper position I can defy the laws of physics and stop something on the rifle from moving?
Off hand is simply snugging up the rifle properly. An 8 lb. combat trigger doesn't make it easy, but that is how it is done. Otherwise, when you properly load your bipod in the prone (just like a bolt action) the slop become irrelevant. Some put a little twist into it via the grip to snug things up, I just load forward - whatever works for you.
Instead of talking out of your asses, and provided you have a modicum of shooting skill, why don't one or more of you cyber snipers do a little testing. Should take little more than some time, ammo, a loose fitting rifle and a used earplug.
Some AR lower manufacturers put a tapped hole in the lower receiver that aligns below the rear takedown pin lug on the upper receiver and you can put a nylon or brass tipped set screw in there to take out the slop. I've also seen others in the upper receiver where it meets up with the ring of the lower where the buffer tube goes. This would take a little more gunsmithing than some might be comfortable with.
Unless you are trying to free recoil the gun in a rest it's not hard to take up the movement between the upper and lower. If you are trying to shoot accurately with just the use of your two hands good luck to you. Try shouldering the rifle and using a cheek weld - all part of a position. A sling will also contribute. I'm not going to even guess at your level of experience or skill - anyone on the Internet can create that bio.
As to your moment about a "properly fitted upper and lower receiver" - what is the "proper" tolerance and please define the variances and resultant accuracy degradation for us as a general rule of thumb. The rifle I took to camp perry had PLENTY of slop between the upper and lower receiver and I was certainly able to place in the top 50 out of 1300+ competitors. I shoot this rifle all the time and have tried o-rings, accuwedge, adjustable tension screws, etc and cannot say with any evidence that it contributes to the overall accuracy of the platform. Thousands and thousands of rounds through the gun all geared at improvement in accuracy.
If you believe that zero movement between the two gives you the advantage, that's great. I have. Found attention to other details pay much greater dividends.
I'm sure you have a different perspective.... I respect that. Good luck in your quest
Last edited:
A barrel change with a dumbass putting too much torque on the barrel nut while in the upper jig vice would cause this.
some "slop" is in built in there for a reason - in the theater the the rifle was intended to go into, if say there is some debris that gets into the workings of the rifle, the extra "slop" gives the rifle extra freedom to operate, where as if everything was tight fitting, a few grains of sand and such with lock everything up.
same principle of why glocks sounds like a baby rattle when shook. room for if gunk gets in, the platform still operates (to some extent).
was the barrel change to a heavier or longer barrel? the extra weight up front may just be making the amount of "slop" more noticeable as there is more weight pulling down on the hinge making it perceived there is more "slop" there now - but is actually the same amount that was there all along.
same principle of why glocks sounds like a baby rattle when shook. room for if gunk gets in, the platform still operates (to some extent).
was the barrel change to a heavier or longer barrel? the extra weight up front may just be making the amount of "slop" more noticeable as there is more weight pulling down on the hinge making it perceived there is more "slop" there now - but is actually the same amount that was there all along.
+1 for ORD and Oryx here. They are correct and know what they are talking about.
My varmint, national match, and long range uppers are sub-moa regardless of slop
in receiver fit. That being said I keep at least 6 to 10 spare upper receivers so that I
can match them up for a more perfect fit when assembling an AR, as clients who purchase
high dollar AR's expect a great fit between receivers. Most of the manufacturers of the
better quality upper and lower receivers offer matched sets for a premium price. I simply
match my own before assy. to avoid the sloppy fit. If one truly believes that an Accuwedge
works, let them believe---Dr's give placebo's to patients and they have the same results as
those given proper meds.
My varmint, national match, and long range uppers are sub-moa regardless of slop
in receiver fit. That being said I keep at least 6 to 10 spare upper receivers so that I
can match them up for a more perfect fit when assembling an AR, as clients who purchase
high dollar AR's expect a great fit between receivers. Most of the manufacturers of the
better quality upper and lower receivers offer matched sets for a premium price. I simply
match my own before assy. to avoid the sloppy fit. If one truly believes that an Accuwedge
works, let them believe---Dr's give placebo's to patients and they have the same results as
those given proper meds.
Agree. In my experience movement between the upper and lower does not hurt accuracy or anything else.
Fundamentals change, physics does not. Sure, you can take the slop out by shooting slung up, by applying torque to the rife, etc. How does that work with positional shooting?
Your rifle will have one zero when slung, one when applying torque, one with a good load put on the bipod, and on and on.
All other things being equal, a tight fitting upper and lower enhances accuracy (whether it is the shooter or the weapon itself does not matter) AND has no ill effects on reliability.
I can't believe anyone on a forum that focuses on precision accuracy would say otherwise. To do so is to perpetuate misinformation.
The accuracy of the upper is determined by the upper. The accuracy of the whole system, upper, lower and shooter, is determined by more than just the upper.
Last edited:
Same way I build ARs, having several receivers helps if one doesn't seem as tight. Use a high quality receiver such as Mega and fit is usually fine.
That being said, I have had and seen "sloppy" fit receivers that would shoot just as good as a tight fit set. Might be voodoo, not sure, lol.
Can someone please clarify which law of physics is contributing to the inaccuracy related to upper an lower tolerances?
Further, couldn't it then be determined that the best shooters in the world with the AR platform have ZERO tolerance between the upper and lower receivers? If not, they can simply take up the "slop" and pick up a couple more X's? Now that the word is out, we should start to see much tougher competition next year.... Probably in the first match! Millions of AR's can become accurized overnight!
Further, couldn't it then be determined that the best shooters in the world with the AR platform have ZERO tolerance between the upper and lower receivers? If not, they can simply take up the "slop" and pick up a couple more X's? Now that the word is out, we should start to see much tougher competition next year.... Probably in the first match! Millions of AR's can become accurized overnight!
You know, you try to be polite and the clowns just don't stop.
How about this, if you think the "slop" in your AR is affecting your accuracy - you are doing something wrong.
My LR308 pattern, shoots 3/4 MOA all day with FGMM 168 SMKs, it has slop. My 5.56 of various flavors all shoot about 2 MOA with M855 and M193, both I believe are 4 MOA spec ammo. The good stuff is =< 1 MOA out of those same ARs. This does not require a three or four thousand dollar rifle, or the latest trend/fad/excuse for not doing right. If someone wants to squeeze another 1/8 MOA out of a gun, it isn't gonna come from a snug fitting lower/upper...but you do start to get closer to the more expensive end of the spectrum.
This, of course, is just my opinion based on experience.
