Explain how upper lower fit dosent effect accuracy

[Sincerd]

Ok so you have a sloppy upper. That can have vertical movement from the lower. People always say that it dosent effect accuracy. How is that different from limp arming a stock. Or just shoulder and get some poi movement?

Also the takedown pin has some movement when closed. Which isn't normal from what I've seen. I think that is the actual cause.

 

[acudaowner]

tried to use a little rubber gasket kept loosing those , tried another fastener it would not hold in place very well finally switched to a bolt and a nut and have not seen or had a problem in the ar we did that with a few others it was or has not been an issue only one and whether it does or does not make it better there is no slop between the lower and upper anymore not even a little wiggle it's not going anywhere till I want it to and the gun shoots great . Best of luck with yours .

 

[Desert_Racer]

It still comes down to having good fundamentals, regardless of how much slop is in the upper and lower. You need to exert the same pressure on the gun every time. Does it help to have a super tight fit? Sure, probably. But I have had, and do have, very accurate rifles that have quite a bit of slop between the upper and lower. They still shoot sub MOA, until my fundamentals fall apart.

 

[tomme boy]

There is MOA, sub MOA, and SUB 1/2MOA. If it is loose you will get larger groups.

 

[smoothy8500]

People always say that it doesn't effect accuracy.

I think that comes from CMP and NRA Highpower shooter's perspective. However, their accepted accuracy of 1-1/2 moa at 600yds provides a very good score. Considering the limitations of 4x scopes, sling/glove, reading wind, etc, the slop between upper and lower is not that significant.

 

[bigjake83]

Ok so you have a sloppy upper. That can have vertical movement from the lower. People always say that it dosent effect accuracy. How is that different from limp arming a stock. Or just shoulder and get some poi movement?

Also the takedown pin has some movement when closed. Which isn't normal from what I've seen. I think that is the actual cause.

Who's stating it doesn't???

The only time I've seen this clam if from people who can't shoot better than MOA no matter what firearm their using so in their mind is makes no different but in actuality they're just not a good enough shooter to see the difference.

Carrier tilt can and dose make a difference in CONSISTENT and REPEATABLE ACCURACY, all moving part need to operate direct to the center of the Bore Line.

The optimum goal is to have a snug fit that is achieved by quality machining work, you do NOT want to induce stress to the upper and lower receiver and many people do this by using the tension screws that some lowers come with or cheap rubber wedges, this is where QUALITY MATCHED receiver sets with tight tolerances achieved by precise machining make the difference, JP and Seekins are perfect examples of this.

 

[RUTGERS95]

my current most accurate rifle is loose. Doesn't matter what you have or don't have if you do not posses proper breathing, muscle memory, and cheek/shoulder position. Having a loose or tight rifle will only be important to maybe .1% of shooters who are capable of getting every last tenth of an inch out of their rifle which many, including people who will respond here, are not capable of despite what they think.

 

[Rocketvapor]

Satisfied with 1/2 MOA?
I'm not.

 

[bigjake83]

Satisfied with 1/2 MOA?
I'm not.
View attachment 7859841

What are we looking at?

 

[powdahound76]

Dick pic.

Cant see it? Exactly!!!





Sorry, not relevant at all. And funny in my own mind!

Do have one with a little movement that regularly shoots 1/2 MOA.
Not high dollar stuff. Aero lower, BCM upper. Proof barrel, JP bolt

 

[Rocketvapor]

National Match Shim

nationalmatchshim

 

[candyx]

The front take down pin area check with a feeler gauge between the lower and upper lug. Then purchase brass washers to fill the gap less .001". This takes out the movement between the lower and upper.

 

[JINKSTER]

Slop ='s Slop and in the words of Pvt Gump?..."That's all I have to say about that"

 

[RUTGERS95]

Dick pic.

Cant see it? Exactly!!!





Sorry, not relevant at all. And funny in my own mind!

Do have one with a little movement that regularly shoots 1/2 MOA.
Not high dollar stuff. Aero lower, BCM upper. Proof barrel, JP bolt

I gotta admit, I was wondering and thinking I'm missing something. I looked at this 6 ways to Sunday and was fking lost!

 

[Neurotic]

The front take down pin area check with a feeler gauge between the lower and upper lug. Then purchase brass washers to fill the gap less .001". This takes out the movement between the lower and upper.

I do the same with stainless shims from McMaster. Most receiver sets have 0.003-0.008" of clearance, even my tightest fitting ones. Typically the factory tight ones are that way because of the relationship between the pin and mating surface. Regardless, shimming the pivot pin can really tighten up a receiver set.

The optimum goal is to have a snug fit that is achieved by quality machining work, you do NOT want to induce stress to the upper and lower receiver and many people do this by using the tension screws that some lowers come with or cheap rubber wedges, this is where QUALITY MATCHED receiver sets with tight tolerances achieved by precise machining make the difference, JP and Seekins are perfect examples of this.

The tension screws should only apply load to the upper tang/lug between the screw and the takedown pin, and the lower between the pin and the screw. This should be harmless.

The way I see it, fit matters but not a huge amount unless it's crazy loose. Also, if you shoot with a front rest, bag or bipod, keeping some load through the upper into the rest will prevent movement. I think it's mostly this reason (fundamentals) why fit isn't a huge issue. FWIW, all my ARs will shoot between 0.5 and 1.25 MOA with decent ammo.

 

[wvfarrier]

I learned a trick during my time in the Army. We would take a foam ear plug and crush it in the rear of the lower under the upper takedown lug. It worked awesome to tighten up a sloppy fit.

 

[mtrmn]

I learned a trick during my time in the Army. We would take a foam ear plug and crush it in the rear of the lower under the upper takedown lug. It worked awesome to tighten up a sloppy fit.

THIS^^^^^
Maybe the slop doesn't affect the accuracy of the upper, but it certainly DOES affect the accuracy of the shooter. And you don't have to throw a lot of money at every little problem that crops up. Adapt and overcome.

 

[Sincerd]

I found out Adco will drill and thread a receiver tension screw in a lower for $80. Not something I plan on doing, but worth knowing.

 

[bfoosh006]

Having a snug upper to lower fit will help you wield the AR much more consistently.

IMHO, it is just like bedding a bolt gun.

Even match Ar shooters will sling the AR tight... for consistency.

 

[David4570]

I used one .002” thick stainless 1/4” ID washer from McMaster on each side of the upper receiver pivot lug to keep the upper from moving laterally at the front pivot. May not matter much but feels great for the little it costs.
Add JP .001 oversized pins and the fit firms up nicely.
I also like cleaning a weapon.
Anal & OCD