Receiver Wobble, what is acceptable?

@KRC .. great thinking outside the box, with the...
"Use a ring binder hole reinforcement (remember these?) " ... I would think the plastic ones would be reasonably resilient.

Do you have some results from your nut and bolt alteration ?

And Thanks for pointing out various other notable examples of sloppy upper to lower fit.

To bad these aren't still available...https://www.midwayusa.com/product/1003363678

ToolAA said:

I like trying to improve things too. This wasn’t a personal attack by any means. Sharing experiences ideas and information is necessary to haven informed discussion. My post and any subsequent responses should simply be read in this context.
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Click to expand...

@ToolAA ...

Completely agree, with this statement.. the internet can make conveying comments difficult... no tone, no visual content or demeanor available.
Just words... and Lol, I am far from a good writer.

So I am saying the same... and this is not an attack at all.

Do you have the access to the mentioned '70's report concerning fitment ?

Honestly, my Google Fu is not working every time I have searched. ( For years )

I would love to read it.

Amazingly... I found the report this time.

Here is the link....https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=2ahUKEwjl2MyEgbHkAhUxCjQIHWVrDjsQFjAAegQIABAC&url=https%3A%2F%2Fapps.dtic.mil%2Fdtic%2Ftr%2Ffulltext%2Fu2%2F772939.pdf&usg=AOvVaw1mmuiZMZ9wqPkdWK-6JKNd

Some key things I noticed concerning the loose upper to lower testing

1. the test considered.... "Looseness between the upper and lower receivers should be considered to have a significant effect on accuracy if such looseness causes a change in extreme spread of more than 2.2 inches at 100 yards."

"The 2.2 inches criteria was chosen because new rifle acceptance criteria is 4.8 inches extreme spread at 100 yards and the user rejection criteria is 7.0 inches extreme spread at 100 yards. It is felt that any single parameter which could degrade the weapon from new-weapon-status to unfit-for-use is significant."

That to me is amazing, and shouldn't apply to modern AR's... a "considered" difference of 2.2 inches is a lot.... a whole lot.

So their parameters was concerned with "Combat Accuracy", IMHO.

I wish the handguards had not been included , or tested separately.

We all know how much traditional handguards can affect AR precision, that si why we "free float" the barrel with modern tubes.


Text from the test..


2.2 EFFECT OF LOOSENESS BETWEEN UPPER AND LOWER RECEIVERS ON ACCURACY

2.2.1 Objective
The objective was to determine the effect of looseness between upper and lower receivers on the accuracy of M16A1 Rifles.

2.2.2 Criteria
Looseness between the upper and lower receivers should be considered to have a significant effect on accuracy if such looseness causes a change in extreme spread of more than 2.2 inches at 100 yards. The reasoning applied in Section 2.1.2 was also applied here.

2.2.3 Method
Ten H16A1 Rifles returned from combat in Viet Nam were measured for looseness between the upper and lower receivers. The three weapons exhibiting the most looseness were rebarreled and fired in this subtest.
First, each of the three test rifles was fired two ten-shot
targets by each of two shooters under each of the following conditions:

CONDITION DESCRIPTION
A The original looseness was left in the handguards and between the receivers. Firing was done from a benchrest. The handguards and upper receiver were rotated to opposite extreme positions for alternate shots.

B Same as "A" except that the handguards and upper receiver were allowed to seek their own positions.

C Same as "A" except that firing was done from the prone position.

D Same as "A" except that the handguards and upper receiver were allowed to seek their own positions, and firing was done from the prone position.

E The original looseness was left in the handguards. The looseness was removed from the receivers by inserting shims between them. Firing was done from a benchrest. The handguards were allowed to seek their own positions.

F Same as "E" except that firing was done from the prone position.

Page 6

Then, each of the three test weapons fired was fired two ten-shot targets by one shooter under each of the following conditions:

CONDITION ...............DESCRIPTION

CONDITION DESCRIPTION
A The original looseness was left in the handguards and between the receivers. Firing was done from a benchrest. The handguards and upper receiver were rotated to opposite extreme positions for alternate shots.

B Same as "A" except that the handguards and upper receiver were allowed to seek their own positions.

C Same as "A" except that firing was done from the prone position.

D Same as "A" except that the handguards and upper receiver were allowed to seek their own positions, and firing was done from the prone position.

E The original looseness was left in the handguards. The looseness was removed from the receivers by inserting shims between them. Firing was done from a benchrest. The handguards were allowed to seek their own positions.

F Same as "E" except that firing was done from the prone position.

Page 6

G All looseness was removed from both the handguards and the upper receiver. Firing was done from a benchrest.

H All looseness was removed from the handguards. The original looseness was left between the upper and lower receivers. The upper receiver was rotated to opposite extreme positions for alternate shots. Firing was done from a benchrest.

2.2.4 Results
The average extreme spread for all weapons and shooters is recorded by condition in Table 2.2-1. In addition, Table 2.2-1 also notes the difference in extreme spread between condition "A" and each of the other conditions. Since condition "A" exhibits maximum looseness and succeeding conditions have leqs looseness, any trend toward increased accuracy as the looseness is removed, should be reflected in consistently negative numbers in the AES column.
Only one condition differed significantly in extreme spread from condition "A". Condition "H" averaged 2.5 inches larger than condition "A". No cause for this unexpected increase in extreme spread could be found during the test. However, it was noted that the increase was due almost entirely to vertical stringing of the shots. It is hypothesized that perhaps the manner in which the handguards were epoxied to the barrel nuts was responsible.

2.2.5 Analysis
No detrimental effects on accuracy due to loose upper receivers and/or loose handguards were discernible in this test.

Page 7

TABLE 2. 2-1

EFFECT OF LOOSE HANDGUARDS & LOOSENESS BETWEEN UPPER & LOWER RECEIVERS ON ACCURACY

AVERAGE FOR ALL WEAPONS AND SHOOTERS.........

CONDITIONS..........A.....B......C.......D......E.......F........G.......H....
.
Extreme Spread.....4.5...3.9....4.7....4.5....3.7....3.9....5.8 ?...7.0

Chanage in
Extreme Spread.....0...-0.6 ?..+0.2...0.....-0.3....0.?...+?.3....+2.5



1, All extreme spreads are for ten-shot targets fired at a range of ?00 yards

"End quote."



Sorry about the ? marks... the text was illegible.

Firstly, my apologies to ToolAA for my overly aggressive/defensive post.

I realize that what I do with my AR’s are not what 19 of 20 (99 of 100? 999 of 1000?) shooters do with their AR’s. Nor is it what these rifles were designed to do.

- Free-floated, heavy varmint contour 416R SS barrels, hand-lapped and cryo-treated.
- Two stage triggers with modified springs.
- Modified bipods (lever pins drilled out and replaced with – you guessed it – nuts and bolts tightened to eliminated free play) and rear bags.
- High magnification scopes. (from 30X up to 50X max magnification)
- Handloaded ammunition, tuned to each rifle.
- Premium bullets, chemically coated, hand dies with controlled neck tension.
- Powder dispensed with an electronic dispenser with modified programming to make it SLOWER and more precise, and then weighed on a .0001g balance.
- Oh yeah – the use of windflags.

The reference material/study that concludes that free play between the part of the rifle you hold and the part that aims and fires the bullet does not matter is completely irrelevant to the above application.

I don’t post images of “best groups” as I consider these types of posts a bit bogus. I have shot tiny groups, only immediately to be followed by less than spectacular (or outright crappy) groups. Cherry picking groups images can be misleading.

I developed the nut&bolt takedown pin replacement method as an extension of other methods I was using previously to reduce free play, such as using two tiny strips of cleaning patch material squashed between the two halves. I also have used an Aero lower with the adjustable take-up screw that supposedly tensions these two parts. I have found the nut&bolt method far more positive. Can I say this has reduced my group size by .XX inches? Not really. But I would no longer feel confident without this modification to my rifles.

The cool thing about these AR rifles is that they are like Harley’s or Jeep’s. They are relatively the same to start, and are then used as canvases to express our individual styles and personality. Mine? They scream OCD.

bfoosh006 said:

Amazingly... I found the report this time.

Here is the link....https://www.google.com/url?sa=t&rct...2/772939.pdf&usg=AOvVaw1mmuiZMZ9wqPkdWK-6JKNd
.

Click to expand...

Thanks for digging that up. I had read a summary in IIRC Guns and Ammo some time ago. Admittedly when I got my first AR I tried to “FIX” a lot of things that I perceived as slop or problems. In many ways those early efforts were often money and time wasted. I’ve got an entire bin of miscellaneous parts, rails, rings, spacers and whatnot, that I purchased to fix something.
I’m sure that I wanted to purchase Accuwedges at one time or another because I used to get irritated at things like this. However over time I’ve found that shooting more and focusing on marksmanship fundamentals have created the greatest accuracy improvements for me.

Good luck with whatever journey you take. Eventually you’ll end up with a bin of miscellaneous parts and then convince yourself that you have about half of what you need to build another rifle.


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If you are not happy with the accuracy of your rifle, try taking the slop out and testing it yourself.

The AR-15 rifle is not exactly a benchrester's dream. It was never meant to be.

KRC said:

Firstly, my apologies to ToolAA for my overly aggressive/defensive post.



I realize that what I do with my AR’s are not what 19 of 20 (99 of 100? 999 of 1000?) shooters do with their AR’s. Nor is it what these rifles were designed to do.



- Free-floated, heavy varmint contour 416R SS barrels, hand-lapped and cryo-treated.

- Two stage triggers with modified springs.

- Modified bipods (lever pins drilled out and replaced with – you guessed it – nuts and bolts tightened to eliminated free play) and rear bags.

- High magnification scopes. (from 30X up to 50X max magnification)

- Handloaded ammunition, tuned to each rifle.

- Premium bullets, chemically coated, hand dies with controlled neck tension.

- Powder dispensed with an electronic dispenser with modified programming to make it SLOWER and more precise, and then weighed on a .0001g balance.

- Oh yeah – the use of windflags.



The reference material/study that concludes that free play between the part of the rifle you hold and the part that aims and fires the bullet does not matter is completely irrelevant to the above application.



I don’t post images of “best groups” as I consider these types of posts a bit bogus. I have shot tiny groups, only immediately to be followed by less than spectacular (or outright crappy) groups. Cherry picking groups images can be misleading.



I developed the nut&bolt takedown pin replacement method as an extension of other methods I was using previously to reduce free play, such as using two tiny strips of cleaning patch material squashed between the two halves. I also have used an Aero lower with the adjustable take-up screw that supposedly tensions these two parts. I have found the nut&bolt method far more positive. Can I say this has reduced my group size by .XX inches? Not really. But I would no longer feel confident without this modification to my rifles.



The cool thing about these AR rifles is that they are like Harley’s or Jeep’s. They are relatively the same to start, and are then used as canvases to express our individual styles and personality. Mine? They scream OCD.

Click to expand...

No apology is really needed, but thank you. I’m on a personal internet mission to try and undo the decline of modern society via social media. Everyone is an expert and an expert critic these days. It’s funny how sometimes these discussions go off the rails real fast.

I could see from your initial photos that you had a wood stock and hand guard on that specific rifle and your follow up post really does explain that yes you are chasing something that is not what most users/owners are going to be going after. I too enjoy the planning and building process almost as much as the shooting part.

As to accuracy and what was missing from my initial post was that it is indeed a highly relative term. If you can create consistent groups of better than 0.5 MOA than you indeed are controlling many variables inherent within the platform and that would be commendable.

I also agree with your statement about cherry picking groups. I used to get really excited when I would have 3-5 shots touching each other. I’m more interested now in the ones which are not. I start questioning everything, the wind, the ammo, the reloading process, how accurate was my chronograph reading accurate on that shot? But once I got opportunities to shoot further distances the what accuracy meant at 100 yds was totally different than what it means further down range.

Some of my proudest AR moments have been getting 5 consecutive dings on a 10” steel plate 500 yds away in light wind with a 1-4x scope. Now-a-days if I had enough time and money, I would spend most of my time on the matt in the grass behind the scope.

Thanks again for the reply. Good luck with your builds.


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