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#2275747 - 08/24/12 02:03 PM Re: AR Build Question.....Squaring an Upper Receiver?? [Re: Gman757]
Varminterror Offline
Die Hard Member II

Registered: 03/23/12
Posts: 1451
Loc: Kansas
Pretty simple to find out if you're over thinking it or not. Remove your barrel nut and see if the flange on your extension is mating flush with the face. Equally, you could buy the $35 lapping tool, and place it in the receiver, then spin it to see if it maintains contact evenly. If it DOES, then leave well enough alone. If it doesn't, then add the polishing compound and spin it flush.

The cutting pilot is a more aggressive tool. Personally, if I had a receiver so out of true that I needed a cutter, I'd probably return/exchange it. If I could not do so, then I would buy the cutter, turn it by hand with a T-handle (well lubricated), then use the lapping tool from the original post to finish up the cut and clean up the face.

You can also use the original lapping tool to somewhat polish the internals of your receiver. Just add polishing compound to the full length, instead of gun grease.

If you DO use the lapping tool, grease the heck out of the shank, and orient it so the ports (ejection port and bottom) are pointed up so you're not drooping grease out the bottom.
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#2276011 - 08/24/12 09:52 PM Re: AR Build Question.....Squaring an Upper Receiver?? [Re: Gman757]
Hooked Offline
Die Hard Member III

Registered: 01/01/08
Posts: 3803
Loc: Nebraska,USA
I searched and found a older post; there is a good link in one of the replies that tells how much material would need to be removed for gas tube alignment...or shim added.
http://www.predatormastersforums.com/forums/ubbthreads.php?ubb=showflat&Number=1914915
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#2281670 - 09/01/12 08:14 PM Re: AR Build Question.....Squaring an Upper Receiver?? [Re: Varminterror]
Gman757 Offline
Die Hard Member

Registered: 10/15/09
Posts: 757
Loc: FL
Just a little followup for the guys that offered advice:

As I stated before I bought the squaring tool from Pacific Tool and Gauge
. ( I am a little hardheaded) I also bought my upper receiver and decided to go with a Vltor MUR upper. These are supposed to be a little thicker walled and well made.

I don't have a machine shop so the only way I knew how to check for square is with the squaring tool itself and the thread idea from OldTurtle . I lubed it up and worked it into the upper all the way to flush with the barrel nut threads. I then took a very thin piece of thread and tried to work it in between the upper and the tool to see if there were any gaps.

It was nice and tight all the way around so I kept easing the tool out and checking with the piece of thread and applying a fair amount of force to the thread as I did so trying to force it into any gaps. The thread showed the same clearance around the complete circumference of the upper face at various depths. I'm calling it square......

It is probably a waste of time.....but I know now, and if I check my next upper receiver and it needs lapping, the tool is my tool box. $30 for the tool did not break the bank.




I used both hands and pushed the thread into the seam 360 degrees. Just holding it here for the pic.




Edited by Gman757 (09/04/12 12:55 AM)

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#2281762 - 09/01/12 10:00 PM Re: AR Build Question.....Squaring an Upper Receiver?? [Re: Gman757]
Hooked Offline
Die Hard Member III

Registered: 01/01/08
Posts: 3803
Loc: Nebraska,USA
Looks like your good to go then. I wouldn`t call it a waste of time considering how far off mine was..(and why would a builder of fine rifles go through the trouble of squaring them if it wasn`t worthwhile?). At least you now have a method of both checking and truing if you get one thats not so square.
Good luck with the build, and thanks for the update.
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#2281965 - 09/02/12 10:01 AM Re: AR Build Question.....Squaring an Upper Receiver?? [Re: Gman757]
Yotecallr Offline
Die Hard Member III

Registered: 05/01/01
Posts: 2445
Loc: Central Iowa
I guess it's ok to square up a receiver, but not needed. Companies like RRA and Noveske don't and they shoot pretty well. After all you're not building a racing engine, you're just slipping in the barrel to the receiver and tightening the barrel nut. And what would the difference in accuracy amount to?
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#2282020 - 09/02/12 11:53 AM Re: AR Build Question.....Squaring an Upper Receiver?? [Re: Yotecallr]
Gman757 Offline
Die Hard Member

Registered: 10/15/09
Posts: 757
Loc: FL
Originally Posted By: Yotecallr
I guess it's ok to square up a receiver, but not needed. Companies like RRA and Noveske don't and they shoot pretty well. After all you're not building a racing engine, you're just slipping in the barrel to the receiver and tightening the barrel nut. And what would the difference in accuracy amount to?


Yotecallr......

You'll get no argument from me as to whether it's necessary or not.

When I decided to venture into building my own I ordered a few manuals and did some research to find out which tools I needed and how to properly go about it. There is a good bit of info out there from both sides of the fence on this.

Your statement itself is the reason I decided to check my uppers...."you're just slipping in the barrel to the receiver and tightening the barrel nut". Since joining the barrel to the upper is the basis for the rest of the build why not make sure it's the best that it can be?

I need the most accuracy I can achieve from the upper to help make up for my shooting. smile

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#2282040 - 09/02/12 12:39 PM Re: AR Build Question.....Squaring an Upper Receiver?? [Re: Gman757]
OldTurtle Offline
Moderator

Registered: 12/20/05
Posts: 18089
Loc: East Central FL
[quote]After all you're not building a racing engine, you're just slipping in the barrel to the receiver and tightening the barrel nut. And what would the difference in accuracy amount to[/quote]....I guess that all depends on your intended use and to what degree you like perfection....

My competition rig has been tuned as much as I can figure out to insure that is will hit where aimed...As with my reloads, the best that I can produce will suffice, but anything less becomes an exercise in futility....

When I was younger and into performance muscle cars, the same thing applied...It's a little embarrassing to be sitting along he side of the road due to a sloppy rebuild while the rest of the guys are out having fun....
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#2282124 - 09/02/12 02:50 PM Re: AR Build Question.....Squaring an Upper Receiver?? [Re: Yotecallr]
dtech Offline
Die Hard Member III

Registered: 12/17/04
Posts: 2140
Loc: Bemidji, MN
Originally Posted By: Yotecallr
I guess it's ok to square up a receiver, but not needed. Companies like RRA and Noveske don't and they shoot pretty well. After all you're not building a racing engine, you're just slipping in the barrel to the receiver and tightening the barrel nut. And what would the difference in accuracy amount to?


It's funny you mention those two builders. I have had them, and many other factory, custom and semi-custom uppers in my shop that simply needed squaring to make them shoot. There isn't any one manufacturer out there that consistently produces an upper that does not benefit from being squared. Most folks that receive an AR that shoots pretty well would have no idea that simply squaring the upper could make that same AR shoot much better. I have been fortunate to work with the AR platform long enough to actually see just what a "before" and "after" difference there really can be.

Accuracy is a linear function. Very un-square = poor accuracy and POI shift when changing bullet weights. A little out of square = pretty reasonable accuracy and very little POI shift. if you are lucky enough to have a great barrel, why would you settle for an upper that only shoots in the .5's and .6's when it could be in the .2's and .3's???

I have squared thousands of upper receivers over the years. Almost every one of them needed at least a little squaring, many of them, if left untouched, would have produced .750" groups with a perfect barrel, perfect ammunition and Venatic doing the shooting....

I came from a background of medical and industrial electronics. Both were VERY unforgiving when it came to mistakes or poor quality parts. If there was ever anything I could do to make a part work better or last longer, I did it. I did anything I could do to help ensure that the machine was going to run well, keep running, and I wouldn't get a phone call because of a problem. That same mindset has stayed with me in my "retirement career" of building AR's and it has served me well.
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There is a very fine line between "Hobby" and "Mental illness"

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#2282152 - 09/02/12 03:20 PM Re: AR Build Question.....Squaring an Upper Receiver?? [Re: dtech]
GLShooter Offline
PM Sponsor

Registered: 01/09/05
Posts: 709
Loc: AZ
Thanks for sharing that Mike. I know that every little bit helps. The 20 Tactical you built me is one of those one hole guns if I do my part. Nothing better than looking through the scope and thinking you missed the paper knowing you darn sure didn't!!

If I am shooting PD's or trying to hit that one MOA X ring at 500 yards I want all I can get in my corner. I've always had mine squared up and have never had a disappointing bad shooter. Straight and square can't be beat.

Greg


Edited by GLShooter (10/07/12 12:19 PM)
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#2304027 - 10/07/12 09:57 AM Re: AR Build Question.....Squaring an Upper Receiver?? [Re: dtech]
Yotecallr Offline
Die Hard Member III

Registered: 05/01/01
Posts: 2445
Loc: Central Iowa
Thank you for posting all the information Mike. The 243 wssm upper I bought from you was extremely accurate and now I now that squaring the receiver IS important. I ordered the tool from Brownells and I have a receiver to use it on, maybe two.
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#2305644 - 10/09/12 02:22 PM Re: AR Build Question.....Squaring an Upper Receiver?? [Re: Gman757]
dtech Offline
Die Hard Member III

Registered: 12/17/04
Posts: 2140
Loc: Bemidji, MN
I was waiting for a batch of barrels to cool that just came out of the Norrell's oven and thought I would do a little math on receiver squaring.

Shooters often talk and read about "MOA" and I'm not sure how many actually know what it is, so I'm going to start there. Simply put, a minute of angle is 1/60 of one degree. A circle divided up into degrees has 360 equal parts, and each degree has 60 minutes in it, so a circle has 21,600 minutes of angle. If you have a circle that has a radius of 300 feet or 100 yards, one minute of angle is going to be just over 1" or 1.0472". Visualize a triangle that is 1.0472" at it's base, and has two equal sides that are 300 feet long. This is the spread of a 1 MOA group at 100 yards. As the range gets longer, the "1 MOA" group gets bigger. A 1 MOA group at 200 yards is 2.0944, or double that of a 100 yard 1 MOA group.

Where the two 300 foot legs of this triangle come together is the head of your case, or basically your primer-pocket. This means that with a 24" barrel, the muzzle only has a + or - of a little over .003" of an inch to stay within a 1 MOA group.

As you get closer to where those two 300 foot sides come together, the amount of error gets less and less to move the point of impact at 100 yards. On an AR-15, if the front of the receiver is out of square by only .001", it will move the POI about 3.5" @ 100 yards. If it is un-square by the thickness of an average human hair, it will move the POI over a foot!

The average receiver that I square is probably about .002", but they run all the way from perfect to .008" or more. Very few are "perfect", perhaps 1 out of 50.

POI is really irrelevant to accuracy. The part that kills accuracy is the fact that a barrel mounted into an un-square receiver will not allow all of the bolt-lugs to touch. The barrel will be tilted with respect to the travel of the bolt, and it's lugs.

Where I talked about "POI shift" in an earlier post, I was referring to a shift in bullet impact when switching from one bullet-weight to another. In other words, if you have your scope dialed in so that 50 grain bullets are hitting dead on at 100 yards, and the POI shifts 3" to the right when you switch to 60 grain bullets, it may be due to an un-square receiver. I have had many customers notice that when they put a new scope on one of my uppers that they normally don't have to move the adjustments much at all to have it dialed in. That is simply because they are square!

Sorry for the long post, and I hope it helps explain things a little...
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Mike Milli
There is a very fine line between "Hobby" and "Mental illness"

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#2305647 - 10/09/12 02:30 PM Re: AR Build Question.....Squaring an Upper Receiver?? [Re: Gman757]
BOBTAILS Offline
PM senior

Registered: 03/28/05
Posts: 7198
Loc: behind the crosshairs
Very cool post mike. I like reading stuff like this I can actually understand it. Thanks.
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#2305664 - 10/09/12 03:17 PM Re: AR Build Question.....Squaring an Upper Receiver?? [Re: dtech]
Yotecallr Offline
Die Hard Member III

Registered: 05/01/01
Posts: 2445
Loc: Central Iowa
I wish you had the time to make a sticky on "The accurate AR and what it takes to build one". People would appreciate your talent more, and us garage gunsmiths would do a little better at what we are trying to accomplish. I'm getting my squaring tool today and I can tell you my receiver is not square, because the example of differing bullet impacts you gave is what I'm experiencing. Thanks for the above info Mike.
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#2305684 - 10/09/12 03:45 PM Re: AR Build Question.....Squaring an Upper Receiver?? [Re: Gman757]
dtech Offline
Die Hard Member III

Registered: 12/17/04
Posts: 2140
Loc: Bemidji, MN
There has been a rather uncanny turn of events in the last hour. I left the shop to pick up the mail, have lunch and do my banking. When I picked up the mail, there was a small priority mail box that contained a customer receiver that was sent to me to be squared.

When I opened the box, I knew I had to square it right away, and I think you will see why....

Here is a picture of the face of the receiver after being squared. You will notice that there is still some anodizing left in one area. The cutter was touching all the way around at this point, so I didn't cut any deeper. The barrel-extension WILL rest perfectly on the face of this receiver. This receiver really was not bad, I only had to take about .002" off to get it squared.

The reason why I wanted to square it right away was because of "who's" receiver it was. Like I said earlier, none of them never need squaring.....
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Mike Milli
There is a very fine line between "Hobby" and "Mental illness"

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#2305717 - 10/09/12 04:51 PM Re: AR Build Question.....Squaring an Upper Receiver?? [Re: Gman757]
Yotecallr Offline
Die Hard Member III

Registered: 05/01/01
Posts: 2445
Loc: Central Iowa
Wow. What do you charge do square a receiver and turnaround time?
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