Upper Receiver Lapping Tool


Anyone heard of this before? Are there benifets, or is this just a gimmick?

It is used to true up the upper receiver before mounting a barrel.  Can also be used to get a barrel nut just a little bit further onto the upper receiver to line up the notches at the proper torques.

What more can be said than that?



I find it remarkable that it's even necessary, but surprisingly often it'll show that the bore of the upper is *not* perpendicular to the face.



What I don't know is how often the bore of the upper is not actually axial to the upper itself.





 

I agree with both observations.  Yet it will true the face of most.

I find it even stranger that a M700 needs to trued in a lathe

Has anyone used one? Will this process have noticeable improvements in performance? Should this be done on a service rifle (competition) build?

Yes I've used them on all of mine, less two MEGA's (wouldn't fit).
Can't say if it improved the performance as they were new builds

It certainly couldn't hurt and will take one more thing out of possible problems

I used it on a LAR blem upper. It didn't need it. Others report it helped their brand uppers. It varies.

What it does is get the upper squared. No telling how square the barrel nut really is, unless you check it, too. Then the extension needs to be checked, it's sandwiched in, too. What it does help do is reduce the amount of some setups with windage, it generally centers the L/R adjustment rather than have it cranked all the way over. That will help the shooter more than add accuracy.

Considering some makers might likely be selling uppers sorted from contracts, I would try to check it at least. It takes a lot of lube, too, and you will discover all you want to know about tolerances if it doesn't fit. I'd describe it more completely but caution prevents me.

Anyway, it's a very small increment in accuracy. The quality of the barrel has a lot more to do with it, and a lot of good builders charge extra. It may not be worth it for them - but they are likely getting the nice square uppers in their batch already.

I used mine Sunday for the first time, my barrel nut was 1/8" from lining up for the gas tube at 70 ft lbs so I hit the face with the lapping tool, lined up perfectly at 40 ft lbs after that.  Took about 25 seconds of polishing to get to that point.

I purchased one when I did my second build and had a stubborn barrel nut that just would not line up for the tube even at or a little over the very top end of the recommended torque values.

I spent several hours trying to get it to align but it just wasn't happening so I got online and ordered the lapping tool ... then waited.

The tool came several days later ... with time spent reading the instructions, setup, lapping and torquing the nut I spent a total of about 30 minutes and the nut aligned perfectly and within the proper torque values.

Of course if you have a lathe you don't really need this tool ... just a mandrel that will hold the upper in the lathe.

I've done 4 uppers and they all needed it.   That is not to say that the sights wouldn't line up if I didn't do it,  I'm just talking about the wear pattern when using the tool.   I wouldn't say it is a necessary tool but it is nice to have if you have sight alignment or barrel nut alignment problems.   I will use it for any builds that may do but I'm not going to take any no-problem factory built uppers apart just to square it in hope that it will somehow be a better rifle.

I also have it and have used it .... Its not a something you need to have it something you want to have and do...

What grit do you use 600 or 800 ?

Ive used both.  I prefer the 800 does a cleaner job imho.

I used Permatex Valve Grinding Compound, 1.5 oz tube was $3.09 at my local machine supply store.  It does not have a "grit" rating, the abrasives break down during use and become finer the longer it is used according to the website.
http://www.permatex.com/products/Automotive/specialized_maintenance_repair/rebuilder_aids/Permatex_Valve_Grinding_Compound.htm

I got this "kit" of 3 different compounds from Midway

http://www.midwayusa.com/viewproduct/?productnumber=486249

I mainly use the "polishing compound" 600 grit but I have broken out the "smoothing compound" 320 grit on one REALLY ruff looking one I did ... then I switched to the 600 for a couple of turns ... never had a need to the "cutting compound" 220 grit .... Yet.

I will say this though ... this type (silicone carbide) has a tendency to "embed itself" so it should not be used where there are any moving parts because it will continue to "lap" the surface long after it's been cleaned off.

Guys, I would like to inject my 2 cents here. I build custom match rifles and have had hundreds of uppers through the shop.
I take some issue with this tool just because of its one size fits all profile. This tools pilot is cut at .997"  and specs on an upper are 1.000"(+/-.002") this leaves .003" of play on a perfect spec upper, I have measured upper tunnels from .994"(like Winmags mega) to 1.009" so regardless of how careful one is there is most likely going to be slop around the pilot of this tool which in turn will not cut true. It can be of help for an average shooter but don't be fooled into thinking you are improving too much in the way of accuracy unless you LUCKILY happen to have a great fit (pilot to tunnel) from this tool. I have had to repair uppers because this tool made things worse.

We use a cutter on a centered pilot (sized for the particular upper(11 pilots for AR15 and 7 for AR10)) that runs the entire length of the upper, The cutter is placed in a lathe and the upper fastened to a jig on the toolholder, everything is 100% square and centered  to the tunnel on the upper. Generally the cut from the receiver face is about .002"+/- ,

When building a match rifle we will either cut a custom upper or use a "tight" upper so the barrel extension can be custom fitted to the tunnel and trued as well.
You will also find differences in barrel extension and once in awhile an barrel nut, these are all just from the tooling when these parts are cut and can't be avoided; just improved upon.

Not much different that truing and printing a bolt gun.

Just some food for thought.

No offense.  Most here don't have your resources.
Most can afford a lapping tool

No offence taken Win, I am  just pionting some things out that one might want to think about before purchasing this tool. I think that what the OP was looking for; objective views.

I charge $30 to true a stripped upper that is absolutly true, after reading my explaination on how his tool works or might not work can you be absolute this one size fits all tool has cut true?

This...


I completely understand that mounting the upper on a properly sized mandrel and putting it into a lathe would render a slightly better result but us "garage" gunsmiths don't have those kinds of resources ......... yet anyway and besides ... most of the uppers I have dealt with have been a very tight fit on the lapping tool so I don't think I'm getting very much "slop".

i agree with gator,  i have used the tool, and on all of the uppers i have put on it,  i have had to actually work the tool into the reciever very slowly, and using some clp to get it through while working it very slow...  i can also appreciate the value of a well built match rifle,  however,  for your average build that you want to do as much as you can yourself... i feel this tool is just fine,  and is a great way to go the extra steps to make you feel better about your build...  i have been very happy with the results...
i would rather use this tool than not..!!!

All four I have done were very tight in the receiver.   Tight enough that I use some fine compound to lap the carrier raceway first and then clean it up before doing the front.   I'm positive the tool I have has no room to wiggle.  
The only real problem I could see by using this tool is if the carrier raceway itself is not centered in the upper.

Who cares if it's centered in the upper as long as it's centered to the barrels bore

I would think that anyone who intends to mount optics from the upper would care.

its nice to hear from an expert, I have only used it for polishing material to get a upper barrel nut to set, but I do agree on a precision setup your is the best way. Ive never built a match rifle its nice for an expert to weigh in...

There are some valid points made. I think the best application for the tool is with "off brand" uppers that are suspect. The idea is to check the upper for square by standing it on a flat plate (small pane of glass,) and using an accurate square to see how it lines up.

Point being, how do you determine whether its measuring parallel to the machined axis, is the upper rail surface actually parallel to that, will the barrel bore be coaxial with the upper, etc.

As pointed out, this tool isn't that accurate. I have no doubt a precisely fitted mandrel with perfectly centered axis that pilots a cutter with literally no runout will do a better job. With the average CNC results from the major vendors, and a barrel that can actually benefit from the truing being a high dollar item, most of us using the lapper are really buying a feel good accessory.

Add in the other factors: is the inside bearing surface of the nut exactly square, the outer thread axis coaxial, the barrel extension shoulder square, the internal and external thread axis on the extension and barrel coaxial? We're attempting to lap one of SIX interlocking dimensions to get them ALL coaxial and square. A different machine could cut at least three, not even located in the same state.

Just imagine a cutaway view of the connection - barrel nut, extension shoulder, upper threads, extension threads, barrel threads, barrel centerline. I appreciate the gunsmith explaining what's up doing that. Builders like H at ARP have said as much - it's not done except as an extra charge item, and the results of not doing it certainly don't seem to hurt. Uppers still come out literally more accurate than shooters.

It's just like the myth that balancing an engine to +/- for each component. Much tighter than factory specs is actually a machine shop joke - it's good money for not doing much. Smokey Yunick went to some great lengths to get pictures of the engine running and found nearly four quarts of oil clinging to the crank, a moving mass of unbalanced weight that changes constantly. You can't have a balanced street engine without crank scrapers and a dry sump - it's flat out a waste of money.

I'm coming to the conclusion a upper lapper is the same thing, the money should go to a better barrel, rather than finessing a minor point and only truing one of 6 related items that contribute.

I think it's more like buying a good wrench to use on multiple engines instead of a single set of good sparkplug wires to use on a single engine.





The cost of the tool isn't going to buy that much better of a single barrel but could true up many uppers.





If you have to finesse 6 related items - you'll never get anywhere if you don't start with the first one.




It's not a cure-all, and I don't think it make the weapon 'more accurate', especially by itself, but it helps to bring things back to spec.



Just my opinion.
 

i agree with kaos,
brining the reciever closer to a tighter tolorance is better than not... and like he said time cost of 21-35 dollars depending where you get it from is not a bad investment,
the AR 15 platform allready has very tight tollorances to beging with... i had a very reputable precision gun smith tell me one time that he could true up everything for me on an Ar i wanted him to work on but he is a good friend of mine and said that what he would charge me to do that work, wouldnt bring enough differance to justify the cost "TO ME" he told me just get a match barrel and put it on to spec and you will do just fine... i trust this mans opinion becuae he builds some of the best M40's there are and builds compition long rang rifles and is a long range instructor so i never thought of getting the work done again, how ever i did purchase this tool and feel that at around 30 bucks..!  you cant go wronge to true up or bring to a tighter tollerance or get it closer to spec by do it your self just work slow and take your time it will only take but a moment and then your done...

this is just my opinion on this matter...  if in fact i was looking to build the ultimate AR and price was not an issue, than i would probably get the work done professionally to match grade spec and go about getting everything trued even the bolt face, this of coarse woould only be for my own self piece of mind and bragging rights becuase at long range comps as long as you get in the ring you want then you get the point/kill...

Tag for future builds.

 I wonder how many "youngsters" here know who Smokey Yunick was ???????? I VERY nearly bought a Yenko Camaro in .....'68 I think it was..Probably saved my life by NOT getting it.

 Interesting discussion guys...Thanks!

I've read about truing the upper receiver to account for bolt life in alternate calibers.  For instance: a 7.62x39 bolt has a bit more bolt thrust than a 223/556 does and having the lugs have a straighter path to ride into can help with bolt life.  I'll admit I'm not building for benchrest accuracy but combat accuracy and reliabilty in every upper I touch.  If part of the weapon can be helped in longevity/function then by all means do so.  I have handled uppers that made me wonder what they thought QC was and other uppers which were a dream to build off of.  Not all uppers are created equal even if the same forge mark is on it.  It's the machining of the company doing it that is important.

I've read of at least one guy who was able to bring a skunk back to being a shooting rifle with one of these.



That being said, it seems to be one of those tools you have in the box "just in case".  I gave some thought to picking one up when purchasing the tools to build my 6.5, but decided against it (already ruinously over budget) for now.  I went with a good upper and trusted the name.  If I put the rifle together and it prints way off somewhere beyond sight adjustment, I might pick one up and see if the issue is the upper, but I don't see it as the sort of thing I have to have ready all the time.