Upper Receiver Lapping

[Havoc23]

Good Afternoon Everyone,

This topic has probably been beaten to death before, but unfortunately I am not to tech suave and could not find anything using the search function.

I am just looking for some suggestions in relation to lapping an Aero Precision M4E1 upper receiver. As you all may know the M4E1 upper has an internal barrel nut that threads into an extended portion of the forged upper receiver. Before I complete the upper assembly of my build I was wanting to lap it but the only lapping tools that are for this specific type of receiver are sold in the US and won’t ship to Canada. So I have come up with two options 1. Order the PTG lapping tool and get it milled down at a machine shop to fit and hope it works properly or 2. Take it to ATRS and get them to do it professionally on a lathe.

Just looking for some input.

Thanks,

Havoc

 

[just having some fun]

Why do you need to lap it?

I have done a few ar's and none have been lapped .... instead of lapping I have used a shim between the barrel and the nut to torque it correctly

Last one without a shim lined up at 30lb.. went to 45lb and saw next hole was so far off... install a shim .. Torque was 36 lb and hole lined up

I have heard of some people using a High torque to get holes to line up... not going to go there

 

[JohnnyP636]

Good Afternoon Everyone,

This topic has probably been beaten to death before, but unfortunately I am not to tech suave and could not find anything using the search function.

I am just looking for some suggestions in relation to lapping an Aero Precision M4E1 upper receiver. As you all may know the M4E1 upper has an internal barrel nut that threads into an extended portion of the forged upper receiver. Before I complete the upper assembly of my build I was wanting to lap it but the only lapping tools that are for this specific type of receiver are sold in the US and won’t ship to Canada. So I have come up with two options 1. Order the PTG lapping tool and get it milled down at a machine shop to fit and hope it works properly or 2. Take it to ATRS and get them to do it professionally on a lathe.

Just looking for some input.

Thanks,

Havoc

Currently out of stock but they sell lapping tools, they are always re stocking items so you can contact them and ask
https://truenortharms.com/ar15_default_store_view/catalogsearch/result/?cat=0&q=lapping

However personally if it needs to be moddified, I would just call my buddy who does lathe machining and have him make me one from scratch

 

[JohnnyP636]

Why do you need to lap it?

I have done a few ar's and none have been lapped .... instead of lapping I have used a shim between the barrel and the nut to torque it correctly

Last one without a shim lined up at 30lb.. went to 45lb and saw next hole was so far off... install a shim .. Torque was 36 lb and hole lined up

I have heard of some people using a High torque to get holes to line up... not going to go there

Lapping isn't for lining up gas tube holes or barrel nuts, many uppers have intolerance between the bolt/carrier bore and the flat face of the upper where the barrel extension sits flat up against the upper. If its off no amount of shims will fix that, only lapping or machining will.

This is more about getting accurate tolerance which should lead to better accuracy and reliably, you are basically squaring it up perpendicular to the bore

I have also assembled many AR's without lapping, but that doesn't mean they couldn't have benefited from it if I did do it. It all depends on the tolerance of the parts out of the factory, some will be worse the others, and maybe if your lucky some are perfect already

 

[Gunnerlove]

Does it shoot without needing machine work?

Just put it together and find out.

 

[Havoc23]

Lapping isn't for lining up gas tube holes or barrel nuts, many uppers have intolerance between the bolt/carrier bore and the flat face of the upper where the barrel extension sits flat up against the upper. If its off no amount of shims will fix that, only lapping or machining will.

This is more about getting accurate tolerance which should lead to better accuracy and reliably, you are basically squaring it up perpendicular to the bore

I have also assembled many AR's without lapping, but that doesn't mean they couldn't have benefited from it if I did do it. It all depends on the tolerance of the parts out of the factory, some will be worse the others, and maybe if your lucky some are perfect already

Hey JohnnyP636,

This is why I want to get it done. I would like to get the most accurate tolerances out of the rifle. Knowing my luck the one I got would not be perfect and would require to be lapped.

 

[Havoc23]

Does it shoot without needing machine work?

Just put it together and find out.

Hey Gunnerlove,

I am not sure how it shoots as it is still being assembled. I would rather spend the 5 or so minutes it takes to do it, or get it done before it’s completely assembled then shoot it and find out it should have been done then have to spend time tearing it down, getting it done, then rebuilding it. Rather do it before hand and spend the extra time on the range with it.

 

[just having some fun]

Aero is one of the best top notch Manufactures

Have you ever heard of problems with a Aero upper or lower ? I do not think so


If you have it was prob with a part going on a aero.... not the aero part

If it was ### company ... ya I have held a few in my hands from them ..... One I took a dremel to one because it would not fit a Aero or a stag
took a file to a hand guard ### because it would not fit a aero

If I was going to do another build it would be Aero upper & lower ..... I wish they had a NR set

 

[beltfed]

Lapping...many uppers have intolerance between the bolt/carrier bore and the flat face of the upper where the barrel extension sits flat up against the upper. If its off no amount of shims will fix that, only lapping or machining will.

Sounds to me like a machinist's wet dream, and not at all reality.

Hey JohnnyP636,

This is why I want to get it done. I would like to get the most accurate tolerances out of the rifle. Knowing my luck the one I got would not be perfect and would require to be lapped.

Hey Gunnerlove,

I am not sure how it shoots as it is still being assembled. I would rather spend the 5 or so minutes it takes to do it, or get it done before it’s completely assembled then shoot it and find out it should have been done then have to spend time tearing it down, getting it done, then rebuilding it.

So, to summarize:

- You don't currently have the upper, haven't assembled it, never mind inspected it, and you are concerned with doing something that is 99.9999999% not required to save on the 20 or so minutes it takes to dis-assemble and re-assemble an upper receiver?

OK then....

 

[Dietz]

Aero holds some of the tightest machining and tolerances in the industry.

I wouldn't sweat it, honestly. I think you'd be better off spending that money on ammo.

 

[hbean]

Don't waste your money on lapping your receiver, all you will be doing is remove the anodizing finish and accelerate the wear on your receiver. Spend your money on a good quality barrel, matching bolt and the proper weigh bullet to match your barrel twist rate, will do lot more for your accuracy.

 

[Beater]

I thought the bolt lapped itself in with the first 100 rounds silly me

 

[JohnnyP636]

Sounds to me like a machinist's wet dream, and not at all reality.





So, to summarize:

- You don't currently have the upper, haven't assembled it, never mind inspected it, and you are concerned with doing something that is 99.9999999% not required to save on the 20 or so minutes it takes to dis-assemble and re-assemble an upper receiver?

OK then....

Whatever buddy I have been CNC machining for 20 years, not everything comes of the CNC 100% perfect tolerances like people tend to believe that everything CNC'd or machined is perfect. Like I said I have never lapped an upper, but the theory I stated is true, its not my theory I didn't make it up. That is why they sell lapping tools and people lap uppers for better tolerance, inaccuracy will show very quickly with lapping. If there is any as you wear off the anodize in the high spots first. Does it need to be done or will it make a difference in his shooting, no I never said that did I? However he asked about the tools, not for our opinions on if he should do it or not

So I guess guys shooting precision rifles that lap their scope rings to be 100% are just having wet dreams

OK then ...

 

[jadam]

Alternatively, lapping is a known, repeatable way to remove one of the many variables in an AR system that may affect accuracy. Wanting to take it out of the equation is no more odd than torquing to the right spec or anything else. Plenty of people do it. Plenty of people check which bullets their barrels like too. Just because you don't doesn't mean it's wrong or right.

 

[beltfed]

lol, easy there - no slight on machinists intended.

OK - lets say someone goes out and buys an upper and a barrel to screw into that upper and the tolerances are out.
Why the fVck would someone then spend dough to machine the tolerances to be "100% perfect" in your words? Why wouldn't they just send them back for a refund or new components?
Just what is "100% perfect tolerance" in your mind? And where and who has the data to say that it even matters?

I think they sell lapping tools for the same reason they sell booze and a plethora of other stuff - for guys to feel good about tinkering with something that doesn't matter.

Let's not confuse or compare lapping of scope rings or other precision rifles with ARs...

Alternatively, lapping is a known, repeatable way to remove one of the many variables in an AR system that may affect accuracy.

Does it though? There is strong evidence to suggest that it does nothing.

 

[JohnnyP636]

lol, easy there - no slight on machinists intended.

OK - lets say someone goes out and buys an upper and a barrel to screw into that upper and the tolerances are out.
Why the fVck would someone then spend dough to machine the tolerances to be "100% perfect" in your words? Why wouldn't they just send them back for a refund or new components?
Just what is "100% perfect tolerance" in your mind? And where and who has the data to say that it even matters?

I think they sell lapping tools for the same reason they sell booze and a plethora of other stuff - for guys to feel good about tinkering with something that doesn't matter.

Let's not confuse or compare lapping of scope rings or other precision rifles with ARs...



Does it though? There is strong evidence to suggest that it does nothing.

LOL ok you must be right, and everyone that makes, sells, and uses these tools and processes are just stupid and wasting their time

My company has an acceptable tolerance range policy for our product that we manufacture and sell. If I get a drawing from another company for a part that they would like me to machine, their tolerance requirements will be on the drawing. It may be tighter or looser then mine.
So I do not now what every AR upper manufactures tolerances are. I do know that I have bought many AR parts that did not fit properly with other brand parts. Either too tight or too loose for my liking, but again how can I say who's fault it is when I do not know each companies acceptable tolerance range? I could sent a part back for them to inspect and measure it and say its within our tolerance were sending it back as is.

I just went thought this recently with a barrel from Maple Ridge Armory, and a titanium gas block from SLR rifleworks. Maple Ridges barrel journal and shoulder for the gas block had a very large radius in the corner not allowing the gas block to slide on enough for the gas port holes to line up. I got a lot of the same kind of comments from some members here, one wouldn't let it go and seemed to be very set on making me into an idiot. (that doesn't matter, wont make a difference, your wasting time and money) I still took the time to make my own dimple alignment and drilling jig (ah gas block set screw dimpling another thing people like to argue isnt required/waste of time) and put a bigger chamfer using a counter sink bit to allow it to slide on more and align better.

You tell me who's part should I have blamed and sent back? Maple Ridge for having too big of a radius in the corner, or SLR for not making their chamfer large enough to clear it?
Yes the rifle very well could have worked just fine without the extra work and alignment, but can you fault me for using my spare time, money and ability to make it better. I think I spent $2 and 2 hours, and I have used the tool I made more since then

 

[Epoxy7]

Don't waste your money on lapping your receiver, all you will be doing is remove the anodizing finish and accelerate the wear on your receiver. Spend your money on a good quality barrel, matching bolt and the proper weigh bullet to match your barrel twist rate, will do lot more for your accuracy.

^^^ This.

I don't know where all this AR voodoo keeps coming from. Unless you are buying some complete crap parts that were never finished before anodizing, then you shouldn't need to lap anything on an AR rifle. Waste of time/money which will actually deteriorate your firearm by removing the protective coating/hardening.

LOL ok you must be right, and everyone that makes, sells, and uses these tools and processes are just stupid and wasting their time...

If you buy a quality known upper/lower and a quality known barrel then it's unlikely there will be any issues. If there are then it's a manufacturer defect and should be sent back. All the ones I've had built with known parts have been perfect fits. The AR15 is very standardized and there are tons of them out there. If you are having to buy the tools and lap, then how much did you really save with those "inexpensive" parts?

If you're willing to buy it, someone will make it and sell it. AR accuracy voodoo is nothing new. It's especially prevalent with the AR308 rifles which have been used extensively as precision rifles since early 2000. Some people don't understand that a sub .5 moa AR rifle isn't magic and is very easy with the right parts.

With regards to SLR and maple ridge armory... There's your issue. Two newer companies, one building off spec non restricted AR like rifles and the other new to building barrels and has had a number of quality issues reported on here. You won't have that with an Aero and a known quality barrel.

 

[jadam]

lol, easy there - no slight on machinists intended.

OK - lets say someone goes out and buys an upper and a barrel to screw into that upper and the tolerances are out.
Why the fVck would someone then spend dough to machine the tolerances to be "100% perfect" in your words? Why wouldn't they just send them back for a refund or new components?
Just what is "100% perfect tolerance" in your mind? And where and who has the data to say that it even matters?

I think they sell lapping tools for the same reason they sell booze and a plethora of other stuff - for guys to feel good about tinkering with something that doesn't matter.

Let's not confuse or compare lapping of scope rings or other precision rifles with ARs...

Does it though? There is strong evidence to suggest that it does nothing.

Lapping the receiver face, while absurd to some is well within the norm to others. There are folks that do all sorts of things to straighten the bolt carrier group in the upper so that the dynamic system of the AR is aligned as consistently as possible. I don't weight sort my bullets or measure the meplats but there are folks that do. All of these things can reasonably be expected to have some (perhaps unmeasurable) impact on consistency. That's all. You have to decide if the juice is worth the squeeze.

 

[Sinasta]

Lapping the receiver face, while absurd to some is well within the norm to others. There are folks that do all sorts of things to straighten the bolt carrier group in the upper so that the dynamic system of the AR is aligned as consistently as possible. I don't weight sort my bullets or measure the meplats but there are folks that do. All of these things can reasonably be expected to have some (perhaps unmeasurable) impact on consistency. That's all. You have to decide if the juice is worth the squeeze.

This.

 

[beltfed]

Lapping the receiver face, while absurd to some is well within the norm to others. There are folks that do all sorts of things to straighten the bolt carrier group in the upper so that the dynamic system of the AR is aligned as consistently as possible.

OK - lets for a second say you buy an upper and a barrel and you take some measurements to see if everything isn't "100% perfectly true". What are you lapping?
The upper receiver face where the barrel nut tightens the barrel to the upper so that it is perfectly 90 degrees?
Tell me - why does that matter? The upper receiver is only a case; it doesn't dictate or affect accuracy of the barrel

The bolt carrier group has, essentially, no bearing on accuracy. The bolt is the business end of the bullet fire-y bits (which for all intents and purposes is floating) locks into the barrel extension and voila - centered and repeatable - every time. The only (three) things that truly matter on the AR is the 1) barrel (complete with extension) and 2) the bolt and 3) the round being fired. The rest of it is superfluous nonsense that makes those three things work.

I think you guys are buying into the whole snake oil - and there appears to be a lot of it out there for the AR and a lot of people gobbling it up.