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M5E1 Lapping Tool

HogWild45

Private
Minuteman
Dec 10, 2019
8
2
Hey y'all. New to the forum, glad to be here. I'm currently building an Aero M5E1 with the matching M5 lower. I'm putting an expensive Wilson Combat match grade barrel on it and I'm trying to squeeze as much accuracy out of the weapon as I can. I've read that lapping and then Loctite on the barrel extension is a good way to get a hair better MOA. I have two questions: Which lapping tool do you all use and is there a website or service that loans these out? I don't plan on building another 308 so don't want to buy the tool. Thank you everyone for your time. I'm really excited to finish this build.
 
I have this one


My aero upper didn’t need it that bad I did it anyways though. Lol.
 
I would contact Aero and ask, but you might need a certain lapping tool just for their M5E1 upper. I’m sure they will say it does not need lapping, they all say that, but I would highly recommend doing it and securing it with Loctite just like you plan. I’ve yet to see a perfectly trued upper no matter who made it that didn’t benefit from truing. Here’s a link to a company that makes a tool for that upper and I’ve never run across anyone who rents them out. I would buy it and resale it if I didn’t want to keep it and consider that the cost of doing business. Let us know how your build goes!

 
I bought mine from PTG, cost $30. It was "Out of Stock" when I ordered it, but it shipped after only a couple of days.
 
I used the wheeler ar10 lapping bar and it fit in the m5e1. Also, i covered the barrel extension with loctite 620 and slid it into the receiver, then torqued it up. I went to disassemble it later and the loctite got all into the internal threads of the receiver and barely was able to get the barrel nut off. Now that receiver is pretty much trash as it's completely filled with loctite in the threads. So maybe but the loctite on the inside of the receiver itself, then slide the barrel in to avoid getting as much loctite out the front.
 
I used the wheeler ar10 lapping bar and it fit in the m5e1. Also, i covered the barrel extension with loctite 620 and slid it into the receiver, then torqued it up. I went to disassemble it later and the loctite got all into the internal threads of the receiver and barely was able to get the barrel nut off. Now that receiver is pretty much trash as it's completely filled with loctite in the threads. So maybe but the loctite on the inside of the receiver itself, then slide the barrel in to avoid getting as much loctite out the front.

That's always a risk. Especially on the M5e1 because you cant really wipe off any excess.

I would reccomend some molly grease on the barrel nut threads anyways but in this case its crucial.
 
Removing Loctite Red. Infrared Thermometer for keeping track of the work piece temperature.

I did mine by applying the Red to the inside of the receiver where the extension is inserted. This did not produce the issue you described.

Once the barrel nut was tightened, I wiped the interior of the receiver down with a shop cloth moistened with Odorless Paint Thinner. This may not be the ideal solvent, but for the uncured Red, it seems to have worked OK.

Loctite sells a cleanup solvent, but that's for CA Glues, not the threadlocker.

Greg
 
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I bought just the M5E1 tool for $37.50 from G&G. It arrived quick!

And this is my first build (still waiting on a Criterion barrel to arrive) so very interested in this topic. There are a lot of threads that simply ask if the AERO M5E1 receivers need lapping, in other words, is AERO machining beyond the norm. Not sure answers to those questions help because regardless of their machining, generally, YMMV. Videos are often lacking in coverage/quality sufficient for a new guy to approach this with confidence. I watched some accurizing videos from Criterion and sent Michael some questions.

1st, Do you need to protect the female threads unique to the M51E one-piece design from the lapping tool when refacing the receiver? A lot of lapping videos show lapping on the face of male thread extensions whereas the M5E1 turns that inside out with it’s integral free-float anti-rotation tabs, i.e., handguard mount.

2nd, Would turning the lapping axes vertical and turning the tool by hand be advisable?

3rd, When Michael at Criterion refers to a ‘sleeve retainer’ in the videos they show Locktite 409. Seems like it’s functioning as a bedding compound – So, my question was, does this adhere to both surfaces and make future barrel swaps more difficult? (something a little different than the thread runover mentioned here). I didn’t see a release agent employed so was thinking it does not – I use release agents when bedding other actions for sure. The problem with a ruined receiver here changed my mind and really makes me wonder about those future barrel swaps. Regardless, I’m wondering if holding the 409 back off the end of the last ¼” extension might be advisable to avoid the thread issue?

4th and last one, Is there any danger of negatively impacting headspace by being too aggressive with refacing the receiver face on the M5E1 receiver, or on any of them really?
 
I would be cautious and protect any threads.

loctite 409 is basically super glue. you could use almost anything for bedding compound. not my first choice.

headspace is predetermined by the barrel and barrel extension at the factory. only negative impact of over doing it would be your feed ramps overhanging the upper and or the barrel alignment pin hitting the back of the upper slot.
 
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I talked to a couple gunsmiths about trueing the receiver face and they both told me to lap by hand and to turn the receiver vertical so force is equally distributed downward. I only removed material until you could see the anodizing come off all around. This was on a standard M5 upper receiver with a 24-inch Criterion bull barrel in 308 and it shoots extremely well for a gas gun. I considered bedding it, however I had a very tight fit between the extension and receiver to begin with.
 
I'm waiting on some 220 grit lapping compound before I continue (G&G sent 120 grit with their tool and it felt like gravel from my drive) but the more I look at the M5E1 the more problematic it seems. The way I see it there is a big difference in how you'd want to handle the M5 and M5E1. Not so much in the lapping, though I do wonder like the previous poster mentions if it wouldn't be best to orient vertically rather than horizontally in the vice as I hand-turn. But the big difference I envision is in the bedding. With the exposed receiver extension of the M5, you have the opportunity to wipe off excess as it squeezes out over the raised flange of the extension. Whereas with the shrouded nature of the M5E1 that excess is going to squeeze out down inside - where it can't be reached very well, possibly as far as the female threads of the Enhanced integral Free-float fixture, and even run into the interface between the outside surface of the barrel extension flange where the barrel nut will apply torque. I've got about .0035 of tolerance (though it feels much tighter) and how to apply just the right amount of bedding on that surface in order to minimize excess squeezing out is my question/concern.
 
Criterion recommends Loctite 609. Saw it in there video series on there site
 
I have a standard lapping tool . Think I paid $30. If you live near lasalle county Illinois you can use it at any time. I would also be willing to ship it to you if you want to pay shipping to and from .
mom me if interested
 
I have a standard lapping tool . Think I paid $30. If you live near lasalle county Illinois you can use it at any time. I would also be willing to ship it to you if you want to pay shipping to and from .
mom me if interested
I am near Lexington, and I appreciate the offer, but I don’t think the standard tool will fit inside the M5e1
 
did G&G Rifleworks go out of business? can't find a link that still works. looking for the M5E1 Enhanced lapping tool ...
 
did G&G Rifleworks go out of business? can't find a link that still works. looking for the M5E1 Enhanced lapping tool ...
They are gone. There are other manufacturers that offer them but at over double the price.
 
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@rpoL98,
If you know someone with a lathe you could pick up a large frame lapping tool from PTG and have them turn it down to fit.

FYI, I put a proof barrel in a m5e1 and did not lap it. This is the one and only 100 yard group I shot with it after I installed it. I wouldn’t worry about it if I were you.

870EA5D9-59E2-4B1D-8398-329571A7D0AB.jpeg
 
They are gone. There are other manufacturers that offer them but at over double the price.

Wow, wasn't for lack of work I would think. I emailed them well over a year asking about when they'd have the set of 4 in stock as you got a break on the price. They acted like it would be soon but never saw them, never got a notification. I guess it was a good thing I bought both the E1's when I saw them in stock.
 
Between the aluminum upper and the steel barrel and nut, there's a battery created due to dissimilar metals. I'd rather put something like Never Seize on the threads vs any sort of locktite.
 
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bought the X-Caliber tool. $81 shipped. The mandrel is an extremely snug fit with the receiver bore, which is a good thing, very nice. wheel bearing grease makes it all good. First use was for a FDE M5E1. probably most of the work was I'm guessing was hitting the cerakote coating high spots, but kind of surprised to see some bare aluminum indicating the receiver face did benefit from being lapped, well, similar to other AR uppers.

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