Facing AR-15 receiver

[mi223]

Facing recivers is stupid.

All recivers are machined on modern cnc equipment. If done correctly they should be boring the ID, face and threading in one operation. I don't know that they do but based off my experience I can't see why you wouldn't.

If they do, the face will be as square to the bore as the the machine is capable.

Just because your 120 dollar lapping tool from Brownells didn't clean up even, means the tool isn't seated straight in the bore. You now made it less square because you were sold on some black magic marketing and because you are stupid to.

Your 120 dollar lapping tool is not consistent enough to do shit reliably.

And also accurately measuring squarness of a receiver face would be incredibly difficult without a modern CMM. Not saying it can't be done but most home smith's don't have the tools to do so.

Lapping receiver faces is stupid and you are probably a stupid Biden voter if you lap your receiver face!

Change my mind!!


ETA. most any discrepancy in how square the face of the receiver is more than likely coming from the anodizing. But how much discrepancy are you going to get on a .001-.002 thick coating

 

[Rocketvapor]

This has been a varying point of view for years.
Some even claim to have seen a benefit from lapping.
(If it's on the internet it must b true )

I'll continue to lap mine as I don't normally buy high end stuff.
I be stupid and cheap

My Wheeler tool now fits really good from the rear end *with a light coat of oil). Don't have an empty upper at the moment.
Paint won't last but I don't do many uppers now.

 

[srt-4_uk]

Criterion doesn't sell lapping tools yet they recommend lapping. Can you guess what tool they use?

 

[PappyM3]

…

And also accurately measuring squarness of a receiver face would be incredibly difficult without a modern CMM. Not saying it can't be done but most home smith's don't have the tools to do so.

…


ETA. most any discrepancy in how square the face of the receiver is more than likely coming from the anodizing. But how much discrepancy are you going to get on a .001-.002 thick coating

So, when I put a barrel in and it can wobble a bit when trying to apply uniform pressure to the receiver face, that isn’t telling me the face is not square?

And after lapping, when the barrel rests flat on the face and no longer wobbles, that means my $120 lapping tool ruined my upper?

You’re right that most any discrepancy is from the anodizing. But you’re wrong to insinuate that anodizing is too thin to make a meaningful difference.

* And when I say wobble, I’m not talking about lateral play from the gap between the receiver ID and the receiver extension. I’m talking about angular movement.

 

[papershredder]

Graingers ?

Maybe. Quick search I done showed MSC doesn't stock them. Mcmaster-Carr is a miss. Looking through Precision Brand's website shows only stainless available in those thicknesses. They don't have online purchase options so it will either be a phone call or find a vendor. I haven't done a thorough search to find those yet, but so far, Amazon might be a viable option.

 

[ron_c]

Amazon might be a viable option.

316 Stainless Steel Shim Stock, 0.001" Thickness x 6" Width x 12" Length, Stainless Steel Sheet Shim, 2 Pieces​

Caution: this stuff will cut you up. I have 3 cut places. (so far)

 

[Oryx]

So, when I put a barrel in and it can wobble a bit when trying to apply uniform pressure to the receiver face, that isn’t telling me the face is not square?

And after lapping, when the barrel rests flat on the face and no longer wobbles, that means my $120 lapping tool ruined my upper?

You’re right that most any discrepancy is from the anodizing. But you’re wrong to insinuate that anodizing is too thin to make a meaningful difference.

* And when I say wobble, I’m not talking about lateral play from the gap between the receiver ID and the receiver extension. I’m talking about angular movement.

I think everyone gets the tool concept, but I'd love to understand the degree of angular measurement you think you have by using a barrel as your measuring tool and trying not to account for the differences in tolerance between your barrel extension and receiver. How much material are you removing from the receiver face by lapping and whether or not it has corrected this angular "measurement"? Can you explain your measuring process regarding the results and how can you be sure that it is more true to the receiver centerline?

As you lap with your drill, how are you controlling the concentricity of the tool and tolerance differences between tool and receiver?

I'm not saying that the tool doesn't work, but without measuring before and afterwards, and controls over the interface between the tool and work piece it seems like more of a "feel good" practice. May not hurt anything either ... just curious.

 

[papershredder]

316 Stainless Steel Shim Stock, 0.001" Thickness x 6" Width x 12" Length, Stainless Steel Sheet Shim, 2 Pieces​

Caution: this stuff will cut you up. I have 3 cut places. (so far)

Just 3? lol, I'm well aware of those sharp edges. I've handled enough sheet metal over the years. Round off any corners with shears at every opportunity and lay the piece flat on the table and work the edges over with a diamond hone to remove those razor blade-like burrs around the edges. Even then .001" sheet will still be sharp!

 

[JohnCarter17]

To me, if your goal is to build a precision gas gun... spend a little more and just buy a receiver set from the factory that is square.

That said, if a gun has been painted or cerakoted over the barrel nut threads then yes I would definitely lap it square. I have done Lapped a reciever for this reason.

Damn, and here the rest of the known universe of AR builders have been, buying uppers from the "not square" aisle at the factory outlet.

FFS.

 

[Rocketvapor]

Another failure in Mil-Spec tolerance stacking and advertising jargon.
Buy a receiver set spec'd to better than Mil-Spec, or an oversize barrel extension that gives you a THERMAL FIT.
How many would complain that the barrel won't go in the receiver though?

Ask the high end receiver companies and they will tell you no need to lap THEIR receivers.
Barrel sellers usually recommend lapping though.
Shimming sounds good, if you can get a thermal fit and not get cut up with shims putting it together.
Gooey filler? Oh well, better than nothing.
I see it just like the sellers that won't guarantee accuracy without buying their Bolts but won't tell you the actual head space they set to or what chamber dimensions you end up with by buying their bolt.

 

[supercorndogs]

I think everyone gets the tool concept, but I'd love to understand the degree of angular measurement you think you have by using a barrel as your measuring tool and trying not to account for the differences in tolerance between your barrel extension and receiver. How much material are you removing from the receiver face by lapping and whether or not it has corrected this angular "measurement"? Can you explain your measuring process regarding the results and how can you be sure that it is more true to the receiver centerline?

As you lap with your drill, how are you controlling the concentricity of the tool and tolerance differences between tool and receiver?

I'm not saying that the tool doesn't work, but without measuring before and afterwards, and controls over the interface between the tool and work piece it seems like more of a "feel good" practice. May not hurt anything either ... just curious.

With the tool relatively tight in the receiver bore I think it is reasonable to assume it is making it flatter, assuming the tool is flat. How much as you say, there is no way to know without before and after measurements. Whether it makes a difference is the question. I am sure at some level it does. Then the personal questions come, Can I shoot the difference? Should I do it anyway for good feels or just move along?

 

[Oryx]

With the tool relatively tight in the receiver bore I think it is reasonable to assume it is making it flatter, assuming the tool is flat. How much as you say, there is no way to know without before and after measurements. Whether it makes a difference is the question. I am sure at some level it does. Then the personal questions come, Can I shoot the difference? Should I do it anyway for good feels or just move along?

I hear what you're saying and that's why I stated that everyone understands the concept, but you have to admit ... there's a lot of assumption in the majority of the comments made regarding the subject and little to no measurements.

 

[Rocketvapor]

Flatness of the lapping surface wouldn't matter if the tool fit the bore.
Think of spinning the receiver in a lathe with a single cutter.
If aligned it cuts flat, even if it cuts only at one point as it goes around.

 

[Rocketvapor]

Thermal fit info:

Coefficient of Expansion for
416R Stainless Steel is about 6 uin/in per degree F

7075 Aluminum is about 13 uin/in per degree F

Referenced to an assembly temperature of 70F,
heating a receiver to 220F, cooling to about 200F at assembly will expand the bore by about 0.001690". The barrel cooled to close to 4F (normal for home freezer) warming to about 10F at the time of assembly (work fast) would shrink about 0.000360". A total change of about 0.002300".
If the barrel extension (plus any shims) was 0.001" larger than the receiver bore at 70F this would result in an assembly clearance of about 0.0013" and a thermal fit of 0.001" after temperatures returned to ambient (70F). The original mismatch.
During operation (extension and receiver both heating up) the zero clearance temperature would be about 143 degrees F above assembly temperature or about 213F.

The zero clearance temperature (hot barrel/hot receiver) for a half thousandths thermal fit would be about 71 degrees F above assembly temperature or about 141F.

 

[NCgreentick]

I have found that there can be high and low spots across the thickness of the supposedly flat front of the receiver.

 

[rpoL98]

Maybe. Quick search I done showed MSC doesn't stock them. Mcmaster-Carr is a miss. Looking through Precision Brand's website shows only stainless available in those thicknesses. They don't have online purchase options so it will either be a phone call or find a vendor. I haven't done a thorough search to find those yet, but so far, Amazon might be a viable option.

McMaster-Carr

 

[papershredder]

McMaster-Carr

Why didn't that show up on the day I searched? Their website is funny at times.

Thanks

 

[CoriolisEffect]

If you want to face a receiver, use a lathe, or don't bother. As with anything, there's the right way to do it, and then all the other ways. The tolerance that is required to make a lapping tool that fits into the majority of upper receivers is slop that can be completely dialed out on a lathe.

For the people saying it's not necessary, maybe someone else's goals and requirements are more stringent than your goals and requirements. You can either accept that you aren't chasing perfection and leave us be, or get on board. The ultimate goal of this exercise is to ensure that every component that touches or effects the firing of the cartridge is perfectly colinear with the bore.

 

[supercorndogs]

Flatness of the lapping surface wouldn't matter if the tool fit the bore.
Think of spinning the receiver in a lathe with a single cutter.
If aligned it cuts flat, even if it cuts only at one point as it goes around.

If the the tool fits the bore it would matter less. The looser the tool is the more it matters. A high spot on the lapping surface would cause a low spot if it was spun back and forth not making full rotations like in some of the instructions given earlier. In that case your hi point may never leave one small area and you would end up with a dip. Lapping is nothing like single point lathe cutting. Lapping is process of wearing 2 parts together. So if you want the front of your receiver to be flat, then you want your lapping tool to be flat. Usually when lapping you start with two surfaces that are as flat as possible.

 

[Charger442]

If you want to face a receiver, use a lathe, or don't bother. As with anything, there's the right way to do it, and then all the other ways. The tolerance that is required to make a lapping tool that fits into the majority of upper receivers is slop that can be completely dialed out on a lathe.

For the people saying it's not necessary, maybe someone else's goals and requirements are more stringent than your goals and requirements. You can either accept that you aren't chasing perfection and leave us be, or get on board. The ultimate goal of this exercise is to ensure that every component that touches or effects the firing of the cartridge is perfectly colinear with the bore.

i think this is an important distinction to make.

if you are doing it "by hand" with a lapping tool then my reaction still stands, as "why?" or "why even bother?"

if you are really doing it properly with a lathe, you've taken the process to more of a "blueprinting" of the receiver, by truing the face and possibly chasing the threads. atleast then i could see the thought process being followed with the correct procedure.

but in the end i would still have to ask the question if it really actually matters in overall accuracy.

 

[CoriolisEffect]

i think this is an important distinction to make.

if you are doing it "by hand" with a lapping tool then my reaction still stands, as "why?" or "why even bother?"

if you are really doing it properly with a lathe, you've taken the process to more of a "blueprinting" of the receiver, by truing the face and possibly chasing the threads. atleast then i could see the thought process being followed with the correct procedure.

but in the end i would still have to ask the question if it really actually matters in overall accuracy.

In general, I would say that it likely does affect accuracy, the question ends up being to what extent. If the exit of the barrel is not colinear with the chamber, your cartridge is either not going to be totally supported by the bolt face, or the cartridge is not going to be colinear with the chamber/bore. Either of these scenarios will result in asymmetric forces being applied to the projectile as it is fired from the case. I imagine the only way to truly quantify the benefit is via A vs B testing. I think the fundamental baseline conclusion is simply that it won't hurt anything if done properly and can only improve accuracy potential.

 

[Rocketvapor]

I think the distinction for improvement lies in the initial quality of the upper you are using.
Go high end and expect things to be correct. If they weren't you would hear about it all over the web.
Spend less and expect less. That's where lapping may show the most benefit but only with a proper extension to receiver bore fit.

I question the Gooey filler bedding many use. Once cured it might prevent movement, but initial alignment?
Wouldn't the goop be shifted in alignment to the receiver face?
An "interference fit" that has to be tapped in isn't a zero gap fit. Close, but not zero, especially at an elevated temperature.
I would think the only way to prevent wobble would be a thermal fit for the highest expected running temperature.
Be careful with sharp edged shims and a hot receiver.
Again, buy higher up the food chain to get a good fit.

It was mentioned to test how well these cheap lapping tools work. The ONLY people that would do that would be the people selling the lapping tools. But then you would expect bias in the results.
A seller of uppers won't do it to show how far out their uppers were.
Barrel sellers might, but they usually also sell lapping tools.
Completed upper sellers might if they added in the "cost" of the lapping hidden in their price.

I thought my wheeler tool was OK, but now question the 0.003" misfit. This winter when I put together another long AR to replace my high count barrel I'll try the shimmed up wheeler and a true thermal fit.

 

[CoriolisEffect]

I think the distinction for improvement lies in the initial quality of the upper you are using.
Go high end and expect things to be correct. If they weren't you would hear about it all over the web.
Spend less and expect less. That's where lapping may show the most benefit but only with a proper extension to receiver bore fit.

I question the Gooey filler bedding many use. Once cured it might prevent movement, but initial alignment?
Wouldn't the goop be shifted in alignment to the receiver face?
An "interference fit" that has to be tapped in isn't a zero gap fit. Close, but not zero, especially at an elevated temperature.
I would think the only way to prevent wobble would be a thermal fit for the highest expected running temperature.
Be careful with sharp edged shims and a hot receiver.
Again, buy higher up the food chain to get a good fit.

It was mentioned to test how well these cheap lapping tools work. The ONLY people that would do that would be the people selling the lapping tools. But then you would expect bias in the results.
A seller of uppers won't do it to show how far out their uppers were.
Barrel sellers might, but they usually also sell lapping tools.
Completed upper sellers might if they added in the "cost" of the lapping hidden in their price.

I thought my wheeler tool was OK, but now question the 0.003" misfit. This winter when I put together another long AR to replace my high count barrel I'll try the shimmed up wheeler and a true thermal fit.

You don’t even really have to go that “high end”. You can get a BCM blem stripped upper for $90, they have an undersized barrel extension bore that allows you to simply thermal fit the barrel without any bedding or shims. Then you only have to get it faced before assembly.

 

[Rocketvapor]

Thanks for the suggestion but for prone I really like a right side charging upper.
Just a preference.

 

[357Max]

I have always lapped the receiver face with the receiver upside down & horizontal. Just makes the most sense to me. Aside from the last round mag is always putting pressure on BCG to top of receiver. That's were uppers start to show ware, top side. I've lapped about 8 & none have been flat. Your definitely not going to single point cut a monolithic upper.

Edit: I meant to add another pic. Trying to thermal fit the barrel in this monolithic with a full wrap of .001 ss shim was a complete PITA. I screwed up at least 2 shims & then decided to cut the shim long to help get it started. That worked and then I trimmed the excess with an exacto knife.

 

[357Max]

I'm about to assemble an 18" SPR build. Perfect test bed for this.
Just received a barrel wrench today so this is ready to go together.

Upper Build list:
VLTOR Mur upper that's unmodified. Or BCM thermal fit. Have both.
Mega Wedge lock 12-5/8" rail that I had to mill out the front of (I know sacrilege).
Proof Carbon 18" 223W 8T. Gas system is .815 dia & 5/8" shorter than RL so intermediate I guess. The gas block is Iron, pick rail on top, fully adjustable, keyed to barrel, retained with a nut, & straight gas tube attaches via flared compression fitting like a brake line.
SRC low mass BCG
Geissele Airborne CH
Precision armament Hypertap brake
Area 419 Keymod Arca rail (I also had to mill this to fit).
Topping it off will be a RRS 34mm mount & an XTR 3 3.3-18 SCR-2 mil.

The plan is to assemble this without lapping the upper or bedding/shimming the extension.
The only upper mod I will do from the get go is to install an accushim in the upper. I have contempt for a sloppy fitting upper to lower connection. Rear take down pin will have a snug drag fit.

Personally I think sloppy extension fit (VLTOR I'm looking at you) has a much bigger potential to affect precision.
So what say you Hide, VLTOR or BCM thermal??

I fucking hate trying to do a thermal assemble with a wrap of .001 shim. Given that, you fuckers will prolly say VLTOR.

Will then run some brake in rounds through it & shoot some 5 shot groups with Razor Core 5.56 77 OTM, 223 PMC X-tac 77 OTM, & Sig 223 77 OTM.

Disassemble, lap, bed/shim, rinse and repeat with same ammo.

If all goes well I'll have it together tomorrow & if my flt home Friday doesn't get FUBAR I'll shoot part A Sat.
I'll do a separate thread for this & will drop a link here when that happens.

 

[srt-4_uk]

Proof Carbon 18" 223W 8T. Gas system is .815 dia & 5/8" shorter than RL so intermediate I guess.

So I have this same barrel and struggled to find a longer handguard that would accommodate the gas block. Strike Industries Gridlok with the front sight removed will fit. If you don't wanna hack up the Mega.

 

[357Max]

So I have this same barrel and struggled to find a longer handguard that would accommodate the gas block. Strike Industries Gridlok with the front sight removed will fit. If you don't wanna hack up the Mega.

To late. I like the way it turned out. LWRC buis will go on the front.

 

[Constructor]

Barrels had to be tapped into every Vltor receiver I have had or built, those and Mega were always tight.

 

[357Max]

Barrels had to be tapped into every Vltor receiver I have had or built, those and Mega were always tight.

I've only done 4 VLTOR's newer versions but all have been loose (including the monolithic). It's a shame cause they have some extra beef & are well machined aside from the loose extension.

The one I might use for the SPR build is an old school Vltor & it's loose. Would need a full wrap of .001

I've got a few BCM's & they will need to be tapped in.

 

[357Max]

While were kind off on the subject. For some reason White Oak quit making the oversized extensions.
Does anyone know of any oversized ext. currently available???

 

[srt-4_uk]

To late. I like the way it turned out. LWRC buis will go on the front.

Looks real good
I just picked up a CMT Billet and VLTOR MUR last week and both had sloppy fit as well.

 

[Rocketvapor]

Spray on extension shim
I also use the Accushim on my long ARs.
I plastic shim the stocks (that don't have a tightening screw like the MBA).
Makes them hard to adjust, but that's the point, right?

OK, back on topic while we wait for the results of your before and after test.

 

[rpoL98]

I'm about to assemble an 18" SPR build. Perfect test bed for this.
Just received a barrel wrench today so this is ready to go together.

Upper Build list:
VLTOR Mur upper that's unmodified. Or BCM thermal fit. Have both.
Mega Wedge lock 12-5/8" rail that I had to mill out the front of (I know sacrilege).
Proof Carbon 18" 223W 8T. Gas system is .815 dia & 5/8" shorter than RL so intermediate I guess. The gas block is Iron, pick rail on top, fully adjustable, keyed to barrel, retained with a nut, & straight gas tube attaches via flared compression fitting like a brake line.
SRC low mass BCG
Geissele Airborne CH
Precision armament Hypertap brake
Area 419 Keymod Arca rail (I also had to mill this to fit).
Topping it off will be a RRS 34mm mount & an XTR 3 3.3-18 SCR-2 mil.

The plan is to assemble this without lapping the upper or bedding/shimming the extension.
The only upper mod I will do from the get go is to install an accushim in the upper. I have contempt for a sloppy fitting upper to lower connection. Rear take down pin will have a snug drag fit.

Personally I think sloppy extension fit (VLTOR I'm looking at you) has a much bigger potential to affect precision.
So what say you Hide, VLTOR or BCM thermal??

I fucking hate trying to do a thermal assemble with a wrap of .001 shim. Given that, you fuckers will prolly say VLTOR.

Will then run some brake in rounds through it & shoot some 5 shot groups with Razor Core 5.56 77 OTM, 223 PMC X-tac 77 OTM, & Sig 223 77 OTM.

Disassemble, lap, bed/shim, rinse and repeat with same ammo.

If all goes well I'll have it together tomorrow & if my flt home Friday doesn't get FUBAR I'll shoot part A Sat.
I'll do a separate thread for this & will drop a link here when that happens.

i think the only thing you're going to find is where the zero is. the lapped set-up will be colinear, iron sights would be more true (centered for zero) than unlapped.

my guess, accuracy will be the same. POI will shift.

lapping the receiver face addresses the barrel/receiver alignment, not the barrel accuracy. unless you really have a wobbly AF front receiver face, but then, hypothetically, if you had that situation, you shouldn't've bought the receiver from Delta Team Tactical, and you shouldn't be posting on Snipers Hide.

shimming of the barrel extension would improve accuracy, though. separate from lapping.

 

[papershredder]

While were kind off on the subject. For some reason White Oak quit making the oversized extensions.
Does anyone know of any oversized ext. currently available???

I found these guys on a google search a few months ago. I haven't bought anything from them or read any reviews about them, so caveat emptor. But, if they're legit, they might take on custom work.

 

[supercorndogs]

I have a great shooting 223 upper built on an AR-Stoner Billet upper receiver I got from Midway for 39 dollars. Simple simple I just put WOA barrel in it. The upper receiver is not that important.

First two pictures {3 groups} are a Mcgowan 20 practical barrel glued into a BCM blem receiver. The set of 2 is 27.5 with 32g Nosler and the single one is 26.5 {pull down LC844} with a 32g Nosler. The POI was a little different between charges. Squares are .86".

Last one is the 22 Valkyrie I just put in a RRA upper receiver, no loctite just flattened the front with glass and sand paper because I was bored and it was 101 degrees outside. I loaded 10 with a shorter OAL then used the first 5 of them on a clean barrel. The load is 25.5 of Varget with a 70 Nosler RDF. I just picked something inside book. That is the last of the first 50 rounds down the barrel. I reloaded the brass with the same charge, and 15 of the shorter OAL.

I am interested to see if it continues to tighten up over the first couple hundred rounds. Then maybe I will do a 5x5 then glue and 5x5.

I shoot both of these rifles Weaver 2-10x36 Tactical scopes that don't have adjustable parallax, so its easy to move shots around a little if I am not careful.

 

[Bhobbs]

Ask yourself this… do you really think that a $50 lapping tool is going to make the receiver as square as a $500K CNC?

Buy a high quality receiver like a VLTOR MUR and then bed the extension with loctite 620.

Yes, I do. I design and build injection molds and CNCs are great but still leave room for improvement. More often than not, I have to grind 5+ thou off a mating surface to get it truly flat. I lapped my Aero upper and it was more out of square than I thought. Is it worth it in the long run? Probably not. Am I accurate enough to see the difference? Definitely not. Is a few minutes of extra work worth reducing as much error as possible? Sure, I think so.

 

[357Max]

It's done. I'm a glutton for punishment. BCM would have been easy button.
Built with an unmolested VLTOR MUR 1 upper. No facing & no shim/bedding.
Torqued barrel nut to 60 lbs. Indexed the gas tube since it'll have to come off for lapping. I'll reinstall clocked the same.
Gas block has min. .060 clearance to rail all around including the ferrel under top for tube (had to mill clearance for the fitting).
Unfortunately the highest 34mm scope mount I had was a MPA @ 1.250 so the rear buis won't fit.
I'd planned on sighting in irons for before and after but that's not going to happen.
Assuming I make it home from TX Friday night, I'll break in & shoot some groups this weekend. Then tear it back down, lap & shim extension.
It'll be all factory 77gr match ammo for this test, couple varieties. I need some brass formed to this chamber anyway.
Head space was Go + .002 with the Sharps bolt.

It's not a light weight, but 7lb - 11oz isn't to bad considering all HD parts in it.
Lower has AR Gold trigger, Ambi safety, Teal Blue Bravo Ambi bolt catch, BCM mod 3 grip, & VLTOR EMOD stock with the RE10/A5SR extension & A5 buffer/spring setup.
Plan on shooting this in some IWI gas gun matches (after lapping & shimming).

 

[supercorndogs]

Is .06 what its supposed to have? I found a couple of low clearance spots on my gas block. I have been grinding on the gas block, and filing the inside of the rail to get some more clearance. The barrel is dimpled so I couldn't cheat a little one way to get more clearance on the gas adjustment side.

 

[357Max]

Is .06 what its supposed to have? I found a couple of low clearance spots on my gas block. I have been grinding on the gas block, and filing the inside of the rail to get some more clearance. The barrel is dimpled so I couldn't cheat a little one way to get more clearance on the gas adjustment side.

Depends how rigid your rail is & barrel profile. With a Med/heavy barrel & stiff rail I’d let it fly at .045
I’ll be shooting mine in PRS style matches & with an Arca rail you can get some leverage on the front of handguard so .060 seems about right for me.

Just mock it up & squeeze the end of the rail/barrel with your fingers to see how flexible your set up is. They all move.

Hell I also notched the front sight to match length of block. I’m just cutting al kinds of high end shit here.

 

[357Max]

I shot the first part with unlapped upper & no shim or bedding on receiver.

Facing an AR receiver. Does it matter?

Another thread on the same/sim subject inspired me to try putting it to the test. Link here to other thread. https://www.snipershide.com/shooting/threads/facing-ar-15-receiver.7133119/ Since I was about to build an 18" 223 Wylde on quality parts I figured it'd be a good test bed to maybe shed...

www.snipershide.com

 

[kjk200]

...

Does the shim stock have to be STAINLESS?

I only have 4 uppers to bed...so could I use regular steel shim stock that I can get for free?

Or do I need to bite the bullet and get the stainless (that I will never use again)?

 

[msgriff]

For those looking for shim stock in smaller quantities , TriggerShims is a good source and have a variety pack of 3 different thicknesses $14 shipped.

 

[kjk200]

For those looking for shim stock in smaller quantities , TriggerShims is a good source and have a variety pack of 3 different thicknesses $14 shipped.

THANK YOU! THANK YOU! THANK YOU!
Order placed for the shim stock and even found some shims for the bolt release to tighten it up for my Magpul BAD lever!

 

[Romeo458]

I lap all my uppers now. I've done 3 that are cary handle, one was a before and after. That one I don't remember exact but the windage was not on zero when the rifle was zeroed. A couple clicks one way or the other. After lapping the windage starting at zero stayed at zero. All three handle uppers I've done the windage adjustment stayed at actual zero. I think lapping is worth it

 

[357Max]

THANK YOU! THANK YOU! THANK YOU!
Order placed for the shim stock and even found some shims for the bolt release to tighten it up for my Magpul BAD lever!

Here is the shim stock I use.

Check out Teal Blue Bravo. I’ve got 3 of them that’ve been flawless. Requires a little work to the lower, but well worth the effort IME.

 

[supercorndogs]

20" Wilson .224 Valkirie barrel, RRA upper receiver from my predator pursuit, and American built arms Handguard, YHM QD 5.56 Phantom suppressor. Anderson Lower, with RRA NM trigger, RRA operator carbine stock, with standard buffer and spring. Nothing shimmed to remove slop in the upper lower or adjustable stock. Upper to lower fit is not exssively loose but rattles if you shake it.

American Built Arms Pro M-LOK Free Float Handguard AR-15 15 Aluminum

The American Built Arms M-LOK Free Float Handguard for AR-15 rifles is designed to be slim and lightweight. Weighing less than 11 ounces, the aluminum...

www.midwayusa.com

The fit of barrel to receiver was not tight or loose. I couldn't fit about 1/4" wide piece of paper between the receiver and barrel extension. I wish I would have used my feeler gauges. I guess i kind of forgot I had them. I would know very close to what the clearance was then. ITs not a tight or press fit, but not the loosest one I have felt either. Its not glued or shimmed. Not sure on the torque, the handgaurd used a hex head, I don't have a crows foot big enough for. I would guess around 40ftlbs of force, which is closer to 60ftlbs since I use anti seize on the threads and where the nut contacts the barrel extension.

The groups with the 70 RDF are hard to disquish which target is being shot. A couple approaching sub-MOA, then dog shit, POI shift dog shit.

Then i will direct your attention to the upper left corner. I may have to revise the idea that my 1 in 9 22-250 will not stabilize these 70 RDF blems. I think these are just dog shit bullets, that will get used for blaster ammo. I was having trouble getting anything that was acceptable, so I tried a different bullet. 60g Seirra HP varminter over 25.5g of Varget, the same charge I was using with the RDF.

The first 5 were high{right in rotated picture}, I adjusted the zero, and didn't get the rifle back in my shoulder quiet right, so I wasn't looking through the scope quiet right either for shot 6 {above the second square right of in rotated picture} So I adjusted position but not zero and shot the next 4 center.

 

[supercorndogs]

I will mess around with some more bullets. I would consider it square enough already. Curiosity may get the better of me and i might glue it in. Its nice to be able to pull barrels with no fuss though. The load is probably a no go, I was using 26.4 in the 223 with 60 bullet. Sierra says max is 26.4 for the Valkyrie. Hodgdon data has the 223 making 3150 with 60g @27g, Seirra data has the Valkyrie making 3k with a 60g @26.4. I assume there is some more top end there. I have an assortment of light and heavy .224 bullets. I definitely want to try another heavy bullet and get some groups a little further out. I am interested to see how fast it can move a 50g for predator calling load.

 

[Mike_in_FL]

I'm wondering if anybody who has posted in this thread has tried the Seekins IRMT-3 upper?

There isn't anything to face, at least not that you could get to easily or a different lapping tool. You can attach the V3 handguard directly to this upper, so monolithic-y.

I purchased an 18" RGS Seekins barrel some years ago. I'm thinking this is a Rock Creek button barrel. I finally build it on Friday night and I had also purchased one of those other accuracy things, the Lantac E-bcg. And it wouldn't work. I should probably make a video trying to show this but I'll explain it as best I can.

When the bolt is fully extended from the front of the bcg, it would go into the barrel extension. If it was depressed like a 1/4", forget it. It would lock up solidly on the face of the extension with the tail of the bcg stuck in the RE. So I pulled an old BCG out of one of my other uppers with some wear and it fit fine. I shot it yesterday, probably 50 - 60 rounds and now the Lantac fits, at least more so than it did. I can still occasionally get it to not go into battery.

As much as I harp on headspace gauges, I can't put my hands on my .223 right now, any other caliber I own, no problem, lol. I did notice that until you tightened the barrel nut snug, the indexing pin had a tendency to feel like it was wobbling/turning in the receiver. I had no problems getting the action to close on ammo or pick up from the magazine.