What tools are needed for an AR upper build?

[Hokie_PhD]

I just got a Magpul BEV block after looking at the various options and this seems to be the best value. I also got a Tapco wrench. Again, it wasn't the cheapest but it seemed to be a good value.

So other than my torque wrench, and the punches and hammer that I used to put the lower together is there any other tool that I'll need? I can't seem to think of any, and it looks like the upper is going to be easy to put together.

 

[1stmarine]

They are all pretty basic with a few exceptions like the standard barrel nut key.
I have a few but one of those that come wilt the barrel nut on one side, castle nut on the other and brake, etc.. some are quite inexpensive.
But depending on your hand-guard choice you might not need the barrel nut. Some models use a large wrench and the gas tube rides over it.
Some might come with a wrench (my troy did) but some assume you have a regular wrench so those always come handy if you don't have one.
Same thing goes for the torque wrench they assume you have it but you can always eyeball it. It is not that critical as soon as it is tight and well indexed.
If you have classic gas blocks you will need some pretty good punches, ideally hardened because those can be a PITA to drive in or out.
Otherwise many come now with small bolts like m3, m4 allen or torx. The clamp style blocks are the way to go, easty to move in and provide a very tight seal.
For the vise they sell all sort of inventions but you can do a good job with two nice blocks of wood and put the upper sideways flat on the rail and well
supported on the bottom. I see less flex with this than some of the plastic ones they sell. I have those too.
For the lower support you can use an old magazine maybe one with the lips broken that is not good anymore, and just take it a part, insert a piece of wood
in the body and then close it. Then when you put that on the vise you will not crash it. then put your lower there if you want.
for the pins like the bolt release use some lube and some masking tape or duck tape even better so you do not blem the receiver. A little brass hammer will help
but the tape is always need it. Can also use some pliers. Some moder ones do not use pins anymore and instead they use a special screw with threads in the end.
you might need allen keys in several places including one that is deep enough to reach inside the handguard otherwise a screw driver.
Some grease, some oil and the rest is just regular tools. For the scope rings you can a bunch of reasonably priced inch-lbs torque wrenches or screw drivers
w/o the need to pay more for expensive gunsmith edition ones.
Have fun with the legos!

 

[Geno]

Good read! Thanks!
Geno

 

[Varminterror]

What tools are required and what tools I actually touch when building an upper might be different lists.

A guy doing a duct tape and vice grips build can get away with a lot less, but when I'm building an upper, instead of just assembling a pile of parts, the list below represents what I use.

When I build an upper (aka, let's see if I can remember everything without actually putting one together to check myself):

• Upper clamshell block, lower magwell block, & bench vise to hold them
• Roll pin starters
• Roll pin punches
• Poly wrapped Maul (leatherworking tool, but makes sinking roll pins REALLY simple)
• Receiver tenon lapping tool & Compound
• Sheet shim stock, antiseize, & shears for barrel extension fitting
• Heat gun & freezer for fitting the barrel
• Length of hardwood dowel (forget dia) to tap barrels OUT of the upper
• Files, sandpaper, popsicle sticks, dowels, & lapping compound to dehorn the bolt & barrel extension, lapping ejector bore, & optimizing extractor
• Flat jaw, dehorned needle nosed pliers for holding small pins
• Drill bit, steel punch, & tapered reamer for gas block cross pins (for A2 style or other pin on gas blocks)
• Wheeler Fat wrench & Torx bits for clamp on gas blocks & scope rings
• Empty case with spent primer (plugs the chamber so I can blow into the muzzle to feel gas block alignment)
• Rod shank for aligning barrel nut
• Barrel nut spanner pin wrench & torque wrench (mil-spec always on hand, but have a few crow's feet and other proprietary spanners)
• Old picatinny ring base to clamp on the receiver and force the handguard rail into alignment while tightening
• Set of levels for aligning the handguard, front sight, muzzle brake, receiver, scope reticle, etc + plumb bob
• Scope ring lapping spindle
• Socket & adapter to mate my torque wrench to tighten ring bases or mounts
• Cut dummy cartridge & Marlin 1895 mainspring to lap the bolt lugs
• Thread chaser & bore alignment arbor
• Piloted 90* Face cutting reamer & pilots for indexing muzzle devices (cold blue/black as needed)
• Laser boresighter
• ETA: Power drill to run the lapping spindle and polishing dowels
• Castle nut wrench

 

[Hokie_PhD]

1stMarine thanks. I'm trying to see if there are any special tools I need that I don't have. That said, I think your list is great.

Varminterror, I've read both for and against lapping the upper I take it you feel this is worth the time and effort. Do you think that someone doing their first upper should do this or put it together first then either take it apart and lap later or on the next build?

 

[Varminterror]

You'd be hard pressed to convince me to take apart an upper just to lap/true the tenon, unless I had some pretty serious accuracy issues with the rifle when it got hot. I only take my uppers apart when changing barrels, and usually don't even pull the barrel from the receiver, I just spend the extra $50 and replace the upper along with the barrel - all I really reuse is the handguard (I tend to assume the gas block is burned out with the barrel too). With many of my uppers, I've epoxied the upper to the barrel, so it's an "all in" deal when those barrels go bad. $550 instead of $500, but better potential for precision = worth it to me.

I do see value in lapping the receiver - if for no other reason than to let me ensure perfect alignment of the gas tube with 40-45ft.lbs. of torque. I face the tenon, install the barrel, "seat" the threads progressively up to 65ft.lbs., then back out and start over on torque. If 40-45lb doesn't line up, I lap a little more until it does. Just a personal preference.

A great number of very accurate rifles are built without truing the receiver, just like a great number of very accurate bolt action rifles are built on non-blue printed receivers - but the most accurate in each class are built on trued receivers. When things get hot and start pushing on each other, it makes my brain itch less knowing I spent the $30 for the spindle and extra 10min to lap the receiver. I've built and rebuilt hundreds of AR's, and I've put that 10min into almost all of them. The 'smith I first apprenticed under trued on the lathe, once I finally break down and get a lathe of my own, I'll do the same - considering that even better than the lapping spindles. That might give you a perspective on my opinion on it - I'd rather have even MORE truth in my receivers than the spindles ensure.

It's a very low cost tool, and it's a very low effort, low energy job. Well worth it to me when I'm building a $1,000-3,000 AR with a $300-500 custom barrel and expecting 1/2-3/4MOA groups. I can say I doubt it is worth the effort to true a receiver for a chrome lined $65 mil-spec barrel - so take my opinion with a grain of salt as applied to your particular build.

But as you can see - I do a lot of work on my uppers which I do not believe most AR guys do, and many would say isn't necessary. Not many of us lap the locking lugs of the upper. I do. Many guys use crush washers to clock muzzle devices, I generally use an interference fit = an extra 30min on a 2min job. I tune the bolt for optimal function and reliability, and might spend an hour each dehorning, "melting," and tuning the bolt and extension alone - many guys would say it's overkill.

 

[Hokie_PhD]

Thanks
Now you have me wondering if my shooting is worth all of that effort. Or conversely, if it would improve it ;-)
You're also making me lust for a mill and lathe more than I already was!

I'm interested in what others think!

 

[Varminterror]

My shooting skill isn't worth all of the blueprinting, custom barrels, high dollar optics... certainly not any more at least... but I'm dead set on living in a world where I have to live up to my rifles - I just don't like the idea of looking at a group and thinking "this is the best this rifle can do" instead of thinking, "this is the best I can do." Whenever I find a rifle I can outshoot, I either sell it, or modify it.

 

[Hokie_PhD]

I'm a long way from outshooting anything. I've gone from not being able to hit the broad side of a barn to being ok. But I fully understand what you're saying. I'm hoping that I continue to keep improving, then have to worry about such things!

 

[1stmarine]

Some people true the receivers and some don't. I think quality receivers do a great job for a tight fit like mega, SI, seekings etc... and
might try w/o lapping first. One thing you will need to check is to avoid step on the lands so that might need a bit the stone and pehaps
polishing with a rotary tool. Also quality barrels that come with a matched bolt are pretty tight with full contact and with use they will mold
and stretch a bit. In any case I keep several quality bolts (some as spares) from different sources and choose the one that headspaces best to my liking.
I think most people who are mechanically oriented they have lots of the tools but some can be specialized.
If you want to perfectly align the gas block make a small yet precise witness mark in the barrel with a pencil and another in the block. and just line them up.
When I chamber barrel in my lathe I always put a very small and thin witness mark in line wiht the center of the port. Same thing if I manufacture a gas
block that is rare these days. I hope barrel and gas block manufacturers they also start doing that.
Use some grease on any threads to prevent galling. dip the springs in some grease so when you put them in they do not fall off even upside down.
This also helps them with friction and rust over the years.
There is plenty of good advice from others. I am sure there are 1000 tips and tricks we can come up with and you will learn many as you move
forward and from others. Modular platforms like this and glock, etc.. are the legos of the firearms enthusiasts. So have fun and be proud.

 

[boom boom]

I just got a Magpul BEV block after looking at the various options and this seems to be the best value. I also got a Tapco wrench. Again, it wasn't the cheapest but it seemed to be a good value.

So other than my torque wrench, and the punches and hammer that I used to put the lower together is there any other tool that I'll need? I can't seem to think of any, and it looks like the upper is going to be easy to put together.

My advice is to buy a bolt disassembly tool to lessen headaches. Brownells and Midway sell several different versions but it makes it easy to remove the ejector without chasing the spring everywhere. I use headspace gages on my builds simply because its the way I roll from building up bolt actions. You should have a bare bolt when doing a headspace gage check unless you have the rare military one with a rebated rim. The assembly tool is also useful if you detail clean your bolt every now and then--more so if you use cheap and dirty ammo.

The Peace River aka Brownells and Wheeler receiver clamshells for use in a shop vise are also useful as well as the bev block. Geissle reaction rods are useful for lining up suppressors and for general barrel work as they remove the torque pressure (along with the bev block) from the upper receiver to the barrel extension which can take more. Get a starter punch for starting irritatingly small gas block tube retaining pin--keeps the end from mushrooming and the pin lined up. Reminds me of the Krag front sight pin that had its own special punch just for that task. Saves aggravation versus using something like a vise grip which can slip and mar your gasblock and barrel finish. Oilers that have precision tips also help in putting just the right amount of oil to slide some of the pins in. There is also a block for ensuring proper gas key stakings that is useful if you mess around with gas keys rather than buying a new carrier. Block costs about the same as a new carrier but amortized over builds can be very useful. A good bore sighting cartridge can also lessen time to zero at the range. Those are my two cents.

 

[MachIVshooter]

Decent vise, couple blocks of soft pine, armorers wrench, hex key to install your gas block. Hammer and 3/32" punch for forward assist pin if you buy a stripped upper.

That's assuming a flat top upper. If you're doing a carry handle upper, the blocks need to be profiled and a piece of .500" stock inserted in the upper to prevent crushing it.

I won't use clam shells or take down pin blocks. Good way to tweak things. Just drill one of the pine blocks to relieve for the take down pin lugs and clamp the thing horizontal between them in your vise. The receiver willl bite into the soft pine, keeping it from distorting or rotating out of the vise.

If you're installing an A2 FSB on a virgin barrel, that's more involved, and I don't recommend trying to drill for the pins unless you have the fixture or a vertical mill. You cannot use standard twist drills for this, and you'll never get it right with a hand drill or drill press with vise. It's a bore with center cutting end mill then ream the tapered hole proposition.

https://www.midwayusa.com/product/1006923279/ar-stoner-front-sight-taper-pin-reamer-ar-15

ARs are easy. Pre-set headspace, things basically all self-align, barrel nut torque is very moderate. You haven't had fun until you're trying to loosen the barrel on a bolt gun that was installed by a factory gorilla to 200+ ft lbs. Without damaging it or the receiver.

 

[MachIVshooter]

When I chamber barrel in my lathe I always put a very small and thin witness mark in line wiht the center of the port.

There should not be a port until the chamber is cut, barrel extension installed and headspace set. The shoulder for the gas block shouldn't even be profiled until that is done.

When making an AR barrel from a blank, the very first operation is facing off the rear and threading the tenon. Then you install the extension & pin. Next comes chambering. Then you profile the barrel & thread the muzzle. The gas port is the second to last step if using an A2 FSB, and the very last step for a clamp or set screw gas block.

 

[1stmarine]

If you don't want to spend on gauges ask around but you only need the no-go gauge. for the go you can put a few rounds in there and make sure they chamber w/o problems including and specially a couple of dummies sized from your dies if you are going to reload. Color mark them so you don't confuse them with live rounds.
Even for the no-go gauge you can improvise with a bit of scotch tape. just stickt it to the base and cut all around this will give you 2 thousands for the haze scotch tape. Verify with calipers.
Yes you can use some calipers even if you don't reload.
If you are going to reload I would actually get a couple of sized cases with my own dies and do the headspace with those and this information will tell you how much the headspace tolerances
are for your given sized brass vs. commercial and also decide whether you want to find another bolt or simply size the brass so slightly w/o moving the shoulders too much.
These things must be done with the ejector plunger removed and with everything very clean and shiny as any foreign particle will screw up your measurements.

Alternatively if you have a vise you can also use it to disable the bolt. Simply cut a case or use a 9mm case (if it is a 223) then on one side drill a 1/2" hole in a little piece of 2x4 with a 1/4 drill
and put the bolt tail there and on the other put a used case with or without a dowel and simply clamp it slowly and this will compress the spring. then punch the pin out (put a cloth under) and then
wrap the bolt with your fist as you slowly unscrew the vise. very simple, and free.

I suggest you inspect before installing the barrel because the head-space alone is not a guarantee the barrel is safe to shoot. A barrel might have ok headspace and still hide a huge mistake so
get a nice light and inspect the chamber for obvious problems, drop a round and see if there are problems of play as this might be a sign of run out during chamber or even someone who was
reading the news paper when operating the machine and cut the tenon too short. This might still pass the headspace test but might leave the chamber useless and compromise support.
It is a very rare even but I have seen this first hand a couple of times over the years both with 5.56 barrels from "popular" AR makers. Same thing with bores off center for not dialing the barrel
from the bore and typical mistakes any company with some QC should catch right away. This is such rare even that nobody should be paranoid but at the same time if one is taking the time
to check head-space and learn the rifle why not avoid Murphy's law, you know. It is also a good time to make some close up pics and take inventory of parts that who knows, one might need one day for who knows
what reason. It could be a warranty claim, if could be a failure it could be an accident and liability issue. Who knows. ....I have all my firearms with detailed pictures and even inside when I clean
them up and recently I was able to use some of those pictures to resolve a situation too long to explain here.

 

[RussellC]

I always true the receiver with a lapper and compound I got from Brownells. I think it tightens accuracy overall, and am sure it helps with guns that begin to lose accuracy early in the warmup...

Another tool I havent seen mentioned yet is aset of crows feet wrenchs. With those handguards whose barrel nut goes under the gas tubes without the need for timing, it allows you to use your torque wrench instead of just some funky lightweight wrench that came with the upper.

It seems to me that the torque is critical on barrel nuts, it seems to me that too tight, like an untrued upper receiver, gets more inaccurate quicker as it heats up.

Russellc

 

[Varminterror]

Another tool I havent seen mentioned yet is aset of crows feet wrenchs.

I know I threw the kitchen sink at it, so it was easy to overlook it - but I had them in there!

Barrel nut spanner pin wrench & torque wrench (mil-spec always on hand, but have a few crow's feet and other proprietary spanners)

 

[RussellC]

I should have known. I just couldnt use the stamped wrench I was provided. It literally bent trying to tighten. I contacted the manufacturer of the hand guard, who in turn suggested crowsfoot wrenches. Unfortunately, the flats on the barrel nut were not wide enough. Again called the manufacturer who redid their barrel nut with wider flats to accomodate!

To the OP, if you use a crowsfoot wrench, attach it at a right angle to the torque wrench. Im told this gives a truer reading than other orientations.

Russellc

 

[Varminterror]

To the OP, if you use a crowsfoot wrench, attach it at a right angle to the torque wrench. Im told this gives a truer reading than other orientations

It does.

The torque wrench is calibrated to provide the specified torque with the axis of the wrench pivot concentric to the axis of the load rotation based on the length of the handle. By throwing the spanner wrench on the end of the torque wrench, we're adding length to the leverarm, so we're applying MORE torque than the wrench reads. By running at a right angle, we're bringing the length of the lever arm closer to the designed length. Think about a string tied to the end of the handle and reaching down to the center of the stub shank - when torquing ideally, that string will reach the center of the load rotation too. If the string wouldn't reach the axis of rotation, you're actually applying MORE torque. If you go past 90 and the string reaches PAST the load axis, then you're NOT applying as much torque as the wrench reads.

 

[cfullgraf]

I only take my uppers apart when changing barrels, and usually don't even pull the barrel from the receiver, I just spend the extra $50 and replace the upper along with the barrel - all I really reuse is the handguard (I tend to assume the gas block is burned out with the barrel too). With many of my uppers, I've epoxied the upper to the barrel, so it's an "all in" deal when those barrels go bad. $550 instead of $500, but better potential for precision = worth it to me.

The last couple AR-15s that I've assembled, I "glued" the barrel to the upper. I haven't had to replace a barrel yet but I have been wondering how I would do it. Replacing the upper along with the barrel is such a simple and easy solution.

To the OP, lots of good tool lists and information already posted that I cannot add to. One comment, though, building AR-15s is kind of like Lays potato chips, nobody can build just one. So, a set of AR-15 tools will not go to waste.

 

[RussellC]

So true. I used to buy lower receivers when I found one I liked at a good deal. Everyone turned into a completed rifle.

Now, I only buy upper receivers or barrels. They seem to only turn into uppers.

Russellc

 

[MachIVshooter]

All the talk of lapping/truing receivers. Guys, let me tell you something as a person who often works in tenths, and sometimes down to 20 millionths; running a mass produced lapping tool in a hand drill, you are more likely to screw it up than improve it. You cannot do better with a $20 tool and a Ryobi drill than a 6 figure millturn or machining center does with a dedicated stepped reamer that cost more than your rifle.

If you really insisted on it, the only way to do that precisely is to put the thing in a cat's head on a quality lathe, indicate the bore of the receiver longitudinally at several points to the depth that the barrel extension fits, and face it off.

In some cases, there are things that need to be hand fitted by the end user. Competition 1911 barrels that are purposely made oversize, chromoly piston rings that need the end gaps filed, things like that. The precision CNC machined upper receivers and barrel extensions of an AR aren't in this category. I have the machines and the thousands of dollars in tooling and measuring equipment to do just about anything I want very precisely, I build custom bolt rifles with $1,500 receivers and $800 barrel blanks, and still don't mess with the mating face of an AR receiver or barrel extensions.

Put it this way; If names like Starrett, Mitutoyo and Brown & Sharpe aren't familiar to you, if you wouldn't know how to get a bore or radius to run concentric and axially true to within a couple of tenths, then you should probably leave it alone. Don't mean to come across as condescending at all, but this conversation comes up frequently on various boards, and I just don't understand why people who are afraid to tear apart a S&W revolver without YouTube would be perfectly comfortable inserting a cheap tool coated in grinding compound down the bore of a precision made part and spinning it with a homeowner grade general purpose drill motor, thinking that it will somehow be better than it was. Call me jaded from spending too much time fixing other people's mistakes on cars and guns alike, but I maintain the opinion based on empirical evidence that the extreme majority of gun owners have no business playing gunsmith.

 

[RussellC]

Point taken. In any event, it has helped mine remain more accurate as they heat up. If the gun is grouping one hole, what am I gaining with thousands of dollars worth of equipment? If I was building high precision actions for a living, it might be worth it. I will continue to hand lap mine. And yes, I am familiar with Starrett and mitutoyo, and own some.

I havent had a single one not improve, yes once I started doing this, I dis assembled my other ARs and did it to them. Nary a one ruined.

Point also taken about not everyone being suited for this. But on an AR upper receiver, carefully lapping a small amount, observing how much is removed until you have a nice uniform lapped surface isnt exactly rocket science either.

I would farm out a precision bolt receiver for truing, but AR uppers are not exactly in that category, not to be condesending, its just fact.

Russellc

 

[RussellC]

As an aside, just wondering how much you charge to fix "other peoples mistakes" on this precision made 50-100 dollar part?

Russellc

 

[MachIVshooter]

As an aside, just wondering how much you charge to fix "other peoples mistakes" on this precision made 50-100 dollar part?

I don't. There'd be no point in cleaning up the face when they've broken through the anodizing inside the receiver, oblonged the barrel extension bore. We sell them a new one and advise them to leave it alone.

The concept behind receiver face lapping is not flawed, but the intended method of execution is. The tool in question here is in the same category as the little threaded pieces with a stubby pilot they sell for threading muzzles without a lathe. Our bodies aren't rigid, not a human being on earth can keep things as straight as machines. No matter how careful you are, no matter how steady you believe your hands to be, you're going to put pressure on an axis you don't intend to, be it using a tap, a die, a reamer, a file or a lapping tool. You may not realize just how much until you start doing things with machines that you used to attempt by hand.

And no, an AR upper is not in the same category as a $300-$1,500 bolt rifle receiver, but only because it's cheaper. If you woudn't "risk" this procedure on a bolt rifle, why do it on an AR? If you have no way to rotate the receiver perfectly true along the bore axis and indicate the face, then you don't really know if you made it better or not..........

 

[Varminterror]

running a mass produced lapping tool in a hand drill, you are more likely to screw it up than improve it. You cannot do better with a $20 tool and a Ryobi drill than a 6 figure millturn or machining center does with a dedicated stepped reamer that cost more than your rifle.

With all due respect - I agree with the second half of this statement, but I humbly disagree with the first half. A lapping spindle can't out perform a proper lathe, but that's not what we're "competing" against when it comes to stripped forged uppers.

I've turned uppers on center and measured runout pre and post lapping. I do agree the lapping tools do not yield the same results as truing on a lathe, but I've personally seen the results in runout reduction coming from a factory fresh upper to a lapped upper. These things leave the factory ROUGH - I've seen angular offsets, wobble, raw forging stubs... Spinning them on center shows a lot of change. Lapping with the spindle DOES improve this. It's not as true as turning on a lathe, but I have PENNIES invested in the tools per job I've done with them over the years, compared to sending out to a machinist and having them faced.

So no, lapping with a spindle doesn't match turning on a lathe - but that's not what a guy is comparing against when they buy a factory forged upper. I've not seen it to be difficult to improve the perpendicularity on the tenon from factory condition, even with a hillbilly toolkit.

And by the by, since you laid it out there, I'm not averse to pulling apart an S&W revolver without youtube either. I was working under a smith rebuilding revolvers before youtube was a glimmer in someone's eye.

(On a similar note, some years ago when I was still partnered with a machinist/smith, I also did a test of the PT&G piloted facing & lug cutters for manual blueprinting on some "spare" Rem & Mauser receivers. Similarly, the kit did not produce the same runout as turning on a lathe, but it DID in all receivers improve the truth of the faces and lugs when checked on the lathe. It doesn't replace a lathe, and for the cost of the tools - unlike the AR lapping spindles - it's not less expensive than having a smith blueprint the receiver, unless you're doing a bunch of them, but it DOES improve the "truth" of the faces to the bore axis over how they left the factory).