Tips and Recommendations for Building a Better AR15After nearly a hundred AR15 builds over the years of all types, shapes, sizes, configurations, and accessories including both forged and billet receiver, I have learned a few tips which have made my AR15 builds better, cleaner, less scuffed, less-problematic, and certainly easier. I would say that once a month still I pick up a new trick or tool that yet again improves my ability to build a quality rifle.
TOOLS
It should go without saying that using the right tool for the right job can make all the difference in the world, however when we all start our first build we do it exclusively with a claw hammer and ⅛” punch. The result is that the build usually has the scraps and scratches that makes it look like it was put together with a punch and claw hammer. Sure you can build an AR with this, however it you want to do it right without crying out in pain or anguish every five minutes you should plan on investing in some tools over time to make the job easier and more professional. Geissele particularly has offered some really excellent firearms specific tools and shop accessories.
Apron & Gloves - Get a long sturdy apron you can use in the shop with a pocket you can keep a supply of rubber gloves in. This are the single most awesome pieces of equipment you can own. Why? Because now you can actually do something in those dozen or so 5, 10, or 15 minute windows in the day all without getting covered in grime or getting a spot on your shirt right before you head out for dinner. $40 for a quality heavy duty long cooking apron + Rubber gloves is a wonderful thing. The pictured Geissele Shop Apron is long, large, adjustable, with plenty of pockets to keep tools and extra gloves handy.
Action Rod & Receiver Blocks - Your lap or the towel on your kitchen table is not going to securely hold the receivers and at some point that gorgeous set of receivers are going to go careening off your lap or table and bounding across a floor. Believe me, swearing during said event will not help prevent them from impacting the floor. The lower and upper receivers need to get securely mounted to something in order to work on them and the three tools I use continuously are a heavy mounted bench vise, the Geissele Reaction Rod $99, and Precision Reflex AR10/AR15 Upper Assembly Vise Block $53. All serve different purposes. Any heavy shop vise mounted to an immovable bench will work - my bench is bolted to the floor and wall to I can apply lots of torque without flipping my bench over (yes I did that with before I learned the hard way). A vise does not need to be elaborate or even new, but just functionally solid - I picked up one of my larger vises on clearance a Lowes for $25.The Geissele Reaction Rod teeth lock into the barrel nut extension and allow you put God level force on a stubborn barrel nut without putting any stress on the upper receiver itself. It also allows you to turn the receiver around the rod which is crazy handy for installing handguards, optics, gas blocks, muzzle brakes, and forward assist pins. The PRI Vise Block is handy because it allows you to have the upper receiver securely pinned up to check the operation and fit of charging handles, bolt carrier, and optics mounting and to pull and push things on and off the receiver.
Geissele also makes a Reaction Block which will hold most lower receiver builds by the buffer tube. This is a handy third hand when I am assembling lower receivers and is a unique product since not many people have any options to affix a lower to a vise.
Punches, Hammers, and Misc - All punches should be considered disposable/consumable items. Use them often and they will break and deform - just throw them away and buy new ones. Invest in a good quality set of straight un-tapered drift punches. I think mine are currently a sets of $15 Bostich or Stanley drift punches ranging from the size of a paperclip to around ¼”. You will need a very fine punch at some point if you ever replace the charging handle latch and the larger ¼” punch tipped with a spent 22LR case makes a great sight drifting tool. Another set of punches which are extremely high on my list are the Geissele Roll Pin, Trigger Fitting Pin, and Gas Block Pin Punch Set. They do wear out and I am probably on my fourth set, but they are simply indispensable.Whether you are attempting to get into building cheap or buying everything on this list, a set of Starting Punches and Center Punches have to be on the list. The purpose built Geissele punches are REALLY handy, however the Starting Punches are used to get the Bolt Catch, Forward Assist, trigger guard, and gas block pins started and driven in as far as the punch will allow and the center punch is used to drive it just a tad further and recess the pin. Invest in a set of these and you will drastically reduce the chances of maring up a receiver.
A 2 or 3-ounce brass hammer is your friend for any gunsmithing chore. In all but the most rare situations have I ever had to reach for an extra small ball peen hammer for the extra power. My 2-ounce brass hammer was $4 on Amazon so there is no reason everyone should not have one. A good non-marring rubber mallet is also a good investment and they are cheap to come by.
A set of fine needle nose pliers, an extendable magnetic pickup tool, strap wrench for handguards with “no wrench” barrel nuts, ball head hex/Allen wrenches, and set of channel lock pliers are basic tools that you will always use continuously.
LUBE
When assembling an AR15 you should be using some type of high grade lithium grease to very lightly lube the receiver threads and barrel extension to avoid metal to metal seizing. A lube I love and use for everything from ARs to Glocks is a $10 jar of copper lithium based high heat Anti-Seize from O’Reily Auto Parts. A tiny little bit goes a very long way.Andrew Barnes of Barnes Precision Machine turned me on to Mobil One Synthetic Motor oil as an all purpose lube. Along with WD-40, I now use Mobil One almost exclusively on all my guns as a general purpose lube. I have been testing Geissele’s new Go Juice which been a great lube as well and is formulated for the general purpose lubrication needs of firearms. Beyond the above lubes, a builder does not really need any other lubes with the exception of a spray can of brake cleaner for cleaning.
LOCKTITE
Do not be afraid of LockTite. Every muzzle brake, scope ring, handguard screws, selector screw, and castle nut I install gets LockTite applied. My only regret when doing a build is not using the Red permanent LockTite on the muzzle and castle nut which will delivers an extremely well built gun that will never loosen up. The barrel nut is the only thing that does not get LockTite applied.
LITTLE TIPS
Beyond using the above mentioned tools for their appropriate purpose, there are some other tricks I have learned along the way. - The trigger should always get installed before the safety selector - I still screw this order up all the time.
- Always consider upgrading the trigger guard before installing the standard one, even on the world's cheapest lower receiver… this part sucks to install, uninstall and reinstall and come on, cheap extended trigger guards are like $5.
- A thick leather glove placed in the vise jaws is the non-marring third hand you are looking for.
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Brownells AR15 receiver lapping tool
it works and improves accuracy.Use a pencil and mark on the barrel’s gas block shoulder where the gas port hole is centered. Also mark the center of the gas block hole on the face of the gas block. When you assemble the gas block on the barrel all you have to do is line up the two witness marks for perfect gas port/gas block alignment.![]()
Turn the un-installed gas block over and hold it next to the barrel in the position it would be installed. You should be able to see both the barrel’s gas port and the hole in the gas block. Make sure that when the gas block is slammed all the way up to the shoulder on the barrel that both gas ports are going to perfectly align. I have had many gas ports which require the gas block to be mounted up to 1/8” back away from the shoulder for proper alignment.- In my opinion, 300 Blackout and 7.62x39 AR barrel gas ports should be 3/32” minimum to function correctly. All of mine are ⅛” gas ports. If you see a 1/16” gas port on a 300BO or 762x39 barrel it probably will not cycle correctly and will have to be drilled out and opened up, but always test it first before any modifications.
- Sliding an old gas tube or similar sized steel rod backward from the receiver exiting the front of the receiver will help you time/index the barrel nut to assure you get it perfectly aligned. If it is not straight, it could cause the case tube to hit the gas key funny and prevent the BCG from cycling reliably.
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Precision Reflex Barrel Nut tool is the
Ultimate Answer to stubborn barrel nuts. - Sometimes handguards need lube to slide onto a barrel nut.
- Using a Brownells Receiver Lapping tool to lap the face of your receiver will improve your overall barrel to receiver fit and has proven to me to increases accuracy.
- LockTite the Grip Screw, muzzle device, and castle nut and optics mounting screws.
- Super cheap sub-$50 upper and lower blemished receivers will not give you a “precision build” unless you get really...really lucky.
- Always upgrade and install an adjustable gas block on 5.56/.223 builds - or other type of adjustable gas system unless you are buying a premium barrel with a tuned gas port. Adjustable gas block are inexpensive upgrades and you will send me fan mail once you get it tuned.
- If you get frustrated, stop and walk away for a while… have some Black RIfle Coffee and come back to it later after you are really jacked up on caffeine.
- A ¼” steel hitch pin and 1/16” punch from the hardware store will make installing the front pivot pin infinitely easier. Slide in the hitch pin, slip the spring and detent through the holes on the hitch pin, push down with the punch and turn 90-degrees. Now carefully push and slide the hitch pin out with the front pivot pin. Done.
- The tiny hole on the front detent pin is for a paperclip or small punch to push down the detent to be able to remove the pin.
- Do not crush the selector spring while installing the grip… say this three times.
- The rear takedown pin can be removed with a stiff sewing needle without removing the buffer tube. Use the needle to push back the detent enough to rotate the rear pin 90-degrees and then removed. The reinstall is easy.
- Yeah - sometimes fitting is required with sandpaper or a file. Just go slow.
- Anything which has been painted will likely suck to assemble. Use an Xacto knife and sandpaper nail file to “tune” areas for install. If there is any type of paint or coating on the face of the receiver’s barrel nut threads a receiver lapping tool is highly recommended.
- Yes, all Pinned front sight pins do require the force of God to drive out. Note - these pins are tapered and one side in smaller than the other. Hit the smallest sized head of the pin for removal otherwise you are tightening the damn thing. A large head starting punch and and large hammer will help get the pins moving.
- Use the Primary Weapons Vise Block to lock in the receiver and level the top of the receiver on a flat surface. A piece of wood under the lower receiver works as well. Place a level on the top of the optic turret to assure the optic is level with the receiver.
- Lubricate your buffer spring before assembly to quiet it down.
- WD-40 is one of the most popular CLP - Cleaners Lubricants and Protectants. I use a lot of this to prep parts.
- Wipe down the receivers and all moving parts before assembling them with some type of CLP… like WD-40.
- Check every single bolt face at the range to assure it is the correct for the caliber you have the barrel for. I have had two situations where I was shipped the wrong caliber bolt.
- Any AR rifles chambered in anything other than .223/5.56 should be labeled with a brightly colored zip tie around the muzzle so it reminds you this one is not like the others and you don’t make your gun go boom in a bad way.
- A large $5 white beach towel on the workbench will help you see everything and also will prevent the dreaded parts bounce of doom which requires 20 minutes of looking for a dropped part.
- A small dab of vaseline on the end of a pin or other tiny parts will usually help it stick in place to make it easier for you to install it. Excess is easily wiped off.
- Low quality and cheap parts and receivers will still give you a functional build, however do not kid yourself that it is high quality. I have had more than my share of $30 parts kit parts fail or not fit correctly. Have fun with the cheap kits and experiment with paint and other DIY receiver finishes.
Obviously those folks who build AR15s as a job probably have other tips. In my experience this should cover the big tips, tricks and tools help you have a fun... build on.