AR15 Wobble, Loose AR15 Receivers, Tighten.AR15 

Whether shooting for a trophy or for who buys lunch you do not have to spend a fortune to have a competitive rifle. The purpose behind a Budget Build is to assemble a quality, attention to detail rifle using select components in certain areas and not over spending in other areas. The above scoped Budget Build has just enough spice to make it a reliable, pleasure to shoot tack-driver.
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Begin with name brand stripped commercial 7075 aluminum receivers. Gauge pins and pin bores and the play between receivers. Check for a good fit between the upper receiver pivot pin lug and the lower receiver pivot pin lugs. The upper receiver for the Budget Build is an Aero Precision, Aero seems to be more generous with the width of their pivot pin lugs however this may vary batch to batch. The lower receiver is by LRB also known for manufacturing M1A receivers. To tighten and align the receivers an AR15AccuShim was installed. 
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Lower Receiver Parts Kit: Good lower parts kits and kits excluding the hammer and trigger are available from Brownells, etc. To remove play and improve trigger performance the standard .154" trigger/hammer pins were replaced with oversize .156" pins. Secure the pins with longer #4-40 x 1/4" Allen/Button Head Screws with Blue Loctite applied sparingly to the upper threads. The hammer J-Spring was removed and the hammer and trigger were centered with .004" shim washers from TriggerShims.com. Check Safety, etc.
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Barrel: Criterion 20" Hybrid Contour Chrome Lined 1-8 Twist. Criterion Barrels are available in various lengths and contours from Brownells. More info: www.CriterionBarrels.com Prior to ordering check the barrel gas block location, machined diameter and machined length.
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Barrel nut lube and proper tightening/timing coordinated with gas tube and handguard alignment helps accuracy. Do not under tighten or over tighten. Avoid barrel shims if possible. To gain a degree or two with a steel barrel nut: Remove nut, clean all related threads with brush, solvent, air, then lube, reinstall, tighten-loosen, clean, repeat. This method can cause the nut to travel too much, allow room for that possibility.
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Stock Assembly: Fulton Armory Fixed M16 A1 length sold with the A2 butt-plate, metal door, etc. Check fit between the stock pin and pin bore in the lower receiver. To remove play/twisting place a suitable size rounded piece of electric tape on the alignment pin, install stock.
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Handguard: Any Free Float Style that aligns, clearances properly and provides solid support for a sling and bipod. When using an inexpensive Free Float Rail Handguard with the steel locking ring consider replacing the soft aluminum barrel nut with an improved replacement steel barrel nut found online. Additional set screws can be installed on the handguard sides. Rail height rifle length gas blocks use a 12.5" float handguard, carbine length rail height gas block use a 7.250" float handguard.
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Charge Handle: BCM Original Mod 4 Medium, visit BravoCompanyUSA.com for latest designs.
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Gas Block: BTE Clamp Type Rail Height Aluminum or a Diamondhead Clamp Type Rail Height Steel Gas Block with the rail extension removed for hand-guards extending to the gas block. For a cleaner look and less reflection paint the gas tube black or use a Nitride Gas Tube. If necessary the barrel port and the gas block port can be aligned with a suitable diameter/thickness shim washer. A pair of machinist bubble levels or parallels aligns the block with the upper receiver. 
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USGI Flash Hider: Before installing the flash hider magnify the barrel muzzle crown and check for imperfections. When tightening a flash hider use proper tools and limit force applied to the threaded end of the barrel. If necessary thin the washer to position the hider. The gripper block from an AccuShim Kit can be modified to hold the washer for surfacing by hand. 
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Bolt Carrier Group: Cryptic Coatings, Fulton Armory, etc. McFarland 1 piece gas ring. 
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When using a riflescope it's a good idea to add inexpensive rail type A2 style detachable backup sights found online. Should the offset sights have slotted attachment screws replace with Allen/Socket Heads. Installing a 1/16" Kick-eez Products Cheek-eez Pad on a fixed stock is an inexpensive improvement. For an A1 length stock trim 3/8" off the pad pointed end and position 1/8" from a fully extended charge handle. No trimming needed for an A2 Length Stock. The pad helps transitioning from the scope to the backup sights and is available from Brownells, eBay, etc. Scope Pictured: Nikon 3.5 - 14.
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Bipod: An inexpensive 6"- 9" Tilt Style can be bolted direct to many rail type float handguards by removing its unreliable attachment hardware and rubber pads. If desired the forward slotted extension can be removed. Drill and tap a 1/4"-20 hole in the handguard and using Blue Loctite install a suitable length 1/4"-20 screw from the inside of the handguard. File and thin accordingly the hex side of a 5/16" ID flange nut to fit the bipod squared opening. For bench grinder work wear eye protection and secure the flange nut with a bolt and jam nut. Place bipod on stud, place the filed side of the 5/16" ID flange nut into the bipod square opening, secure assembly with a 1/4"-20 nut. 
The tensioning knob on such bipods can work loose. To help remedy the problem remove the securing nut, remove the knob and install an appropriate size star type lock washer, reinstall tensioning knob and securing nut.
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Magazine: 20 round USGI or equivalent. Use small files to remove burs, clean thoroughly, test feeding and loaded storage swelling, etc.
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Ammunition: A well made barrel deserves quality brass case ammo.
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Rifle Cleaning: A one piece smooth rod that will not damage rifling is a priority. Use compressed air, AR brass chamber brushes, etc. A barrel can be quickly ruined by improper cleaning.
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Transport Case: Plano Air Glide Vertical Model 1301. Inexpensive and holds most any scoped rifle.
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Add to the list understanding the penalties associated with the misuse of firearms. Law Enforcement does not accept excuses or apologies.
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Parts used for the above Carbine Budget Build: Anderson Receivers, 16" 1-8 Twist Nitride Barrel USGI Profile, AR15AccuShim Installed. KNS Side Swivel Pivot Pin, Diamondhead Gas Block With Extension, Nitride Gas Tube. Free Float Handguard, Steel Barrel Nut, Detachable Carry Handle and Front Sight equipped with Trijicon Night Sights, Fulton Armory A1 Buttstock with an A2 Metal Door Recoil Pad, 1/16" Kick-eez, M16 Silent Sling. Cryptic Coatings BCG, Rock River Arms Trigger Group, JP .156" Hammer/Trigger Pins, BCM Medium Charge Handle, USGI Flash Hider.
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18" Budget Build
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Installation Basics
 
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National Match Shim
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Gun Store 9 Packs 
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AR15AccuShim
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Feedback
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Questions
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