With gratitude and a Hat Tip to Harrison, manufacturer of the AR Performance barrels we sell.  I consider his barrels to be the best for the money in all respects: Better ballistics, improved accuracy, increased velocity, longer life, and easier cleaning.  Purchase directly from Harrison at and when he runs dry I might have what you are looking for:

  • Free Shipping
    On orders over $80.  Your credit card is not charged until your order is ready to ship.
  • Phone calls 
    We are a small manufacturer.  I have 1 cell phone and the pace of operations sometimes keeps me from answering. We ain't got no secretary either, and anyone who knows enough about ARs to answer your questions correctly has got his head stuck in a lathe or mill anyway.  If
     you need to talk to me email your phone number and I will call you as soon as possible.  Emails are the best way to reach me.
  • Short stroke? Align gas block/port location and the dimple. 
    Most gas blocks have a hole .298" from the rear of the gas block. That matches the port in our barrels. If you use a handguard with a cap the cap forces the gas block forward another .033" unless you use a FSB with a hole at .265" from the rear. The rear set screw in the gas block is where the gas port in the top of the gas block is drilled. To align the holes place the rear set screw in the dimple on the bottom of the barrel. Remove the rear set screw, align the hole in the dimple and tighten the front set screw then replace the rear.  

  • Can I shoot 600 to 1000yds? 
    The barrels we sell for civilian use are not made to shoot 600 or 1000 yds.  Use a high end real match grade barrel.  Our Socom 556 and 20" 556 barrels are very accurate with 69 and 77gr SMKs and they can be shot at 600 but If I was really going to shoot 600+ yds I would step up to a 6BR or something with a purpose built barrel and not use a lightweight hunting barrel and be disappointed because of trying to do something that it wasn't designed to do.

  • Barrel Cleaning and break in 
    AFTER building the upper run a patch with solvent through the bore to remove the protective oil, grit and dust that accumulated during shipping and building the upper to make sure there are no metal particles that may destroy your barrel on the first shot. DO NOT try to remove the black surface, that helps keep copper fouling down and provides a barrier between the copper bullets and the bare metal. After the patch with solvent run 1 patch with alcohol. Then 1 patch with light oil like Rem oil or WD40. Then follow with 1 dry patch to remove the excess oil. Follow the same alcohol,light oil, dry patch sequence after cleaning with copper cleaner below. For break in keep the copper cleaned out of the barrel. Use a good foaming copper cleaner every time you come back from the range. A blue patch means there is some copper fouling in the bore so you should repeat the process until the patch comes out white. Then alcohol, oil and dry patch as stated above. The barrel will copper foul less and become easier /faster to clean each time. When the day arrives that you clean and no blue comes out you can ease off of the cleaning and shoot until the barrel loses accuracy, when it does clean it again with copper remover. Keeping the copper out so a good layer of carbon can coat the bore is the objective.

  • Scope mounts & accuracy 
    Do not put 1 scope mount on the receiver and 1 on the handguard; accuracy will be terrible because of flex in the handguard.  Use a cantilever scope mount mounted on the upper receiver.  Squeeze the trigger and follow through (hold the trigger back, do not allow it to reset until the bullet contacts the target) to get the best accuracy.  Use a good sand bag or rest on a stable platform not the hood or tailgate of the truck.

  • Why do we sell nitro-carburized barrels instead of chrome lining them? 
    Nitro-Carburizing, Melonite, or QPQ is a heat treat process that hardens the barrels to approximately 70 Rockwell so they last longer, are more corrosion resistant inside and out, and it also decreases friction in the barrel which can increase velocity.  Chrome lined barrels can decrease accuracy as it is a built up layer inside the barrel.  Nitro-carburizing changes the structure of the metal without building a layer in the bore increasing performance but not decreasing accuracy.

  • What do you recommend for a piston system? 
    Stay away from piston systems. Except the Sig 416: Extreme AR Testing.

  • Where does the 5R rifling come into play?
    Four years of testing has shown that the land to groove ratio can cause significant variations in peak pressure created in the barrel as well as velocity obtained.  As a result, the land to groove ratio was changed to reduce peak pressure, which allows stiffer charges in our hand loads and obtains more velocity without increasing pressure.

  • "Match" and "ultra match" barrels , what are they? 
    The term "match" and "ultra match" are used too loosely, most companies advertising "match" barrels for $200 are just using the term as a sales gimmick. True "match" barrels are lapped to start with so a quick inspection with a bore scope will tell you if it could be a match barrel or not.  If it looks like rumble strips on the side of the highway then you know it's not a match grade barrel.  Match barrels are held to tighter tolerances than production barrels and are lapped and air gauged. Match grade barrels will not make bad ammo shoot well, they allow good ammo to shoot to it's capability. Our production grade barrels are the same brand that Wilson Combat uses.

  • Ammo is sticking in my chamber, what is wrong? 
    If the ammo is handloaded it could be that the case was not sized down enough, it should be .003-.004 below the chamber size in every dimension. If it is factory ammo measure the case with calipers or a mic. and compare the dimensions to SAAMI spec, if the ammo is larger than SAAMI spec that is the problem. You may have to set the sizing die as tight as you can while still being able to cam over.

  • Will you build an upper using my parts? 
    Yes, send them to us. $50 to assemble an upper.  Contact us.  Here is a good video on AR-15 assembly:
  • Will you work on my upper or lower or rifle? 
    Yes, we are set up as a smithing shop, however, we do not flute customer owned barrels. 

  • What lower assembly do you recommend? 
    Cimarron Mfg. AR-15 lower.

  • Do I need to use a .300 bore device on the AR Performance 5.56 barrel since the thread pattern is 5/8 x 24?  Do you recommend any for that caliber/muzzle thread combo? You can use a .30 cal device, 5.56 muzzle devices in 5/8x24 threads are rare.  I do make a very effective muzzle brake in 5/8x24 for the 5.56 and .30 caliber barrels.  It is also loud, and parkerized.  It's main purpose (besides irritating the shooters next to you on the line) is to get you back on the target more quickly.  This brake needs to be timed on the barrel (no ports on the bottom, so no dust signature) and might require a lathe/gunsmith.  Comes with a crush washer.
  • What is the difference between a precision hand load and a reloaded cartridge? 
    To get sub MOA groups, the loads have to be tailored to match the rifle and you must be very meticulous with the loading.  If you want to test the accuracy of your 5.56 barrel try 24gr of RE15 with a 69gr SMK set to an OAL of 2.285" that is more accurate than ANY factory load.

  • Can I use 5.56 mags in my XXX rifle? 
    No, the 7.62x39 requires 7.62x39 mags, the 5.45x39 use 5.45 mags, the 6.8 needs 6.8 mags. In general most cartridges require a special mag except the 6mmx45, the 300 Blackout, or other cartridges based on the .223/5.56.

  • Can I use steel case ammo in ARP barrels? 
    Yes, the mid gas system allows more time for the cases to shrink back down aiding extraction. The Nitro treatment makes the chambers 70 Rockwell (very hard) and very slick also aiding extraction, Our Nitro carburized barrels were made to handle steel cased ammo.

  • What do I recommend for a 3 gun rifle? 
    If the shots are 0-300 yards a lightweight 16-18" .223 with a midlength gas system and a light carrier and buffer tuned to work together. If more into combat style shoots you may want an H2 buffer and heavy tactical spring. The twist would depend on the bullets you plan to use and any other uses you may have planned for the rifle.EO Tech sights seem to be a little faster to locate the targets and I usually have no problems connecting on targets out to 300yds. If you happen to shoot longer ranges you may want to consider an ACOG or a low power scope with a wide FOV. If you shoot smaller local shoots and they do not use flashers and the Range Officer relies on sight and hearing the ding then a 6.8 could clarify those judgement calls when the steels are out at 200 yds or more.

  • Understanding AR gas systems.
  • What is the difference between 6061 and the 7075 Aluminum used in the uppers and lowers that you sell? 
    6061-T6 provides a tensile strength of 42,000+/- psi, and a yield  strength of 35,000 psi.

    7075-T6 provides a tensile strength of 76,000+/- psi, and a yield strength of 63,000 to 69,000 psi.

    Since 7075 is considerably more expensive compared to other aluminium alloys, it is only used when cheaper alloys would not be enough to do the job. It is most commonly used in applications that require high strength-to-density ratio. As such, 7075 is the alloy of choice when it comes to transport applications (automotive, aviation and marine) 

    Due to its lightweight nature, 7075 is also used in the production of hang glider airframes, rock climbing equipment, lacrosse stick shafts and bicycle components. Alloy 7075 is also used in the manufacture of M16 and precision rifles for the American Army. 


  • Do I have to pay or am I paying excise tax on a stripped lower receiver? 
    No.  This link will help you understand everything about Firearms and Ammunition Excise Tax (FAET) more clearly: 


  • I am having trouble sleeping at night?
    Try reading government regulations; I suggest reading FAET regulations to help with sleeping issues: 

  • I am having trouble staying awake.
    Try reading government regulations; I suggest reading FAET regulations to stay awake:

  • All about 80% lower receivers.


  • AR-15 PISTOL:  REVIEW OF REGULATIONS - this is not legal advice, you and your lawyer determine what is legal
    A factory fresh AR lower receiver that has never been part of a firearm can be used to build a pistol, carbine or rifle. If a lower receiver is built into and registered as a pistol first, it can be stripped down and converted into a rifle in the future. If the receiver is built into a carbine or rifle first, it must always remain part of a rifle and cannot ever be used to build a pistol.  (edit: therefore I recommend that all new lowers transfer to you as a PISTOL, which opens the option to build your lower as a pistol and then a rifle later, and then back to pistol as you wish.  If your lower transfers to you as a RIFLE, there is no such option.)

    It's not necessary to use a lower receiver stamped "Pistol" or one that is marked with the specific caliber of ammunition you plan to use when building an AR pistol. The markings are irrelevant just as long as the lower is brand new from the factory at the start of the build. Many companies are marking their lowers "Multi-Cal" these days in order to avoid confusion.

    Attaching a shoulder stock to an AR-15 pistol changes its legal status from Handgun to a Short Barrel Rifle (SBR), which is a violation of BAFTE regulations. If you wish to build an SBR, ensure that all of the proper paperwork and tax stamps are in order before attaching a shoulder stock.

    Attaching an AR-15 pistol upper assembly with a barrel shorter than 16" to a rifle lower is also considered an SBR and will get you in trouble without the proper tax stamps in place.

    Although it's a common practice to attach a vertical grip to the handguards of AR rifles, attaching one to AR pistols changes their legal status from Handgun to Any Other Weapon (AOW), which requires a BAFTE tax stamp like an SBR.

    It's legal to own and attach a stabilizing arm brace to an AR pistol, such as the the Sig Sauer SB-15 or the Shockwave Technologies Blade.  However, the braces must be used according to their intended design.  If you shoulder them like a rifle stock you're going to get in trouble.  Theoretically it's OK to "cheek" the braces (rest them along your jaw line), but cheeking looks like shouldering from certain angles.  Because of the legal status of the stabilizing arm braces being how they are used, I've opted not to include them in this review.

    All credit for this AR Pistol Regulation Summary (ARPRS) goes to the NRA, of which I (Randy) am a life member:

veteran owned
On Mark ARms, LLC
113 Mill St. Unit A
Silver Cliff   Colorado   81252
if you need to talk to me, email or text your phone number and I will call you as soon as possible.
best way to contact is via  email or text

THAT EVERY MAN BE ARMED  it's not my tagline, it's yours.

The pacifist is road-kill, the porcupine the fauna of liberty.


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