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Tech Support

Stripped Lower Assembly Instructions

Notes to Gunsmiths and Armorers:

  • Takedown Pins: Use the supplied speed pins to secure your upper receiver to your CAV-15 lower receiver.
  • The CAV-15 pivot and takedown pin holes are by design off set to make the upper and lower fit very tight together.  this also assures the pin do not roll out during use.  You may have to use a soft hammer to put the rear pin when attaching to a standar AR15 upper.
  • If you lose or misplace the supplied pins, replacement pins can be ordered from GWACS Armory
  • The CAV-15 MKII lower receiver uses a carbine buffer and spring.
  • The CAV-15 MKII lower receiver uses standard mil-spec fire control pins.

Though the area of the receiver that accepts the hammer pin is wider than aluminum AR15 receivers, it uses a standard fire control pins. Simply center the pin in the hole, and ensure it catches on the J-pin in the hammer.

  • Check all pinholes before you Assemble gun!

Parts vary slightly between manufacturers and some parts may fit tighter than others, especially the safety selector detent.

  • Safety selector detent pin/spring load from the top. The spring may need to be trimmed for proper fit. The top of the detent should sit at 0.20” (+/- 0.020) from the base of the selector hole.
  • The 5/64th roll pin attached to this sheet is to capture your buffer detent pin and spring.

CAV-15 Technical Notes:

  • If the Safety Selector Detent will not fit into the hole for the selector spring and detent, You may take a #27 drill carefully and lightly use it to clean any remaining flashing and the detent should then fit.
  • Selector spring and detent load from the top. Selector then slides over.  Fire control parts can be installed and removed with it in place. Before inserting selector check spring tension and trim the spring if needed. The safety can be removed by placing half way between safe and fire and pushing out.
  • The fit of the take down pins on the CAV-15 is intentionally tight. This is intended to keep the upper secured to the lower. The pins may require the use of a rubber hammer and punch to remove. The fit will wear in over time the more the rifle is disassembled for maintenance.
  • If your magazines do not drop free from your lower, and you have verified that they are good magazines follow these instructions:
    1. Separate the upper from the lower.
    2. Looking down from the top into the lower, look to see where the magazine is dragging with a magazine inserted.
    3. Use a safe edge file to remove material from the mag well in the tight areas until the magazine drops free.
    4. Check the fit frequently so you do not remove too much material.
  • If the buffer detent roll pin does not line up properly when hammed in to the lower, try inserting it from the opposite side to remedy the problem.
  • If the buffer detent does not sit high enough to capture the buffer, it can be fixed by relieving material from the shoulder of the detent to allow it to sit higher.

CAV-15 .45 ACP Technical Notes

  • You will need the following parts to build a .45 ACP CAV-15 Carbine:
    1. Complete CAV-15 MKII Lower
    2. Olympic Arms .45 ACP Upper
    3. Hahn Precision M3 Grease Gun Magazine Block
    4. Heavy 8oz+ buffer (Hahn Precision or Slash)
    5. M3 Grease Gun Magazines
  • Failure to use the heavy 8oz+ buffer will result in damage to the lower.
  • M3 Grease Gun Magazine Fit:

The CAV-15 MKII has the center of the magazine well wider to be capable of accepting grease gun mags. This feature was designed based on some USGI surplus mags it had at the time (2003). Recently new batches of magazines have surfaced and there are manufacturers making new M3 Grease Gun Magazines. These magazines appear to be dimensionally different than the older USGIs we have. Users have started to encounter problems with these magazines in the CAV-15 lower.

If your M3 Grease Gun magazines are fitting too tightly into your lower, do not force them in. Doing so risks damaging the lower. Fortunately, the CAV-15 receivers' construction lends itself to end user fitting and modification.

The area that is too tight is usually the very front of the mag well where it is narrow for .223/5.56mm magazines. Follow the steps below to give M3 Grease Gun Magazines a better fit.

  1. Separate the upper from the lower.
  2. Looking down from the top into the lower, look to see where the magazine is dragging with a magazine inserted (do not insert the mag all the way if it is tight.)
  3. Use a safe edge file to remove material from the mag well until the magazine moves in and out freely.
  4. Check the fit frequently so you do not remove too much material.

CAV-15 MKII Armorer Notes

Differences between CAV-15 MKII Receiver and standard aluminum receiver.

  • Selector spring and detent load from the top. Selector then slides over.

    Note: Selector does not need to ever be removed. Fire control parts can be installed and removed with it in place. Before inserting selector, check spring tension and trim spring if needed. Safety can be removed by placing half way between safe and fire and pushing out.

Hammer pin will be recessed on both sides of hole. Insert until “J-Pin” engages center notch.

Take down pins are intentionally tight. Pins insert left to right into the receiver and are not captured in the receiver. Long pin in front, short pin in rear.

Unlocked blowback pistol caliber uppers must use appropriate weights (9mm 5.5oz, .45 7- 8 oz. Or heavier to avoid damaging the lower)

458 SOCOM requires the stiffer carbine spring installed that comes with that upper

300 AC work well with the 3oz carbine buffer, you may want to use an H2.

Buffer Detent is held in by 5/64thx1” Roll Pin (Buffer Detent Assembly is not needed for function of the rifle)

Parts Needed to Complete Lower:

  • 1 Carbine buffer and spring
  • 2 Hammer/Trigger pins
  • 1 Hammer with spring
  • 1 Trigger with spring
  • 1 Disconnector with spring
  • 1 Bolt catch with roll pin
  • 1 Bolt catch detent with spring
  • 1 Safety selector
  • 1 Selector detent with spring
  • 1 Buffer detent with spring
  • 1 5/64thx1” Roll Pin Provided with the lower (provided with the stripped lower)
  • 1 Mag Catch with button and spring
  • 1 Long ¼” Speed Pin (provided with the stripped lower)
  • 1 Short ¼” Speed Pin (provided with the stripped lower)
  • Tools for assembly and Armorer level repair:
    • Roll Pin Driver 5/64”
    • Roll Pin Holder 5/64”
    • Hammer
    • Razor Knife
    • May need Small file (safe edge)
    • Diagonal pliers
    • May need a #27 Drill bit (safety detent)


Possession and/or ownership of firearms is subject to various federal, state, and local restrictions, laws and regulations. Buying, carrying, or using a firearm without compliance with local, state, and federal law is a crime. It is your legal responsibility to learn and obey the laws that apply in your area. The buyer has complete responsibility to ensure he/she is in full compliance with all applicable local, state and federal law regarding possession of firearms. GWACS Armory LLC reserves the right to refuse the sale of any firearm to anyone who may be in violation of the laws of the State of Oklahoma and the United States of America pertaining to the purchase of a firearm. This includes, but is not limited to, "straw purchases", which is a purchase or the attempt to purchase by an individual for another person knowing they are not permitted to possess a firearm. Further, the buyer assumes any and all responsibility to insure any firearm purchased is handled safely. OUR PRODUCTS ARE INTENDED FOR ADULT USE ONLY. GWACS ARMORY LLC SHALL IN NO WAY BE LIABLE FOR ANY SPECIAL, INDIRECT, PUNITIVE OR CONSEQUENTIAL DAMAGES RESULTING FROM ANY USE OR MISUSE OF ANY ITEM OR PRODUCT PURCHASED OR OBTAIND FROM THE GWACS ARMORY LLC.

Limited Lifetime Warranty

GWACS Armory LLC CAV15 MKII lower receivers come with a limited lifetime warranty against any manufacturing defects, subject to the terms listed below:

  1. Any GWACS Armory CAV15 MKII found to have a defect in manufacturing will be replaced at no cost to the buyer within one year of the date of purchase.  Buyer must provide proof of purchase at the time any claim under this provision of the warranty is made.  After one year, GWACS Armory will only replace a CAV15 MKII lower receiver based on the damage warranty below.
  2. After one year, GWACS Armory will replace any damaged GWACS Armory CAV15 MKII lower receiver (stripped receivers only – receiver with no buffer, buffer spring, or trigger assembly group) for $35.00 (thirty five dollars) plus shipping.  When submitting a claim under the provision of this warranty, claimant must send to GWACS Armory the stripped damaged lower receiver along with the payment of $35.00 (thirty five dollars).  Include a return shipping label.
  3. GWACS Armory will honor the damage warranty listed in paragraph 2 above on any and all previously produced CAV15 MKII lower receivers, whether produced by GWACS Armory or any previous manufacture of CAV15 MKII lower receivers.  Claimant must abide by the requirements in paragraph 2 in order to submit a claim pursuant to this paragraph.  Further, a claim submitted under this provision will be considered the transfer of a firearm, requiring the claimant to successfully pass any background check required by local, state, or federal government, as well as complying with any local, state or federal laws governing the transfer of firearms.
  4. This warranty does not cover any unauthorized or illegal modifications made to any CAV15 MKII lower receiver.  It further does not cover any add-ons, attachments, upgrades, or any other part or accessory that is added by the buyer/owner of a CAV15 MKII lower receiver.
  5. When submitting a claim under this warranty, claimant must send the lower receiver along with any required documentation and any necessary payment to:  GWACS Armory LLC, ATTN: Warranty, 907 S. Detroit Ave., 6th Floor, Tulsa, OK 74120.

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7130 S. Lewis, Suite 300
Tulsa, OK. 74136
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