+1-800-504-5897 Help Center Check Order Status
About Us Policies Reviews How To
Free Shipping & Free Returns*

FREE SHIPPING on Over 250,000 Products

Shop now and get Free Value Shipping on most orders over $49 to the contiguous 48 states, DC, and to all U.S. Military APO/FPO/DPO addresses.

Enjoy our FREE RETURNS

We want to ensure that making a return is as easy and hassle-free as possible! If for any reason you are not satisfied with your purchase, simply return the item within 30 days of receipt, and we'll cover the cost of return shipping. Learn more about our Return Policy.

  • Entire Store
  • ...
  • Apparel & Footwear
  • Astronomy
  • Everything Else
  • Eyewear
  • Hunting Gear
  • Lab Equipment
  • Military Gear
  • Outdoor Gear
  • Photography Equipment
  • Police, EMS & Fire
  • Shooting
  • Sport Optics
  • Sports & Hobbies
TIP
Shopping Cart

Long stroke piston greatness - Primary Weapons Systems MK109 MOD1-M 9.75-inch Upper Receiver

by David, Verified Owner from TX, United States Written on April 18, 2026
Review for Primary Weapons Systems MK109 MOD1-M 9.75-inch Upper Receiver
Primary Weapons Systems MK109 MOD1-M 9.75-inch Upper Receiver
Primary Weapons Systems MK109 MOD1-M 9.75-inch Upper Receiver
$1,209.95 $1,129.95 Save $80.00
View Product
Write a Review View All Reviews
Compare (0)
1 item has been added
Add at least two items to compare

David's Review of Primary Weapons Systems MK109 MOD1-M 9.75-inch Upper Receiver

The adjustable gas block is very helpful when switching between Supers and Subs. Shoots great. I recommend it.
Pros:
  • Adjustable gas block
  • less gas back at you
Cons:
  • pricy ,but worth it
Best Used for:
  • hunting
  • targer practice at best
Would Recommend: Yes
Was it helpful to you? Yes | No
Share