+1-800-504-5897 Live Chat 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

Heckler & Koch Complete MR556 Upper Receiver Kit 81000584

Heckler & Koch Complete MR556 Upper Reciever and Barrel Assembly, 16.5 in Barrel, 81000584
Heckler & Koch Complete MR556 Upper Reciever and Barrel Assembly, 16.5 in Barrel, 81000584
1 of 1 images
Heckler & Koch Complete MR556 Upper Reciever and Barrel Assembly, 16.5 in Barrel, 81000584

Tap Tap to Zoom

Government Export Restriction Government Export Restriction
Government Restriction Government Restriction
Questions & Answers
Would this H&K model upper be piston; if so is there adjustable gas settings? Expert Answer

The Heckler & Koch Complete MR556 Upper Receiver Kit uses a gas piston setup, however, it is not adjustable.

by Ethan, Gear Expert, September 21, 2022
This upper require special trigger groups? Can you answer this question?
View All Q&A You Have a Question? Ask!
Customer Reviews
Helpful Positive Review
Fantastic Purchase by Zack B, February 29, 2024
Upper kit included very nice HK soft case which I feel deserves to be mentioned in item description. Shipped quickly, in good condition and dropped right onto a milspec lower. Only gripe is that HK stopped shipping these with any irons.
5/5 found this helpful
Read 1 Review

Product Discontinued by Manufacturer

Heckler & Koch Complete MR556 Upper Receiver Kit has been discontinued by Heckler & Koch and is no longer available. Our product experts have helped us select these available replacements below.You can also explore other items in the Gun Parts, AR 15 Parts, Rifle Parts, AR15 Upper Receivers yourself to try and find the perfect replacement for you!

Product Info for Heckler & Koch Complete MR556 Upper Receiver Kit

The MR556A1 Upper Receiver Kit includes a complete upper receiver/barrel assembly, bolt carrier assembly, buffer, and buffer spring allowing most high-quality 5.56 mm AR-style rifles to be retrofitted to HKs pusher rod system.image

Features of Heckler & Koch Complete MR556 Upper Reciever

  • Complete MR556 Upper Receiver/Barrel Assembly HK 16.5 inch cold-hammer forged barrel, upper receiver with forward assist, extended convertible charging handle, HK Free Floating Rail System handguard
  • Complete MR556 Bolt Group Assembly
  • Tungsten Filled HK Proprietary Buffer
  • HK Proprietary Buffer (Action) Spring
  • NOTE: The MR556A1 Upper Receiver Kit is not classified as a firearm and can be purchased without a Federal Firearms License ( FFL).

Package Contents:

  • Heckler & Koch Complete MR556 Upper Reciever
  • Bolt
  • Buffer
  • Buffer spring
  • Rifle length M-LOK handguard
  • 16.5" medium contour barrel assembly

Firearm Case

1–40 / 40
Previous
Best Rated
MTM Tactical 39in Rifle Crate, Dark Earth, TRC39
MTM Tactical 39in Rifle Crate, Dark Earth, TRC39
(8)
List: $119.40 (Save $9.41)
$109.99
Blazin' Deal
Voodoo Tactical 42in Padded Weapons Case w/Die Cut MOLLE
Voodoo Tactical 42in Padded Weapons Case w/Die Cut MOLLE
(3)
As Low As (Save Up to 46%)
$117.14
See all 11 models
15% Bonus Bucks
Ulfhednar Gun Case w/backpack straps 140 cm, NSN N, UH040
Ulfhednar Gun Case w/backpack straps 140 cm, NSN N, UH040
(3)
List: $498.00 (Save 10%)
$448.20
Plano Rustrictor AW2 Rifle Case
Plano Rustrictor AW2 Rifle Case
(1)
As Low As (Save Up to 11%)
$159.49
See all 2 models
5% Bonus Bucks
Ulfhednar Gun Case w/Backpack Straps
Ulfhednar Gun Case w/Backpack Straps
(4)
As Low As (Save 10%)
$358.20
See all 2 models
Best Rated
Savior Equipment Fiddle Master 30in Violin Rifle Case, Black, 31in H x 13in W x 4in D, RC-VIOLIN-BK
Savior Equipment Fiddle Master 30in Violin Rifle Case, Black, 31in H x 13in W x 4in D, RC-VIOLIN-BK
(34)
List: $159.97 (Save 13%)
$139.97
Best Rated
Pelican VAULT V800 Double Rifle Case, 56.11in
Pelican VAULT V800 Double Rifle Case, 56.11in
(34)
List: $282.00 (Save Up to 23%)
$229.95
See all 2 models
Blazin' Deal
Voodoo Tactical OPMOD Double Rifle Weapons Case, 42 in, 42 in, Coyote/Black, OP-7619061000
Voodoo Tactical OPMOD Double Rifle Weapons Case, 42 in, 42 in, Coyote/Black, OP-7619061000
(10)
List: $214.99 (Save 46%)
$117.14
Evolution Outdoor President Series Case
Evolution Outdoor President Series Case
(1)
As Low As (Save Up to 11%)
$57.99
See all 2 models
Best Rated
Pelican VAULT V700 Case, Takedown Firearms, 39.61in, Black, VCV700-0000-BLK
Pelican VAULT V700 Case, Takedown Firearms, 39.61in, Black, VCV700-0000-BLK
(12)
List: $221.00 (Save 23%)
$169.95
Best Rated
Pelican Vault V730 Tactical Rifle Case wl/wf, 47.1in
Pelican Vault V730 Tactical Rifle Case wl/wf, 47.1in
(18)
List: $261.99 (Save Up to 23%)
$209.95
See all 2 models
5% Bonus Bucks
Ulfhednar Gun Case/Shooting Mat Combo, Cordura Material, UH041
Ulfhednar Gun Case/Shooting Mat Combo, Cordura Material, UH041
(1)
List: $598.00 (Save 15%)
$509.99
Eberlestock E2B Sniper Sled Drag Bag - 57in Long, Black
Eberlestock E2B Sniper Sled Drag Bag - 57in Long, Black
$399.00
See all 3 models
Best Rated
Eylar Extra Large 53in Waterproof Roller Hard Rifle Case w/Foam
Eylar Extra Large 53in Waterproof Roller Hard Rifle Case w/Foam
(10)
As Low As (Save 48%)
$207.99
See all 6 models
Best Rated
Armageddon Gear Precision Rifle Case
Armageddon Gear Precision Rifle Case
(12)
As Low As (Save Up to $4.36)
$261.01
See all 9 models
Galati Gear 35in. Riot Gun Case 105819
Galati Gear 35in. Riot Gun Case 105819
(1)
List: $98.95 (Save 18%)
$80.96
Best Rated
Pelican Storm Cases iM3100 Long Hard Gun Case, 39.8in
Pelican Storm Cases iM3100 Long Hard Gun Case, 39.8in
(18)
As Low As (Save Up to 14%)
$304.95
See all 3 models
Boyt Harness H48SG Single Long Gun Case, 48in, Black, 40139
Boyt Harness H48SG Single Long Gun Case, 48in, Black, 40139
(6)
List: $165.00 (Save 15%)
$139.79
Best Rated
Savior Equipment Urban Warfare Double Rifle Case
Savior Equipment Urban Warfare Double Rifle Case
(61)
As Low As (Save Up to 15%)
$94.97
See all 20 models
On Sale
M&P Pro Tac Gun Case, 42in, 110025
M&P Pro Tac Gun Case, 42in, 110025
List: $119.99 (Save 35%)
$77.49
Best Rated
Magpul Industries DAKA Grid Organizer for Pelican Vault
Magpul Industries DAKA Grid Organizer for Pelican Vault
(7)
As Low As (Save Up to $13.00)
$99.95
See all 4 models
Blazin' Deal
Plano Element Gun Eqpmnt Case 44 in Double Tact Gun w/Gray Accent, Black, PLAM9440
Plano Element Gun Eqpmnt Case 44 in Double Tact Gun w/Gray Accent, Black, PLAM9440
List: $299.99 (Save 36%)
$192.49
Best Rated
Eberlestock Sniper Sled Drag Bag Gun Case
Eberlestock Sniper Sled Drag Bag Gun Case
(11)
List: $380.00 (Save Up to $11.00)
$369.00
See all 5 models
Birchwood Casey Single 36in Gun Case, Black, 600D Polyester, Rifle, BC-RBG36
Birchwood Casey Single 36in Gun Case, Black, 600D Polyester, Rifle, BC-RBG36
List: $104.99 (Save $9.00)
$95.99
On Sale
Eylar Large 48in Waterproof Roller Hard Rifle Case w/Foam
Eylar Large 48in Waterproof Roller Hard Rifle Case w/Foam
(3)
As Low As (Save Up to 50%)
$189.49
See all 6 models
Boyt Harness H41XD Tactical Rifle/Carbine Case, 41in, Black, 40149
Boyt Harness H41XD Tactical Rifle/Carbine Case, 41in, Black, 40149
(1)
List: $253.00 (Save 28%)
$181.99
Best Rated
Savior Equipment Specialist LRP Single Rifle Case
Savior Equipment Specialist LRP Single Rifle Case
(10)
As Low As (Save Up to 15%)
$239.97
See all 12 models
Best Rated
Bulldog Cases & Vaults Ultra Compact Ar-15 Discreet Carry Case, 29 In. - Navy
Bulldog Cases & Vaults Ultra Compact Ar-15 Discreet Carry Case, 29 In. - Navy
(43)
List: $66.99 (Save 14%)
$57.59
10% Coupon
Eylar Standard 44in Waterproof Roller Hard Rifle Case w/Foam
Eylar Standard 44in Waterproof Roller Hard Rifle Case w/Foam
(8)
As Low As (Save Up to 53%)
$169.49
See all 6 models
Boyt Harness H52SG Hard Sided Single Long Gun Case, 52in, Black, 40156
Boyt Harness H52SG Hard Sided Single Long Gun Case, 52in, Black, 40156
(3)
List: $180.00 (Save $10.51)
$169.49
Best Rated
Elite Survival Systems Covert Operations Discreet Carry Cases
Elite Survival Systems Covert Operations Discreet Carry Cases
(31)
As Low As (Save Up to 31%)
$95.99
See all 7 models
Evolution Outdoor Rawhide Series Waxed Canvas Rifle Case, 48in, 44347-EV
Evolution Outdoor Rawhide Series Waxed Canvas Rifle Case, 48in, 44347-EV
(2)
List: $74.99 (Save $3.50)
$71.49
Plano Diverge Eva Shotgun Cases
Plano Diverge Eva Shotgun Cases
As Low As (Save Up to 19%)
$129.99
See all 3 models
Plano Pro-Max Single Scoped Rifle Case,Black, PMC153104
Plano Pro-Max Single Scoped Rifle Case,Black, PMC153104
(2)
List: $75.99 (Save 25%)
$56.99
On Sale
Bulldog Cases & Vaults Double Tactical Rifle Case
Bulldog Cases & Vaults Double Tactical Rifle Case
(14)
As Low As (Save Up to 31%)
$106.99
See all 6 models
Voodoo Tactical Scope Rifle Scabbard, Coyote, 20-8915007000
Voodoo Tactical Scope Rifle Scabbard, Coyote, 20-8915007000
(2)
List: $119.95 (Save 15%)
$101.95
On Sale
Plano Diverge Eva Soft Gun Rifle Cases
Plano Diverge Eva Soft Gun Rifle Cases
As Low As (Save Up to 23%)
$123.99
See all 6 models
Flambeau 513SN Double Coverage Black Polymer 5 Scoped Rifle Or Shotgun
Flambeau 513SN Double Coverage Black Polymer 5 Scoped Rifle Or Shotgun
List: $131.99 (Save $4.00)
$127.99
Bulldog Cases & Vaults Double Split Series Rifle Case, 48in, Green, BD395
Bulldog Cases & Vaults Double Split Series Rifle Case, 48in, Green, BD395
(1)
List: $90.99 (Save 20%)
$72.99
Best Rated
Browning SA-22 Fitted Rifle Case, Black/Tan 1428608090
Browning SA-22 Fitted Rifle Case, Black/Tan 1428608090
(17)
List: $359.99 (Save 32%)
$245.89
Next

Heckler & Koch Complete MR556 Upper Receiver Kit Accessories

1–6 / 6
Previous
14% Coupon
Midwest Industries HK416/MR556 Handguard, M-LOK
Midwest Industries HK416/MR556 Handguard, M-LOK
(5)
As Low As (Save Up to $11.00)
$230.95
See all 5 models
Heckler & Koch Rifle Magazine, MR556, 5.56mm, 10 Rounds, Black, 10, 235642S
Heckler & Koch Rifle Magazine, MR556, 5.56mm, 10 Rounds, Black, 10, 235642S
List: $84.99 (Save $1.50)
$83.49
14% Coupon
Heckler & Koch MR556 9" M-LOK Handguard
Heckler & Koch MR556 9" M-LOK Handguard
As Low As (Save Up to $16.01)
$209.99
See all 2 models
Heckler & Koch Rifle Magazine, MR556, 5.56mm, 30 Round, Black, 10, 251770S
Heckler & Koch Rifle Magazine, MR556, 5.56mm, 30 Round, Black, 10, 251770S
List: $96.97 (Save $2.98)
$93.99
Best Rated
Geissele HK MR 5.56 Rifle Trigger Assembly, 4.75 lbs, Black, 05-220
Geissele HK MR 5.56 Rifle Trigger Assembly, 4.75 lbs, Black, 05-220
(5)
List: $475.00 (Save 13%)
$415.49
Heckler & Koch Rifle Magazine, MR556, 5.56mm, 20 Rounds, Black, 12, 233609S
Heckler & Koch Rifle Magazine, MR556, 5.56mm, 20 Rounds, Black, 12, 233609S
List: $95.71 (Save $5.72)
$89.99
Next

Related Products to Heckler & Koch Complete MR556 Upper Receiver Kit

Image of Heckler & Koch VP9 Match OR Slide Conversion Kit Heckler & Koch VP9 Match OR Slide Conversion Kit (7) List: $599.99 (Save 26%) $446.49 Best Rated
Image of Heckler & Koch SP5 Three Position Buttstock Heckler & Koch SP5 Three Position Buttstock (4) List: $820.99 (Save 17%) $679.99 Free 2 Day Shipping
Image of Heckler & Koch SP5 Three Position Buttstock Heckler & Koch SP5 Three Position Buttstock (4) List: $820.99 (Save 17%) $679.99 Free 2 Day Shipping
Image of Heckler & Koch Threaded Barrel, HK VP9, 9mm Heckler & Koch Threaded Barrel, HK VP9, 9mm (2) List: $303.99 (Save 12%) $268.49 Free 2 Day Shipping
Image of Heckler & Koch VP9SK Optics Ready Slide Conversion Kit Heckler & Koch VP9SK Optics Ready Slide Conversion Kit List: $449.99 (Save $40.00) $409.99
Image of Heckler & Koch USP Ambidextrous Safety Lever Kit Heckler & Koch USP Ambidextrous Safety Lever Kit (2) List: $67.99 (Save $1.50) $66.49
Image of Heckler & Koch Threaded Barrel, USP40 Tactical Heckler & Koch Threaded Barrel, USP40 Tactical (4) List: $303.99 (Save 11%) $269.99
Image of Heckler & Koch Universal LE Modification Trigger Kit, HK USP/USP Compact/HK45/HK45 Compact Heckler & Koch Universal LE Modification Trigger Kit, HK USP/USP Compact/HK45/HK45 Compact (2) List: $150.00 (Save 22%) $116.79
Image of Heckler & Koch Folding Stock for HK SP5K Heckler & Koch Folding Stock for HK SP5K (3) List: $461.29 (Save 14%) $398.49
Image of Heckler & Koch Folding Stock for HK SP5K Heckler & Koch Folding Stock for HK SP5K (3) List: $461.29 (Save 14%) $398.49
Image of Heckler & Koch Threaded Barrel, USP Compact 45, .45ACP Heckler & Koch Threaded Barrel, USP Compact 45, .45ACP (2) List: $303.99 (Save 11%) $269.99
Image of HK 51000939 VP OR ELEVATED NIGHT SIGHTS made-in-usa-flag HK 51000939 VP OR ELEVATED NIGHT SIGHTS List: $71.99 (Save 20%) $57.79 14% Coupon
Image of HK 51000939 VP OR ELEVATED NIGHT SIGHTS made-in-usa-flag HK 51000939 VP OR ELEVATED NIGHT SIGHTS List: $71.99 (Save 20%) $57.79 14% Coupon
Image of Heckler & Koch MR556 9" M-LOK Handguard made-in-usa-flag 2 models Heckler & Koch MR556 9" M-LOK Handguard As Low As (Save Up to $16.01) $209.99 14% Coupon
Image of Heckler & Koch MR556 9" M-LOK Handguard made-in-usa-flag 2 models Heckler & Koch MR556 9" M-LOK Handguard As Low As (Save Up to $16.01) $209.99 14% Coupon
Image of Heckler & Koch Threaded Barrel, HK USP45 Tactical, 45 ACP Heckler & Koch Threaded Barrel, HK USP45 Tactical, 45 ACP (3) List: $303.99 (Save 12%) $268.89
Image of Heckler & Koch Threaded Barrel, USP9 Tactical, 9mm Heckler & Koch Threaded Barrel, USP9 Tactical, 9mm (3) List: $225.99 (Save 12%) $199.99
Image of Heckler & Koch P30L, 9mm, Threaded Barrel Heckler & Koch P30L, 9mm, Threaded Barrel (1) List: $289.99 (Save $11.50) $278.49
Image of Heckler & Koch MR762 14.7" M-LOK Handguard made-in-usa-flag Heckler & Koch MR762 14.7" M-LOK Handguard (1) List: $257.00 (Save $8.51) $248.49
Image of Heckler & Koch MR762 14.7" M-LOK Handguard made-in-usa-flag Heckler & Koch MR762 14.7" M-LOK Handguard (1) List: $257.00 (Save $8.51) $248.49
Image of Heckler & Koch Meprolight Tritium Night Sight 4 models Heckler & Koch Meprolight Tritium Night Sight As Low As (Save Up to 28%) $65.99 14% Coupon
Image of Heckler & Koch HK45 Series Ambidextrous Safety Lever Kit Heckler & Koch HK45 Series Ambidextrous Safety Lever Kit (1) List: $74.29 (Save $2.80) $71.49 14% Coupon
Image of HK 51000982 HK45C TACTICAL THREADED BRRL 4.57 HK 51000982 HK45C TACTICAL THREADED BRRL 4.57 (1) List: $205.99 (Save $16.00) $189.99
Image of Heckler & Koch Thread Protector Cap, HK45,HK45C,USP45,USP45C Heckler & Koch Thread Protector Cap, HK45,HK45C,USP45,USP45C (2) List: $50.85 (Save 15%) $42.99

Heckler & Koch Complete MR556 Upper Receiver Kit Unavailable & Discontinued Models

List of Unorderable Models

  • Heckler & Koch Complete MR556 Upper Reciever Kit, 16.5 in Barrel, 81000584 , MPN: 81000584 , UPC: 642230262607 , Code: 13-URC-MR56UR-81000584
Compare (0)
1 item has been added
Add at least two items to compare