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MFI SIG 550/1/2 & 556 NATO Bayonet Lug & Roll Pin. (Taper roll pin per instructions.)

Designed specifically to fit the SIG 556 & SIG 522 Series Rifles & Pistols.


Limited Supply: only 3 remaining
Was: $88.00
Sale: $39.75
Save: 55%
Save: $48.25
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- USPS Priority Upgrade / 1st In L -
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Fits: SIG Sauer 556 Rifle, SIG 551-A1, SIG 556 Pistol, SIG 550, SIG 551, SIG 552 & SIG 522 (.22 caliber)

SIG USA does NOT supply any of their rifles with bayonet lugs. They do however provide a mounting point / round hole type of socket at the bottom of the gas block to attach the lug. The MFI SIG 550/1/2 Bayonet Lug slips into this hole and is held in place by a drive pin / roll pin (included with every lug) that is easy to install.

This allows the attachment of most US / NATO (M7, M9 or M11) bayonets. This is NOT for Swiss bayonets.

SIG Switzerland only made this lug in very limited production as at the time of production they were not members of NATO and had no intentions for this weapons platform to be exported in large quantities. So the production of the NATO bayonet lugs was done as cost effectively as possible. The lugs were intended for only the Civilian USA market and thus did not justify high dollar RND, tooling and mass production in the same quality as the rest of the weapons platform. These lugs were simple castings with rough finishes. Cast parting lines, grind points and uneven seems were normal. Holes for the roll pin were also cast as part of the mold and often had to be widened or elongated to fit properly.

To stay as close to the original as possible MFI followed SIG's original process which has been a head ache to say the least. Our lugs bare all the same tell tale signs / defects you would find on the original lugs. So "YES" uneven surfaces, cast lines, rough grind points and rounded roll pin holes are 100% Normal. We do hand fit every single lug that we ship to be 100% sure that it will mount and function properly. We also grind down one end of the roll pin to help the customer get these started with ease.

NOTE: SIG USA 522 Rifles (.22 LR Caliber) do NOT have enough barrel sticking out the front end to accommodate a bayonet. You will be short by about 3/4 of an inch. The LUG will fit in the hole on the 552 Rifle and Pistol and still looks cool... just not functional. Some early SIG 522's do not have the roll pin drilled in the gas block. No worry as you can still mount one of our Bayonet Lugs by using epoxy. Because you will never mount anything to it, the lug should stay in place.

SPECIAL NOTE: SIG 556 Rifles & 556 Pistols with Quad Rail Hand Guards that use this same hole / socket as a hanger point will NOT be able to mount this product, unless you hand file or grind down the rear of the lug to allow the RIS Hand Guard mounting stud to fit into the same hole at the same time as the lug. This is possible, but requires hand fitting.


In accordance with the Joe Biden & Beto O’Rourke directive I personally as well my company no longer own(s) or possess any firearms or ammunition. This includes but is not limited to: Handguns, Pistols, Shotguns, Rifles, NFA items, Hog Legs, Fire Sticks, Smoke Poles and or Thunder Clubs.

All firearms that appear on our web site, regardless of what is written about them, are not owned by the company nor possessed by anyone associated with MFI and may even be CGI / PhotoShop.

Therefore regardless of any new firearms laws / taxes, no probable cause can EVER be assumed on any property (stationary or mobile) owed by myself or MFI.

AGAIN: We are 100% in compliance with any possible new “Biden / O’Rourke Public Safety Act” and therefore NO PROBABLE CAUSE could ever be assumed.

Lastly anyone arriving with a warrant of any kind will be assumed to be an IMPOSTER with intent on murdering us and will be treated as such without warning.

Those invading our territory may receive serious and even fatal wounds from rusty blades, clubs with bent nails, spear tips, arrows and or crossbow bolts.


  • 100% Made In the USA.
  • The main housing is made of Grade 4 STEEL (same as the original).
  • The Drive Pins / Roll Pins are High Tensile Spring Steel (same as the original).
  • Heat Treated: Rockwell 30.
  • Fits: SIG Sauer 556 Rifle, SIG 556 Pistol, Original SIG (SANS) 550, SIG 551, SIG 552 & SIG 543 Series.
  • Designed specifically for NATO / US Style Bayonets: M7, M8, M9, M10 & M11 Bayonets.
  • Coating / Plating is identical to the original 1980's series: These are SIG Swiss Mil. Spec. Parkerized in a SIG Gray.
  • Cost Effective: Highest Quality at the lowest price is always our goal. We achieve this by making these in high volume. This equates to greater profits for distributors and re-sellers. Nothing else on the market compares in versatility, quality and cost effectiveness.
  • 100% Mil. Spec. copy of the original: We spared no expense to get these absolutely correct.

Fits All SIG 556 & 522 Style Rifles & Pistols:

  • SIG 556 Standard Rifle
  • SIG 556 Patrol Rifle
  • SIG 556 SWAT Rifle
  • SIG 556 Pistol
  • SIG 556 Classic Rifle
  • SIG 522 Standard Rifle
  • SIG 522 Pistol
  • CDNN SIG 551A1 Rifle
  • West Coast Armory SIG 551 Rifle


  • 1 - Bayonet Lug
  • 1 - Roll Pin


This item is NOT RESTRICTED FOR DOMESTIC US SALES in any way and we offer DOMESTIC USA shipping to ANYONE. We ship to all 50 US States as well as all US Territories i.e. Guam & Puerto Rico. Sorry we can NOT ship to ANY APO address regardless of actual location.

This item is 100% RESTRICTED FOR EXPORT OUTSIDE THE USA. The US Department of State regulates / restricts this product and it is NOT EXPORTABLE outside the USA even to LE, Governments or Military without State Department approval.

This approval is AVAILABLE through MFI as we are an ITAR / Dept. of State Registrant with the Directorate of Defense and Trade Controls Office. We can obtain a US State Dept. Export License for you.

Please feel free to contact us if you have any questions on this issue.


How to install the roll pin in the Bayonet Lug or Front Sight.

It is easy to mess up the roll pin when you first try to install it. Read below to avoid the pitfalls. There is a first time for everything and that is a part of any weapons system.

When SIG installs these at the factory they have a special fixture or a second person to hold the weapon. While a fixture or third person is NOT required it sure makes it a lot easier. All you need is someone to hold the weapon while you hold the punch and hammer.

It is a lot easier to file or grind down the roll pin at one end and then gently collapse the same end with a vice grips of pliers so that it just fits / sits in the hole. This will free up one hand. This is almost a requirement.

While the photo below shows the roll pin in the front sight the principle is the same for the bayonet lug. For the Bayonet Lug you will want to level and back the lug's mounting point with a block of wood. Roll pins are designed to be hard to drive in and it will require significant force with a hammer and punch.

Lubing the roll pin and hole will help getting this done faster.

Be sure to look through the hole to guaranty the alignment.

Good luck...

These roll pins are specially made for us so, if you mess up the roll pin you can buy a spare from us on this page:




  • MFI
  • Available
  • New

Shipping Information

  • Item Requires Shipping
  • 0.2 lbs.
  • $1.31

Customer Reviews

Comment Total Reviews (5)

MFI Sig Bayonet Lug
  • Currently 5/5 Stars

Reviewed by:

Product ownership: Less than 1 week

Purchased from: MFIAP.COM

Wow... Looks just like the original SIG SANs Bayonet lug I paid twice as much for! Excellent quality and fit. My hats off to Michael and everyone at MFI for the Great Service Too! I got the order in less than 2 days!

Perfect copy.
  • Currently 5/5 Stars

Reviewed by:

Product ownership: Less than 1 month

Purchased from: MFIAP.COM

I can't tell the difference between the MFI bayonet lug and the Swiss part I got from CoGunSales except the Swiss part has a # stamped on it, and cost more. Thanks for the deal MFI.

Awesome, Super Fast Shipping!!!
  • Currently 5/5 Stars

Reviewed by:

Product ownership: Less than 1 week

Purchased from: MFIAP.COM

I ordered the bayonet lug which fit perfectly along with the front and rear flip sights on 2/1 (Friday) and received and installed it on 2/4 (Monday). Great products and great prices, Thanks MFIAP!!

Great Product! Simply needed to grind a little to fit P556 Swat.
  • Currently 5/5 Stars

Reviewed by:

Product ownership: Less than 1 month

Purchased from: MFIAP.COM

The bayonet lug for my Sig P556 Swat needed to be gound down a little to fit with the handrail anchor. A small amount of grinding on the back and it fit like a glove. Thanks!!

Bought it for my 552 / 556P build.
  • Currently 5/5 Stars

Reviewed by:

Product ownership: Less than 1 week

Purchased from: MFIAP.COM

I got this as when I finally got my paper work on the 556P / 552 SBR it just seemed like I was missing something. Now it looks perfect. Cheap too... Super fast shipping...

One of the few companies who actually has someone who answers the phone and does not need to transfer you to someone else.

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