How To
Use this YouTube video for all New 2025 MFI Scope Mounts with 4 set screws on the legs.
The below is for Pre-2025 MFI Scope mounts with roll pins that hold the hooks in place.
- Be sure the weapon is unloaded and the safety is on.
- Remove all 4 of the small bolts from the mount.
- Open / pull outward the bottom of the hook / lock point on all 4 points.
- Place the mount on top of the weapon's scope mounting points and press down. While pressure is applied press the mounting points back inward toward the receiver.
- Place the small bolts back into the 4 holes and down into the mounting points and tighten by hand to avoid cross threading. Alternate from bolt to bolt as you tighten to keep the mount level. Use a 5/64 Allen key / hex wrench to finish tightening (do not over tighten). The mount is now installed. To remove simply reverse the aforementioned instructions. Maximum Torque is 4-5 inch pounds. Never use Loctite or any other thread locking compound as it will take a torch to get the mount off or you will strip the bolt heads. Once attached to the weapon this mount should NOT be removed. It does NOT interfere with the iron sites or any other operation such as cleaning. On and Off removal will result in stripping the threads on the hooks. SPECIAL NOTE on HK MP5K, SP-89 and Clones of Similar Models: The added length of this mount may interfere with use of the cocking handle. There is limited room for the cocking handle to be placed in the full open & locked back position.
HAND FITTING / TROUBLE SHOOTING
Because there are so many G3 / MP5 variants (genuine and clone) out there & in 6 different calibers, that span 30+ years of manufacturing changes, some hand fitting may be required. The issue mainly stems from the fact that in order to get a good solid fit we have to hold very tight tolerances. The tolerances that the manufacturers hold to are far less stringent. This mount unlike other HK style mounts does NOT squeeze the receiver via a cam mechanism or utilize a side to side lock. We are clamping to the small gusseted shelves in an up and down fashion. This "sandwiching" type of mounting system is far more robust and stable than any side to side type of mount. Again we are dealing with a tolerance of +/- thousands of an inch (less than the thickness of a couple playing cards).
Manufactures of these weapons can easily fall out of spec without knowing because:
- Some hold tolerances only to +/- hundredths of an inch as there is no solid Mil. Spec. for this area.
- Using thicker or thinner steel for the stamping.
- The application of too much paint.
- Dripping paint over the ledge of the shelf.
- Use of old or worn tooling.
- Not making the final milling pass to flatten the shelf / ledge.
- PROBLEM: My MFI mount SLIPS OFF when tightened or does NOT grab the shelf or shelves as it appears the legs / hooks are NOT long (width) enough to make solid contact with the receiver ledge. ANSWER: For this there are 2 possible answers:
- There is a glob of paint / paint drip that is covering the sharp right angle of the lower part of the ledge where the hook / leg hits the receiver. Look to see if this might be the issue. If you cannot see a clear delineation in the shelf that makes a sharp right angle for the ledge then take a probe / hand file / sharp pointed object and run it across the ledge to remove the excess paint.
- Your receiver is out of spec and falls in the very narrow spectrum. Contact MFI for a wider / longer reaching hooks / legs. If you are familiar with knocking in and out roll pins we can just send you a set of our special longer legs / hooks. If not you can send us the mount and we can swap out the hooks for you FREE OF CHARGE. You pay only the shipping to us. You will likely still have to hand fit the legs to your receiver as we make these extra long to accommodate the wide variety of out of spec distances. (see below #3) NOTE: Each steel leg / hook costs us $7.00 to make. So we supply these on a per needed basis only. You may be required to send in the old legs for length verification. Otherwise a set of (2) legs / hooks are available to buy for $15.00 (which includes S&H).
- PROBLEM: My MFI mount does NOT sit flat / level on the top of the receiver. NOTE: There should be a uniform gap / space between the bottom of the mount and the top of the receiver. ANSWER: You likely have not fully seated the mount over the anti-recoil stop block (the part sticking up just forward of the rear sight on a G3 (HK 91 / HK 93) or the welded taps in the center of the receiver on a HK MP5). With the mount just sitting on the top of the receiver (no screws or bolts in the hooks / legs) it should sit flat and level. If NOT... Although quite rare... You likely have a CETME, HK Clone or Mid 1980s HK91 build using after market rear sight blocks that have the tower portion (part sticking up) that is too tall. Generally the fastest fix is to file down the tower with a hand file. We are talking about only a few hits with a hand file to knock the high spot down. The other option is to mill out the MFI rail from underneath where we already have the cut out slot.
- PROBLEM: I cannot get all of the bolts / screws in the hooks / legs of my MFI HK Low Profile Mount. Meaning... When I look down from the top of the mount, through the hole where the bolt goes in the main body of the mount, I see that the hook / leg is sitting at a slight angle pointing inward towards the center of the receiver. DO NOT force the bolt in as you may cross thread or strip the threaded holes in the legs.
- First be sure that the mount is centered on the top of the receiver. It is normal to have some side to side play to center the mount. If it is centered then continue to step "b". If NOT then you will need to do step "b" to all legs / hooks in order to have the mount centered on the receiver (this is very rare).
- b. Use a hand file or Dremel fiber cutting wheel (use the side of the wheel) & remove a small amount of the material on the leading edge of the leg / hook where the leg / hook hits the receiver ledge / shelf. You need to remove the same amount from ALL of the legs on the 5.5" and 6.5" long mounts. Mounts that have 6 legs you will remove the Same amount of material on ONLY the 4 REAR legs. So try to remove the same amount of material from each leg.
ANSWER: Your receiver is slightly out of spec and falls in the wide receiver spectrum. Remember that we have to gauge our legs for the MOST COMMON tolerance. In this case you actually have a higher quality weapon in that the steel being used is likely a hair thicker than normal. All you have to do is remove a small amount of material from the part of the leg(s) / hook(s) that are not allowing the bolts to go down into. Follow these steps:
Do NOT remove material from the set of legs forward of the ejection port as this area does not have the shelf / mounting point built into the receiver like the rear does. This will take some time and require you to mount and dis-mount the MFI HK Low Profile Mount from the receiver several times. In doing so you will end up with a Rock Solid mounting platform custom fit to your weapon.
