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Posted: 9/14/2026 10:32:59 PM EDT
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Guys, I purchased two AP series, the AP53 and the AP5-SD, Both firearms are out seriously of spec. The receivers will not take any original HK stocks. In addition the selector from safe to fire requires an extraordinary amount of pressure to switch modes it takes two hands to switch. even trying to remove the end cap is near impossible. It’s a struggle. And the take down pin needs to be punched out to remove. I tried several original HK stocks none will fit. The dimensions of the MKE receiver is out of HK spec. Am I only having this problem? |
| The encap on both is so tight I needed to use a rubber mallet to get them off. Sadly none of the hk stocks fit the MKE receiver I have tried on the MAC clone all hk parts fit without a problem. MKE has a better finish as the MAC looks like someone painted it with a spray can |
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Originally Posted By FightingHellfish: When my AP5 was new, it was so tight I had to tap out the pins with a punch and mallet and getting the stock on and off seemed almost impossible. After a few hundred rounds everything settled in and the pin and stock fit are perfect. That was my experience with my ap5sd as well. I had to bend a couple of places on the mke a3 stock and tap it on with a rubber mallet. Very tight fit but I would rather have that than a loose or wobbly stock. After a few hundred rounds it no longer requires a mallet to remove or install but still nice and tight. |
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Originally Posted By IraMarlowe: The encap on both is so tight I needed to use a rubber mallet to get them off. Sadly none of the hk stocks fit the MKE receiver I have tried on the MAC clone all hk parts fit without a problem. MKE has a better finish as the MAC looks like someone painted it with a spray can The finish on the MKE looks better because there's a 1/2 an inch of paint on it. Not sure about the selector lever but betting the other stuff is due to the paint. The after market stock I got was a pain to take on and off for a bit, but it got better. It's like you had to angle it just right to get it to go on, now it slides on and off perfectly. |
| Same as all the above. Both my AP5P and and AP53 were super tight with HK or aftermarket stocks and pins. They loosen up a bit with use. I suspect its the paint but cannot say for certain. |
"Have a smile for breakfast, you'll be shitting joy by lunch.” - Joe Abercrombie
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I had to do fitting. At first it was a slow work it in with some oil to polish the paint off. But then i saw lines forming in the reciever groove. I ended up doing some slow removal of material on the stock arm itself after softening the groove up a bit using a polishing bit...  I really only needed to thin the paint in most places, but the tab at the front of the stock arm needed some metal removed. Going slow with a fine sharp file... Polished and blued and they are now smooth as silk. Eta: I think the main problem is the shape of the reciever groove vs the shape of the stock arm. Make it so the arm sits into the reciever a little deeper... Probably idnk.  I Probably got lucky and it was a combo of everything |
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Also tossing this in here... The mke ambi packs, gritty and heavy. Especially with the selector. I took mine a part to do some cleanup via a stone and polishing. But the grit remained. I found out the grit was this piece tied to a spring arm that does absolutely nothing in a semi gun. Part of that would ride on the trigger, causing the grit. I assume it was a left over part from the 4 pos ambi group that they left in there. It also applies pressure to the selector. Find the spring arm back there, pull it off of what it's resting on and let it pull itself inside of the trigger box. Then try it out. Selector lightened up by a bunch, selector is much easier to move, but it's still solid, and the best of all. The grit is gone! I left the parts in place to see if there was any weirdness, and so far that's a solid nope. Easy to revert with a hook pick until i get around to fully gutting those parts out. Edit: going off of memory here, I'm too lazy to yank the pack out for a better description. 
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