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7/19/2026 11:29:45 PM EDT
I have one of these (but a blem) that I bought last year in anticipation of SBRing my AP5.

16th of this month, I found out I got the approval letter and stamp. So I finally went to put it on today, and I cant get the pin to fit in all the way, its getting caught the stock endcap. I saw that there was some need for fitting, so Im curious as to what would be the best way to go about it.
7/19/2026 11:34:34 PM EDT
[#1]
My MKE A3 stock fits on my AP5 better than the HK A3F stock I have. Triple check you've got the pin holes aligned (receiver and stock) just right - use something like a Glock tool or pin punch to "feel" through the channel and make sure the alignment is good and there no "ledges" caused by misalignment of the receiver and stock cap.
7/20/2026 9:21:34 AM EDT
[#2]
I had to bend some edges then smack the crap out of my mke a3 stock to initially get it to fit.  It is a very tight fit.
7/21/2026 5:16:58 AM EDT
[Last Edit: FishKepr][Edited] [#3]
Try putting the stock on closed; fork first, then end-cap.  It helps to get that last bit aligned and seated.
“I don’t want a valuable life lesson, I just want an ice cream.”
Space Corps Directive 196156: 'Any officer caught sniffing the saddle of the exercise bicycle in the women's gym will be discharged without trial.'
7/21/2026 9:30:32 AM EDT
[#4]
Quote History
Originally Posted By FishKepr:
Try putting the stock on closed; fork first, then end-cap.  It helps to get that last bit aligned and seated.
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That's how I do it.
7/21/2026 10:58:51 AM EDT
[#5]
Quote History
Originally Posted By SSeric02:

That's how I do it.
View Quote View All Quotes
View All Quotes
Quote History
Originally Posted By SSeric02:
Originally Posted By FishKepr:
Try putting the stock on closed; fork first, then end-cap.  It helps to get that last bit aligned and seated.

That's how I do it.


That is also how I did it, was the easiest way to get it on.

Also, looking through the left side of the end cap, it is literally just a tiny bit that is off, just enough to get caught on the inside. Just a millimeter at most.
7/22/2026 3:59:47 PM EDT
[Last Edit: FishKepr][Edited] [#6]
When I encountered this, I took a Dremel with the smallest sanding bit and opened up the hole in the end cap on the side with the clearance issue. It did not take much, just enough to let the pin pass through.
“I don’t want a valuable life lesson, I just want an ice cream.”
Space Corps Directive 196156: 'Any officer caught sniffing the saddle of the exercise bicycle in the women's gym will be discharged without trial.'

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