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Discussion Starter #1
I have a virgin M92 trigger guard, no mag catch holes... What would be the most correct and accurate way of drilling these?
 

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If it's a random unknown virgin TG, then here's the way I did it (look about halfway down in this link):

http://www.theakforum.net/phpBB2/viewto ... c&start=75

However, there's an easier way if this is a virgin "AK-74 trigger guard" from K-Var. Since these are all the same, I can give you measurements from the edges so you don't need to do the "caliper transfer" method that I used.

Also, all you need to do is find the hole center on one side. Then, it's easiest just to vise it in to your drill press and assure that the flat trigger guard surface (through which you will drill the hole) is perpendicular to your drill bit, and then drill through both sides of the trigger guard in one pass.

-Thirtycal
 

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Thanks for your reply thirtycal, this is for a Yugo Krinkov M92 virgin trigger guard. I understand the only difference between an AK-74 tg and an AKM tg is the dimple in the magcatch, no?
 

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oj_diaz said:
Thanks for your reply thirtycal, this is for a Yugo Krinkov M92 virgin trigger guard. I understand the only difference between an AK-74 tg and an AKM tg is the dimple in the magcatch, no?
Well it depends on what you consider to be a 'difference'. If you're talking about outward appearnce, yes they all look alike.

If you're talking about measured sizes using a digital caliper, they are all different.

So it depends on how much error you are willing to accept. There is a correct measurable center location for that hole, and that location is relative to the upper plate of the TG (where the rivet holes are). It is not simply a matter of measuring from the lower edge or side edge of the trigger guard. Yes you certainly can do this, and you can probably get pretty close, but realize that "close" may not be "correct". There's alot of geometry involved in the trigger guard latch, and it has to be relatively close to ensure that the mag is held securely and in the correct position.

What sounds like a 'minor detail' could actually mean the difference between the bolt correctly stripping off the top round and chambering it, and the bolt just riding over the top of the cartridge and chambering nothing. This is not likely, but I believe it's possible.

I probably sound like I'm overcompliating things, but locating that hole correctly on a random virgin TG is somewhat complicated. I have already worked out the geometry on the K-Var AK74 TG. Since I have worked that out, I can give you measurements for that hole location... But be aware that if you apply those measurements to your Yugo TG, the hole may no be in the correct location. But then again, you might get lucky and it will work fine. I can look up the measurements and post them tonite.

-Thirtycal
 

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Discussion Starter #5
I would appreciate that, will also read your other post in more detail later. Thanks for your help!
 

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Ok, a big warning here - this is NOT how you should locate the hole on a virgin trigger guard. The critical thing to realize is that the only 'landmark' that is important on the trigger guard is the upper plate with the four rivet holes. This is the reference point from which the hole location should be determined. In the photo below, I'm taking a shortcut because I already did the 'transfer process' using dividers to transfer the hole location from a known good trigger guard to a virgin K-Var AK74 trigger guard. I described this method in the link above.



So, as long as we can assume that the dimensions for all K-Var AK74 trigger guards are the same (+/- a few thousandths), then it's safe to use the 'front' and 'bottom' edges of the trigger guard as reference points (as seen in the photo). To do this, clamp a straight edge to the front and bottom edge of a trigger guard, and use this as a 'ledge' upon which to reference one leg of a digital caliper. Then extend the other leg to measure the correct distance in both the X and Y for the hole location. Use the caliper distance values in the photo, and carefully study how I've oriented the trigger guard for both the X and Y dimension. Scribe a line for each measurement, and where the lines intersect, set it with a center punch and drill the hole. Use a #9 drill bit (0.196") and if you have one, finish it with a 5mm reamer.

Oh yea, you only need to mark one side of the trigger guard. Once you know where to drill the hole on one side, just set the trigger guard in a drill press (being careful to set the trigger guard both level and perpendicular to the drill bit), and drill through both sides in one pass.

Use this information at your own risk :neutral:

-Thirtycal
 

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Thank you, thirtycal. I am seeing how other people have done this in the past to gather information for when I have to do it myself. I don't have the benefit of having an old TG to measure from, so I am seeing the methods others have used to do it before me to gin up my own course of action.
 
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