Marushin XM177 - how to install pins that are wider on one end?

So... I gave up and got myself a Marushin kit to build :-)

I hit the stumbling block very quickly, when I met the first retaining pin which is slightly wider on one end.
Such pin holds bolt catch button attached to the lower receiver, similar ones hold forward assist inside upper and two parts of forward assist together (#35, #100)

How do you put these in all the way? :-///

Manual suggests to hammer them in using supplied long, thin rod as the driver, but this doesn't work for me.
Pin goes in a bit, but 1-2mm still stick out of the hole. Insides of the hole are polished and verified for lack of obstacles. In case of forward assist, pin can go in from both sides, so it's not the thin end that blocks, it's the fat one.

Should I just remove the excess?

Yes you have to be careful with the bolt catch one as hitting the pin too hard may end up breaking off the end piece

The forward assist one should not be a problem if you use the "drift" rod supplied

The bolt catch ones seem more and more tight these days and I presume this is from tooling wearing out or qulity control issues.

Either spin the pin down a little or file the hole a little wider and then tap gently with the drift pin.

I presume you are inserting the pin from the correct side ( silly to ask but worth checking )

DOC

Hi Smootik
The really do require a hard whack!! I know sometimes it seems a bit to hard, but I have never broken anything yet
These parts do need to be a very tight fit so removing material may cause problems later. So try a hard hit! support rear on wooden block for the whacking !!!!

Out of interest, did magazine catch part #163 come pre threaded? as have seen some threaded some not ???

Well there you go smootik , Johnny will guarantee you won`t break it so whack away.

I`ve known of several people breaking this part so tend to take a different route.

Francky is always on hand to get you another lower receiver

when it comes to the forward assist pin you can hit this pretty hard although be sure to take care that the drift does not slip off and cause an unsightly mark in the upper part of the housing.

I`ve seen loads of people do this too

DOC

Plenty of "Timmy Mallet" training when I was younger !!! confidence is a preference! its what made Britain Great!!

Smootik, You said you had done the obivous and checked the holes for obstacles, Now check the pins narrow end goes in the rear hole cleanly (ie reverse the direction to check it is not a problem at the rear hole) then correct the pin direction and go for it, but DONT miss and hit the tiny little delicate peice of the receiver Or take the easy option and go with Docs way to be honest the bolt catch is the one part that does not need to be as tight an interferance fit as they make it, unlike the forward assist, of which I have seen countless examples of people who have lossed this "in the field" as a result of it being loose due to turning the pin down to fit easier. Docs advice is good about the drift slipping an causing nasty mark! take your time:)

Thanks for your encouragement :-)
I'll give these pins another try.

Part #163 was already threaded. I have to admit I am so far positively surprised by quality of the kit. Only holes for any of the smaller pins are the only non-quality areas. They require smoothing as there is a lot of casting faults inside and at the edges. Tolerances (?) are way too tight. This could be due to decreased tooling quality, as you wrote.
After careful adjustements narrow end of the pins go freely in the holes - but initially they didn't at all. I suspect that even after corrections these holes are still not good enough to hammer in the wider end of the pins :-/
As the last-resort I think of filing down the pins, and superglueing them in place.

Other than that there are some casting lines and circles, internals need polishing, yet no major hiccups - I completed the lower so far (without that one pin). One part that needed improvement was fire selector switch. It did not lock positively in three positions. I found that the locking pin barely enters holes on the switch itself, and filed the holes slightly larger. After polishing hole sides and making sure pin can enter/exit them without blocking, switch now works much better.

I use a thick wooden plank as a base when hammering. There's always a risk of rod slipping though, I'm not as versed with tools as JohnnyV ;-D

Best of luck mate, it takes a bit of fiddeling, but when its up and running its a great model, one of my fav and of course you can bling it up with all sorts of goodies

"Use the force", with non-capital "f" was the right solution after all.

I gradually applied more force to the hammer and found a right spot to drive the pins in without breaking anything (and just a tiny scratch or two). Head of the pin has mushroomed as a result of hammering, so a fraction of mm still sticked out of the hole. Filed these down to be flush with the surface, as it was not possible to push them further without damaging the receiver.

Now I just hope I did not assemble and install forward assist backwards...

BTW - noticed now that the upper part of the bolt catch button scratches against the upper receiver when both parts are put together. Hopefully correcting this does not require removing the pin I just hammered in ;-D

Oh I should have mentioned that you dont want to make the bolt catch pin too secure as on at least a dozen occasions I have known people to have their bolt catch break ( the textured part flies off ) facilitating the removal of the pin and changing the catch.

this catch does come under some force when the bolt is caught open.

on two of these occasions the removal of the pin has led to the tiny little delicate piece of the receiver breaking off because the pin is being forced against it and it has nothing to support it unlike when the pin is whacked into place


by far the best proof is experience .

DOC

Oh well, I will rember it the next time :-)

Just get a mate to support it on the corner of a bench when tapping it out... necessity is the mother of invention

Good point. One man doesn't quite have enough hands to handle it all safely ;-)

For other pins it's relatively easy to use a wooden plank as a support, but pin that holds the bolt catch is more tricky.