Pins not tight

[NCspecV81]

Anyone know why the take down pins on my m4 carbine is not tight? I havent made any adjustments to the diameter of the holes and my oring is still affixed to the flash suppressor. They arent like flying or falling out but they are loose enough where I can push them out without exerting much strain. I havent noticed any accuracy problems but im not the surest shot. Any ideas?

[wobblinwheel]

I've noticed the same with mine. I used to have to loosen the flash suppressor (as per owner's manual) and then tap out the pins. Now I can simply push them out with my fingers WITHOUT loosening the suppressor. Can't figure this one out, as I haven't been taking them out enough to wallow out the holes. I hope it doesn't get any looser! The pins do have detents to keep them from falling out, though.

[George Wood]

I also have noticed this issue. Hope this is normal and not the start of a bigger problem.

[techmike]

This is a new one for me. My Colt is 1.75 years old, and I cannot remove the pins w/o loosening the comp. Is anything else loose? This deserves a call to Umarex customer service IMO. Please keep us advised!

TM

[NCspecV81]

I haven't noticed anything else loose, but when I first got it that it was very, very snug. Then like a day later I went to take it apart to install a few things and to do a little maintenance I could remove the pins with my hands only without undoing the flash suppressor. Anyone know if there are any other pressure points I should be inspecting? Is the upper receiver and outside barrel wall permanently attached? I'll take some pictures of the gun here in a few both assembled and taken apart for you guys to maybe see if there's any glaringly obvious flaws that I'm not familiar with on this gun.

[NCspecV81]

sorry for the double post but I did get some pictures. I didn't know where to host them so I put them in a winrar file.

http://www.mediafire.com/?do2dxs82oemzlpz

[wobblinwheel]

I would be my guess that it's the "monkey-metal" (very soft) trigger-group housing that the tensioned-barrel is pulling against. Got a feeling that over a short period of time, and a fair amount of shooting, that the pin holes could elongate somewhat. I wouldn't think this would affect barrel tension as it pulls against the breech area. I actually like the idea of being able to break the gun down WITHOUT constantly having to loosen the suppressor. I think it's best to torque it down where it belongs and leave it alone as long as possible. The tension on the barrel does have a marked affect on your accuracy!

[rodent.22]

Fellas my OPS # BP024XXX bought new in June '09 has a TIGHT pin when the flash suppressor is tight. The suppressor must be loosened to remove the pin. I've taken photos of my rifle in case there are any obvious differences. The first photo shows the rear pin, very simple, no detent ball. The second photo shows the pin hole with the suppressor loose, both inner holes and the outer holes are evenly aligned, letting the pin to be easily removed. The third photo shows the pin hole with the suppressor tightened. If you look closely you can see the inner hole (silver color) is pulled slightly forward which locks the rear pin in place when installed. The fourth photo shows the upper pin holes with the pin in place. It is  quite a loose fit. The fifth photo shows the pin in the lower reciever, a tighter fit but still easy to push out. The sixth photo shows the pin installed, and it sticks out about 1/8''. The flash suppressor only moves the barrel extension forward about a .0001 or so, not much. If the face (forward) surface of the barrel extension is dirty or carbon buildup is present on this area it will prevent the barrel extension from pulling forward enough to tension the pin. It has to be that the upper and the barrel extension are prevented from seating together by dirt or debris. the barrel extension is not soft enough to elongate the inner holes, besides the upper and barrel will bottom out before the hole could be stretched over that .0001 th or so....Just my 2 cents worth.

[NCspecV81]

looking at those pictures I believe it's the trigger pack not allowing the pin hole to internally close up on the ball detention.

[img width=800 height=533]http://farm6.static.flickr.com/5147/5578055273_e570367bc4_b.jpg

With the suppressor screwed down tight it seems my bolt assembly is at the right recess in the upper.

[img width=800 height=533]http://farm6.static.flickr.com/5306/5578639586_c47f345f80_b.jpg

[techmike]

I think I see the problem. NCspecV81, can you try something for me? Try putting the original pistol grip on,  (while you have the upper and lower separated) and tighten it up. Then put the rifle back together and tighten the compensator. Now check the pins. Let me know what you find.

TM

[NCspecV81]

stock grip definitely tighted up the rear take down pin. I did do some more modding and found out that the magpul grip isn't all the way flush where the trigger pack meets the grip. A dremel and a few minutes has resulted in a significantly tigher take down pin. I'm going to have to get more intricate than the use of a dremel to take it down the rest of the way. Consider this one solved.

[rodent.22]

great!! :thumb:

[wobblinwheel]

The spring-loaded detent for the rear take-down pin is located in the trigger housing, not in the pin (#33 in parts diagram, 1 of 5 used). The SLOT for it is in the pin. Not doubting that the grip could have an effect on how things tighten up, but just wanted to point out that there IS a detent ball assembly for both pins to help keep them from falling out.

[techmike]

stock grip definitely tighted up the rear take down pin. I did do some more modding and found out that the magpul grip isn't all the way flush where the trigger pack meets the grip. A dremel and a few minutes has resulted in a significantly tigher take down pin. I'm going to have to get more intricate than the use of a dremel to take it down the rest of the way. Consider this one solved.

Excellent. :thumb: This rifle looks and feels so much like a M4 that I sometimes forget that M4 parts don't drop in.

[NCspecV81]

Well I knew originally the magpul wouldn't drop in. I did modify it originally to line up with the fastener and the one protruding piece that seems to have a heavy function on the operational ability of the trigger pull. I don't mind the modding since it definitely gives ones personal touches to the rifle. I find myself spending more modding time on this one than I do my other, more expensive rifles and pistols.

I've been impressed with the reliability. I've been doing a stress test over the past 2 boxes of ammo. I'm throwing in different bulk packs to get a nice poll of what ammo works the best. So far I've only had 1 light strike that ended up firing after I reinserted it back into the magazine. I kind of want to see how long it takes before I'll actually need to clean it versus getting misfires due to fouling.