View Full Version : Locking lug adjustment?

January 30, 2009, 01:06
So I put an STG kit with an Imbel Para bbl on a DSA receiver, I think it turned out satisfactory but with a few small issues. The one that concerns me is when I close the gun it locks but the locking lever does not return all the way like it is not fully locked. Has anyone dealt with this? Thanks for any help. Mick

January 30, 2009, 13:28
If you're referring to the catch that holds the back of the upper/lower together then some "free space" is normal. The lever is designed to have positive spring pressure to work properly. If the lever bottomed out this wouldn't happen.

January 30, 2009, 13:49
I have an Imbel kit and a DSA receiver. In my initial fitting I noticed that the receiver would not fully close, and therefore the catch would not properly engage the lug on the receiver. Upon closer examination, I believe I determined that the lug on the DSA receiver was actually contacting the lower assembly and preventing full closure. I dremmeled away some of the metal on the lug where it looked like the contact was occuring and checked often. Now it closes all the way and the latch functions properly.

If you sprinkle some flour (or other white powder) in your lower and then try to close the receiver, you should be able to tell where the contact. This is what I did.

Hope this helps. Good luck.

January 30, 2009, 16:27
Thank you, I will give it a try. Mick

Andy the Aussie
January 30, 2009, 17:21
Don't forget what brownknees said though, you DO NOT want that lever going all the way forward, that is considered (and is) a defect.

It was a common enough adjustment here to take a little metal off the bottom of the receiver lug to allow it all to sit a bit lower in the TMH and thus tighten the lockup, be careful here though.


January 30, 2009, 17:38
We're both kind of sort of right.
My comments refer to an upper that IS fully seated on the lower.
If that isn't happening then you need to fix that problem FIRST.
If they close fully & there is solid engagmeent without the lever fiully returning to the rest position then you're GTG.

January 30, 2009, 18:53
Why do you need spring pressure on the lever? What would happen if you didn't have it? On mine the upper receiver was definitely not closing, and was not lined up with the lower, but I now want to make sure I didn't take off too much.


Andy the Aussie
January 30, 2009, 19:05
Basically spring pressure on the lever indicated that the locking lug that goes into the upper to lock it is also under pressure and as such is applying pressure to the upper to ensure a fit between the two. DO NOT grind on the lug on the receiver to make the sliding lug from the lower fit NEVER. If something needs adjusting work on the cheapest part, that would be the sliding lug in the lower.


January 30, 2009, 19:29
Thanks Andy. I'll pull out my rifle and check it. I also just remembered that it was the front part of the lug that was contacting the metal block in lower receiver. So what I did was ground away part of that metal piece in the lower receiver.

January 31, 2009, 00:15
My first build the locking lever went all the forward when closed with no apparent issues and the rifle is one of the best I have owned. This build the receiver closes fully but the lever does not return full forward so I was not sure if it is right. I have to be a little firm when closing it also.

January 31, 2009, 17:00
When my receiver is closed the takedown lever does not go all the way forward, so I guess it is good to go.

I also took a picture to show micky where I dremeled. If you look in the middle of the pic, opposite the takedown catch, you can see where I cutout some of the metal.

http://img216.imageshack.us/img216/2950/lockingluglz1.th.jpg (http://img216.imageshack.us/my.php?image=lockingluglz1.jpg)

Sgt Rock
January 31, 2009, 22:14
WHAT! Filing on the receiver! The first rule. Always work on the cheapest part. If you file anything file the catch. Cheaper than a receiver.

Andy the Aussie
January 31, 2009, 23:07
While I agree with you Sgt and advise the same, it was also common practice out here to take a little off the bottom of the receiver lug to stop it bottoming out in the TMH and thus tightening the fit. There was little that we could do to a rifle to be used in service rifle matches out here but the upper/ lower fit was one.


February 01, 2009, 00:17
SGT Rock, I do agree that you should mess with the cheapest part. In this case the front of the lug on the upper receiver was contacting the metal cross piece in the lower receiver. This was preventing the two from fully closing. Believe me it was obvious that the two were not lined up properly. My option was to either file the lug on the DSA upper receiver ($450) or file the cross member on the used Imbel lower receiver ($100). Filing the catch wouldn't have fixed the problem.

Sgt Rock
February 01, 2009, 14:32
Apparently I misread the post. My apologies. Recent lockup problems involving century receivers (I don't own any) was too fresh in my mind. I should have noted that a DSA was in question (never had a problem yet with one). However I would still work on the cheaper part if possible and in this case is. I'm sure what little filing was done on the bottom of the receiver lug won't affect it's strength at least on a DSA.