Old Colt upper won't fit on new LCW lower.

[Drjones]

Hi guys.

I got an old M16 upper (triangular handguards, pencil barrel & all that) from a guy on ARFCOM and it just won't fit on my Lauer lower.

Both takedown pins won't go in all the way at the same time: if I remove the front pin (closest to the magwell) the rear pin slides right in but then I cannot insert the front pin at all.

Conversely, if the front pin is all the way in, the rear pin will go all but 1/4" in, and when I look at the other side, I can see that the holes are misaligned by about 1/16".

What do I do?

How do I fix this?

Should I try another lower? Is it possible that this one lower is perhaps out of spec? Is the upper out of spec?

Thanks!

[JKG]

Someone will chime in with the correct answer I'm sure.

I've heard that certain Colts had oversized pins. There's parts or conversions to fix this I believe. Maybe this has something to do with it, but if the holes were oversized in the upper it would seem like it would fit and be really loose. Hopefully its something that you can fix.

[ARWizzard]

Some of the old Colt uppers have a large hole, new uppers have a small hole. If yours indeed is a large hole upper you will need a large hole to small hole adapter. Most of the larger parts dealers carry them in stock. If you can't find one I think you can order one from Bushmasters website if I'm not mistaken. They have adapters going both ways also. They have a small hole to large hole so you can put a new upper on an old Colt lower also. If you still don't understand please PM me. I think I might have an extra.

Your Lauer lower will be a small hole lower. I have one just like it. The only downfall to all this is you will have to pull out your front push pin on your Lauer lower to intall the adapter. This is the only way to fix your dilemma that I know of. Maybe they have come out with somthing new lately. Anyone?

Okay! It's called reverse offset pin on Bushmasters website. Here is a link.

http://www.bushmaster.com/shopping/lowers/we-003.asp

[Stickman]

M16 uppers are all small hole, but its not uncommon to have to tap the pins into place with certain upper/ lower combinations. Its not a big deal, and it will loosen up after awhile.

[Blitzer]

Originally posted by Stickman
M16 uppers are all small hole, but its not uncommon to have to tap the pins into place with certain upper/ lower combinations. Its not a big deal, and it will loosen up after awhile.

The post reads:

{Conversely, if the front pin is all the way in, the rear pin will go all but 1/4" in, and when I look at the other side, I can see that the holes are misaligned by about 1/16".}

Please explain, how a does one insure that 1/16" variance gets loosened up?

:rofl: :supergrin: :upeyes: :rofl: :alex: :brickwall: :chatter: :eyebrow: :freak: :notlistening: :rollingeyes:

[B.Reid]

The old Colts had a strange offset double screw. That is about as good as I can explain it. Slotted on both sides. Not sure where you would get one these days.

[ARWizzard]

The SP1 Colt uppers have a large hole. Alot of folks call these M16 uppers and they do appear identical. You need to check and see if it a large whole or small hole upper. DO you have a newer upper you can compare it with?

[Drjones]

Originally posted by ARWizzard
The SP1 Colt uppers have a large hole. Alot of folks call these M16 uppers and they do appear identical. You need to check and see if it a large whole or small hole upper. DO you have a newer upper you can compare it with?


No, I don't have any other uppers at the moment, but a buddy of mine may be getting one in the next few weeks.

Do you have any measurements I could use to determine whether the upper is small or large hole?

[GSquared]

If you read through the description from Cheaper Than Dirt, I think that this is what you need. It is not only a diameter change, but an offset as well.

http://www.cheaperthandirt.com/ARR116-47511-2701.html

[jonathon]

If the front take down pin fits just fine with no play, then it's a small hole upper. The other way to tell is if the front and rear take down holes on the upper are different sizes.

Try giving it a couple good taps with a rubber mallet, if it goes through the problem is more or less tolerances stacking.

[Blitzer]

Originally posted by jonathon
If the front take down pin fits just fine with no play, then it's a small hole upper. The other way to tell is if the front and rear take down holes on the upper are different sizes.

Try giving it a couple good taps with a rubber mallet, if it goes through the problem is more or less tolerances stacking.

I wouldn't give it "a couple good taps if there is 1/16" of offset. You could crack the bosses or twist them and jam everything up royal!

Get the correct parts. :upeyes: :upeyes: :shocked: :rofl:

[B.Reid]

Originally posted by GSquared
If you read through the description from Cheaper Than Dirt, I think that this is what you need. It is not only a diameter change, but an offset as well.

http://www.cheaperthandirt.com/ARR116-47511-2701.html

Yep that is what they look like. I had an SP1 and that is the kind of pivot screw they had.

[vanfunk]

You have an old USGI M16 upper. It has the small (.250") openings for the takedown pins, as does your Lauer lower. I would trust that a USGI upper is more likely to be in-spec than a commercial lower. It is not a matter of using an offest pin - that is for mating Colt commercial large-hole uppers to small hole lowers and doesn't apply in this case.

HTH,
vanfunk

[Drjones]

Originally posted by vanfunk
You have an old USGI M16 upper. It has the small (.250") openings for the takedown pins, as does your Lauer lower. I would trust that a USGI upper is more likely to be in-spec than a commercial lower. It is not a matter of using an offest pin - that is for mating Colt commercial large-hole uppers to small hole lowers and doesn't apply in this case.

HTH,
vanfunk


Well thanks, but where does that leave me?

Is the lower out of spec, and should I return it?

I guess I should try mating the upper to another lower & see what happens....

[ARWizzard]

Do you have any way you can measure the hole on your upper and compare it to the front pushpin hole on your lower. I would almost be positive that the hole on your lower is in spec. I'm not convinced that you have a true M16 upper. Can you post some close up photo's of the upper and lower holes side by side? Also, try and find an almost new upper to try on your lower receiver to check for fit.

[Drjones]

OK, so should I get the one from Cheaper Than Dirt, or the one from Bushmaster?

[Skintop911]

I believe all new LCW lowers are supplied by Superior.

Hard to tell what specification they might be meeting.

Can you mic out the pertinent dims and post them?

[halfmoonclip]

Originally posted by vanfunk
You have an old USGI M16 upper. It has the small (.250") openings for the takedown pins, as does your Lauer lower. I would trust that a USGI upper is more likely to be in-spec than a commercial lower. It is not a matter of using an offest pin - that is for mating Colt commercial large-hole uppers to small hole lowers and doesn't apply in this case.

HTH,
vanfunk

What vanfunk said. I think there is an excellent chance that what you have IS a USGI M-16 upper, as there are a ton of them out there.

Even if you can't mic the holes as Skintop suggests, try inserting something like the butt end of a 1/4" twist drill bit into the lug holes on the upper. (Don't remove any metal; just use the drill end as a gauge.) At least determine if the two holes are the same diameter.
If they are, then something is out of spec, or a couple things collectively are out of spec. One sixteenth sounds like a lot of error. Have you tried just giving the pin a good shove with a non-marring tool?
Try it on your buddy's lower before you go buying anything.
Was there a bolt carrier group with your upper?
Moon

[halfmoonclip]

So ya' know, I just had a look at the takedown pin hole in a pair of Colt uppers; my NOS A1 and a current production HBar.
In both cases, the pivot hole was 1/4" round, as was the takedown hole. HOWEVER, the takedown was noticeably oval in a longitudinal direction, and a 1/4" punch would wobble fore and aft in that hole.

Soooo, in which direction is the OP's takedown pin hole out of alignment with the lower?
Moon

[Drjones]

Ok, I need to get this taken care of.

Attached is a pic of the upper, FRONT pivot hole - note that there already seems to be some sort of shim installed. I tried tapping it out with a few LIGHT taps with a hammer & punch, but no luck.

If I could get that shim OUT of there, it would probably solve my problem.

Any thoughts?
Thanks

[Blitzer]

Originally posted by Drjones
Ok, I need to get this taken care of.

Attached is a pic of the upper, FRONT pivot hole - note that there already seems to be some sort of shim installed. I tried tapping it out with a few LIGHT taps with a hammer & punch, but no luck.

If I could get that shim OUT of there, it would probably solve my problem.

Any thoughts?
Thanks

If it an added part try a little heat from a torch first then attempt to tap it out. Otherwise see a gunsmith.

;)

[weaponizer]

Originally posted by Drjones
Ok, I need to get this taken care of.

Attached is a pic of the upper, FRONT pivot hole - note that there already seems to be some sort of shim installed. I tried tapping it out with a few LIGHT taps with a hammer & punch, but no luck.

If I could get that shim OUT of there, it would probably solve my problem.

Any thoughts?
Thanks

What you have in there is an offset bushing, just use the proper punch, and make sure you secure the pivot hole, and just knock it out, it should come right out....BUT... you are going to have a big hole now... So you need to put the bushing back, only in a different spot, notice how its offset, well put it on the pin, and rotate it till it lines up, and hammer away, ( carefully of course) and it will always be in the right spot for future takedowns....

http://www.pkfirearms.com/store/get_items.aspx?type=0&term=12

[Blitzer]

Originally posted by Copycat
What you have in there is an offset bushing, just use the proper punch, and make sure you secure the pivot hole, and just knock it out, it should come right out....BUT... you are going to have a big hole now... So you need to put the bushing back, only in a different spot, notice how its offset, well put it on the pin, and rotate it till it lines up, and hammer away, ( carefully of course) and it will always be in the right spot for future takedowns....

http://www.pkfirearms.com/store/get_items.aspx?type=0&term=12

Or get some offset pins. ;)

[weaponizer]

Originally posted by Blitzer
Or get some offset pins. ;)

I believe that the offset pins are just for large hole lowers with small hole uppers, he has a large hole upper, and a small hole lower :)

[avmech]

Offset pin for large hole lower/small upper. Bushing for small lower/large upper.

[GLOCK35TX]

I would just dump the upper. If you have a Lauer lower that is one of the best made. It was produced by LMT (Lewis machine and Tool)

The check out Model 1 sales for a new upper that is compatible