M11a1 - upper hard to get onto lower.

[jmanc62]

I just picked up a m11a1 and when I took off the upper to clean and oil it was very challenging to get the front securing pin back through the lower, front hole. Is this normal to have such tight tolerances? Is there something I am missing?

Any tips would be appreciated.

Thanks

Jim

 

[Jack007]

What vintage? Is it an actual SMG or an open bolt semi? The later guns often suffered from missed tolerances between upper and lower. There is a built in tolerance that allows the upper to move in and out a tiny bit and an even smaller one allowing it to move vertically. I would check the alignment by putting the pin in without the upper. It should slide right in and be perfectly straight.

 

[jmanc62]

What vintage? Is it an actual SMG or an open bolt semi? The later guns often suffered from missed tolerances between upper and lower. There is a built in tolerance that allows the upper to move in and out a tiny bit and an even smaller one allowing it to move vertically. I would check the alignment by putting the pin in without the upper. It should slide right in and be perfectly straight.

Thanks for your reply. It's an RPB overstamp SMG so I think late 70s/early 80s (guess). The alignment without the upper is perfect. The upper struggles to sit back into the lower far enough for both sets of holes to align (just slightly off). With enough effort, I was able to get it to work but the effort required seemed a bit much as compared to my experience with an m11/9 or m10.

 

[LawBob]

Make sure safety is off

The safety only should be used when the bolt is back.

 

[jmanc62]

Make sure safety is off

The safety only should be used when the bolt is back.

Thanks for your suggestion - yes safety is off.

 

[LawBob]

Also, you can pull trigger and the sear will give you a little more play. I have to do this with the baby ghost upper bc it’s front is in contention and needs to slide on horizontally rather than tilt under and down.

Sometimes the buffer plate back of the spring might not be centered properly on the back of the lower.

 

[LawBob]

Also oil the pin

 

[Jack007]

Sometimes the buffer plate back of the spring might not be centered properly on the back of the lower.

Good catch. Maybe try to assemble it without the bolt assembly and see how the uppers fit?

 

[Landric]

Also check the back of the ejector rod, a little extra material there can cause a tight fit or no fit at all. I got one assembly where I had to dremel a little material off the back of the ejector rod to get it to fit into my lower. If it fits without the bolt but is really tight with it that might be the issue.

 

[MitchWerbellsGhost87]

Also make sure your selector switch is in the full auto position. I’ve seen an instance where the gun was switched to semi auto and the trip was further forward as a result and the very front end tip of the trip was hitting the trunnion and not allowing it to line up properly with the takedown pin holes. Only ever saw this once, but I’m sure this problem has occurred with other guns.

 

[theduke]

I have had a upper that was extremely tight.

Its now as one......Plan is too shoot it and hope it comes off easier than it went on.

 

[LawBob]

I have had a upper that was extremely tight.

Its now as one......Plan is too shoot it and hope it comes off easier than it went on.

Don’t forget oil the sides of the upper a bit.

Like your lady, dryness can be uncomfortable to insert.

 

[LawBob]

Well the ba

Good catch. Maybe try to assemble it without the bolt assembly and see how the uppers fit?qell

Well the baby ghost install method is to slide the upper horizontally into the hooded part of the lower by depressing the trigger.

That has the added benefit of ensuring the buffer/end plate are centered as the upper is inserted against the rear of the lower, rather than the traditional angled insertion and lower the upper to the pin.

 

[CKxx]

Consider this a plus. Mine has an egged out pin hole and flaps around. I've been meaning to get it fixed but "mail it in and I'll fix it eventually" gunsmithing seems to be standard.

 

[LawBob]

Consider this a plus. Mine has an egged out pin hole and flaps around. I've been meaning to get it fixed but "mail it in and I'll fix it eventually" gunsmithing seems to be standard.

Call Sam at Ps.

 

[Fulautotank]

Also check the back of the ejector rod, a little extra material there can cause a tight fit or no fit at all. I got one assembly where I had to dremel a little material off the back of the ejector rod to get it to fit into my lower. If it fits without the bolt but is really tight with it that might be the issue.

I had to do this just today with a new bolt group for my mac10 except that it was the recoil/op rod.
It was rounded so I took a dremel and flattened it. All good now.

 

[boomer535]

Your recoil spring rod on your bolt assembly is probably too long. File it down just a hair.

 

[jmanc62]

Sorry this thread took off and it didn't notify me. Thank you for all of your input. I wound up really oiling it up and pushing it in - some seriously tight tolerances!!!