I’m attempting to attach a barrel from my old Colt LE6920 onto my new Colt upper and I’m having a hard time getting the barrel stud into the receiver notch. Shouldn’t it just slip in easily or do I need to bust out the rubber mallet? I’m asking because when I took the barrel out of the old upper it slid right out.
Should slide right in. I’ve never had any problem installing a new barrel into a used receiver.
If you’re going to retain the FSP, I’d especially hesitate to use the mallet. If it doesn’t go in straight you could end up with a canted front sight post - es no bueno.
Edit: My bad, just re-read your post and realized you’re putting an old barrel into a new receiver…that’s something I have only done twice and it went right in both times.
It should fit. Check the barrel pin and the receiver notch for burs or anything of that nature. If you have a set of calipers, measure the diameter of the pin and the width of the notch. I’ve heard of there being some wiggle room in there so its safe to say that some may be tight. As long as the interference isn’t more than a few thousands I would grease everything up and slowly work it in. If it absolutely won’t fit, get in touch with the people who sold you the upper.
I would apply a decent amount of lube to the barrel extension. Make sure that the pin is good and that the receiver channel is good. Insert the barrel as far as you can and then using a rubber mallet slowly tap the barrel into the receiver via the FSB and you should have no problems.