Just finished putting the lower receiver together on my M16A1 parts kit gun build. The butt stock itself has a small amount of side to side wobble/slack movement. Is there anyway I can correct this to tighten the stock up to the lower receiver? Also while I have the floor where can I pick up the correct slick finished butt plate that has the metal trap door. The original is cracked and I picked up what I thought was a replacement form ebay put it's not even close to the original, as the trap door is a molded foam and the butt plate does not fit the stock that well.

Numrich has used surplus replacement plates for $5ish.  No metal door included.  I've got a few metal doors I'll never use.  Search M-16A-1 lower parts under AR-15 / M-16.  I usually swap 2 or 3 plates for best fitment but really only use trap door stocks on competition shooters to add weight personally and really don't care if not perfect.  Sure doesn't effect shooting.

You're kinda in it now and I'm guessing you're trying for period correct stock so with most any butt plate on any gun not factory installed you will probably have to do a little finesse work.  The Freund Precision govt cage replacements are not known for fitment, reason I usually keep more than one to choose from.  All the stocks seem a little different in dimension and so do the plates IMO but never mic'd.  It is a mass produced battle rifle so don't expect perfect fitment unless you probably do it yourself or buy NIW..

**However the stock itself has a small amount of movement at the receiver. I can move the stock in a twisting motion, side to side about a 1/16"

On other end of stock is hump worn?  Hole in receiver for hump is usually round,  hump is more oblonged.  Sounds like a little play in this area.  Tighten upper screw a bit more or follow Stoner post.

Just to make sure we are on the same page....

**The butt plate is tight to the stock
**However the stock itself has a small amount of movement at the receiver. I can move the stock in a twisting motion, side to side about a 1/16"
**I'm unhappy with the butt plate because it's a cheap foam replacement.

The side to side twisting movement can probably be reduced by "bedding" the boss on the stock to the receiver. The boss being the molded "nub"that mates to the recess (1 inch below centerline of buffer tube) that is in the receiver. The recess/boss act as a key to keep the stock from rotating. Do you know how, or have you heard of bedding a bolt action rifle? Same principle could be used for your situation.

Is it just the butt plate that's cracked, or is the trap door broken too?  The plates are usually broken, but the metal doors are pretty sturdy.

The door slips out of the plastic plate.  If it's not broken too you can use it in your new butt plate.

OP,
Check post edit.

I figured had to do with the boss where it slides up into the received. I do not know how to bed or correct the slop to it thou.

My metal trap door is fine. I original thought that I could put my trap door on to the cheap foam replacement however it does not fit into the new butt plate.

I had a similar problem.  When I tightened the stock screw into the buffer tube, it didn't pull the buttstock in far enough to make a tight fit with the back of the receiver. The screw was as tight as it would go, but the stock still had wobble in it.



I fixed it by putting a stretchable silicone washer around the buffer tube screw then reinstalling it.  The shim effect of the washer pushed the stock solidly into the receiver and eliminated any play.  Cheap and easy fix.

I'll give the washers a try. I originally thought about putting a metal washer under the butt plate to help the butt plate from cracking in the future. Should accomplish the same results as the nylon washer.

If that doesn't work for you, let me know and I'll shoot you a couple of the silicone ones in the mail.  The silicone ones are nice because they conform to the shape of the recess where the screw goes.

In the past I've cut a narrow piece of the metallic duct tape and stuck it on each side of the part of the stock at the front where it goes into the recess on the lower.

Paladin

OP give JHUD an IM, I'm pretty sure he has a NOS Type E buttplate he can sell you, he sold me a complete NOS Type E stock w/hardware back in the day when Type E's were scarce/hard to come by. Unfortunately that was in like 2009/2010 before all these kits hit the market and drove down the prices on Type E stocks. You could also try member Boywonder777, and websites such as Apex, Sarco, or Numrich for the end plate as well.