Top & Bottom Of Rec'r Fit Way-Too-Tight

[Bounty1]

I have a WH that has been fine in every respect except one. The bottom and top part of the rec'r fit way too tight.. There is no way I can just slide off the rear grip portion from the top portion. I need to use a wooden block and a rubber mallet and pound it off from the front of the trigger guard after the front grip has been removed.for cleaning and to field strip it for whatever reason and takes about 15 "whacks".. Obviously it is "out-of-spec". I know PK could fix this, but he seems to have quite a waiting period, and I don't want to have to wait 2 years or so to get it back.. Is there anyone else anyone knows who could do this work, or any other suggestions to get this resolved?

Thanks

[mnshooter]

If you have access to a GI grip frame, try that.

Otherwise, a good straightedge should help identify any warps.

[TD.]

Bounty1,

While the wait for PK. to re-manufacture a WH Thompson is now over 2 years, he routinely does smaller jobs involving the Thompson gun with a quick turn around time. Since you do not want just anyone working on your submachine gun receiver, I would contact PK. and ask him if he could improve the fit of the receiver and frame. This may be something he could do in a relatively short period of time. Since you would have to send the gun to him for this repair, this would also be a good time to have an original Lyman rear sight and/or a new barrel installed (getting rid of the original WH barrel greatly improved functionality on my 1928 WH). I know you will be satisfied with his work.

 

Let us know how it turns out.

[Chopper28]

If PK can't get to it quick enough, try John Andrewski he is excellent.IMHO.

[reconbob]

If you are able to remove and attach the trigger frame as described - mallet and wooden

block - it is not so badly bent or out of tolerance that it can't be easily fixed. Now, what I am

about to propose is considered to be completely un-acceptable by many, and I would not use

this on a Colt, but here it is: - get some very fine valve grinding compound - this is an abrasive

silicon carbide grit mixed with oil or grease and is like a paste. You want a grade so fine that

when you rub it between your thumb and finger it does not feel gritty. Apply this compound to

the rails of the trigger frame and slide it on and off - in your case tap with a mallet. The

compound will abrade only the tight spots. You will find that as you slide/mallet the frame back

and forth that it starts to go a little farther on. You will probably need to wipe off and reapply

the compound to keep it "sharp". The only down side to this is that the compound will remove

the bluing on the rails, but mostly only where the tight spots are and will not remove the bluing

from the outside of the receiver or trigger frame since there is no contact there. The bluing is no

doubt worn on the rails already anyway. Other ways of

doing this - swiss files, precise application of emery cloth, etc.will also remove the bluing.

When you get the frame to slide all the way on, give it a few more cycles, then degrease and

clean and remove all of the compound. Lightly oil the rails and now you will have a perfect fit.

In a way you are lucky because the fit you will end up with will have no looseness or rattle.

There could be several reasons why your frame doesn't fit - long term stress relieve, improper

machining to begin with, slight damage, etc. But removing as little as 0.0005" (thats one half of

one thousanth of an inch) could make the difference between too tight and a perfect fit. You should

fix this because hammering with a mallet approach could cause galling of the rails.

Disassemble the trigger frame and take the bolt out of the receiver before doing this - you don't

want the compound where it does not belong.

If you don't feel up to this you can send the gun to Phila Ordnance (me). I have done this fix

dozens of times and the customers have been very pleased with the work. We charge $75/hr for

gunsmithing and there is no way this would take more than an hour if you have already removed the

parts from the trigger frame and receiver. Turn around time would be a week or two.

 

Bob/Philly O

[mnshooter]

Also see Bob's excellent photo in the Nov. 25, 2011: "Trouble installing my 80% display receiver on my lower".

The photo on page 2 shows a warped grip frame on a surface plate.

Edited June 3, 2012 by mnshooter

[Bounty1]

thanks to all for your input. Yes, I already can see the wear marks on the frame where the fit is tight. I tried using some very fine files to take some of the metal off, but that didn't seem to improve things much.

My worry about using some "grit" to smooth things up is that it is "soooo" tight, that I'm afraid if I put a little abrasive on the rails and try this, that I may not be able to get it off at all.

I also want to have this in shape for the S &S in Indiana in October, so no delay would be greatly helpful to my worry factor. I may wait until after that to have this work done to keep my anxiety level down.

BTW - It has always been this way since day 1, so I'm sure it was a sloppy job of machining.

I will be in touch with Bob of Phila to discuss this tomorrow.

Thanks to all for your input.

[roertmcw]

My first WH 1928 had a problem with the grip – it wiggled. I used a vice and warped the grip (not the receiver) to fit. I sold that gun and then I got a ‘new’ one. It had problems too until PK fixed it. Over two later, a Lease Lend kit a real Lyman sight and I won’t tell you the money cost, I am very happy.

 

The moral is I would ask not to mess the receiver. Hack all you want with the lower but not the receiver. You can get a new lower but you can’t get a new receiver. I have heard most of the WH guns were out of spec and it if you grind or polish the receiver it will be harder to fix it later, and cost more too.

 

My two cents, Robert.

[reconbob]

I want to emphasize that the fix I described is the safest, least intrusive fix I know of, and

perfect for this particular gun. The fact that the frame will go all the way on indicates that

it is not so badly bent or out of tolerance that it needs to be re-machined or straightened

like the one referred to by mnshooter in a previous post. We do not know if the receiver

is improperly machined or damaged, or if its the trigger frame, or both. I have measured

receivers and frames we have given this treatment to and usually there is no measurable

dimensional change when you do this. Nothing is getting "grinded" nothing is getting "polished"

both terms imply significant metal removal. Probably the best word would be: "lapped". So

doing this will fix the problem and preserve the receiver for posterity. I would add that before

doing this I would check the receiver with gages and test frames we have here (since we make

both receivers and trigger frames to 1942 US Ordnance specs). If an original GI frame fits

AOK then we know that its the frame, not the receiver. But the fix will probably not dimensionally alter

the receiver. I have worked on frames like this where only 5 or 6 cycles (sliding the frame on and off)

with the compound have been all that is needed to go from way-too-tight to perfect fit. Of course,

we don't know what Bounty1's frame will be like, but again, the fact that it will go all the way on

(with a little help) means its really close...

 

Bob

[PK.]

This problem with WH’s is always (in my experience) due to warpage in the receiver, bowing the sides outward. This also creates a bolt pocket that is oversized. The worst thing you can do is remove metal from the interface because then the bolt pocket can’t be returned to its proper dimension without making the frame/receiver to lose. Removing metal is a classic case of treating the symptom and not curing the disease. The proper correction will make the frame and receiver fit well and restore the bolt pocket to its correct dimension, preventing damage to the receiver by a sloppy bolt.

[thirtyround]

Gentlemen, not to change the subject, but thought this would be a good spot in the thread to ask. The response is so technically positive, I have no doubt Bounty1 will obtain the desired results he's looking for. I submit a question, kind of a 180, what would one do to correctly address a very loose/sloopy trigger housing / receiver fit?

[roertmcw]

I should have said do not it you self, find a good Thompson smith who has the blueprints and the skills to fix it.

 

Sorry, Robert

[reconbob]

I am sticking to my guns (ha-ha) on this one. The fact that the frame already slides

fully into position - albeit tightly indicates that almost no material needs to be removed

to get the right fit. We still do not know if its the receiver, the trigger frame or both that

are out of tolerance. If, in fact, the receiver is bowed and needs to be "returned" to its

proper dimension (bending?) my 0.0005" that might get lapped off is a tiny fraction of

the combined allowable tolerance for the fit of these parts. If the receiver is not bowed

and the trigger frame is machined a little off then this is a safe fix. I repeat that most

times I have done this you cannot measure any dimensional change.

 

Bob

[james m]

I'd have to say I agree with reconbob here and the "fix" he's described is likely viable and I can't forsee it causing any problems down the road. If the receiver was that warped I'd agree another more involved fix would be in order however; getting the frame on at present would probably be impossible if that was the case . For whatever it's worth I've used this same "honing" technique with semi-auto pistol frames/slides in the past without any problems.

Jim

[jim c 351]

I don't know wether reconbob or PK is correct with regard to this problem. I think this might best be resolved, not by thompsons at 20 paces or who agrees with whom, but by a simple micrometer measurement at both ends and center of bolt channel.

And the proper reply to PK is "thank you sir , I'll check that out first thing".

Of course this is just my opinion.

Jim C

[Bounty1]

Thanks again to all for your input. What you have said, essentially, is that my frame to receiver fit is "off" a little unless the frame is bowwed. (sp). I don't think that's the case. It has been a really good shooter for many years, and naturally I baby it as do all TSMG owners even if it is a WH. It has never jammed a round or given a feeding or firing problem through thusands of rounds, but taking it apart for cleaning is a real chore.

I will check with PK (PK, please provide email address) and "reconbob" (also provide email address) so we can discuss this.

I will be out of town after 6/13 thru 6/28, so will not be able to "ship" to anyone until I return.

Thanks again, and PK and RECONBOB, please provide me with your email addresses.

[Bounty1]

To Jim C 251.

Thanks for your input, but me and the checking of dimensions I would rather leave to someone else. I can barely change the oll in my car. So I will wait and talk to them.

The big problem is not getting the lower back on, it's getting it off that's a bitch. I don't have a workshop to do this stuff, and I'd rather leave it to someone who has done this before.

I have no doubt your suggestion is correct, but unfortunately, I'm not the person to be trusted to do it.

Thanks for your input

Bounty1,,

[reconbob]

Just to keep the record straight here, I do not consider this to be reconbob vs PK. I have the highest

regard for PK - he is probably the master of repair and restorations of West Hurleys

and also works on original Thompsons. I defer to his judgement and expertise on all things West Hurley.

My side of the street is the manufacture of 80% and 100% machined receivers and the assembly and sale of

working/shooting post-sample guns to Class 2's, Class 3's, and Police Departments.

My thinking on this trigger frame is that since it will slide onto the receiver, it does not rise to the level

of a bowed or warped receiver as described in PK's post. And I think my fix is correct and applicable in

that case. Should it turn out that Bounty1's receiver is bowed then by all means PK has the experience

and expertise to return it to its proper dimensions.

 

Bob/Philly O

 

(Philaord@aol.com)

[Shattered]

I will weigh in on reconbobs suggestion... and change the recipe a bit. Try Diamond Dust lapping compound. It comes in numerous colors (grits) with white being the least invasive. I'd try the white Diamond Dust and just work it back and forth until you get it to an acceptable level of friction. I've used this stuff in MP5's with brandy new locking pieces where the fit was so tight, you couldn't turn the locking piece by hand in the carrier... you literally needed a pair of Vice grips to rotate the item. After about 5 minutes of rotating and on and off motion, It was now removable by hand. Once you get where you want to be, completely remove the Diamond Dust... do it again... and once more. The idea is to get it all out. It's a very doable solution and can be done while watching Band of Bros...

 

It'll work the same way in your receiver parts.

[timkel]

I saw a tight fit issue on a WH thompson before. First I checked the receiver dimensions and they seemed OK. Swapped to a different lower. It was better but still tight. Then while comparing the WH upper receiver to a military receiver I noticed one difference. The WH receiver rails were machined square. The edges of the rails were perfectly square, almost sharp. On the Bridgeport receiver, the edges were rounded just slightly. The edges were not cut to a specific radius but deburred. They were not sharp to the touch. Looking in the recesses of two different lower receivers, I could see the grooves were cut the same way.

I decided to stone the edges of the upper receiver rails(top and bottom). Just enough to deburr the edges. This gave a better fit and solved the problem. Now the lower fits perfectly, snug, with no wiggle.

I think the ReconBob post above that mentions using grinding compound would accomplish the same thing.

Edited June 5, 2012 by timkel

[mnshooter]

Gentlemen, not to change the subject, but thought this would be a good spot in the thread to ask. The response is so technically positive, I have no doubt Bounty1 will obtain the desired results he's looking for. I submit a question, kind of a 180, what would one do to correctly address a very loose/sloopy trigger housing / receiver fit?

 

I second the question.

Hope someone out there will offer some informative advice.

[reconbob]

OK, ok. What to do if the frame is too loose. In this case you want to leave the receiver

alone and fix/solve the problem by "fixing" the trigger frame. The first thing I would suggest

is to try every trigger frame you can get your hands on and see it you get lucky and find one

that fits better. There are frames out there that over the course of 70 years may have warped,

or are a tighter fit than others.

You could peen the rails on the frame, and re-fit the frame. This is no good because while

you can restore the nice no-rattle sliding fit it damages the rails.

There is a safe temporary fix that I have used on both Thompsons and on the buffer/stock

assy. of my MG-42, and that is to coat the rails with some type of epoxy. This will restore the

nice fit, but will wear out over time as the epoxy will wear, and/or crack and flake off. But it is

harmless and is not permanent.

The epoxy is not as important as the "release agent". Brownells sells a little "Acra-glass"

kit that is an epoxy with release agent. In this case you would clean - like really clean - degrease

followed by acetone - the rails of the receiver and trigger frame. Coat the rails of the receiver

completely with the release agent which is brushed on and let dry. (Its a thin fluid.) Also put the release

agent on the top of the trigger frame rails, and on the surface the bolt slides on, but not on the

"groove" that the "tongue" on the receiver slides in. Mix up the epoxy and brush a thin coating

on the trigger frame rails and slide onto the receiver. Let it set and cure. When its ready tap

the frame will a rawhide mallet and it will slide off the receiver. Clean up the extra release agent

and epoxy. Put on a light coat of oil and slide the parts back and forth until you get the right

fit. The epoxy is soft enough that it will be "cut" by the steel rubbing on it. You will end up with

a thin strip of epoxy in the "groove" of the trigger frame but thats all you need. Over time it will

wear/flake off but until then you will have a perfect fit. You can also do this with the fit of the

buttstock slide on the trigger frame. This can last for months depending on how much you handle

and shoot the gun.

When I do this on my MG-42 it lasts several outings but the hammering of the buffer by

the bolt on a 42 is much different than the rails of a Thompson.

And yes, if you do this wrong you will end up gluing your trigger frame to your receiver

so caveat emptor. But you asked...

 

Bob

[mnshooter]

Thanks Bob.

There was a joke in one of the old gunsmith newsletters that Brownell's used to mail out.

The exact details hardly matter, but the punch line went something like:

"Ok, l let the epoxy set up overnight. Now tell me again; how do I get that release agent in there?"

Edited June 5, 2012 by mnshooter

[Bounty1]

I am getting some really great information from all of you.

Timkel: I checked the rails on my WH, and yes, they are as square as can be. I may try stoning that lightly and see what happens but I will wait to see if there are any more posts as to the possible problem.

I will have to take a look at the photo that was mentioned by "mnshooter" also before proceeding with anything.

thanks again for the input.