18 replies to this topic

[BA2157]

Hi everybody,
I got a WH 28 that just started giving me problems. It
won't fire one or two shot burst or single shot in semi,
it wants to run the full clip. It may fire two shots then
next pull the whole clip. I have not had this problem
before it just started it one day out at the gravel pit.
I fired one 3o Rd clip at two to three shot burst just
fine then the next 30 Rd clip it started, I shot a burst
then it ran the clip and been that way since.
I have tried different ammo, recoil springs, cleaning
everything, clips, holding my mouth a different way and
it still does it.
Can any body help me, please. I am about ready to
use it to stick some Tomato plants with it.
BA

[John Jr]

Replace everything in the lower and try again.

[BA2157]

John Jr

you think maybe the sear spring my be gone weak
and not jumping back up fast enough

[John Jr]

Possible, could be the disconnector as well... try that .

Jr

[BA2157]

Thanks all

I have replaced all the springs in the lower along
with a new rocker, for the semi action, but still
full auto till clip runs out. Its great for just dumping
clips but will not burst groups or shoot semi more
than twice. its like the bolt ain't comming back far
enough for the sear to catch. I have had this gun
since 1984 and I havent had any trouble till now.
I am a machinist by trade and understand the
workings of this model, but this don't add up.
I though maybe my ammo wasint hot enough,
I had some of my reloads, so I tried a box of
miltary ball and still same song.
I took the lower back down and check for burrs
or anything out of the orinary and double clean
and lube all, didn't see anythingout of place. Went
outside with 10 Rd in clip and tried again. The first
pull it shot twice then the secound pull it dumped the
clip with out my finger on the trigger.
You'all got me.
BA

[Balder]

Ammo not powerful enough and/or too strong recoil spring?

Balder

[BA2157]

Hey Balder
Do you reload and if so what load do you use
in a Thompson?
BA

[OldFalGuy]

I am an admitted newbie with Thompsons but been around this stuff for 30 years. If as stated his sear/disconnector looks good could the surface of the bolt that contacts them be worn in some manner which results in these runaways?? JUst seems if he has been rocking along for many years the spring would not have gotten stronger and he has swapped aobut with good ball ammo it seems something has degraded to make this condition exist-Probably worng but that is how we learn.

Mark

[Hawkeye_Joe]

That was my first thought when he stated that it was running away .. if it is not the lower parts that are the problem then try replacing the bolt or checking the bolt for problems. Seems like the bolt hold back catch is not functioning.

[BA2157]

That is my next guess is to try a new bolt. The old
one looks ok, just shinny where the sear has been
engageing it. Can't tell it it is whorn or not, don't have
a new one yet to compare.
I have fired this weapon on and off for the past
20 years and probabley ran 7000 to 8000 Rds
through it so the bolt could posibly be shot. I will
pick up a new one and try it. I got to get my
Tommy Gun well again, I enjoy shooting it too much.
I own four other Machine Guns but the Thompson
is my favorite.
Thank to all for the help
BA

[JimFromFL]

A lot of great advice.

Here is some more info to muddy the waters.

Is the ammo the same as before?
Is the bolt being slowed down by either the mag, dirty ramp or barrel opening where the bullet sits?

I have experienced problems that were attributed to the above.

Good luck and let us know the results.

[BA2157]

Hey Jim
I have tryed different ammo from hand loads, factory to
miltary ball and all result same. I have tryed different
clips from 30 rd, 20 rd and even a drum with same
result. But what do you mean where bullet goes in
barrel? I clean barrel out and looked with light and
don't see anything. Is there something with the
barrel I don't know or looking over. This condistion
just started like you filp a switch. I shot a 30 rd clip
at 2-3 shot burst and it shot fine, then the very
next clip it started the run away problem. I tryed
that first clip again and still run away.
Did something happen to the throat of the barrel
or maybe the chamber that I can't see?
BA

[Balder]

BA2157,

I use 230 grains home cast round nose bullets over 4.7 grains of Bullseye, works fine in the Thompson and my pistols.

Good luck, hope you find the source of your trouble.

Regards,

Balder

[giantpanda4]

Simple question - does the bolt stay back after the last shot?
If not, the bolt isn't coming back far enough. Mainspring probably - or loads (as mentioned).
If so, sear/trip/bolt should be OK.

[Norm]

I am not an expert, but I seem to remember and old post which someone (fullauto 45, I think) mentioned that you could put a piece of scotch tape where the acuator handle is SUPPOSED stop (across the top of the receiver.)

After firing, look at the tape. If it is broken, the acuator went full travel. If not, it is short stroking.

Regardless of why the bolt doesn't lock back, this should tell you IF the bolt is getting there to begin with.

My $.02 worth

[Motorcar]

I'll give you $5,000 for that broken down gun that won't run right!

[BA2157]

Hey thanks everybody for the help,
giantpanda4 that is a good quest. no the bolt
does not stay back after last shot, it is down agaisnt
the mag. I ain't even though of that. By that, the bolt
can't be going back to lock in the sear noch.
But now why ain't it going back. My ammo is plenty
hot, trying it will miltary ball. 230gr FMJ ball.
Bolt moves fine by hand and is not binding will
recoil spring.
There is some rub marks in ejector grove on the bolt,
think that might be enough to slow bolt down.
The h-peice seams to be moveing slick.

Question: If I take a wood dowel and run down the
barrel and push against the bolt face to act as a round
is being fired, how much pressure does it take to force
the bolt back out of battery?

Oh and Motorcar if I can't fix this and give up I will
start the bidding at $5000.00. LOL
Or still may stick a tomato plant with it.
Norm I will try that tape thing tommorrow just to
double check it. Good ideal.
Again thanks all
BA

[PK.]

Put a wooden dowel down the barrel against the bolt face and stand the gun on the end of the dowel on a bathroom scale, push on the butt- it usually takes about 40# to disengage the lock (don’t count the weight of the gun).

Clean the top of the receiver with degreaser and use masking tape to determine the travel of the bolt.

You have received very good direction concerning many possibilities that could be causing this. Something apparently has changed in the bolt, actuator, lock, receiver relationship and I am concerned about the possibility of metal being moved through battering over time.

Insure that there is nothing in the recoil spring hole in the actuator (such as a piece of broken spring).

If none of the suggestions offered throughout this thread produces a cure, I suggest you have it inspected.

[TNKen]

I shot some Winchester White Box Wal-Mart special in my 28 with varying results. The ammo works fine for the most part, but occasionally I get a round that won't cycle the gun fully. When you let off the trigger, it only cocks to the second notch.

IMI is hotter and consistent. I also have some Spanish and FN ball ammo from WWII that I haven't tried yet.


Have you manually checked (cycled) the gun yet??? Cock the gun open, hold the actuator knob, and squeeze the trigger. Holding the trigger down, let the bolt go fuly home (not slam down) then re-cock with the trigger still held down. Go through several cycles, then start the bolt back and about half way through the cycle, let off the trigger and see what happens. I'm curious to see whether letting off the trigger will stop the bolt from cycling and let the gun re-cock.

Not the same as with live ammo, but it might give you a hint of something.

Good luck. These guys are better at this than I am, but that is my contribution.

Ken