Picked up my first Thompson last week. Now I have questions.

[Deavis]

The form 4 cleared in 310 days on my Savage/Bridgeport M1.

 

Questions:

 

1) My gun has a '28 barrel installed and the comp is loose. Does anyone have a spare pin about? Mine is likely not original (aside from the 28 barrel in the M1 receiver). Someone bubba'ed the the threads with 2 pin slots at some point.

 

 

2) How to measure cyclic rate? I used a PACT timer but the splits seemed too long (500 rpm) and the total burst times from first to last too short (1200 rpm). I don't think the timer is accurate enough.

 

3) Cleaning schedule? How often? Any special lube points other than the obvious bright/worn areas?

 

4) If I baby the trigger on semi (bench rested it for groups) the gun doubled. Worn part/spring?

 

5) accuracy at 50 yards with GI ball was 5". There was some lateral dispersion I attributed to a slightly lose comp/sight. What kind of accuracy should I expect?

 

6) Ultimately I need an M1 barrel swap. Recommendations? I'm on the PK list for a planned Westie overhaul, but don't want to wait YEARS for a swap on this M1.

 

7) I have 8 pounds of bullseye and 5000 fmjs to load. I was going to load from 5 grains and reduce it incrementally for a little softer shooting. I'm kind of thinking in the 4.5-4.7 range. I was wondering about squibs.... If I had one that somehow escaped powder charging, would the bolt likely fail to cycle another round and fire it?

 

Many thanks in advance.

 

-AD

Edited August 14, 2017 by Deavis

[giantpanda4]

I might try to handle a a few of these questions....

 

#3) I clean after every use and about every 500 rounds during a event where we shoot more than that. S&B or military ammo is dirty ( so is Bullseye), will cause issues if you do not clean it.

 

#4) Do not baby the trigger - it will cause doubling as the bolt drags on the sear and sometimes does not have enough force left to go back far enough to engage the slot.

 

#7) 5.0 gr. Bullseye is a good load, it is what I use when reloading.

 

JMHO, YMMV.

 

ps - #6, maybe you can do a little more research and do your own barrel swap? It really is not too tough - though having the right tools helps.

 

And of course - congrats on your new acquisition! Maybe we will see it at one of the how and Shoots?

Edited August 14, 2017 by giantpanda4

[DukeNukem]

Get reconbob to change your barrel. I have had him two of mine and it's less than a 4 week turn around

[ppgcowboy]

I feel I can answer a couple myself,

 

Number 2) MyRPM from tactical measurements is an app that works great for measuring your rpm. They have a free version and one for $20. I paid the $20 as I use it a lot and wanted the designer to get rewarded for his efforts. With 28 internals I am well above 600rpm, I clocked an M1 and just over 600, and you can really hear the difference between the two. If you use it let us know what you get.

 

Number 7) The second part of the question is if you have a primed case and fail to give it a powder charge and then seat a bullet, it will not cycle the bolt, but it will expel the bullet and it will lodge into the barrel about an inch or so maybe a little less. So under no circumstances should you manually cycle the bolt and fire. You will bulge the barrel. Treat each and every malfunction as a possible stuck bullet and check the barrel. When reloading, use a chronograph and check your charges, I like to be around 925fps. A lighter charge or a heavier charge will not be much as you are a little under military specs for .45acp in a Thompson. I use a progressive loader, it is a Dillon xl650 and it has a powder check station and you have to love it.

[DINK]

Regarding the PACT timer- the only time I have had inaccurate results from mine is when there is a hard surface near the muzzle that bounces the sound to the microphone, so you get two impulses for each shot. This is a good way to get a 1200 RPM measurement out of a Thompson. The microphone in the PACT timer is designed to pick up transient noises, so it is quite accurate even at ridiculous cyclic rates. I recently timed a buddy's MAC at 1455 RPM and it was a legit cyclic rate.

 

When you are timing the gun, make sure you are out in the open with nothing for the muzzle blast to echo off of.

[Adg105200]

1. If you are looking for a 28 pin, Sarco has originals. http://www.e-sarcoinc.com/tmpcompensatorpinorignew.aspx

 

There are original M1 front sight pins out there as well. I just can't remember where I got mine.

 

Andrew

[jl7422]

You might want to ask PK about the barrel swap. The wait times for a full overhaul and a straightforward barrel swap may be vastly different. They were for me.

[joseph12297]

Gunparts.com has M1 sight pins