Page 1 of 1

1928 Thompson cocking bolt

Posted: Mon Oct 08, 2018 2:29 pm
by Lord Elpus
Having not touched this Thompson cosmetically, I thought I would put the bolt in the correct place, so first step done, marked out and cut slot, now to look for suitable piece to make a slotted bolt handle/head as per original. I will probably make it from aluminium bar, I did have some knocking around, the hardest job is finding it!
Andy

Re: 1928 Thompson cocking bolt

Posted: Wed Nov 21, 2018 9:38 am
by Lord Elpus
Have got around to doing a bit more to this conversion, was going to make it eventually an “ebb” conversion, but at first wanted to just do a swop over from side to top fake bolt runnning action.
Now I knew there wasn’t going to be a lot of room along the top........but there is in fact none at all! So I’m hoping when the “ crimp strip” is removed from the top of the gearbox there might be enough room to put in the original slide plate, I may have to take some material out from the inside top of the receiver, but if I’m going down that road I’m going straight in for the ebb conversion, this means machining down the top section of the gearbox.......so it might end in disaster, but I do have a couple of gearbox cases sets spare, they happen to be the same as the P90 (if you didn’t know).

Re: 1928 Thompson cocking bolt

Posted: Mon Mar 18, 2019 2:45 pm
by Lord Elpus
Just a quick update, on this, used original “side slide” plate, bit of a chop down and repositioned the spring all fits together ( with a few Anglo Saxon expletives) is quite short on pull but I want to make it work with the gearbox later, so didn’t want to cut too much from the plate, but for the working on “fake bolt action” could be cut down a bit more for longer stroke/ pull.
I see this as “ stage one” on this modification, so if anyone wants to try it or want me to do it, let me know. There’s a bit more smartening up to do will post finished pics.
Andy

Re: 1928 Thompson cocking bolt

Posted: Mon Mar 18, 2019 2:47 pm
by Lord Elpus
Pic’s didn’t come out in order(when do they ever!) but middle pic shows spring just tucked up inside.

Re: 1928 Thompson cocking bolt

Posted: Wed Mar 20, 2019 7:13 am
by Lord Elpus
A couple of pic’s of the trimmed and adapted slide plate to fit,

Re: 1928 Thompson cocking bolt

Posted: Mon Mar 25, 2019 5:52 pm
by Lord Elpus
Did a bit more today, slotted top of g/box case and same to piston, it looks like this will work, but I’m thinking the thin slide plate won’t stand up to the job for long. I don’t want to take off anymore from the top of the g/box, so as to fit a thicker plate. So I’ll be looking to machine down thickness of top receiver, all that’s needed is maybe 1 mm.

Re: 1928 Thompson cocking bolt

Posted: Sun Apr 21, 2019 6:30 pm
by Lord Elpus
A bit more done the blowback mechanism, thought I would bolt it all together so adjustments could be made if necessary. Originally planned to weld it all in one piece. So if this prototype works I will do welded pieces.
Not yet made handling piece, but it all works!

Re: 1928 Thompson cocking bolt

Posted: Tue Apr 23, 2019 7:49 pm
by Lord Elpus
Finished for now, running on a 7.4 lipo, with gates mosfet, on single shot relaxes spring on every shot. Auto does the same.....most of the time, stock rof , will put some pellets through this, maybe 5000 or so then pull it apart to see if there’s anything going wrong.
Doesn’t run full length as I’ve discovered I would have to cut into the cylinder to achieve that, but works well all the same, will try to do a little video later.

Re: 1928 Thompson cocking bolt

Posted: Wed Apr 24, 2019 6:25 am
by Hänschen klein
How you do it I never know.

Great work and inspiring for others. :good:

Re: 1928 Thompson cocking bolt

Posted: Wed Apr 24, 2019 7:57 pm
by Lord Elpus
Thanks,
I know I’m Probably not the first to do this, but the fact that the bolt was on the side has been bugging me for ages, so I had to have a go at this, and now I will do the rest of my pop guns that need ebb too!
I enjoy doing these things, years of working and making things for cars and motorcycles has given me the patience to do all these conversions, and it is only “toy” time after all not really serious, it doesn’t matter if I bugger it up.....just do it again!
Andy

Re: 1928 Thompson cocking bolt

Posted: Fri Apr 26, 2019 9:50 am
by dadio
Well done , can't wait to see a video of it running ! Great idea that really does correct a glaring inaccuracy in the gun :good:
With the top crimp plate removed could I suggest shim plates on the sides of the inside of the top receiver to fit snug onto the gearbox sides and stop it spreading .

Re: 1928 Thompson cocking bolt

Posted: Mon Apr 29, 2019 9:50 am
by Lord Elpus
I have managed to get a bit of the strip on at the rear end, you can see it in one of the photos,I did think of some side “buffers” as is were, but it complicated assembly a bit, And I just wanted to see it work! Maybe an improved sliding plate that mimics the crimp strip shape will work, but I’m just going to see how long this goes as it is.
I have had some guns apart (AK 47’s) that have had the strip missing from new, and has had no affect on the cases, so we will see.
Have done a little video, but can’t seem to get up on site, I will get someone who’s a lot more computer savvy to sort this, if I can’t grind it, weld it, drill it, or put threads in it, then I’m not very good with computers!