This is something I started about 5 months ago.
The object is to make a compensator that will fit a Cyma M1A1 without modification. UPDATE: Confirmed they will also fit TM Thompsons
I did the turning parts in September last year, but have been trying to work out how to finish it using a lathe.
Well, a couple of weeks ago I bought a milling machine...
Today, I did most of the milling, and just need to work out a fixing scheme.
This pic shows the cut-outs:
How about a tapped hole for a grub screw that locates into a dimple on the underside of the muzzle?
Yup. That's probably going to be the "main" fixer. I'm also thinking of putting a smaller one in the side behind the pin end(s) for added security.
It's already a tight fit.
The problem with the tube idea is that there's no where to attach it in the compensator without it showing.
The compensator also effectively extends the outer barrel by 50mm, so any tube inside diameter restriction could cause the BBs to hit it.
On a "permanent" conversion, it might be worth putting in a slightly longer inner barrel, but then you'd probably glue it on.
A full front end, including new outer barrel, would have the compensator screwed on and pinned. You'd notice that coming loose.
LOL. I was kind of expecting that question last night. 
I'm going to make another one to see how long it takes now I've made the few special tools needed.
I'll let you know.
This pic of a real one shows a drill point, Howabout putting a grub screw in a similar place but angled lower to grip the outer barrel?
What I've done is put in 2.
I've put one in underneath, as indicated by raffles, and one in the side:
It's further back than on the real one (and I have a real one), but its position puts it just behind the pin on the M1A1's sight, helping to the hold it on.
I might put another on the other side, too.
Could someone who wants one of these, and has a TM Thompson, please PM me. I want to check the fit.
So when will the production run start?...so we can put orders in LOL!
I've made one from scratch (i.e. cutting the metal off the bar), and it didn't take nearly as long as the first. I put that down to more practice, and I simplified the way I made it. Because of reduced setup time, more than one at a time would reduce the time each takes, so I'm leaning toward possibly making these to order...
Now I have 2 to experiment with finishes on.
I'm going to paint one black to match my Cyma, and I'm going to try to anodise the other to look blued.
What would people's preference be?
Finish options I can think of are black paint (match to Cyma), anodised to look "blued" (would that match TM?), or raw aluminium straight off the machine (paint/finish yourself).
It has also been suggested to me that some of you might want to use the more permanent fixture method of drilling through your front sight and putting in a pin, replicating the real ones more closely. As they'd be made to order, I could make that job easier for you by drilling the compenstor (which you can then use as a guide), and supplying a suitable pin.
TM is painted.
Any reccommendations on paint?
BTW, my very rare Japanese made 1928 conversion kit has fake parkerisation on it.
I guess that's what the matt black paint is on the Cymas?
Though IIRC, 1928s were blued, not parkerised. I thought parkerised Thompsons were post-WW2 built or refurbished.
Though IIRC, 1928s were blued, not parkerised. I thought parkerised Thompsons were post-WW2 built or refurbished.
Yeah, all the 1928s I've handled were blued.
A Proud Member Of 'Team Spleen!' who play mainly at Gunman Airsoft, Tuddenham, Suffolk.
Today it has been confirmed these will fit a TM M1A1 as well as the Cyma. Thanks for that, Ghost.
Not just fits, fits like a glove. Cracking job mate! 
Thanks, Ghost.
Update:
Painted prototype on my Cyma barrel
Paint is Halfords Matt Black over grey primer.
Looks very nice indeed!
A Proud Member Of 'Team Spleen!' who play mainly at Gunman Airsoft, Tuddenham, Suffolk.
Thanks.
I've decided to make these for sale if people want them.
Please see the thread in the Sales forum for more details on that:
viewtopic.php?f=11&t=10257
Due to a request, I've made one of these to fit the budget Thompson.
3 changes were needed:
- The material was changed to black Delrin (a plastic) to speed up production.[/*:m:2tg1dwhu]
- It needs to have the "pin ends" cut off on the Thompson foresight for it to fit - The budget gun's pin ends are too high for the cut-out option used for the Cyma and TM guns.[/*:m:2tg1dwhu]
- The main chamber needed a larger bore for a short length to accommodate the longer muzzle protrusion of the budget gun.[/*:m:2tg1dwhu][/list:u:2tg1dwhu]
The Delrin isn't really suitable for use on the Cyma or TM. The material's too soft to hold a thread AND the cutouts. But it's ideal for the budget gun.
