KT Chaser and Eraser Conversion

[Ratzkie]

Back in the Golden Age(tm), before The Dark Times(tm), there was a conversation going on about converting .43 Chaser and Eraser pistols to .50. One, for the larger round, and two, now for .50 FSR. The problem was the amount of material remaining, and lack of proper tooling, coupled with expense.

I am here to announce that my foray to a local machine shop today was a success, and that I left behind two KT bodies for him to play with. Once we got on the same page about "I'm not picky- whatever is the easiest and cheapest way to get this bore from .43 (actual .434) to somewhere between .495 and .5", we started moving forward. It's not cheap, but is not $400 for the two bodies I gave him that we started at. We finally got down to "whatever tool you currently have in stock will work, and just clamp it in the mill, forget the holder", and the price came down to $50. For those interested, I am hoping that this is an easy thing for him and the price comes down even further so that I can offer all of you the chance at a converted body. I may buy a couple of the remaining bodies online and have them all done, and then bundle them with the parts below for a reasonable price.

I have created 3d printed 50 cal FSR mags, mag bottom plates, follower, and adapter blocks. I could easily make extended mags from these as well.
I also have the ability to poke a few buttons and make 43 cal rb mags, since those are seriously lacking in the market too. I owe... someone... a couple of them in return for the bodies I was given. Please message me so I can get them to you.
All mags will come with bottom plate, spring, and follower permanently installed and assembled, and would be like $3-6 sold individually as replacements. If you want it printed in something other than PLA, the cost goes up as I outsource (I don't charge middle man fees though). I print in colors other than black for a small fee.

Welcome to the Age of Semi-auto 50 Cal.

[ChoSanJuan]

I remember this thread! Pretty exciting that this didn't get lost to the ether and that head way was made!

[Scougar]

The incredible about this whole thing is.... he's my team mate, yet I started talking about this years ago, and never got around to doing it. So this is great Plus I can bug him to do mine lol. (I don't think he was even aware of our investigations into making these .50 cal, until he joined the team recently lol)


Hopefully this goes smoothly, but I expect hiccups along the way. They are nice little pistols so it will be interesting to see how this pans out.

[un2xs]

I hope your "Just do it" method works out. In the earlier thread we hashed this out a bit conceptually. It wouldn't be the first time I have been involved in an over think of a project.

An airsmith and I talked quite a bit about this. It was/is a long term whenever you get to it project. From memory here are known obstacles of the project:

- The mag conversions are doable. The stack keeper might be tricky due to the larger ammo. A new follower probably needs made.
- Do you want to retain the slide for its looks? Or are you willing to sacrifice it if necessary? It really doesn't do much more function than cock the gun and hold some parts down. It COULD be eliminated.
- Is there enough body to drill out and then ream to proper diameter? In the previous thread it was postulated that it might be better to mill it flat and afix a new properly sized barrel on top. Of course this will probably eliminate the slide. If proof of concept works by simply drilling it out, then ream and flex hone can be further refinements. If I understand correctly, to do it properly you need to drill under bore, then ream, then hone.
- Velocity is going to be a problem. Even with added O-rings for efficiency velocity only was getting up to acceptable velocity with .43. Going up to .50 brings velocity back down. As I recall, air chamber size may be the limiting factor. Not sure if you can respring these to achieve the goal.
- A new .50 bolt will probably need to be made. There should be room for a couple more O-rings than on the original bolt. This should help with velocity.
- Detents probably need changed.
- Isn't there also a connecting rod that needs to be considered?

Will add more if the hamsters in my head wake up.

[Ratzkie]

Yes, I started this project independently, but after a conversation with Scougar I found the old thread. I bother him enough with other projects, he can bother me about this one.

Mag conversions, as mentioned, are taken care of. Drop in parts. I will be investigating baking the mags for heat treat to strengthen them if I can figure out just the right temp and time. This will be my first attempt at this and these are thin parts.
The machinist has two bodies to play with... 4 chances to make something work. We decided that even .001" offset drilling from each end was acceptable- this can be accounted for with the flexihone and a tapered front end to the bolt. I think the most promising attempt will be the 12.5mm (.492") reamer. He was just as worried about "push out" as everyone in the previous thread.

I seriously F'ed my first attempt at doing this myself. I have a body that i have milled the top off of back to the breach. I will probably mill the rest of it off and Alumiweld a brass tube to the top and remake the whole top end for that one, just to see if i can.

Velocity isn't something I'm even considering yet. Yes, fps will be low. I don't know how far you can crank a stock KT (and now i have no body to rebuild mine and test it), but I am guessing into the 300-350 range since that's what the other .43 pistols do. I will need to really tear into the KT parts and figure out what might be expanded for more power. I was "side winder-ing" rounds before bottoming out the adjustment screw, so I'm pretty sure we might be close just maxing it out.

Related to that- new bolts are easy to make, and I plan on adding three orings. One to the front of the bolt, trying to seal the breach, and one on either side of the inlet hole. The bolt does not connect to the transfer rod running to the front, and it is lower in the body and won't interfere with having material removed. I am hoping to make them from a piece of round stock in the appropriate size- one core drill, one side hole, one pin hole, one set screw hole. Bolts will be aluminum or delrin is my guess right now. I also have some 1" grey PVC something-or-other i might try. It seems to turn well and has little thermal expansion.
OH- we might even be able to just turn some steel bolt or set screws down and just thread the pin hole instead. this would save drilling and threading the set screw hole, reducing part cost. I'm thinking one end threaded, to go into the bolt, the other end just a smooth pin in the stock diameter.

I'm not sure what to say about the slide. We could eliminate it, but I personally don't like the body shape without it. We cant just mill off the slide... slides... because of the weakness of the body already. There is also little to grab on to to cock the marker. On the other hand, the slide is large and makes the marker even bigger. That said, I did make 3d printed bodies that slip on, to turn the KT into an (almost full size) M6G from Halo, so who am I to say the gun is too big lol.

[Ratzkie]

OK, after about an hour of playing with all of the parts and getting an understanding of the operation of the marker, I can only suggest one way to increase fps. This is not permanent.

Requiring only a few pieces to be removed to be implemented (transfer rod side panel, transfer rod, adjustment cover, front hammer). This is adding a "puck" inside the front hammer to help compress the spring a little more. Making these out of aluminum rod stock would be fairly simple (on a lathe), and might even be something I could bundle in the conversion kit. From 1/16" to 1/8" thick, I think adding these would give us the additional "valve open" time to increase the velocity back to 280-300. This would (greatly?) increase waste gas as more power would be released to blow the rear hammer back (recock) as well. Kickback would increase as a result.
I'm ok with trading efficiency for accuracy and range.

[un2xs]

How goes the project? Did your puck idea work? Would washers or a coin accomplish the same thing?

[Ratzkie]

Sorry guys, the machine shop has been busy. I skipped the last two weeks and called again today. He went out to his tool storage and found the drill and reamer or two reamers or whatever and hes ready to do it but needs to find the time.

Coins are far too large to fit in the hammer bore. Looking at something around than .25" here. You might be able to find washers this small, but they are going to be pretty thin. You may need several to shim the spring out enough.

[Ratzkie]

Still waiting on the machine shop. I'm not a multi thousand dollar a week customer, so it's a matter of finding the time in the day to do it. It's a small shop with only two guys, and they are super busy. I'm hoping he has good news for me when I call back in the morning. One of these days maybe theyt will get fed up with me calling and get it done. For what is maybe an hours worth of work (and I'm not even that fast at it), it's been more than 3 months now...

[DavidBoren]

It's always a process...

[Ratzkie]

Approaching 5 months as of another week, lol. If this works, I'll need to find another shop to do any more of them. I love supporting small shops, but this place does not need any support from us.
I will be calling again in the morning to find out if they are done.

[infamoussmiley]

I think I have some junk bodies...

[MrKittyCatMeowFace]

Ratzkie Found one on shopgoodwill

[Ratzkie]

The prices of stuff there blow my mind. Not only are they horribly above market price, and people are still bidding, but then you have to add shipping on top too...

[MrKittyCatMeowFace]

Ratzkie i consider myself lucky to have found that site before it got to populated. you used to basically steal markers and gear for well under their worth constantly. ill put some blame on myself since i did introduce some people here too shopgoodwill by me posting links to their on this forums Cool Finds section

[Ratzkie]

Hall. Effing. Luja.
I picked upt he bodies on thursday. Here's the scoop.

He only did one, because the machinist noticed that the breech hole blew out and he doesnt know what this is or how it works so he dodnt want to ruin the second one. Jokes on him, the breech is all closed up with the angle adaptor block. So no issues there, other than light clean up with a dremel.

I just got done reassembling the marker (it's been 9 months, it took me a few minutes lol), and it appears to be working other than a super loose bolt. So that's the next step is to get a correctly sized bolt. I'm looking at like 12 or 12.5mm rod and then doing orings for increased sealing.

After that, I can test the other stuff we talked about, getting the fps up to something useable (hopefully 280!).

[Ratzkie]

Also, I can post photos now! Thanks to whoever did a thing and cleared that up!

[Tarak]

I've got one of these lying around and would totally be interested in some sort of conversion kit and mags if you ever get that far. Good luck mate!