Comparing TX MKl, MKll and LGV pistons
I'm constantly tinkering. Thought I'd post a picture of them. I wonder if perhaps we should try going with a heavier piston in the TX instead of a lighter one. All three pistons give similar output power with a .118, 27 coil Vortek spring. Approx 11.4ftlbs. Very little preload. I will eventually try a .113 or .115 spring with 28 or 29 coils. I like the feel of the heavier piston.
NOTE I made a mistake in the descriptions. But I'm not going to take the gun apart right now just to take another picture
TX MK II piston is 16cm long 92mm stroke
TX MK I piston is 17cm long and 82mm stroke.
I heard rumor that the 22mm set up may be hard on scopes. Don't know for sure though.
Chris, the MarkII piston in the picture is the MarkII FAC version. It's about 5 mm shorter stroke than the MarkIII. You will also come across the standard MarkII with the same piston as the MarkI. I tried the LGU piston that was lightened to 195 gr and it was used with the comp. tube plug shortened from the back. This removes the oring groove and adds 3 mm of stroke, but shortens the transfer port, which is supposed to be good. I didn't like it at all and it struggled to make 11 ft. lbs. I went to the FAC MarkII piston, like in your picture, and a fairly soft spring. Easy to cock and easy 12 ft. lb. gun. I like it this way as well as the MarkI piston with a little more spring. The joy of the TX200, so many options. I would like to try the 22 mm set up some day.
Not to sidetrack Jerry, but
Is there a spring you recommend for your FAC MKIII setup for 12 ft lbs?
I recently purchased a Maccari MKIV TX200 which has one of his Volcanix springs in it for around 14 ft lbs. I'm going to try it as is for a while, but have a feeling I'll want to drop the velocity down to match my MKIII.
The .118 27 coil is plenty for 11.5 ftlbs but I think it would be better with a little more preload. I think .113 with 29 coils would be a little more optimum. Vortek's new 12ftlb kit would be one of my top choices. I like maccari springs also. They seem to be a little softer shooting then Vortek. I'd look for a .113 or .115 spring
As far as the weight of the piston goes I know its going in the opposite direction to present thinking but my TX shoots very well with the heavy piston. I'm surprised it makes easy power with such short stroke also. That may be the reason for the nice shot cycle. The piston isn't traveling very far to build power.
The problem with using the MKIII piston at 12ftlbs is the shot cycle. It's going to be real slow compared to the MKI or MKII. The MKIII engine will easily do 16-17ftlbs. Slowing the output to 12ftlbs is not optimal. You can do 12ftlbs with 75mm of stroke. Imagine how much slower you need to make the piston go with 96-98mm of stroke.
Chris, You've got less mass but need to accelerate that piston a lot to get the power. It has to stop at some point. A human may not perceive it as such. I shot the 22mm kit and yes the felt recoil is very low but I could feel a very high frequency buzz. That's the only way I could describe it. How that translates and compares to forces produced with a heavier piston and lighter spring I don't know.
The feel and preference for a particular shot cycle I'm sure is up to the individual. How it effects accuracy I don't know either. What I do know is the TX for me is the easiest to fiddle with so it keeps me occupied.