So I couldn't help but try again, this time the goal was as per the original goal I had, to keep the OEM seat intact and port the valve to 90% or greater. It was actually really easy...but I can only say that after failing and learning from the experience.
My first step was to drill the throat to .2345". I used the stock spring retaining cap as a centering tool and went from .203" to .2188" and then to .2345". I then took it to .237" and later polished it really well which likely brought it to around .238". My error on my last attempt was not doing this prior to drilling the exit port. I thought about plugging the stock port to create more resistance for the drill bit to help stay centered but I figured using the spring retainer cap plus not drilling the valve exit port first would both suffice, which they did.
Picture 1 shows the valve throat drilled to .2345" and the valve seat sanded down to remove the 'rim' creating more of a flat spot which is larger than my poppet od of .275":
My second step was to drill the valve exit port up to .203" at a negative angle, the degree was minimal, between 5-10...almost straight, and then dremel it the rest of the way as I desired which ended up at .226" front to back, and .234" side to side, making a .23" port.
Picture 2, 3 and 4 are of the valves exit port after being opened up. (You can see the minimal degree / cant required to achieve my porting in pic 2 on the calipers.)
I also removed .1" from the back of the valve as I prefer to create more throw than the stock marauder which aids in reducing required spring/hammer energy. I also ported and polished the surfaces really well after the pics were taken, using 600 grit and following up with automotive polish.
Right now the valve is just setup in my test rig for holding pressure, which so far it is, but I like to give thorough testing prior to tearing down my rifle and swapping valves. I'll let it sit over night and test fire it a bunch in the test rig and see where it starts to let pressure go as I am running a peek poppet and they can be stubborn at low pressures. I will likely have it up and running by this weekend hopefully with a shot or two over the chronograph that edges passed 900 fps, which isn't shabby considering my reg pressure is JUST shy of 2000 psi and I run the stock marauder length barrel of 19.5". This will all be done on just 7.7 lb of hammer spring and 48 gr of hammer. I have a 29 gr hammer that I could alternatively use but it requires 11-12 lbs of spring.
But there you have it, I knew a marauder could be taken to .23" without moving the seat forward, I didn't intend to go to .23"...it kind of just happened. I have .05~.06~" space between the valve exit port and seat which should hold up great. That is at the edge, it increases in thickness gradually as the angle in the porting changes.
***Note porting to .23" with only .238~" throat requires a .04-.045" valve stem, do not modify a stock valve stem in attempt to copy this. Upgraded materials required. Do so at your own risk***
-Matt
My first step was to drill the throat to .2345". I used the stock spring retaining cap as a centering tool and went from .203" to .2188" and then to .2345". I then took it to .237" and later polished it really well which likely brought it to around .238". My error on my last attempt was not doing this prior to drilling the exit port. I thought about plugging the stock port to create more resistance for the drill bit to help stay centered but I figured using the spring retainer cap plus not drilling the valve exit port first would both suffice, which they did.
Picture 1 shows the valve throat drilled to .2345" and the valve seat sanded down to remove the 'rim' creating more of a flat spot which is larger than my poppet od of .275":
My second step was to drill the valve exit port up to .203" at a negative angle, the degree was minimal, between 5-10...almost straight, and then dremel it the rest of the way as I desired which ended up at .226" front to back, and .234" side to side, making a .23" port.
Picture 2, 3 and 4 are of the valves exit port after being opened up. (You can see the minimal degree / cant required to achieve my porting in pic 2 on the calipers.)
I also removed .1" from the back of the valve as I prefer to create more throw than the stock marauder which aids in reducing required spring/hammer energy. I also ported and polished the surfaces really well after the pics were taken, using 600 grit and following up with automotive polish.
Right now the valve is just setup in my test rig for holding pressure, which so far it is, but I like to give thorough testing prior to tearing down my rifle and swapping valves. I'll let it sit over night and test fire it a bunch in the test rig and see where it starts to let pressure go as I am running a peek poppet and they can be stubborn at low pressures. I will likely have it up and running by this weekend hopefully with a shot or two over the chronograph that edges passed 900 fps, which isn't shabby considering my reg pressure is JUST shy of 2000 psi and I run the stock marauder length barrel of 19.5". This will all be done on just 7.7 lb of hammer spring and 48 gr of hammer. I have a 29 gr hammer that I could alternatively use but it requires 11-12 lbs of spring.
But there you have it, I knew a marauder could be taken to .23" without moving the seat forward, I didn't intend to go to .23"...it kind of just happened. I have .05~.06~" space between the valve exit port and seat which should hold up great. That is at the edge, it increases in thickness gradually as the angle in the porting changes.
***Note porting to .23" with only .238~" throat requires a .04-.045" valve stem, do not modify a stock valve stem in attempt to copy this. Upgraded materials required. Do so at your own risk***
-Matt
