9mm and .308 cal Disco Build

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Offline rsterne

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9mm and .308 cal Disco Build
« on: December 24, 2011, 05:12:46 PM »
I got some time over the past few days to start my Big Bore Disco project.... I started with a collection of Disco parts, some new, some used, and I made a copy of the Disco gauge mounting block (complete with the stock 1/8" through hole) and built what amounts to a stock Disco main tube assembly, including a stock fill fitting, valve, hammer with cocking pin, hammer spring, end cap, and trigger assembly.... The trigger assembly and the hammer were polished, and the trigger spring was changed for a lighter one and the "3-screw" mod was done, so I have a nice 2-stage adjustable trigger.... I didn't bend the sear spring to reduce the second stage pull weight, so the total trigger pull is just over 2 lbs....

I recently received some new hammer forged barrels from Stan at AERO-TEC, including a 24" long .357 cal with a 6-groove 1 in 16" twist and a 24" long .308 cal with a 4 groove 1 in 20" twist.... Both barrels are 1/2" OD, and I also received the prototype of a Big Bore Riser breech I designed.... The breech is made from a 3/4" x 1" billet of 6061-T6 aluminum and anodized.... It has a 3" deep socket for the barrel with two 8-32 set screws to locate it.... The front of the breech has a short stub designed to mount a 3/4" OD x 0.035" wall aluminum tubing shroud, located by two 6-32 screws.... There is plenty of clearance between the main tube and the barrel to allow for the shroud.... The idea is to make the two barrels interchangeable, using the same breech and bolt assembly.... I machined identical barrel ports in them with a 7/32" through hole and a shallow 1/4" counterbore for the transfer port to sit in.... The transfer port is made from a short piece of 1/4" brass rod with a shoulder on the bottom for the stock Crosman TP seal.... although a poly port can also be used.... The barrels both have small flats for the setscrews, and the chambers were cut using a tapered reamer so that the portion between the barrel port and the end is slightly over 3/8" to clear the nose of the bolt.... In the case of the .357 barrel, that meant the rifling started about the middle of the barrel port and was full depth about 1/4" forward of the port.... On the .308 barrel, the rifling starts ahead of the transfer port, and in fact you can push a 120 gr. bullet far enough that the base of the bullet is about level with the back of the barrel port before it touches the rifling....



The rear mounting screw for the breech is 8-32, and the head protrudes into the bolt passage about half way.... The front mounting point for the breech is still under the bolt in the loading trough, but it is increased to 6-32, and the front hole in the Disco tube was drilled and tapped to match.... A small recess was ground in the top rear of the Disco valve to miss that screw.... One thing I noticed about this Disco valve was that it didn't have the usual O-ring seal for the valve stem.... I don't know if Crosman forgot it, or if they are cheaping out and leaving it off on purpose.... The weird thing is that there is no machining to even allow the installation of the O-ring, the back of the valve is just flat.... I have purchased one Disco valve since this one and it had the O-ring again.... so I don't know which is current production....

The breech seal is achieved by a 1/2" OD x 3/8" ID O-ring held captive between the end of the barrel and the breech.... The bolt, which has a probe to push the pellets past the transfer port, has a 3/8" nose that seals in that O-ring.... Since the O-ring is pinched just slightly between the barrel and breech, the ID was a bit under 3/8" and it was necessary to polish down the nose of the bolt slightly for the proper fit.... A 9mm pellet slides through the O-ring without friction, however.... The rear section of the bolt is 9/16" diameter.... This allows the bolt to catch the stock cocking pin for the hammer.... but in order to do that, it needs a groove machined in it, wider at the rear to miss the head of the rear mounting bolt....  Once the bolt is rotated to the locked (firing) position, there is an addditional (offset) groove required for the cocking pin to travel in without touching the bolt.... That groove is the one closest to the bolt handle.... I know it looks complicated, but the machining can be simplified now that I have made this prototype....



The bolt is designed so that when drawn to the rear, the front mounting hole is exposed, and when forward, the rear screw is just behind the back of the bolt.... The breech assembly can therefore be removed without removing the bolt from the breech first.... The slot allows for a large travel, and the loading port is long enough for at least a 120 gr. (maybe even a 150 gr.) .308 bullet.... The bolt handle is made from a 2" long 10-32 SHCS with the threads shortened.... The hole in the bolt is 1/2" deep (ie blind) and the screw tightens against the bottom of the hole.... The knob is from a piece of 5/8" diameter brass, 7/8" long.... It is drilled 5/16" to a depth of 0.70" and then tapped 3/8-16 NC for a 1/2" long stainless SHSS.... When the set-screw is tightened, it pinches the head of the bolt handle, making the handle assembly rigid.... The handle is installed using the 3/16" hex in the end.... Also shown is a barrel band which matches the breech in height.... It has an 8-32 set-screw in the lower portion, but has an O-ring in the upper portion to "semi-float" the barrel.... I have another band which is designed to be used with a 3/4" OD shroud, located by a set screw in both openings....

Now to put this thing together and take a few shots.... I expect the velocity to be well under 500 fps with all the stock Disco components.... I plan to test it on CO2 as well as on HPA, so stay tuned....

Bob
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal:
.177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine (Grouse Gun), 2260 PCP Rifle (37 FPE), 2560 PCP Rifle (52 FPE), .22 BAM B-26, .22 BAM B-51, Hatsan AT-4410 Long (70 FPE),
"Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, .308 & .357 unregulated; working on the Mk.III, a .410 shotgun, and .458 cal)

Offline Butcher45

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Re: 9mm and .308 cal Disco Build
« Reply #1 on: December 24, 2011, 05:30:17 PM »
I've always liked the idea of a .308/.32 Disco with a twist rate suited for lightweight slugs.  Shrouded.  What a fun walk-around sqwerl gun that would be!

I'll be watching this build with enthusiasm.

Offline Gary

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Re: 9mm and .308 cal Disco Build
« Reply #2 on: December 24, 2011, 06:27:06 PM »
This interests me. Have you done any mods to the valve? I wouldn't think a stock valve would have enough power to push a bullet out the barrel but what do I know.
Gary

Offline airpuffhunter

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Re: 9mm and .308 cal Disco Build
« Reply #3 on: December 24, 2011, 06:43:54 PM »
come on Bob, those disco conversion are always interesting.
I hope it goes well, and perform better than spected
« Last Edit: March 21, 2012, 05:01:23 PM by airpuffhunter »

Offline Rescue35

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Re: 9mm and .308 cal Disco Build
« Reply #4 on: December 24, 2011, 07:12:45 PM »
so stay tuned....

Bob

Like you had to tell us to do that.

Looking good Bob, keep it up.
  • Trenton, TN
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Offline rsterne

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Re: 9mm and .308 cal Disco Build
« Reply #5 on: December 24, 2011, 07:54:38 PM »
Just a quick report.... The Disco valve does leak out the back around the stem when fired, so I replaced it with another which does have the O-ring.... I also have some blow-by past the O-ring that seals the bolt, I'm going to have to chase that down.... As I figured, the small hole in the gauge block is starving the valve for air and the velocities are down quite a bit compared to the Carbine I did.... I don't think the lack of velocity is due to the enlarged exhaust ports in the valve in the Carbine because I got 498 fps with a stock diameter (0.140") transfer port.... In any case, here are the preliminary results, with two different hammer springs and on CO2.... 77.8 gr. EunJin pellets....

Stock Disco valve and ports, stock gauge block (1/8" hole)

Pressure .... Disco Spr.... 0.040" Spr.

2000 psi ...... 290 fps ...... 355 fps
1500 psi ...... 350 fps ...... 390 fps
1000 psi ...... 350 fps ...... 380 fps
800 psi ....... 340 fps ...... 340 fps

CO2 (70*F) ... 315 fps ...... N/T

The next step will be to drill out the through hole in the gauge block to at least 1/4" so that the average pressure at the inlet of the valve during the shot cycle will be higher.... With the tiny 1/8" hole (which is stock for a Disco) I'm effectively trying to get 40+ FPE of output from only about 5cc of HPA.... and as you can see, it's just not working.... I know the potential is there because I saw over 70 FPE from the Carbine during testing.... Now to pull it apart yet again....

Bob
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal:
.177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine (Grouse Gun), 2260 PCP Rifle (37 FPE), 2560 PCP Rifle (52 FPE), .22 BAM B-26, .22 BAM B-51, Hatsan AT-4410 Long (70 FPE),
"Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, .308 & .357 unregulated; working on the Mk.III, a .410 shotgun, and .458 cal)

Offline rsterne

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Re: 9mm and .308 cal Disco Build
« Reply #6 on: December 26, 2011, 10:28:11 PM »
I drilled out the gauge block today to a 1/4" through hole, and as expected the velocity increased.... However, it was still under 500 fps....

Stock Disco valve, gauge block drilled to 1/4", 0.040" wire spring @ stock preload

2000 psi .... 390 fps
1500 psi .... 450 fps
1000 psi .... 390 fps

The gun is getting a lot of shots, I'm guessing well over 20 between those pressure points.... It would appear that the ports in the stock valve are simply not big enough and/or smooth enough to flow enough air to get over 35 FPE.... Since my Carbine, with a shorter barrel, did that at similar pressures (the valve was ported out) it was time to pull the gun apart again and hog out the valve.... I milled out the exhaust port to 3/16" on a 20 degree angle, drilled the valve throat to 1/4", and streamlined it with my Dremel.... Then I bored out the valve to 0.62" ID (mostly to allow more flow around the head of the poppet), leaving only 2 threads, and shortened the front end to match.... I then tapered the inlet portion and countersunk both ends of the gauge port to streamline the flow.... There is still more that can be done by making a new valve front end with larger passages to eliminate the gauge block, and thinning the valve stem, but I'm trying to learn as much as possible by doing things in a progressive manner.... I also fixed the air leak around the nose of the bolt by simply lubricating the O-ring so that it could move a bit.... Sometimes the fix is almost too simple.... This time I saw quite a large jump in velocity.... Still using the 77.8 gr. EunJins....

Bored out valve and ports, streamlined gauge block and valve inlet, 0.040" wire spring @ stock preload

2000 psi .... 460 fps
1600 psi .... 525 fps
1400 psi .... 545 fps
1200 psi .... 540 fps
1000 psi .... 490 fps

I decided to try a heavier hammer spring, just shy of coil bind and got a few of shots right around 2000 psi of 660 to 680 fps (80 FPE).... so the potential is definitely shaping up.... I plan on doing the remaining valve mods next and eliminating the restriction of the gauge block....

Bob
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal:
.177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine (Grouse Gun), 2260 PCP Rifle (37 FPE), 2560 PCP Rifle (52 FPE), .22 BAM B-26, .22 BAM B-51, Hatsan AT-4410 Long (70 FPE),
"Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, .308 & .357 unregulated; working on the Mk.III, a .410 shotgun, and .458 cal)

Offline rsterne

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Re: 9mm and .308 cal Disco Build
« Reply #7 on: December 28, 2011, 10:23:53 PM »
I made a new valve front end today to incorporate the gauge block and increase the diameter of the through hole.... I moved the O-rings to in front of the gauge hole so that I wont have to deal with shredding O-rings as they pass the hole in the tube for the gauge.... Even though it's deburred, it's a PITA to keep the O-rings stuffed deep enough as they slide past.... so now I don't have to worry about it.... While I was at it, I shortened the threads by 0.20" to help open up the flow inside of the valve....



One of the choke points was the hole in the spring seat in the valve front end, and there is little point in drilling it out because the spring is just over 1/4" ID.... Sooooooooo, I tapered the spring.... I used progressively larger drill bits, inserted the shank end into the spring, and tapped the spring with a hammer on an anvil to increase the diameter.... I ended up with a spring that is stock at one end to fit the valve poppet, and 3/8" OD x 19/64" ID at the other end.... I stress-relieved the spring afterwards by heating it at 500*F for 1/2 hour.... The larger spring ID meant I could drill the valve front end out to 19/64 which increased the area for airflow into the valve by 41%.... Compared to the restricted flow through a stock gauge block (1/8") it's an increase of over 5 times.... The valve now has 2.5 times the area on the inlet end than on the exhaust end.... so the entire reservoir can keep the pressure up in the valve during the shot cycle....   



Other mods include drilling the valve throat out to 1/4" (from 7/32") and thinning down the valve stem from 5/32" (0.157") to 0.115" The exhaust port in the valve has been opened up to just over 3/16" (from under 5/32") and angled 20 degrees and streamlined.... The new ports are 70% larger than stock and a much more direct path.... I also bored out the inside of the valve to 5/8" (from about 1/2"), not so much to increase volume as to unshroud the head of the valve poppet and ease the passage of the air around it.... and shortened the threaded area as well.... The threads are in compression, all they really do is hold the two halves of the valve together to seal the O-ring between the halves.... so strength is not really an issue there.... The tightest restriction in the whole system is the exhaust portion of the valve, everything else has greater flow areas.... I also shortened the valve stem by 0.090".... It now barely protrudes from the end of the valve when the spring hits coil bind (which limits the travel).... and the increased hammer travel will allow the hammer to have increased momentum when it strikes the valve....

All in all, I'm pleased with the progress and look forward to reassemblling the gun with the new valve parts.... Once those trials are completed I will likely work on a new hammer....

Bob
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal:
.177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine (Grouse Gun), 2260 PCP Rifle (37 FPE), 2560 PCP Rifle (52 FPE), .22 BAM B-26, .22 BAM B-51, Hatsan AT-4410 Long (70 FPE),
"Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, .308 & .357 unregulated; working on the Mk.III, a .410 shotgun, and .458 cal)

Offline Rescue35

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Re: 9mm and .308 cal Disco Build
« Reply #8 on: December 29, 2011, 12:09:48 AM »
Not only do you do great machine work and understand the fluid mechanics that take place inside an air gun but you do a great job of documenting and explaining all of it. Thanks Bob and I'm looking forward to your next installment on this project.
  • Trenton, TN
"Research is what I'm doing when I don't know what I'm doing." -Wernher von Braun

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Offline rsterne

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Re: 9mm and .308 cal Disco Build
« Reply #9 on: December 29, 2011, 01:18:49 AM »
Thanks Rescue35.... I've only been doing this for a bit over 4 years and when I started I was sooooooooooo frustrated at the lack of good information and documentation I decided to do what I could to change that.... so as I learn, I record and share as much as possible.... Nice to know it's appreciated....  ;D

Bob
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal:
.177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine (Grouse Gun), 2260 PCP Rifle (37 FPE), 2560 PCP Rifle (52 FPE), .22 BAM B-26, .22 BAM B-51, Hatsan AT-4410 Long (70 FPE),
"Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, .308 & .357 unregulated; working on the Mk.III, a .410 shotgun, and .458 cal)

RWSshooter

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Re: 9mm and .308 cal Disco Build
« Reply #10 on: December 29, 2011, 01:35:59 AM »
You've got my attention!  Great reading!  The workmanship looks very clean.  Thanks for sharing your experience!

Offline rsterne

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Over 90 FPE Today !
« Reply #11 on: December 29, 2011, 10:50:18 PM »
I got a chance to assemble the rifle today using the new valve.... and I'm very pleased with the results.... When I first tried the hammer spring setup I was using previously (1.75" long x 0.040" wire with the stock rear plug) I only got ~300 fps.... It only took me a minute to understand that since I shortened the valve stem the preload on the spring was quite a bit less.... I replaced the spring with a 2.00" long one (also 0.040" wire) and the velocity jumped to over 600 fps (at only 1000 psi ! ).... Now we're talking!.... I then took off the fixed end plug and installed one of my RVAs which has the added advantage that I can change out hammer springs without taking off the stock and the end plug.... I tried three different 2.00" long springs, the other two had wire sizes of 0.042" and 0.045".... I adjusted all three just shy of coil bind (ie maximum safe preload) and got the following results.... Only shots over 95% of the maximum velocity are shown....



The velocity with the 0.040" wire spring peaked at about 1400 psi at 666 fps (77 FPE) and I got 10 shots averaging 649 fps between 1800 psi and 900.... With the 0.042" spring the peak velocity was 713 fps (88 FPE) at 1600 psi and starting from 2000 psi I got 8 shots averaging 699 fps ending at 1200.... With the 0.045" wire spring I got 7 shots averaging 716 fps starting from 2200 psi and ending at 1200, with the peak velocity being 733 fps (93 FPE) at 1750 psi.... The efficiencies were 1.39 FPE/CI, 1.22 FPE/CI, and 1.12 FPE/CI respectively, so I'm quite pleased with that.... I'm pretty sure that this gun can be tuned for a few of shots at 100 FPE with a 2400 psi fill pressure and more hammer strike.... With the current hammer setup, however, I'm pretty well tapped out I think.... At least I got to put the stock on it today.... here's what she looks like....



The next step is to make a cylindrical hammer (ie no waist) and I plan to encorporate an external cocking knob with integral spring guide.... This will increase the hammer weight (and momentum) and while I'm at it, I'll probably set it up for bigger hammer springs as well.... it will depend on what I can find for springs.... While that will allow me to explore the limits of the rifle.... when you consider the small air reservoir and the fact that I already can tune the gun for maximum power with a 2000 psi fill.... they may not be very practical.... Those parts will likely be experimental only and I will probably return to the 0.045" spring and detune the gun slightly below the current maximum.... likely by installing a slightly smaller transfer port to flatten the curve and (hopefully) increase the shot count....

Time will tell.... In the meantime, I'm thoroughly enjoying this build and I'm learning a TON....  ;D

Bob
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal:
.177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine (Grouse Gun), 2260 PCP Rifle (37 FPE), 2560 PCP Rifle (52 FPE), .22 BAM B-26, .22 BAM B-51, Hatsan AT-4410 Long (70 FPE),
"Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, .308 & .357 unregulated; working on the Mk.III, a .410 shotgun, and .458 cal)

Offline Rescue35

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Re: 9mm and .308 cal Disco Build
« Reply #12 on: December 30, 2011, 10:34:45 AM »
Wow Bob,

When you mentioned shortening the valve stem I thought about the hammer also. Have you thought about turning a longer hammer (proportional to the length of stem removed) and returning to the 1.75" long spring. That would add a fair amount of mass. Although it really is mainly academic at this point. You are getting some great numbers there. This thread will be getting printed out and added to the notebook.
  • Trenton, TN
"Research is what I'm doing when I don't know what I'm doing." -Wernher von Braun

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Offline rsterne

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Re: 9mm and .308 cal Disco Build
« Reply #13 on: December 30, 2011, 01:18:15 PM »
Hammer travel is very important because the hammer has more room to accelerate to pick up velocity and hence energy and momentum.... If you keep the travel the same and change the weight of the hammer, you increase the momentum but NOT the energy.... If you keep the weight the same and increase the travel, you increase BOTH energy and momentum.... assuming you have enough spring preload to still be accelerating the hammer when it reaches the valve.... That was my problem - when I shortened the valve stem, the short spring (at low preload) ran out of steam before impact.... Increasing hammer travel works great, but you inevitably have to play with the spring.... I never tried the 1.75" spring with increased preload because I needed more power anyway and went to a heavier wire.... I do, however, have a 0.045" wire spring that is 1.75" long and it has a higher spring rate than the 2.00" spring.... I will try it (before changing the hammer), but it may not have enough travel to deal with the increased hammer travel....

There could have been another factor involved as well.... When I opened up the porting on the inlet side of the valve I increased the AVERAGE pressure during the shot cycle.... because air can rush into the valve from the reservoir easier than it can get out.... This increased pressure was likely slamming the valve shut against the now weaker spring (less preload).... and reducing the velocity in much the same way as it falls off when the valve partially "locks" in the first half of a PCP cycle....

Regarding changing the hammer length as you suggest.... it would no longer be able to catch the sear.... Plus, it would eliminate the extra travel I gained by shortening the stem, which was the whole point.... I will be making a cylindrical hammer (with cocking pin hole) that I can try by itself.... but the back end will be threaded for a cocking rod / spring guide which can be installed also.... That rod will run through the adjusting screw in the RVA and have a cocking knob on the end of it for external cocking.... The entire assembly will be significantly heavier, which will add to hammer momentum.... Lots of things to try yet....  ;D

Bob
« Last Edit: December 30, 2011, 01:20:20 PM by rsterne »
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal:
.177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine (Grouse Gun), 2260 PCP Rifle (37 FPE), 2560 PCP Rifle (52 FPE), .22 BAM B-26, .22 BAM B-51, Hatsan AT-4410 Long (70 FPE),
"Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, .308 & .357 unregulated; working on the Mk.III, a .410 shotgun, and .458 cal)

Offline Rescue35

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Re: 9mm and .308 cal Disco Build
« Reply #14 on: December 30, 2011, 02:13:28 PM »
I didn't think about the sear engagement. Duh.

Since f=m X A my line of thinking, since you had more room meant you could add mass up front. I like your idea on the external cocking, I think you had done this with one of your other guns. That will gain you the benefits of both. More mass and acceleration.
  • Trenton, TN
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1322 supercharged

Offline lloyd-ss

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Re: 9mm and .308 cal Disco Build
« Reply #15 on: December 30, 2011, 05:30:35 PM »
Bob,
Nice project and very nice of you to share such great documentation with everyone.
Lloyd
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Offline echochap

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Re: 9mm and .308 cal Disco Build
« Reply #16 on: January 03, 2012, 09:39:27 AM »
Nice gun and the best write up I've seen on a big bore build. That's a good shot string in the 700s, seems like a compact little mid range gun for medium size quarry. Again, excellent job building and communicating!
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Offline rsterne

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Re: 9mm and .308 cal Disco Build
« Reply #17 on: January 19, 2012, 05:17:13 PM »
I spent a bit of time in the shop today.... it sure felt good to be back out there.... I tried a 1.75" long 0.045" wire hammer spring, and also the same length from 0.051" wire.... The lighter one wasn't as good as the 2.00" long one I tried previously, and the heavier one was only marginally better, peaking at 736 fps.... but it was VERY difficult to cock.... So far (with the stock hammer) the best spring is the 2.00" long x 0.045" wire one....

I had a few 132 gr. cast bullets that had been sized to 0.357", and tried them out.... They were VERY hard to load, I actually had to tap the bolt closed.... They only hit 540 fps (85.5 FPE), probably because of the tight fit.... I will have to get a smaller sizing die to use with this barrel if I want to try anything other than the EunJins....

The next project is to make a new hammer with rear cocking knob and the ability to accept longer/stiffer springs....

Bob
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal:
.177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine (Grouse Gun), 2260 PCP Rifle (37 FPE), 2560 PCP Rifle (52 FPE), .22 BAM B-26, .22 BAM B-51, Hatsan AT-4410 Long (70 FPE),
"Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, .308 & .357 unregulated; working on the Mk.III, a .410 shotgun, and .458 cal)

Offline ronbeaux

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Re: 9mm and .308 cal Disco Build
« Reply #18 on: January 19, 2012, 09:00:43 PM »
I soo look forward to your posts and knowledge. I am committed to advancing in the machine techniques. Thank you!!
DAQ 308 and 458
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2250B
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Sheridan E9A in .20

Offline lloyd-ss

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Re: 9mm and .308 cal Disco Build
« Reply #19 on: January 20, 2012, 02:44:10 AM »
......... I had a few 132 gr. cast bullets that had been sized to 0.357", and tried them out.... They were VERY hard to load, I actually had to tap the bolt closed.... They only hit 540 fps (85.5 FPE), probably because of the tight fit.... I will have to get a smaller sizing die to use with this barrel if I want to try anything other than the EunJins....

....
Bob
Bob, I have some"real" sizing dies and then I have some home made ones that are basically blocks of steel bored out to the correct size.  They don't do a very pretty job, but they work well enough for getting a correct fit for velocity testing.  I just put the bored block on the drill press and use a drill blank in the chuck to push the bullet thru the die.
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An engineer by nature. The affliction is knowing that everything can be made better.
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