Author Topic: MRod .25 cal Valve Mods (Read 23425 times))

gene_sc · « **Reply #20 on:** March 26, 2013, 09:09:02 PM »

Excellent Lloyd.. So the one in the picture is your own design? Again can u explain how you hold your custom valve in the air tube?

Great work

Gene

lloyd-ss · « **Reply #21 on:** March 27, 2013, 12:22:23 AM »

Bob,
I think with the mods you have made to the M-rod valve and porting you should be able to get 100fpe in .30 cal, don't you?
Two different approaches to the same problem.

Gene,
Yes, the valve is my design, but it is fairly conventional. The valve itself is still held in place with the three 10-32 socket head screws just like the stock valve, but the attachment of the breech to the tube is what makes the difference.
So as not to hijack Bob's thread, I put some more info on this thread.
http://www.gatewaytoairguns.org/GTA/index.php?topic=38581.40

rsterne · « **Reply #22 on:** March 27, 2013, 12:50:08 AM »

Hijack away, Lloyd.... not a problem, my friend.... It's all about trying to make an MRod breathe better....

Bob

GadgetX · « **Reply #23 on:** March 27, 2013, 01:37:51 PM »

PakProtector · « **Reply #24 on:** May 27, 2013, 10:03:21 PM »

Thought I'd present y'all with a power update. I got some Hunters Supply 53 gr, .251 bullets. At less than 700 fps they did not fly well...so in went a de-sleeved 22 cal valve with .160 port and sleeve on a .165 barrel port. I got 800 fps, and at 50 yards shot a 5-shot dime-sized group. Was dancin' in the streets. Throat is .250"...I suspect a bit more area between stem and port makes it work better.

Next up, taking a stock sleeve to .169" and the exhaust port to the same, maybe .172" The spot where the OE O-rings ride will be paper thin at that size, but I think I'll see a few more FPE out of it. Also planned is a stem seal. I plan to shorten the rear of the valve about 1.2mm and adding a 2mm thick plate screwed on with an o-ring stuck in between in a liddle relief volume, likely countersunk, held on with countersunk itsy bitsy screws. There is enough flow past the stem to blow moly-loaded 2C45 Krytox all over the face of the hammer( added moly powder to the Krytox and it thickens a bit ).
cheers,
Douglas

rsterne · « **Reply #25 on:** May 27, 2013, 11:25:45 PM »

Quote

I think with the mods you have made to the M-rod valve and porting you should be able to get 100fpe in .30 cal, don't you?

As an update, Lloyd, I would think it would be VERY close to that figure shooting 50 gr. JSB .30 cal pellets.... My .30 cal Disco Double has a 3/16" valve port and hit 97 FPE with a 3/16" transfer port and 102 FPE with a 0.219" transfer port, both at 3000 psi with the 46 gr. JSBs.... I'm guessing the MRod valve with 0.188" ports will be within spitting distance of 100 FPE at 3000 psi in .30 cal....

Bob

PakProtector · « **Reply #26 on:** May 28, 2013, 05:45:50 AM »

Quote from: rsterne on May 27, 2013, 11:25:45 PM

Quote
I think with the mods you have made to the M-rod valve and porting you should be able to get 100fpe in .30 cal, don't you?
As an update, Lloyd, I would think it would be VERY close to that figure shooting 50 gr. JSB .30 cal pellets.... My .30 cal Disco Double has a 3/16" valve port and hit 97 FPE with a 3/16" transfer port and 102 FPE with a 0.219" transfer port, both at 3000 psi with the 46 gr. JSBs.... I'm guessing the MRod valve with 0.188" ports will be within spitting distance of 100 FPE at 3000 psi in .30 cal....

Bob

That tears it...I'm going big...lol But seriously, doesn't speed in that regime take a bit more energy just to accelerate that much air in the barrel? I think I'd add mass to slow it down to 900 fps. All in the name of efficiency, on a rifle that is getting more shots than game spottings on a hunt.
cheers,
Douglas
cheers,
Douglas

rsterne · « **Reply #27 on:** May 28, 2013, 05:36:38 PM »

Well, the pellet choices in .30 cal are two weights of JSB, 46.3 gr. and 50.2 gr.... They are both the same length (0.38"), the heavier one has a larger waist.... We won't know how the BC changes with velocity until we test them, but they are a bit heavier than a scaled up JSB King, with approximately the same SD as a 25.4 gr. JSB Monster .22 cal.... which certainly still have a great BC in the 900s.... While it's true that there is more air to accelerate in a .30 cal barrel, there is also a bigger area for the air to push on to accelerate the pellet (and that air)....

The actual numbers that can be achieved by a .30 cal MRod will probably be heavily influenced by the length of barrel used.... If you stick to the stock 20" barrel, it could be tough to hit 100 FPE.... with a 25-26" barrel, not quite so tough.... Either way, actually tuning the gun for 100 FPE is probably not going to be great, the first shot will likely be the fastest.... To get a decent shot string I'm thinking more in the 80 FPE range would be a more likely result.... That's what I'm hoping for in my .30 cal Disco Double....

Bob

tworr · « **Reply #28 on:** May 28, 2013, 06:19:10 PM »

I'm looking forward to seeing what I can get out of my newly acquired 25 marauder.

It sounds like the bottle marauder would be perfect for these power mods as well as a longer barrel. Where can one get a 25" barrel that isn't a 257 groove?

Todd

PakProtector · « **Reply #29 on:** May 28, 2013, 07:02:24 PM »

Quote from: tworr on May 28, 2013, 06:19:10 PM

I'm looking forward to seeing what I can get out of my newly acquired 25 marauder.

It sounds like the bottle marauder would be perfect for these power mods as well as a longer barrel. Where can one get a 25" barrel that isn't a 257 groove?

Todd

I don't know about 25", but mine is a BSA I got from England, and it is only 24.5" long. But I have to say that .257 stuff is much more common, I may have to get another and barrel it thusly...lol
cheers,
Douglas

rsterne · « **Reply #30 on:** May 28, 2013, 09:53:47 PM »

.25 Auto liners from TJs are .250 groove and .243 land, which is correct for .25 cal pellets.... and bullets sized to 0.250" of course.... They are available in any length, and in 1/2" OD which will fit an MRod (and 7/16" to fit a Disco).... IIRC, he charges more per inch for 29" and longer.... They are a 14" twist....

Bob

PakProtector · « **Reply #31 on:** May 29, 2013, 09:27:27 AM »

Bob,
Any thoghts on 1/4" OD transfer sleeving with OD near the 3/16" ID? Or is it required to cut the barrel and valve to run 5/16"? I assume a drill can be taken to the breech itself fo clear the bigger stuff, or did I miss something?
cheers,
Douglas

rsterne · « **Reply #32 on:** May 29, 2013, 01:17:55 PM »

Don't have an MRod, remember, illegal in Canada... I've only punched out a .25 cal MRod valve as big as I could.... I don't know about the transfer port on an MRod, I've never seen one.... When I go to a 3/16" ID I usually go to a 5/16" OD on the Disco.... I mill a new flat on the valve and barrel that is 5/16" diameter to get a sealing surface and drill the breech and the main tube to 5/16" to clear it.... Using Teflon rod for the transfer port still works with a 5/16" OD up to a 7/32" ID.... Over that I go to 3/8" OD.... The largest I have gone with a 1/4" OD transfer port is 0.166" (the same as a poly tube port).... Thinner wall than that they tend to collapse.... You MIGHT get away with 11/64 (0.172") in a 1/4" Teflon port if you get the length perfect.... If you drill the steel transfer port sleeve in a Disco out to 0.169" it tends to buckle where the rubber seal sits.... sounds like the MRod might be similar?....

Bob

ezman604 · « **Reply #33 on:** May 29, 2013, 01:57:03 PM »

Since I just purchased another .25 Mrod, and since you cannot own an MRod, I again say send it to me or sell it to me and I'll do some real world numbers on it.

PakProtector · « **Reply #34 on:** May 29, 2013, 02:06:21 PM »

I don't know about the Disco, never seen one's insides either...LOL Motorhead has some tubing with .180 ID he's sending. Seems quite a thin wall, and like you mention, length will be critical...I hope I wind up with enough for several tries. That said, I can certainly get the barrel and valve spot faced 5/16, and deill the tube and breech the same. I confess I will be tempted to do one in Al or steel and seal it with square o-rings...and the 3/16 port is certainly attractive. Much more area than the .160 I am now running. Something will have to be done...

cheers,
Douglas

PakProtector · « **Reply #35 on:** May 29, 2013, 02:06:57 PM »

Quote from: ezman604 on May 29, 2013, 01:57:03 PM

Since I just purchased another .25 Mrod, and since you cannot own an MRod, I again say send it to me or sell it to me and I'll do some real world numbers on it.

he did call it first...

PakProtector · « **Reply #36 on:** June 02, 2013, 08:06:37 PM »

hey-Hey!!!,
With a .180 transfer sleeve, exhaust port and barrel port I got 19 shots between 790-810-790 on 750 psi of tank pressure drop. With the smaller port, the speed dropped off much earlier; it took higher pressure to maintain the speed. Peak is now 10 fps faster...but the curve is pretty manageable...

going to have to see about a 3/16 porting and 5/16 Teflon transfer sleeve as soon as I can manage it...

Pressure at start was 2k85 and I ended at 2k1 psi. Turning it up for use at 3k2 fill ought to deliver some more energy...lol...again with the 2-clip tune
cheers,
Douglas

.88 FPE/ci...

rsterne · « **Reply #37 on:** June 02, 2013, 11:17:45 PM »

Quote

19 shots between 790-810-790

What pellets?....

Bob

PakProtector · « **Reply #38 on:** June 03, 2013, 05:40:10 AM »

Quote from: rsterne on June 02, 2013, 11:17:45 PM

Quote
19 shots between 790-810-790
What pellets?....

Bob

The 53 gr that look to be from an RCBS mold. The ones from Hunters Supply that just suffered a price increase of nearly 20%.
cheers,
Douglas

rsterne · « **Reply #39 on:** June 03, 2013, 01:02:13 PM »

So about 75 FPE....

Bob

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MRod .25 cal Valve Mods

Author Topic: MRod .25 cal Valve Mods (Read 23425 times))