Author Topic: Regulating the .25 M-rod ... Early numbers in ... read em & weep ! (Read 7172 times))

Motorhead · « **on:** July 12, 2015, 08:23:13 PM »

For years the word has been DON'T regulate a .25 cal M-rod, low power and too few shots to be had.
I believed this and said it myself many times !!
Then along comes a customer who JUST HAS TO HAVE IT DONE

... so based on what has been learned these past couple years went about doing the .25 based upon this work.

* This thread is to be an on going one and will be uploading some pictures for those who may wish to attempt this on there own

Needless to say I'm pretty happy with end results.

Gen II .25 cal Marauder, 3000# fill, 2000# Reg set point, JSB 25.4 kings.

1) 864 fps
2) 867 fps
3) 867 fps
4) 868 fps
5) 868 fps
6) 865 fps
7) 866 fps
866 fps
9) 863 fps
10) 865 fps
11)865 fps
12) 865 fps
13) 864 fps
14) 860 fps
15) 864 fps
16) 853 fps
~~~~~ Coming off Reg @ 2000#
17) 863 fps
18) 866 fps
19) 863 fps
20) 844 fps
21) 856 fps
22) 847 fps
23) 847 fps
24) 842 fps
25) 833 fps at @ 1600#

Gun comes off the reg right under bell curve peak and give a few more good ones before falling away.

* This is at 42+ ft lbs power
Ave-fpe/cu-in .8
@ 63 psi per shot

Actual mod photos to follow ...

Sfttailrdr46 · « **Reply #1 on:** July 12, 2015, 08:36:25 PM »

Very interesting, now I may have to reconsider and keep the Gen II .25 as a test bed for the future of my tinkering needs

mcc1961 · « **Reply #2 on:** July 12, 2015, 09:05:24 PM »

Very nice string!!

Rdsail · « **Reply #3 on:** July 12, 2015, 09:09:24 PM »

nice job! how much pleanum or tube lenght did you use?

MicErs · « **Reply #4 on:** July 12, 2015, 09:15:12 PM »

Pretty good. Imagine regulating that thing in .22 to something like 20 fpe. Might be nice.

Rdsail · « **Reply #5 on:** July 12, 2015, 09:17:50 PM »

Now you got me thinking. I want to regulate mine at 87fpe.

I should be able to get about 30 shots with the 500cc bottle.lol

Motorhead · « **Reply #6 on:** July 12, 2015, 09:26:17 PM »

Quote from: MicErs on July 12, 2015, 09:15:12 PM

Pretty good. Imagine regulating that thing in .22 to something like 20 fpe. Might be nice.

Already done it ...
50 shots in .22 cal w/18.1 gr @ 865 fps & 30 ft lbs.
80+ shots in .177 cal w/10.3 gr @ 900 fps & 19 ft lbs.

FuzzyGrub · « **Reply #7 on:** July 12, 2015, 09:39:52 PM »

Nice! You squeezed out three more shots than my 25 synrod, at about the same power and Es. Your plateau is a slightly flatter.

caniborrowsomeammo · « **Reply #8 on:** July 12, 2015, 10:57:20 PM »

Scott, I was filling my Srod to 3400-3500 PSI, sure it isn't recommended, but wouldn't that give more usable shots?

Frank in Fairfield · « **Reply #9 on:** July 12, 2015, 11:55:10 PM »

16 shots at 41-42fpe is good enough for me.
If I want to shoot a lot I shoot the .177.
Cheaper, too.

Motorhead · « **Reply #10 on:** July 13, 2015, 12:04:28 AM »

Some pictures ...

Bored out gen II valve to within .010" of seat. Tho not in Pic, throat size opened up as well.

Valve body cap gets a Bigger hole & Shortened threads, Conical poppet spring of much less tension.

Transfer threw body opened to @ .170" and TT seat squared even and centered within hole once within main tube.

Gauge manifold opened both ends to .750" and then opened up above gauge threads.

The "Stack" ... as put back into the tube, added plenum spacer being @ 1 1/4" long thin wall tube.

Acetal / delrin transfer tube w/o out seal rings. ( Compression fit ) 265" o.d. X .170 i.d.

New style cocking bolt with flow around probe, thinned and tapered.

Two turns of hammer spring pre-load, using a custom 26 gram LW hammer ... 25.4 JSB King.

Yup no need for more hammer, less works better ... 42+ ft lbs of power on a 26 gram hammer

Noise ... very little being very quiet for power being produced.

SpiralGroove · « **Reply #11 on:** July 13, 2015, 03:11:56 AM »

Hey Motorhead,
As usual, very nice work

Have you ever tried a LW hammer and or spring guide in a QB?
Kirk

Hey Santa Rosa, Scott: Sure, more shots until one day she blows up on you. I don't think anyone on this site would recommend what you're suggesting.

Sfttailrdr46 · « **Reply #12 on:** July 13, 2015, 06:24:08 AM »

Quote from: caniborrowsomeammo on July 12, 2015, 10:57:20 PM

Scott, I was filling my Srod to 3400-3500 PSI, sure it isn't recommended, but wouldn't that give more usable shots?

Although there is some wiggle room in the safety factor of the design of the air tube I would not want to have the rifle next to my face on a regular basis with the over pressure you are filling to

Motorhead · « **Reply #13 on:** July 13, 2015, 11:36:18 AM »

Quote from: caniborrowsomeammo on July 12, 2015, 10:57:20 PM

Scott, I was filling my Srod to 3400-3500 PSI, sure it isn't recommended, but wouldn't that give more usable shots?

Absolutely NOT !!
These rifles are 3000# rated and would only go 10% over that at most. Being regulated does buy you some shots at the higher fill pressures because you don't get valve lock. But don't get greedy and have rifle unsafe to you or others.

RayK · « **Reply #14 on:** July 13, 2015, 12:45:35 PM »

Excellent job Scott! I suspect you are going to convert quite a few of these in the near future....

Do you know what the gun will be used for? Hunting? Competition (what event)? It should do very well at longer ranges with that power level and tight extreme spread.

Ray

Frank in Fairfield · « **Reply #15 on:** July 13, 2015, 12:46:20 PM »

"
Absolutely NOT !!
These rifles are 3000# rated and would only go 10% over that at most. Being regulated does buy you some shots at the higher fill pressures because you don't get valve lock. But don't get greedy and have rifle unsafe to you or others."

Especially.........Me!
😈😈😈😈

rsterne · « **Reply #16 on:** July 13, 2015, 12:51:51 PM »

Just as a rough guess, I'm thinking about 26 cc for the plenum plus valve volume?.... Sounds about right to give you the power you are getting at 2000 psi.... I would also guess that you have about 185 cc (11.3 CI) of volume left in the reservoir?.... Based on those guesses, for the first 16 shots down to 2000 psi (69 bar drop), you are getting a total of (16x42) = 672 FPE from (69 x 11.3) = 778 CI of air, which would be 0.86 FPE/CI.... However, for 21 shots (presumably down to 1800 psi), that is up to 0.94 FPE/CI, which leads me to suspect that you are actually at about 2100 psi after shot 16, not 2000, as the efficiency shouldn't increase as the pressure drops below setpoint.... Either that or the charge is a bit warm after filling, and your pressure is dropping due to cooling in the first couple of shots in a non-linear manner.... ie you are actually starting at about 2900 psi after the temperature stabilizes.... In any case, just under 1.0 FPE/CI isn't too bad.... I think a larger plenum would move you to over 1.0 FPE/CI, and allow you to drop the setpoint pressure 100-200 psi.... but the resulting shot count may not increase at the same power level because of the smaller reservoir left over.... It's always a trade off with in-tube regulators....

The string is great, nicely done.... I like the way the velocity is stable down to about 1800 psi, you're right on the knee of the curve, for sure....

Bob

moorepower · « **Reply #17 on:** July 13, 2015, 01:50:53 PM »

Would you care to share the part # of the conical spring?

Nick_59 · « **Reply #18 on:** July 13, 2015, 10:23:20 PM »

Nice work. Haven't seen a probe like that before. That reg is very small, who made it?

Motorhead · « **Reply #19 on:** July 13, 2015, 10:27:56 PM »

Quote from: Suntan Sid on July 13, 2015, 10:23:20 PM

Nice work. Haven't seen a probe like that before. That reg is very small, who made it?

Newer GenII rifle, so it must be whats current over the hollow flow threw type.
Regulator is a Dutch HuMa universal sized to tube.

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Regulating the .25 M-rod ... Early numbers in ... read em & weep !

Author Topic: Regulating the .25 M-rod ... Early numbers in ... read em & weep ! (Read 7172 times))