Gen 2 Marauder and Huma regulator?

[GoneShootn]

I hope I don't try your patience with the length, but I think it would be good to first relate the background:

About a year and a half ago, I bit the bullet and bought a Huma regulator for my Gen 2 Marauder .25. I had already installed a Hill lightweight hammer and 262 spring and also a Hill high-flow nylon transfer port. Valve was then and still is stock. I wanted to get a good 16 shot tune at at least 40FPE and had hoped that some of this fiddling around might also improve the Marauder's accuracy, which was not nearly as good as I had expected. That didn't happen. As it was, the MRod was a good 25 yard squirrel gun, and that wasn't acceptable.

Anyway, I installed the regulator and just couldn't get a decent tune with that setup. I knew that the valve would need to be replaced eventually, but, unless I saw improved accuracy, that wasn't going to happen. To top it off, the new regulator was leaking down, so I removed it. I contacted Jeff at Trenier Outdoors, and he agreed to rebuild the reg at a good price. So I packed the reg into a shipping envelope, enclosed a check, sealed it, and applied a label. But, since the Marauder was shooting so poorly, I decided that I wasn't going to spend any more time or money on it so tossed the envelope on the shelf and forgot about it. That was last December, and I haven't shot the Marauder much since then, but, when I did, I was always disappointed at the results.

About the middle of this month, almost a year to the day from when I had tossed the envelope on the shelf, I was puttering around looking for something or other and came upon the dusty envelope. That got me thinking about the Marauder again. Up to that point, I had always cleaned the Marauder barrel with just patches and Ballistol and never with a brush. I decided that it couldn't really hurt anything to give it a good scrubbing with a brush and decided to do that. So I did.

I used Kroil on a .25 cal brush, and, since it would damage the Hill TP to remove the barrel, I didn't do that in order to remove the breech o-ring. I just made sure that the MRod was bottom up and barrel down so as to keep the Kroil out of the transfer port and valve. I gave the barrel about 10 trips in and out with the brush and then ran patches through until came out clean.

Long boring story finally ended, the groups tightened right up. About 3/8" at 37 yds. Got 1.7" 8-shot 100 yd group at the range. Killed 5 squirrels with 5 shots at 37-41 yds, all head shots. FINALLY! Talk about a good Christmas present. I had run a chrony string with results as follows

Beginning pressure - 2850
Ending pressure - 2000
31 shots from 837 fps to 837 fps with a high of 865 fps

In the middle of that was a string of 24 shots from 842 fps to 842 fps with a high of 865 fps. So, I dropped the fill pressure a bit before going to the range but didn't have time for another chrony run. That's where I got the 8-shot 1.7" CTC group.

Anyway, I decided to send the reg to Jeff to rebuild, so I put in a fresh check and sent it off. Service and turnaround by Jeff, right at Christmas even, was amazing. Thanks, Jeff! Now, I have some decisions to make.

First of all, the goals:
1. Accuracy, accuracy, accuracy!

2. I would like to get at least 3 mags at 40+ FPE. The 4040 tune would make me happy, but so would 3 mags at a bit higher FPE.

3. Even at HS=3-1/8, the rifle is a pain to cock, and it's way too easy to double load. I would like to change that.

4. While the Hill High Flow transfer port seems to have good results, I do not like that you must install a new one any time you remove the barrel. I would like to remove the barrel from time to time for cleaning, or whatever, and would like to not blitz the TP in the process.

Current rifle specs:
Stock valve
Valve metering screw full open
Hill High Flow transfer port
Hammer spring = 3-1/8 turns in
Hill lightweight hammer & 262 spring
Stock striker used and set all the way retracted, as the hammer and set-screw striker combo was too light and required much higher hammer spring setting
Regulator set to 135 bar but not yet installed

I realize that the best way would be to splurge for a new valve, either Hill or JSAIR, but I would like to see how close I can get without spending that $ and without DIY valve work that would require a mill. Maybe it's not possible to get very close, but just as the rifle is now, I got a pretty good 3 mag string, as you see above, so I'm hoping that the reg will let me improve on that a bit.

I did a lot of research and reading a year ago on the subject and learned a lot, but that now seems like a long time ago. So, while I will understand if anyone were to say "do your research, dummy!", I am lazy enough to politely ask for guidance from those who have already been down this road. I realize that I'm a bit late to the MRod party, yet here I am. Better late than never. I really like this rifle and would like to see it consistently perform to its capability, preferably without breaking the bank.

So any and all input will be gratefully received and greatly appreciated.

[FuzzyGrub]

IMO, if you are not going to port the oem valve or switch to a higher flow valve, don't install the reg.  Keeping your existing ports and adding the reg, your power and shot count will drop.   No need for high flowing TP with stock valve, and assuming stock barrel port.   The heavier spring was needed with the light weight hammer, but if cocking effort is too much, go back to the stock items. 

I'd do what is needed to add regulation, to get decent power and good shot string.  From a valve standpoint, you could try just opening the exhaust to 0.187" and barrel port to 0.187", which will match the high flow TP you have.  Keeping the lightweight hammer, use one of Hill's light weight valve poppet springs.  That should allow you to reduce some hammer pre-load.

[bear air]

Make sure you VMS is open too.

[triggertreat]

I agree with Fuzzy, you want to open up the valve and ports (including the barrel).  The valve ID can be opened up along with the spring retainer.  I would not go over .1875 on the valve port due to safety concerns.  The inner wall would be too thin over that.  A new HF valve would be ideal, but you can open the stock one up more.  The more you get the valve to flow air through it, the less hammer spring and dwell you'll need to reach your goal.  Also, follow Bob's (Rsterne) regulated tuning advice.  That will help you set the regulators set point correctly for the speed you want.  Your goal is very doable and many have done the 40/40 tune.

[Thane]

Did all of the above + Huma + MDS hammer+ Thinned pellet probe.

Netted 41 shots averaging 42FPE and under 1% ES on the ported stock valve. Then I bottled it for over 100 shots now.

You can do better than the 40/40 on a modified original valve.

[GoneShootn]

Thanks to all for the input.

Question:  The Hill .161 transfer port is made like the stock one and would be removable without requiring replacing the TP each time you take it out. Do I assume, then, that this TP would be too small and not appropriate for my goal and that I would therefore need to stick to the larger plastic ones?

[FuzzyGrub]

Thanks to all for the input.

Question:  The Hill .161 transfer port is made like the stock one and would be removable without requiring replacing the TP each time you take it out. Do I assume, then, that this TP would be too small and not appropriate for my goal and that I would therefore need to stick to the larger plastic ones?

Yes, that TP uses the standard rubber end seals, and is re-usable.  That is about as large as you can go, before the alum TP is too thin and starts to collapse. 

The 0.161" TP, along with opening the valve exhaust and barrel to the same, would be much better than keeping the 0.140" porting.  You will not obtain the 40/40 with it, though.   If that is your goal, or close, should stay with 0.187". 

I don't know the tubing that Tim is using, but the ones I've made, once I got the correct length and squareness, which is not that easy, were reusable for a few times.  If they show signs of visibly crushed, then they are done.  That is usually a sign that they are slightly too long.   My experience, but not with his specific TP.

[triggertreat]

The plastic  Hill TP will expand out after some shots and seal tight to the port opening.  I have reused them before, but currently my ports are .220 at the barrel port and .250 on the valve and TP.  This work was custom done by a professional though (Travis/JSAR).

[GoneShootn]

Thanks to all for the input.

Question:  The Hill .161 transfer port is made like the stock one and would be removable without requiring replacing the TP each time you take it out. Do I assume, then, that this TP would be too small and not appropriate for my goal and that I would therefore need to stick to the larger plastic ones?

Yes, that TP uses the standard rubber end seals, and is re-usable.  That is about as large as you can go, before the alum TP is too thin and starts to collapse. 

The 0.161" TP, along with opening the valve exhaust and barrel to the same, would be much better than keeping the 0.140" porting.  You will not obtain the 40/40 with it, though.   If that is your goal, or close, should stay with 0.187". 

I don't know the tubing that Tim is using, but the ones I've made, once I got the correct length and squareness, which is not that easy, were reusable for a few times.  If they show signs of visibly crushed, then they are done.  That is usually a sign that they are slightly too long.   My experience, but not with his specific TP.

Okay, thanks. If I drill the barrel port to 3/16, or .1875, that's pretty close to the diameter of the pellet. Does that cause any problems?

[Thane]

.187 is considered safe and most report no issues with pellets dropping into transfer port.

Another issue is proximity of poppet seat, very close to transfer port. As you increase the port diameter you thin the section under the seat. I wish I had known this when i drilled, I would have drilled off center, towards rear  of gun, matching the forward wall of port and maintain a thicker section at poppet seat.

[FuzzyGrub]

I have gone to 0.187" on the exhaust on two mrod valves with no issues.  I do not go directly to a 3/16" drill, but go through the number drills from stock ID to the 0.187".  The hole stays centered, vs possibly wandering.  I also opened up the pocket below the poppet, again with number drill sequence.  There I just chuck the drill and turn by hand. 

FWIW: I just did a 25 barrel port this AM using same method.   You do need a ball end tool to clean up the ridge left by the drilling.  I also smooth out the edge transition into the rifling with a 0.25" creative (sp?) point. 

[nervoustrigger]

Cratex point?  Rubberized abrasive bit?

[FuzzyGrub]

Cratex point?  Rubberized abrasive bit?

Yep, that what I meant. 

[GoneShootn]

Well, it's humble pie time. I found an old thread where you guys helped me then, too. Apparently, I was quite chatty. But, hey, that was a year and a half ago, and I'm old. I have trouble with last week, let alone a whole year plus another half ago. So there you go.

Anyway, it seems that I had drilled out the valve and barrel ports to 11/32" and had even bought and installed the Hill lightweight valve spring. Who knew? Apparently, it was right after that that the new reg began leaking, and since the rifle was shooting crappy (crappily?), I just shelved it and went on to other things.

I have ordered some .187 transfer ports from JSAR, b/c cheaper than Hill, but it seems that everything there is back-ordered, so I don't know when they might come. I guess business is good, and that is a good thing. I'm sure they'll catch up soon, but, as for now, I guess I'm in a holding pattern.

Since it's looking more like a new valve is going to be necessary, what are the options - Hill, JSAR (back-ordered), other? Whatever happened to the Cobra Valve? Did it evolve into the JSAR Balanced Valve, or what?

Also, is the MDS hammer still a good option? I remember reading somewhere that there had been problems with temperature, humidity, or something causing expansion and possible binding.

[FuzzyGrub]

JSAR is very busy building rifles.  I hear that someone else is picking up the specialty parts, but it might be a while for that to transition. 

11/32 (0.344") must be a typo, but couldn't figure out what you meant.  5/32 is 0.156", maybe 11/64 (0.172")? 

I would wait to see what you get with Hill's hammer vs changing to a MDS one.  Get it tuned where you want it, and if the cocking effort is still too much, will need a heavier hammer at the slight expense of efficiency. 

[GoneShootn]

JSAR is very busy building rifles.  I hear that someone else is picking up the specialty parts, but it might be a while for that to transition. 

11/32 (0.344") must be a typo, but couldn't figure out you meant.  5/32 is 0.156", maybe 11/64 (0.172")? 

I would wait to see what you get with Hill's hammer vs changing to a MDS one.  Get it tuned where you want it, and if the cocking effort is still too much, will need a heavier hammer at the slight expense of efficiency.

Yep. 11/64. Thanks. If, with the reg and whatever else I may wind up doing, I can drop hammer spring preload to 2 turns, as Tim Hill recommends, then that should be okay. But 3+ is still a booger.