Tuning Marauder regulated at high pressure (2600)?

[Bugman]

I just purchased as used Marauder .177 and the seller mentioned it was regulated but had no knowledge on the make of regulator installed (he was likely second owner). I have no issues with the seller at all, but just curious about the current regulator pressure setting at 2600 psi. Is that a setting that provides better performance with certain goals behind it perhaps better accuracy, or smoothing out the known shot fps variability above that "sweet spot" in pressure. I've googled it but found no earlier threads anywhere that speaks to the that pressure other than that being the beginning of a flat series of fps numbers. I've pumped to 3000 psi and the gauge consistently settles in at 2600 until pressure drops under this mark so it appears to be regulated.

Eventually I'll tear down this rifle for a look see to identify the regulator make and learn how to do repairs (o-rings coming in soon from Oring Store), but currently just trying to understand more about the Mrod as inexperienced owner of this rifle with a goal of "pesting" some flying rats. 

All comments welcome. Thanks!

 

[dizzums]

22-2800 indeed is the 'known' sweet spot for unreged marauders so its likely spot on for power and accuracy ..its counter intuitive, but most pcps do NOT make more fps and accuracy with max fills ..not without mods and deviating from factory tunes ..

 

[nervoustrig]

A 2600psi setpoint for 3000psi reservoir is highly unusual. With such a restricted pressure range, might as well tune it conventionally for a bell curve. In a regulated setup, seldom will the setpoint be above 2000psi or so. For example, you might go up to 2200 or 2400 if setting it up to run super heavy slugs. For pellets, generally in the 1400 – 1800 range.

These generalizations all assume the porting is appropriately sized. In the case of a conversion like yours, the OEM porting was suited for a bell curve centered somewhere around 2500psi. To generate similar FPE at a lower pressure (regulated), the owner will generally enlarge the ports so it can flow better. So one possibility is the previous owner did not do that and therefore had to use a really high setpoint to get the power he wanted.

What velocities are you getting and with what pellet weight?

 

[PigeonMan]

Who one earth turn their 3000 max fill gun with such a small capacity air tube like the mrod at 2600? Lmao. You basically have 400 psi range to shoot before need to refill again lmao. I'm guessing you get like 5 shots per fill? Lmao. 2600 is for unregulated mrod only. A reg mrod should be set between 1300 psi to 1800 psi.

 

[Bugman]

Was doing some adjusting this morning for a low pfs range around 725 (to be quiet around horses). When I purchased this was tuned to around 925fps with jsb exacts 10.34gr. Shot great with that, but need a little more "moderation" to be animal friendly. I do have a Tatsu to use with it, but trying to be a quiet as I can get so thus the effort. I'm attempting to get to 725 with an efficient tune. My first attempt got to that range but, you know, I have to tinker a bit. So trying to optimize spring preload to stroke. After maximizing that with the given velocity set screw setting, so I went in to see where it was set to begin with and it was 1 1/8 turns out. Pretty low. I've since brought that in a bit to get to around 70-715 and that seemed to quiet it down quite a bit. 

When I tear this down I will adjust the reg down, but again, using it now to eradicate some pigeons and waiting for orings to have on hand. 

 

[Bugman]

Understood, but it doesn't fall off a cliff from a fps standpoint below 2600, as still witihin the old "stock" usable range. But yeah, when I break it down I will regulate down quite a bit....

 

[triggertreat]

Could be a reg in need of a rebuild and is creeping up that much, which is common. For a .177, I wouldn't imagine needing more than a 1800 to 1900 psi set point for the best tune and shot count. I only run a 2200 psi set point on my modified .25 cal to reach 54 FPE.

 

[Bugman]

Could be a reg in need of a rebuild and is creeping up that much, which is common. For a .177, I wouldn't imagine needing more than a 1800 to 1900 psi set point for the best tune and shot count. I only run a 2200 psi set point on my modified .25 cal to reach 54 FPE.

I'm beginning to think this might be the case. The pressure gauge seems to "stick" at a few different plateaus, around 1700 or so, then it moves up to 2600 when I pump it back up. I believe a newbie tear down is in order this week. Hopefully the orings I have in will cover this unknown regulator as well. 

 

[Bugman]

Ok. Mystery solved somewhat. I tore down the Mrod this morning and found a Huma regulator (great news....) as I was wondering if their was a regulator at all. So I suspect that a rebuild is in order given that nobody would regulate with pressure that high. I will order rebuild parts. 

Question: While I have this gun torn down, should I repair any other valve related parts (valve stem) given that it looks like it has been shot a lot over the years. I plan on replacing all the orings (oring store is great!). I have to order parts from Crosman Monday for other stuff so while I'm at it....

 

[lennyk]

Ok. Mystery solved somewhat. I tore down the Mrod this morning and found a Huma regulator (great news....) as I was wondering if their was a regulator at all. So I suspect that a rebuild is in order given that nobody would regulate with pressure that high. I will order rebuild parts. 

Question: While I have this gun torn down, should I repair any other valve related parts (valve stem) given that it looks like it has been shot a lot over the years. I plan on replacing all the orings (oring store is great!). I have to order parts from Crosman Monday for other stuff so while I'm at it....

there's not much else to "fix" in a mrod lol

you can open the valve and check the condition of the poppet, it may be squashed a bit and replace it

if you want to go tuning route you can install a lighter hammer and lighter valve spring