Canadian Airgun Forum

I recently picked up a Marauder .177 very nice from what I can tell right now. It has a semi floating barrel with barrel band not touching the shroud/barrel. I haven't done any accuracy testing yet but ran some strings last night. I could use some tips to help fatten the curve increase shot count.

Used this guide as a starting point but it ran way too hot using Technique A. It hit over 950fps using JSB 8.4g.
https://docs.google.com/document/d/1WFD ... rO86U/edit

I readjusted the Hammer Throw (HT), Hammer Spring Preload (HS), Transfer Port (metering screw) to lower the fps. Here is my shot string. This is my first time actually running a shot string checking pressure every 10 shots. I am looking to increase FPE closer to 14FPE. If i knock off the last 20 shots I got an ES of 50.

40 Shots String
High 830
Low 736
AVG 781
Extreme Spread FPS 94
FPE AVG 11.4
AVG PSI per shot 13

Starting pressure 2500 PSI
817
817
830
813
800
767
800
813
802
795
2400 psi
796
801
824
790
780
786
782
785
784
780
2250 PSI
780
784
778
783
772
780
768
763
766
765
2100 PSI
753
757
754
757
749
err
err
744
743
736
Ending Pressure 2000 PSI

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Rodney

Hi,
I've got the Gen1 Marauder in 177 and, imho the best thing to do to flatten the string is add a regulator, about $100. This will increase efficiency and flatten the curve. With a regulator added to mine I get an average of 865 fps, with a low of 860 and high of 870. I also have the reservoir extension and get about 60 shots.
I have the Robert Lane regulator, but I believe he has stopped due to health issues. There are other ones out there that are similar. I had to drill a vent hole for the regulator in the reservoir for mine.
--Sean

Kinda curious about the 2.5 K (psi) fill. Are you filling from a scuba tank?

I did find the sweet spot on the 1701-P to be around 2.65K or so, even though the manual states the gun is factory set-up for 2.9K.

Looks like you have some decent tube volume there.

No advice from this corner- I'm still learning this stuff myself. Will be watching this with a close eye....

Regards,

Doc Sharptail

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"Ain't no half-way"
-S.R.V.

It's jumping around a bit, but I don't think there's much of an initial climb to the string. If it's unregulated you can start at a higher pressure so that the fps starts at the lowest value you are prepared to accept, climbs to the peak and then drops back to the minimum again which defines your end pressure. Of course if it's regulated, you just fill it to the max and be happy

I need to do that, fill higher to get a climb! I'm going to open up the TP tonight to get more power. I wanted a lower fill pressure cause I hand pump.

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Rodney

Rodney,
before i put my regulator in my mrod I experimented myself.
I realise that a bstaley mod (in the mrod case) 3 o'rings was flattins the shot string and gave me about 5 to 9 extra shots.
That is in any configuration possible IMO.
Hope that can help.
https://www.youtube.com/watch?v=flIxgQXC3r8

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Hatsan At44 Tactical .22
Steyr hunting 5 automatic
Ruger air magnum .22
Weirhauch HW100 .22
Gamo Expomatic .177
Benjamin Marauder DougP custom stock
Theoben SlR98 .22
AlEx Custom gun .22 (JezX built masterpiece)
Hatsan Atp2

Thanks for all the tips so far. I made some changes last night.
I will try and post the numbers later.

- Opened up the transfer port
- fully extended the striker then backed off 2 turns
- completely reduced the hammer spring

Got valve lock at 2200 psi. First shot hit 699 got tired after 50+ shots ending at 879 I recall using JSB 10.3g. Ending pressure 1600 but it was still climbing. Looks like my changes got me a fill of 1900-2000psi.

I am still seeing high extreme spreads of more then 80fps. Does a polishing of the hammer and tube help settle it down? This was used but never used.

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Rodney

I don't have a marauder, so the following comments are based on 2240 and 1377 and maybe wide of the mark.

I'm not completely convinced about polishing the hammer. I did it to one, and my impression was that it made it very sensitive to lubrication. Thin films of oil seemed to get trapped between the polished surface and the ID of the tube, which was also fairly polished. It was almost like a surface tension affect made the hammer stick to the wall. On the other hand, greases seemed to get pushed away leaving the surface rather dry. I think this might be a case where a little texture gives the lubrication a place to sit and actually is a benefit.

Is the ES you mention shot to shot variation, or the overall spread from start to finish? For shot to shot variation the only likely explanation is differences in hammer strike, so you'd be looking in the right place. With 2240 style trigger groups a big variable is the sear dragging on the hammer, especially with weaker hammer springs. It shouldn't be as much of an issue with the marauder drop sear design, but is still possible as the sear lift spring holds the sear against the hammer during the shot. You can get an idea of if this is a factor by taking the hammer out and looking on the underside for witness marks from the sear. If there is anything obvious then polishing the part of the sear that contacts there (which is not the normal sear-hammer contact surface) can help. I've even ground out some relief on the underside of some of my hammers to reduce the problem. A weaker sear spring would also reduce sear drag, but if you over do it the gun won't cock reliably without pressing the trigger. On a 2240 a good indicator of sear drag is if you can change the chrony reading by either creeping up on the trigger (most drag, low fps) or pulling fast through the break point (least drag, high fps). That shouldn't work with a marauder trigger, but it might be interesting to try

Burs on the slots in the tube can also be an issue, so some quality time with a file and wet&dry paper can help. And then it comes down to what lube to use in there - and that's a whole religious debate of it's own!

Hope you find the problem - let us know how it goes.

Jim

I might need to fill more pressure to get a better starting point/ curve....

Start Pressure 1900 PSI
Ending Pressure 1200 PSI
JSB 10.3g
AVG FPS 842
High 880
Low 787
Shots 41

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Rodney

Interesting how the shot string settles down on the right hand side at lower pressures. I wonder if the issue might be with the valve stem instead of the hammer. A hammer problem you'd expect to be the same across the string, but if the valve stem was binding a little that might be sensitive to the pressure in the valve.

If you visually smooth things out, the basic curve looks pretty good to me. I know Bob has very high standards and goes for a 4 % ES, but I'd be happy with 10% for most purposes. Looks like your string goes roughly 810 - 880 - 800, so that would fit my criteria and I'd be pretty happy. The 4% threshold would cover about the middle 25 shots - it's a pretty high standard!

Jim

I thought 4% would be easy! I'm going to tear her down when time frees up. Thanks the tips.

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Rodney

Heh, it is easy if you accept the alternatives. It's having a small spread and a long shot string and high power and a small air reservoir that's hard.

Easy for some lol. Your making me want to tear her down now lol. I need a full station pumping gets to me when testing.

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Rodney

Anything sticking, valve stem or hammer, can cause the erratic velocities.... Once you hit the downside of the string, you have too much hammer strike anyway, so any variation won't matter.... The wild swings on the high pressure end indicate something sticking, ie changing shot to shot....

To get a 4% ES you basically have to reduce the pressure range between fill and refill.... If you have more power than you need, the choking up on the transfer port will smooth out the curve and improve the ES.... The use a combination of increased fill pressure and hammer strike to get the velocity back....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal; Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!

thanks for your response Bob.
why would the valve stem stick? I'm going to tear it down this weekend to see what I find.

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Rodney