Is it the air pressure or is it just me?

[jungleexplorer]

My .25 Mrod is all stock.  I had it sighted in at 30 yards and it was very accurate with my cheap 4X crossman/daisy scope.  I decided to sight it in at 50 yards and I saw a different pattern arise.  I shot five sets of 8 shots (one clip) and refilled it to 3000 psi after each.   It seems that the accuracy gets better between 2800 and 2400 psi. The shots above 2800 seemed erratic.  I would say that between 2800 and 2400 psi I could hold a 1/2 inch pattern at 50 yards, but above that, maybe a 2 inch pattern.  I am wondering if this sounds right?

[oldpro]

 Perfectly normal. The Mrods unless tuned for a higher fill get valve lock above 2800. So just fill to 2800 just like your doing.

[Gertrude]

Sounds perfectly normal to me too.
Especially using a 4x scope.
Pellet choice will also play a large roll in your groups at farther range.

[Ribbonstone]

Sounds like you found the sweetest of the sweet spot top me. 

[maraudinglizard]

I have a stock marauder and does the same, it's best performance is around 2600 to 2000. shot count is not an issue with me. The scope that I am using on mine is a Centerpoint 4x16 40mm IR AO Mildot Ret. Pellet weight will make things change at 50yds as well.

[WeeHeavy]

Have you got a chronograph? That will tell you exactly what is going on.

[jungleexplorer]

Thanks guys.  I have a couple questions.

1. Is there any way to stabilize the accuracy over more shots. I get about 4 or 5 good shots now. I would rather have accuracy and more consistent shots then power.  What do ya'll recommend?

2. If I could do only one upgrade (Mod) to make my gun better, what would that be?

Thanks.

[WeeHeavy]

If you have a chronograph, You can find out what velocity the gun is shooting when it is most accurate. Then you can work with the hammer spring tension and hammer stroke so that velocity is what you get from a higher pressure fill (say 3000 PSI). That will help get you more shots per fill within the most accurate velocity range.
I would say it has been shown pretty consistently that the Marauder platform benefits greatly from an SSG. If you're looking for a drop in mod, I would not hesitate to recommend the WAR SSG with the drilled out hammer included. If you go that route, I would wait to tune the gun until it is installed because you will be starting over with a much more simple to tune setup than the stock hammer spring tension and stroke adjustments.
But you will absolutely need a chronograph to get the most out of either situation.

[jungleexplorer]

If you have a chronograph, You can find out what velocity the gun is shooting when it is most accurate. Then you can work with the hammer spring tension and hammer stroke so that velocity is what you get from a higher pressure fill (say 3000 PSI). That will help get you more shots per fill within the most accurate velocity range.
I would say it has been shown pretty consistently that the Marauder platform benefits greatly from an SSG. If you're looking for a drop in mod, I would not hesitate to recommend the WAR SSG with the drilled out hammer included. If you go that route, I would wait to tune the gun until it is installed because you will be starting over with a much more simple to tune setup than the stock hammer spring tension and stroke adjustments.
But you will absolutely need a chronograph to get the most out of either situation.

Thanks rcarlisle.  I do have a chronpgraph.  I did some testing right after I got the gun, but I was focus on finding the best pellet for it and not measuring each shot.  I need to get it out and do what you are saying.  I am using JSB Kings Exacts 25.39gr pellets.

Is it difficult to install the War SSG?   I copied the information below from the wickiedairrifles.com website.  Is this the package you are talking about?  I am assuming because my Mrod is new it would a Gen 2.


"Gen II SSG W/ Hammer
             (Fits GEN ll Only)                 
     The SSG is a device that eliminates hammer bounce and makes tuning a breeze! It was developed by Bob Sterne from the GTA and further developed by WAR to fit inside the Marauder air rifle with no mods at all. This device will make your gun quieter due to no hammer bounce that blows extra air out of the barrel ! It will GREATLY increase your shot count and in some cases has doubled the shot count per fill. This is a must have for the marauder enthusiast"

[WeeHeavy]

Yep, that's the one. When I installed mine, it was the first time I had taken the gun apart. I was a bit apprehensive about doing it, but its a 30 minute procedure if you've never had the gun apart and are paranoid about putting it back together. After the first time, it goes much faster (I blew my valve while tuning the SSG and ended up completely disassembling the gun a week later to replace it with a new valve). It was way easier than I imagined. And tuning it was super easy.

[jungleexplorer]

Thanks

[Old Corps]

Yep, that's the one. When I installed mine, it was the first time I had taken the gun apart. I was a bit apprehensive about doing it, but its a 30 minute procedure if you've never had the gun apart and are paranoid about putting it back together. After the first time, it goes much faster (I blew my valve while tuning the SSG and ended up completely disassembling the gun a week later to replace it with a new valve). It was way easier than I imagined. And tuning it was super easy.

I thought you only needed to remove the end cap to install the WAR SSG. Is that what you meant by taking the gun apart? I'm really interested in getting one but I'm probably more paranoid than you were. Blowing your valve while tuning it scares me. What were your end results after installing the SSG (and replacing the valve)? Thanks!

Ed

[WeeHeavy]

Nope, you've got to take the upper action off the gun and remove the trigger group to get the hammer out. It's pretty simple. Once it is installed, all further adjustments can be made without taking your gun apart. But you have to take it apart initially to install the device. Here's a discussion:
http://www.gatewaytoairguns.org/GTA/index.php?topic=104406.0
And to be safe, I recommend degassing the gun (cuz I am paranoid around high pressure anything). See reply #71 by Iamscotticus for a list of steps.

[Old Corps]

Thanks Robert, really appreciate the reply. I'm sure I could handle installing it but to be honest what turns me off the most is the thought of pumping it back up from 0 psi. I DO have a scuba tank but with it only being 3K I only fill to 2500-2600. I top off a lot with a hand pump & pumping from zero isn't something that excites me. I think I'll keep it stock for awhile.

Ed

[WeeHeavy]

I hear ya. Its not something I would do for pleasure. But this mod is worth every stroke. Took about 10 minutes with my Hill pump. I am always amazed at how quick it goes. The smallish reservoir on the Marauder is a blessing when going from zero to 3000 PSI with a hand pump.

[Ribbonstone]

Just to mention...

Inside of every non-regulated PCP, there is a short area where the velocity is just as uniform as a regulated rifle.

Long string or short, there is normally a place where the valve is really does it's self-regulting trick very well and tosses out a few shots with little variation in velocity.

This isn't from an MRod, but at least it's still a .25.



Now that's a pretty short shot count (rifle has less volume and at this state of tune is pretty much an air-hog).

But if you break it down by percentage:

4% (834-800fps) = 19 shots
3% (834-809fps) = 17 shots
2% (834-817fps) = 14 shots
1% (834-826) = 9 shots

If it's going to shoot great, it's very likely to shoot that way inside that little 1-2% zone.  Certainly NOT the only factor, but at least it's a factor under our observation and control.

[anuthabubba]

You don't have to de-gas it to remove the bolt housing or remove the shroud to install an SSG on a GenI. Did it w/o removing the trigger.

[Old Corps]

You don't have to de-gas it to remove the bolt housing or remove the shroud to install an SSG. Did it w/o removing the trigger on my GenI.

Hmmm, wonder if that holds true with a Gen II.

Ed

[WeeHeavy]

Actually, Yrok is correct. You really just have to remove the rear screw of the trigger group to get the end cap off the pressure tube, but you still have to get the top action off the gun (which exposes the transfer port and seals between the pressure tube and the breach). It is also true that one could perform this operation without degassing, but there is a remote potential for the transfer port to fly off the top of the pressure tube should the valve be discharged by accident. As it was my first time messing this deep into the gun, I chose safety first and degassed it. But, hey, it's all a question of how comfortable you are with the idea of working around high pressure air and how much you value your life and limbs. To each their own.

[anuthabubba]

Or how careful you are. If you have two left hands and no mechanical experience/aptitude or organizational skills, maybe you should get someone else to do it.