Tuning .177 Mrod

[Markez]

Hi its been awhile since I've been on here.
I finally got some time to sit down with the choney and try to tune the Mrod. I got this gun used so I am
not sure if was factory settings or not but it was set at h spring 4 turns in from all the way out and
h stroke 2 turns in and I was filling at 2500 lbs. and shooting down to 2000-1900. I was getting 25-30
shots. My shot strings would start out at 910 fps and end at about 850 fps with no curve at all.  I am
using the ATeam guide to tuning with lots of air and pellets.

1  979.36   2500lbs
2  979.92
3  980.26
4  988.40
5  986.47
6  1000.74
7  998.84
8  986.55
9  1007.32
10  997.77
11  998.01
12  1001.90
13  998.26
14  994.98
15  1001.40
16  991.72
17  994.65
18  990.99
19  991.31
20  986.14     2150 lbs
21  989.85
22  982.38
23  975.57
24  978.73
25  976.75
26  974.79
27  975.26
28  972.99
29  970.18
30  959.34    2000 lbs

Hammer spring 3.75 turns in
Hammer stroke 3.5 turns in
TPort 2.75 turns open

I think I can tweek this more yet but what do you guys think?

[Schmidty]

very nice curve that looks about perfect if you are trying to get about 30 shots per fill!  I wouldn't change a thing especially because they say once you start pushing pellets at that speed leading of the barrel can occur.  I am assuming you are using crosman premier hollow points or something similar.  Maybe try using some heavier pellets you will probobly get more energy out of the pellets.

  BTW not trying to be a stickler, but pressure units are in pounds per square inch (PSI) not just pounds.  You use pounds to describe mass

[Markez]

oops sorry about the lbs. I am using CP heavy 10.5 gr. I thought I might slow it down some and see if I get more shots per fill?

[Markez]

Well next time I want to get it better just slap me! now I can't get back to where I was
and I'm out of air and pellets. I think turn cw when I meant to go ccw and get all messed
up. Then I pounded a hole right though my pellet trap and put a dent in my garage door.

I'll get it. I'm just a green horn at this tweeking stuff. once I started turning those screws
I just can't stop. What is wrong with me?

[Markez]

Update:
I found out why I was having trouble getting back to the above string my hammer stroke
adjusting screw is moving. Even if you keep good records that will mess you up every time.
I think I got back to were I was but I am using a Lighter pellet cuz ran out of the CP heavy
so I am using cphp. the numbers are allot higher but I got that nice curve back.

40 shot string

#1   1073.32
#18 1142.51   high
#34 1091.71   4% as per Bob
#40 1071.71   low

TP wide open 4 ccw
hspring 3 1/5 cw
hstroke 3 2/3 cw

I don't think the setting's on my first post are correct. Dose any one know how to stop
the hammer stroke adjusting screw from moving? Thanks for any help.

Mark

[aack73]

i like that shot string. i would like to peak out just over 1000 fps with the 10.5gr cph.   25 shots til you got back to where you started.  i would be happy to have more of a margin than that.  have you tried filling it any higher with that set up to see what you got?  i've heard of a few different people complain about the adjustments moving. dont remeber how they stopped it. if i can find it i will link it here.

[Markez]

Ya I will have to wait till Friday when I get my new supply of pellets. I will try and up my pressure some and
see what happens.

Mark

[aack73]

 here is all i could find for now.  http://www.marauderairrifle.com/forum/viewtopic.php?f=14&t=1054&p=5302&hilit=hammer+stroke+moving#p5302

i'll experiment more when i get a chrony. i was just using one at my LGS to measure that shot string. i'm not gonna start tuning til i get a chrony.

[rsterne]

Your 1142 fps is above the speed of sound.... I would strongly suggest you back the power down a bit so that you won't have the pellets slowing through the sound barrier as that may lead to accuracy problems.... I try and stay below about 950 fps as not only is the gun more economical, but generally the accuracy is much improved....

Bob

[Markez]

Thanks for the link aack73. I understand now why you need a chrony to tune these.

Thanks Bob I was not planning on leaving it at that speed I was more interested in the
curve. I was surprised by the numbers. I would be happy with 950 fps with a 10.5 gr.
pellet. I agree accuracy is more important that speed.

It's a learning curve for me and I have to say it's been fun.

Mark

[Markez]

looks like I need to take the gun apart to tighten a set screw to keep the adjusting screw
from moving so I think I will wait till I'm done before I go through all that. I got a parts list
and diagram off the Crossman.com web site. More to come later.

[aack73]

let us know. its always good when someone else does the testing and leg work. thanks for sharing with the rest of us.