Help with .25 M-Rod string

[AntlergeekAdam]

I need a litte tuning help with my new .25 cal M-Rod.
I recently ordered an SSG from Travis at Wicked Air Rifles. But until that comes in I'm looking to get a good string.
For this string I'm shooting H&N barracudas.
3,000 PSI fill
1-799
2-804
3-809
4-804
5- err
6-804
7-800
8-err    2,500 PSI
9-err
10-791
11-796
12-785
13-786
14-772
15-756
16-err
End pressure 2,000

[aceflier]

Seems slow for a 21gr pellet. I would open the velocity screw and try. 3100-3200 fill. Just me though. Decide if you want more power or more shots and play around till you are happy. It looks like you are on the 1/4 mark of the curve to me a 3200 fill should give you 4 or 5 more shots at those velocities. For comparison I'm currently shooting 27.8gr Benji Domes at 852-863-852 16 shots.

I'm new to PCP also but caught on quick as to what adjustment did what to my shot string. Pumping is a bear when tunning.

[Habanero69er]

It's a .25, so it's a 31gr Baracuda.

Opening the velocity screw is a good start. Just make sure you remove the grub screw first, then open the velocity screw.

[aceflier]

It's a .25, so it's a 31gr Baracuda.

Oops that seems about right then. I shoot the grizzly at around 800.

[LDP]

What are you going by to determine the fill the Mrods gauge or the fill station gauge?

[AntlergeekAdam]

The fill station gauge. It says 3200 on the gun.

[aceflier]

Fill to 3100-3200 on your fill station gauge and you should be good. I'm filling to 3200 on pump 3400 on rifle. My numbers with 3000 on pump fill are similar to yours. With 3200 pump fill my hig shot is shot 8 .You will be able to throw out those last 2 or 3 shots with lower 780ish 2-3 shots to start. Your fill pressure will directly effect your shot curve. For the power you are pushing you need more psi. Notice your highest shot comes at shot 3 or 4 this will push the plateau down 3 or 4 shots. Or back off on your tune for a 3000 psi fill. But less power.  Good Luck.

[AntlergeekAdam]

OK, I'm using Benjamin domes this time.
I filled to 3200 PSI on pump gauge.
Hammer spring is 6 turns from full CCW
Hammer throw is 1/2 Turn from full CCW
Valve metering is wide open
852
Err
852
855
851
846
838
837
826
818

End pressure is 2,300
I'm looking for 16 good shots from 830-850-830
Is this possible? If so what should my next adjustment be?

[Gear_Junkie]

I'm new to PCP also but caught on quick as to what adjustment did what to my shot string. Pumping is a bear when tunning.

Tim,

Can you pleas expand on what you found out for each adjustment?  I have a .25 MROD on the way, and am trying to learn everything I can about tuning it in advance.  Someone already posted some great setting to try, for the shot string I'm trying to achieve, but I'd love to hear what you learned.

Thanks!

[aceflier]

Basicly It just took time and a tin off pellets for it to click. I have my velocity screw wide open and HT (1/8 allen)2.5 CW and I put in a 10.5Lb hammer spring and turned HS (1/4 allen)4CW. You want to count turns on both HT and HS from full CCW. I am not an expert tuner by any means. I just did what seemed to work for me.

Here is the string I got with 31gr Grizzlys

811.5 3400psi on rifle 3200 pump pressure
815.6
816
820
818.6
821.2
822.5
820.4 2900psi rifle
820.3
817.8
817.7
824.5 wierd one?
822.6
819.1
815.7
811.2  2400psi rifle

I haven't done the math on it but I think it's near 46ft/lbs good enough ES for me.

[aceflier]

OK, I'm using Benjamin domes this time.
I filled to 3200 PSI on pump gauge.
Hammer spring is 6 turns from full CCW
Hammer throw is 1/2 Turn from full CCW
Valve metering is wide open
852
Err
852
855
851
846
838
837
826
818

End pressure is 2,300
I'm looking for 16 good shots from 830-850-830
Is this possible? If so what should my next adjustment be?

Try 4HS and 2 HT

[AntlergeekAdam]

Basicly It just took time and a tin off pellets for it to click. I have my velocity screw wide open and HT (1/8 allen)2.5 CW and I put in a 10.5Lb hammer spring and turned HS (1/4 allen)4CW. You want to count turns on both HT and HS from full CCW. I am not an expert tuner by any means. I just did what seemed to work for me.

Here is the string I got with 31gr Grizzlys

811.5 3400psi on rifle 3200 pump pressure
815.6
816
820
818.6
821.2
822.5
820.4 2900psi rifle
820.3
817.8
817.7
824.5 wierd one?
822.6
819.1
815.7
811.2  2400psi rifle

I haven't done the math on it but I think it's near 46ft/lbs good enough ES for me.

How many pounds is the stock spring?

[aceflier]

Pretty sure it is 6lb

[AntlergeekAdam]

OK. I took your advice and...
HT=2
HS=4
Gun gauge 3200PSI

Err
830
820
824
821
824
826
Err
Err
812
823
813
819
809
816
809
803
800
795
800
792
786
770

End PSI of 1975

Now, what would you adjust to get a little more power with a few less shots? Hopefully around 16 (two mags)

[aceflier]

Go 1/2 turn CW HS 1/8 th Allen

[AntlergeekAdam]

So
HS 4.5
HT 2.125
?

[aceflier]

So
HS 4.5
HT 2.125
?

Keep HT the same
HT 2
HS 4 1/2

[AntlergeekAdam]

OK. I'll shoot a string right now

[AntlergeekAdam]

Crosman domes
Start pressure from Gun Guage is 3,200
Pump gauge is 3100
HT=2
HS= 4.5
832
833
838
833
831
810    don't know why this was so low
830
822
816
806
810
805
806
797
782.     

End pressure is 2,200

Hmmmm

[aceflier]

I think 3200 on your pump gauge will get you where you need to be on that string. It should get you 2 more shots just below the fps of your first 2 shots. You may need to back off 1/4 turn on HS to get 16 shots Or your last string wih 3200 on your pump gauge.  You can also try 1.5 HT and 4 HS. Are you understanding now? Your sweet spot for 16 shots is somewhere between this string and your last with 3200 Fill. You are getting closer.