New 10 Spring Results Mrod 25

[bmazz007]

Hello I just installed the 10 spring in my mrod 25 These are my results.   Please help me tweek  this. I am guessing to much preload   

My settings are     C Preload 3 3/4    C stroke 3/4     cc Valve 3.5

Starting PSI is 3100  JSB Kings 25.4
1- 881
2- 880
3- 875
4- 865
5- 858
6- 848
7 -836    PSI  2300
8- error
9- 817
10-809   PSI 2100
11-800
12-792
13-759
14-748
15-734
16-720   PSI 1500

Seems to be a little bit of a hog

[rsterne]

Try the stroke fully CCW (max) and the velocity at 4.5 CCW from full in.... It would appear you have too much spring preload, back it off until the first shot is about 3-4% below the peak velocity, then record a full string with starting and ending pressures, stopping at about 4% below the peak velocity as well....

Bob

[GadgetX]

You will love it once these experts on this forum help get it dialed in.  I ended up with #10 Hammer Spring, v=4.25, p=7, h=0  JSB 25.4 gr pellets.  Best was 842.6-881.1-843.2 FPS String 24 shots.  That is 40.05-43.80-40.11 FPE, AVG something like 42 FPE. 

Have fun,  buy lots of pellets.

Mike

[bmazz007]

You will love it once these experts on this forum help get it dialed in.  I ended up with #10 Hammer Spring, v=4.25, p=7, h=0  JSB 25.4 gr pellets.  Best was 842.6-881.1-843.2 FPS String 24 shots.  That is 40.05-43.80-40.11 FPE, AVG something like 42 FPE. 

Have fun,  buy lots of pellets.

Mike

How many shots per fill?

[bmazz007]

You will love it once these experts on this forum help get it dialed in.  I ended up with #10 Hammer Spring, v=4.25, p=7, h=0  JSB 25.4 gr pellets.  Best was 842.6-881.1-843.2 FPS String 24 shots.  That is 40.05-43.80-40.11 FPE, AVG something like 42 FPE. 

Have fun,  buy lots of pellets.

Mike

Thats good..... I am having a hard time i tried your settings and I started with 3000 psi and took 9 shots and down to 2000. I am so frustrated.

[GadgetX]

Sorry.  Try removing your Valve.  Spray hole with compress air.  Re-insert.  CW until it stops, back off 4.25 turns.  Mine decided to work well after I tried that.  Also when you inserted the #10 spring was the travel easy or did it bind?

Mike

[bmazz007]

Sorry.  Try removing your Valve.  Spray hole with compress air.  Re-insert.  CW until it stops, back off 4.25 turns.  Mine decided to work well after I tried that.  Also when you inserted the #10 spring was the travel easy or did it bind?

Mike

Mike, Do you mean putting the spring on the hammer on the install? I kinda had to twist it on there.  The really wasn't much  play.

[rsterne]

Sounds like your hammer is binding.... wrong size spring, I'm guessing....

Bob

[GadgetX]

Sorry.  Try removing your Valve.  Spray hole with compress air.  Re-insert.  CW until it stops, back off 4.25 turns.  Mine decided to work well after I tried that.  Also when you inserted the #10 spring was the travel easy or did it bind?

Mike

Mike, Do you mean putting the spring on the hammer on the install? I kinda had to twist it on there.  The really wasn't much  play.

Take some 200 grid wet dry and roll into a cylinder.  Then take spring and slowly sand the inside until it fits not quite snug.  MIke

[bmazz007]

Sorry.  Try removing your Valve.  Spray hole with compress air.  Re-insert.  CW until it stops, back off 4.25 turns.  Mine decided to work well after I tried that.  Also when you inserted the #10 spring was the travel easy or did it bind?

Mike

Mike, Do you mean putting the spring on the hammer on the install? I kinda had to twist it on there.  The really wasn't much  play.

Take some 200 grid wet dry and roll into a cylinder.  Then take spring and slowly sand the inside until it fits not quite snug.  MIke

You think that's it??? I cleaned out the valve.. Did you spring go on a little tough?

[rsterne]

Coil springs get bigger when compressed.... If it's tight in the hammer with no load, it will be tighter when compressed, and may be binding....

Bob

[PakProtector]

hey-Hey!!!,
The 10#-er I got for mine did not bind in the hammer, its ID was too small to fit onto the adjuster guide nipple. I had to reduce the anjuster guide/nipple so it didn't bind. I also found a sizeable burr in the transfer port at the velocity screw junction. I had a crappy shot string like yours and it did not improve 'til I opened the transfer port and made sure there was no burr obstructing the flow.

I'd be quite tempted to get a second valve and try that. Make sure its exhaust port is clear and that the velicity screw needle is all the way out. IMO the 25's are equipped with valves on the small side for upper 800 fps shot strings. I drilled the throat to .234 and the port and sleeve to .152 and got about what you're looking for w/o the 10# spring( 16 shots, 865-895-865 with Kings ).

I bet you can talk crosman out of a replacement valve. For sure the cost of a valve is less than cost to ship the rifle. check the barrel alignment in the breech; it is possible that the barrel is twisted and not matching the transfer sleeve or the notch in the bolt. Re-install the bolt along with its detent screw for this one and examine the barrel port with a flash light.
cheers,
Douglas

[GadgetX]

Told you these experts would help. 

I had to sand my spring on the inside slightly until I was satisfied with the fit.

As you proceed, being a novice, a lesson I learned was even if you are making good notes on settings, if you hit the sweet spot, don't fix it anymore.  I went back to several settings I had, and they where difficult to reproduce.

Mike

[FuzzyGrub]

I have seen what Bob describes in my Prod when I went to the next size larger wire for the hammer spring.  It would jam against the sides of the hammer when compressing.  Would cause bolt jamming and excessive force to pull back.  Some emery to the outside diameter of the spring that fit into hammer, and some lube helped.  You have to remember to keep the spring oriented correctly on latter re-assembly.

[bmazz007]

Told you these experts would help. 

I had to sand my spring on the inside slightly until I was satisfied with the fit.

As you proceed, being a novice, a lesson I learned was even if you are making good notes on settings, if you hit the sweet spot, don't fix it anymore.  I went back to several settings I had, and they where difficult to reproduce.

Mike

Wow your not kidding Mike....

Thank you for your posts I did remove the valve took it all the way out and put it back in. I also took the spring out and sanded the inside of it and now the spring does not bind at all. I will test it when i get home for work today ill post my results


Thank you guys so much!!!