.25 marauder velocity

What pellet?

I want to say that's way low seems that valve full open dont remember no. of turns and the hammer at full stroke and 2.5 to 3ish turns in from all the way out on the hammer spring should be giving you 32+ shots at about 815 and at 800fps you should be getting over 40 with a 3k fill. Obviously it may vary some from gun to gun but should get you close. I would verify for ya but I have already hot-rodded my gen2 synrod some time ago.

Velocity and shot count are low. My poorly tuned Gen 1 gets the same shots but more velocity. Its torn down now due to clipped orings. Need to find a shop to hone the air cylinder. I would open the air screw all the way and retest. There are a ton of posts on tuning. Just use the search feature here before you get too far away from the factory settings.

My Gen 2 shoots the JSB 25 gr pellets at an average of 820 fps with an ES of 7 fps for 16 shots. Super accurate, the only limitation is the shot count.

A stock Mrod will do about 865 fps average for 16 - 20 shots and a 3,000 psi fill with 25 gr. JSB if you want to keep ES on the lower side. Based on that string it looks like it has a very short flat velocity then drops. That would tell me you have to much hammer energy for the psi you are filling it to. If you want to be maxed or close to max on velocity for a stock Mrod theres one thing to check before you start tweaking the hammer stroke and hammer tension. If you are going for higher power you need to make sure the valve screw is fully open. There have been many people who adjust the valve screw fully open but close it back up some when they tighten the grub screw that locks it into place.

So take out the lock screw for the valve screw then turn the valve screw all the way in but dont try to tighten it you should stop once it feels like its bottomed out. Then open the valve screw 5 - 6 turns and that will give a fully open port. Then screw the grub screw back in that locks the adjustment screw. Again be careful and dont over tighten the locking screw cause it will usually just turn the adjustment screw back closed or strip it.

Once you have verified the valve screw is fully open you can start tweaking the hammer spring and hammer throw to achieve the power and string you are looking for. Its been awhile since tuning an Mrod so I dont remember the exact numbers that work for most Mrods. there is a wright up for tuning that will give you the rest of the info. Google the A-Teams mrod tuning guide and follow the tuning procedure. That will get you where you want to be.

If you install a larger transfer port (.162), and either a TSS or SSG, your shot count will go up, and so will the velocity. With nothing else done, mine shoots 25.4 AirArms at 910 FPS, for 25 shoots. 

I think that's pretty good. Yes you "could" get slightly better numbers but ( just me ) I think you are where you will get unless you want to start spending more time & money for just slightly more gain.

Those numbers should do whatever you want your rifle to do. Good job.



John

I think you can do better but thats if you want to spend some more time. I would shorten the hammer travel by a half turn and shoot another string. If you reduce the hammer energy a little you will get a better string. Its your call and like others said if you are happy then just shoot it

If your goal is to get the max shot count I would be shooting for an average speed of 820. You can get around 20 shots. As you can see, the greater the speed the less your shot count. Adding a regulator and an SSG like I have, you can get around 30 shots with an average speed of 840. Others have gotten 40 shots with some fine tuning. If you don't want to do any add-ons, I might suggest tuning somewhere between 820-840 to get a few more shots. You may only lose 1-2 FPE but gain 4-5 more shots

When you shoot a string and the velocity starts out on a flat line like yours then declines the pcp isnt tuned for best shot count. Theres nothing wrong with a declining string if you are after max power and dont care as much about shot count or a better way of saying it is usable shot count. If you are looking for a good mix between shot count and power you want to have a bell curve tune. Heres an example of a bell curve tune: 815 818 822 825 825 822 827 824 826 830 831 828 825 826 825 822 823 820 818 815. The string starts a little slower than the peak of the velocity due to valve lock. Then the shots climb to the peak velocity and drops back down as the pressure in the air cylinder drops. Valve lock occurs when the hammer doesnt have enough energy to over power the air pressure in the cylinder so the valve doesnt open completely. As the air pressure drops with each shot the hammers energy starts to over power the force of the air left in the cylinder causing the valve to open farther until it can completely open the valve giving you the peak velocity. As the pressure drops the velocity drops. 

So if you look at your string it is missing the first part of a bell curve. The current tune has enough hammer energy to fully open the valve from the first shots. So if you want a longer string you will need to reduce the hammers energy to cause valve lock. You can do that two ways. You can shorten the hammers throw or reduce the pre load on the hammer spring. I prefer a shorter hammer travel cause it speeds up lock time but some people prefer a longer hammer travel and less hammer spring pre load. If youre not sure which works better for you you will have to experiment with both tunes and see which you like. Yes you might lose 10 fps from the peak of the velocity but you will have a longer usable shot string. 

Glad I can help. Yes you are correct. Just make small adjustments and shoot a string so you dont go to far. It doesnt take much of a change once you get close to the best setting for your string. If the valve meter screw isnt fully open you might gain back the lost power from lowering the hammer energy with it opened the rest of the way. Again you just have to try it and see. I will just guess here and say if you lose 15 - 20 fps adjusting the hammer to get a better bell curve and the valve meter screw is only open 3/4 of full you might get all or most of that velocity back by fully opening it to 5 - 6 turns instead of the 4 turns its set at now.