Crosman maximus cal 177 tuning?

Regulater will not increase fps. A reg is used to bring the psi in the phlenem down to a lower psi. This makes your shots consistent until the psi in the cylinder drops below your reg setting. Now as for the power increase you can do a couple different things. Drilling the transfer port to be bigger will help. Also a heavier hammer spring or shimming your current spring will help. If you put a lighter spring in the valve it will help further. The fps you mentioned Makes me think you have the European model that's restricted to under 11 fpe. I bet if you order the American parts from crosman and drill out your transfer port you will be fine. Hopefully you don't get in trouble with the law. Do Danes have laws that restrict your power? 

Magnum Airpower in the USA has bolt on parts and how to videos . The company is a good source for Maximus after market parts.

https://www.magnumairpower.com/

Thank you for the wise hints wich transferhole should i drill out? Is it in the valve in the airtank?

Do you have a link for a video to show or a scetch?

Best regards

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Drill out the valve port slightly then ease the angle. I used a Dremel to do this. Drill the transfer port, or make a new one, drill the barrel port to match the size of the valve port. Don't make the port so big that the tiny .177 pellet will be damaged as it slides over it. Make sure there are no burrs, especially inside the barrel, and polish the surfaces up after. A hammer spring adjuster or a slightly heavier hammer spring or slightly lighter valve spring can be used as has been stated in an earlier post. It's easy to waste gas with the .177 so be conservative with your mods.





Enlarge the valve port slightly.



Be careful if you polish the sealing surface as it is easy to cause a leak.



I used this bit and a Dremel



Ease the angle being careful not to disturb the port size or shape on the outside of the valve.







You can also shape the valve stem a bit more as well. You can drill out, think it's 25/64ths if memory serves, and cut a couple of the threads from the cap for more valve volume but I doubt you will need it on a .177. Springs were for co2 pressures you would need heavier than these but lighter than stock for a bit more power.

Brass Don Cothran trigger blade, power adjuster. A little preload goes a long way. Your Maximus can send JSB 13.43 Monsters & 16.20 Beasts.

The SS Grade 8+ screws safely hold my valve to 2700psi. That transfer port is sitting just above them to left on barrel sleeve receiver. 
This, shorter than your Maximus 26” barrel sent a JSB Monster 13.43 grain pellet through a Crow at 110 yards. Perfect heart shot. Came out almost size of dime and I rarely have seen birds never flap once. It was like a stiff vase had been tipped off pole, end over end, DRT. 
I want to install Maximus barrels on my Discoveries as I’ve heard rifling is MUCH better than my 1st generation Discovery .22 and I could gain 40fps or actually quite a bit more if no blow by.

https://www.magnumairpower.com/ source for better valve screws/higher fill pressure safely. Lots of extras.

Good luck

 

Python295

I have a few pictures of the barrel and transfer ports. JamesD has a good pic of the stock port drilled and a nice trigger blade, and hammer spring adjuster as well.





Lots of ways to do the port and barrel. Size should be just a little larger than the stock port. Too big and it can damage the pellet as it goes over. Sorry brain injury and massive memory loss a few years back don't remember doing a .177. You can actually drill out the stock port although it's not easy. The poly tubing is easiest to werq with although it may be a bit soft for higher pressures. I have also used paintball macro line it is harder than the poly refrigerator tubing but a bit more forgiving than the Delrin. I use the Delrin when I go to higher pressures but the fit must be near perfect or you will get a wobbly breech if it's to long or one that leaks when you shoot if it's to short. You can chamfer the end of the Delrin to fit the barrel if you don't have a mill bit to make it flat.



Barrel,transfer port and valve should all have the same size hole.



Clean the burrs from the inside the barrel and polish it up when you are done drilling. If you don't have a tubing cutter you can use a dowel or something similar when cutting the poly tube to help get a straight cut.

1- Yes

2- Yes

3- A lighter spring in the valve is preferred to the heavier hammer spring. 

4- A spring adjuster is preferred to a heavier hammer spring. 

Do not do both a heavier hammer spring and lighter valve spring or you will likely damage parts. Remember your gun is a .177 not a .22 so go easy on the spring changes if you do them at all. Probly just a Hammer spring adjuster and guide, the little black one in JamesD's pic, is all you need.

You be welcome and enjoy your addiction. ;^)

That is very hard to say as every mod you make will change things a bit and the way you do them will also change things. Crosman specs for the gun in .177 at 1000fps and 18fpe. Although that is probly with light pellets for the velocity and heavy for the FPE. So my wild guess is if everything went well you should be 50-75fps over what it did before you started. If you are not there yet there are more things you can do like shaping the stem and stem seal and modifying the bolt probe which should be good for another 10-20fps if done correctly. But remember all the speed in the world will do you no good unless you have a pellet that will be accurate in your barrel at that velocity. I have a Crosman pistol with a 14.5 inch barrel that shoots 13mm groups at fifty yards at 630-640fps. If I take it just a little over that velocity accuracy suffers greatly.

Just changing the transfer port to a larger one is all that really needs to be done in my experience 

O-ring mod is to stop hammer bounce and save air.

Yes a heavier hammer will usually increase FPS to a point but it's easy to waste allot of air that way.

Yes, a heavier hammer spring will increase power. It will also increase cocking effort

It would be best if you do NOT install a lighter valve spring with a heavy hammer spring