Benjamin Maximus power Mod?

[Aged]

Maximus and Discovery are very similar but the hammer spring in the Max is nearly binded when cocked.
That means the preload cannot be increased to enhance power. Even 1/8" extra preload and the spring will bind and prevent  cocking
I think a heavier spring will bind even earlier.
Any ideas to increase power?

[Rivers3Plinker]

Maximus and Discovery are very similar but the hammer spring in the Max is nearly binded when cocked.
That means the preload cannot be increased to enhance power. Even 1/8" extra preload and the spring will bind and prevent  cocking
I think a heavier spring will bind even earlier.
Any ideas to increase power?

Well there's all the other power mods out there involving better breathing for the valve ( more air used )  but if a spring is the first thing you want to try, consider the TRAKAR spring. Bonus for you, they are a Canadian company so no importation and expensive shipping costs.
I have no knowledge about the new Max regarding what spring they put in the gun from the factory or changes to the breach, rear cap, valve position, or anything relative to the Discovery. I can say for sure, the TRAKAR spring is shorter than the factory Discovery spring while also being thicker wire and stiffer.
You might remove that MAX spring, dimension it and post the numbers here.
Note for comparison the TRAKAR specs -

• PART# C0762-102-0445
• OUTSIDE DIAMETER 0.300 inches
• WIRE DIAMETER 0.040 inches
• LENGTH 1.750 inches
• SPRING RATE 13.5 lbs/inch
• MAXIMUM LOAD 9.900 lbs
• MAXIMUM DEFL 1.010 inches
• MATERIAL MUSIC WIRE

Trakar spring link:
http://www.trakar.com/products/compression-springs/?part=C0762-102-0445&submitpart=1

[K.O.]

Make an extended rear cap...

[Dairyboy]

What kind of power are you getting currently? What kind of power do you want?

[Rivers3Plinker]

What kind of power are you getting currently? What kind of power do you want?

Good questions.
Decide what you would like and then build to get there.

[Aged]

Great replies guys, thanks a lot.
Opening ports and the valve seat will work but
might need a stronger spring to open the valve stem.
It's currently shooting Jsb 13.43 gr pellets at 850fps
and I'd like to add another 100fps.
I'm out of town right now so I don't know the dimensions
of the original spring.
I like the idea of extending the rear cap. I wish I had
machining tools. I wonder if drilling the hammer and rear cap
a little deeper it would allow a heavy long enough spring to make the difference? 

[rsterne]

The shot strings I have seen for the Maximus already have the first shot the fastest, or nearly so.... Adding more hammer spring preload (or a stiffer spring) to that kind of setup won't give you much more velocity, if any, but it will sure start wasting air in a hurry....

Bob

[Rivers3Plinker]

Bob is it the declining shot string like newer out of the box Disco? If so it would seem like shortening the spring a few coils might be preferable.
As I have learned, going for higher power with a Disco means fewer shots per charge and getting a flat shot string ( ES ) is challenging.

[Aged]

Bob are you saying another 100fps average for say 20 shots
with the 13.43gr pellets, which I think is only another 3fpe, is not possible?

[Erockrocket]

Bob are you saying another 100fps average for say 20 shots
with the 13.43gr pellets, which I think is only another 3fpe, is not possible?

Not possible, or not advisable.
 

[56S]

The shot strings I have seen for the Maximus already have the first shot the fastest, or nearly so.... Adding more hammer spring preload (or a stiffer spring) to that kind of setup won't give you much more velocity, if any, but it will sure start wasting air in a hurry....

Bob

Bob, thank you for all the excellent information you provide in this forum.  So much of what you type is over my head.  I do find the more I read, the more I understand.  You could say what I know about PCPs you could write on the inside of a match book with sidewalk chalk.
I did try a preload adjuster made from a 5mm flat head screw.  My results were as you stated. 
I did notice the gauge on my Benji pump reads almost 10% higher than the gauge on the Synco.  If I pump to an indicated 2K on the pump my first 10-15 shots are in the 820-830 FPS range with the Crosman 14.3 Walmart specials.  If I stop pumping when the guns gauge reads 2k, my first 10-12 shots start around 800 then increase to the 820 FPS range.
I'm content with the Maximus just the way it is.

Thanks again for your contribution to GTA.

[moorepower]

The shot strings I have seen for the Maximus already have the first shot the fastest, or nearly so.... Adding more hammer spring preload (or a stiffer spring) to that kind of setup won't give you much more velocity, if any, but it will sure start wasting air in a hurry....

Bob

Sounds like 10-32 alloy screws and raised psi would work wonders!

[Dairyboy]

Norm put a string on the maximus awhile back and he got a good 24 shots out of it from 814-840-807 or something like that if I remember correctly with 14.3 JSBs. Haven't tested mine yet but if it's close to that I'm going to leave it as is. Newer discos however really need tuning. My .177 I could only get 15 shots at 20fpe with no RVA. Was alittle hot for my liking made a short stiff spring and with no RVA I'm getting 40 shots at 17fpe avg within 4%.

[npunk42]

I'll go out on a limb here and say you really don't want a 13 grain pellet to fly at 950 FPS. If you want more power you would be looking at getting a heavier pellet to fly at 830-870 FPS carrying more energy or FPE. Correct me if I'm wrong.

[Aged]

I'll go out on a limb here and say you really don't want a 13 grain pellet to fly at 950 FPS.

Why do you think that?

[56S]

I'll go out on a limb here and say you really don't want a 13 grain pellet to fly at 950 FPS.

Why do you think that?

https://en.m.wikipedia.org/wiki/Transonic

[56S]

https://www.pyramydair.com/blog/2011/08/why-you-dont-want-to-break-the-sound-barrier/

[Aged]

If you concider 950fps as being in the transonic zone then it's barely at the start of it and won't have any effect on accuracy. Many benchrest competitors shoot at that velocity and beyond.
In fact .22lr competitors shoot at 1080fps.
If I wish to use it for hunting the higher velocity will deliver more energy to the target. The flatter trajectory will also help with longer shots 

[moorepower]

22lr is not a diabolo pellet.

[56S]

22lr is not a diabolo pellet.

Bingo.  A pellet spins at a much slower rate depending more on aerodynamic drag on the trailing edge for stability.  Weight forward, drag rear.