GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: Aged on September 06, 2016, 05:17:46 PM
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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?
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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 (http://www.trakar.com/products/compression-springs/?part=C0762-102-0445&submitpart=1)
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Make an extended rear cap...
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What kind of power are you getting currently? What kind of power do you want?
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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.
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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?
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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
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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.
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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?
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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.
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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.
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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!
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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%.
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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.
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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?
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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
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https://www.pyramydair.com/blog/2011/08/why-you-dont-want-to-break-the-sound-barrier/ (https://www.pyramydair.com/blog/2011/08/why-you-dont-want-to-break-the-sound-barrier/)
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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
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22lr is not a diabolo pellet.
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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.
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I regularly shoot pellets at 950fps with other guns and there's no problem.
Anyway the topic is about getting the Max to shoot 13.43gr .177s at 950fps.
I believe it can and that's my quest.
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13.43 gr. pellets at 950 fps is almost 27 FPE.... That will be a challenge in .177 with a Disco based platform at 2000 psi, IMO.... In .22 cal, much easier because of the 54% increase in pellet base area for the air to push on, resulting in 54% more force available to accelerate the pellet....
Transonic starts at about Mach 0.8 (900 fps), and you are correct, that is not an accuracy issue per se, it will depend on the pellet and twist rate at 950 fps.... I use 950-960 a lot myself, with many good round-nose pellets such as the JSB Exact series....
I would suggest you plot velocity vs. preload at 2000 psi and see what you get.... If the velocity is on a plateau, increasing the hammer strike will not give you more velocity, only use more air....
Bob
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That would be a problem with the maximus. The spring is within 1/8" of binding when cocked. What I've already tried is adding a spring inside the stock spring (counter wound) with some encouraging results but not enough. I like K.O.'s idea of making an extended rear cap to take a longer heavier spring so I could then use a preload adjuster if I can make one with a hand drill and a hacksaw lol.
Besides a stronger hammer impact I could open up the valve seat. They also sell high flow valve assemblies for the disco but I wonder if it would work in the max.
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are their not instability issues when reaching sonic speeds with jets not having the right wing sweep etc , same applies to projectiles.
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You need to be careful opening up the ports in a .177 cal, as going too big in one place without matching the areas can lose performance instead of gaining it.... If you don't make the barrel port oblong, the stock barrel port on a Disco (0.132") is almost as large as possible without causing loading problems with the pellet.... With care, you can go to 0.140", which is the same diameter as a stock Disco transfer port.... Some small gains can be made with careful port work, but nowhere near as much as you can gain in a .22 cal or .25 cal where the stock ports are too small....
Bob
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Just a side note, but doesn't the Maximus come with a different valve than the Disco? I thought I recalled reading that here when they first came out?
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I also read the valve was changed for a better shot count. Too bad Crosman hasn't released a schematic parts list yet for the max. I'm new to Benjamin products but when I remove the valve assembly on the max today I can compare it to the parts list diagram for the disco and let you know what I find.
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I found that the 0.045 spring on my Maximus to be really hard to cock! I wouldn't even consider making it harder. Opening up the air path would be your best bet if you want more power. The Maximus is really not the best platform for a power gun. The air tube is really too small for high power with a decent shot count. For a hunting gun, where you don't really need a lot of shots, it might be OK, or you could plan on carrying a "Guppy" tank with you.
I actually went slightly the other way with with a 0.042 spring (much easier to cock!) in my .177. I'm going for 900-950 fps, with the best shot count.
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You're right Doug the Maximus was a poor platform for a 27fpe gun in .177. Everything I read steered me to believe it was a Discovery economy model :(
I'm not done yet but I might have to lower my expectations and 900fps is a nice round number.
How did the 0.045" and 0.042" spring affect the power compared to the original? If the porting doesn't achieve my goal I will build an extended rear cap and use a heavier longer spring and adjuster to drive the hammer harder. Being longer should make it a little easier to cock.
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I also read the valve was changed for a better shot count. Too bad Crosman hasn't released a schematic parts list yet for the max. I'm new to Benjamin products but when I remove the valve assembly on the max today I can compare it to the parts list diagram for the disco and let you know what I find.
Last word I had from Crosman was that the parts lists/diagrams would be available near the end of this year. They indicated that the parts lists are usually introduced six months after the product is made available. Some parts may be available now - but probably not all!??
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You're right Doug the Maximus was a poor platform for a 27fpe gun in .177. Everything I read steered me to believe it was a Discovery economy model :(
I'm not done yet but I might have to lower my expectations and 900fps is a nice round number.
How did the 0.045" and 0.042" spring affect the power compared to the original? If the porting doesn't achieve my goal I will build an extended rear cap and use a heavier longer spring and adjuster to drive the hammer harder. Being longer should make it a little easier to cock.
The 0.045 spring WAS the original! Cocking was difficult. Velocity started about 1000 fps, and just dropped off for about 20 shots to about 1000 psi (didn't do a lot of velocity recording). With the 0.042 spring, the cocking is much more comfortable. Velocity starts at about 910 fps, goes up to about 950 fps, and back down to 900 fps after about 40 shots. The curve is pretty flat for the middle 20 shots. I'm still tweaking my FFH to get a long, flat shot curve. I'm not sure about a longer end cap. The cocking stroke is only about 3/4", and I don't know that a longer compressed spring will give you any more, or be easier to cock, than a shorter spring. If you go heavier, you might need a crowbar to cock it.
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Poof that hammer/bolt cavity with Moly bullet lube. That and pull the bolt back with your index finger while pressing on the endcap with your thumb. Reduce friction and improve technique worked for me.
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Been there and did all that. Still very hard to cock. I prefer the 0.042 spring. Crosman introduced this as an entry level PCP, to attract new shooters to that side of the sport. If they want to include kids as part of the equation, the cocking is too hard!
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I would love to have another Synco in 177 tuned to shoot 7.9 gr pellets at 950.
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I got a new hammer spring today from Traker for the maximus. Heavier guage and longer than the original but less coils per inch so it won't bind before cocking.
It works great but is a bit of an air hog as Bob predicted, so I'm not going to mess with the valve seat. The 2500psi fill is cheating a bit and I do it at my own risk - it was an easy way to get the extra power I wanted. I originally bought the gun to save on scuba tank fills since I don't like filling my Hatsan after the tank is down to 2500psi.
I had a graph showing the string of shots but I can't figure out how to include an image on this site.
Then I tried to Attach it but it came back saying it was too large.
Anyway I'll give you the numbers using Jsb 13.43gr .177 cal. pellets.
1-918fps 6-942 11-932 Average velocity 930fps Starting pressure 2500psi
2-922 7-946 12-930 High velocity 942fps Ending pressure 1500psi
3-926 8-936 13-926 Low velocity 901fps New spring dim. 0.3" OD
4-941 9-933 14-919 Extreme spread 41fps/4% Wire diameter 0.05"
5-934 10-943 15-901 Muzzle energy 25fp Length 2" 10 turns/1"
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Please do not assume that the Maximus uses the same quality steel, or even dimensions, as the Disco tube.... nor that it can be overfilled past the recommended pressure.... The valve screws in the Disco should be replaced above ~2000 psi.... AFAIK, nobody has done any testing with the screws in a Maximus.... You are in uncharted territory here.... don't fall victim to your own enthusiasm and/or ignorance....
Bob
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I did do it again. I have read so much about the Discovery that I am subconsciously making decisions based on those facts.
Thanks for the heads up.
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Same gun filled to 2001psi, ending at 1400psi, 13.43gr pellets. Looks like I'm going to have to enlarge and equalize the ports to up the velocity. I'm sure I'll lose more shots per fill but that's what I want. I wonder if I can get a large air bottle attached.
1 850fps High Velocity 905fps
2 856 Low Velocity 867fps
3 863 Average Vel. 877fps
4 868 ESpread 38fps/4%
5 865 Muzzle Energy 23fp
6 876
7 905
8 903
9 897
10 890
11 884
12 883
13 880
14 869
15 877
16 867