Maximus Euro FPS readings Needed ! Please...

[travelbike]

I finally got to chronographing the Maximus Euro yesterday. Used JSB's 8.44 gr. I start out with a 1750 psi fill.

Shot 1 to 10 - Mostly 650 fps but with 3 in the 595's in erratic points

shot 11 to 20 - Still mostly in the 650's but 4 in the 595's at very unpredictable points. Shot 18, gage shows about 1500 psi

Shot 21 to 30 - Mostly in the mid 640's, but 4 in the high 580's in erratic spots. Gage shows 1250 psi at shot 30

Seems to be the gun is too slow. At 650 fps with 8.44 gr, it's about 8 fpe.

Called Crosman to inquire. Tech guy said that the gun is expected to chrono at about 800 fps using 7.4 gr pellet - a 10.5 fpe output. If 10.5 fpe is their baseline, then this rifle should chrono at about 750 fps. Is it normal for gun manufacturers to advertise a 12 fpe gun to actually output 10.5 fpe as a buffer of safety ?

I asked about the erratic fluctuations from the average of 650 fps to about 590's. He said there might be dirt inside the gun internals.

Anybody have Maximus Euro Chrono readings they can share ? Bought the gun after watching the AEAC you tube review where the Euro was going 800 fps using the same JSB 8.44 pellet. I wonder if the gun manufacturers send reviewers are fully checked and tuned unlike production models ?

If the gun is designed for 10.5 fpe, Is it better to get a normal Maximus, then detune it to 12 fpe ?

Again thanks for any help. Thinking of sending it back as warranty he said was for a year.

 

[Skip-in-WV]

Here is what I did to mine.

177 Maximus review. I polished the trigger parts and hammer with a Dremel abrasive disc, shortened the bolt a little to increase the opening to make it easier to insert a pellet, replaced the hammer spring with a lighter 0.042 spring slightly smaller diameter than the 0.045 it came with. I installed the 3-screw modification, but the screw through the bottom did nothing that I could see. It now has 2 distinct stages with no creep and a clean break. The first shot string was dismal. There was no sweet spot. Velocity declined with every shot. I ordered a Free Flight Hammer kit from Steve in NC, and then installed and adjusted it according to directions. Then I got about 40 usable shots.

Again unlike his mine is pretty quiet. I also installed scope ring risers to get more room for my large fingers. I tried every pellet I have and none would group. I even added a second barrel band, moved the arround to several different positions to no effect. After watching a YouTube video I recut the crown using 2 brass screws and valve grinding compound. The groups got worse. Over 1 inch at 25 yards until I tried the H&N FTT 8.4 grain pellets. Now I can get 1/2 inch groups at 25 yards. Maybe I should quit messing with it trying to make a silk purse out of a sow's ear.

 

[AirgunnerSC]

Shoot a gun through the chrony that you have measured the fps before. If the readings are as you recall then shoot the maximus again. This tests your chrony's accuracy.

 

[John "spysir" Blount]

Absolutely normal for any airgun manufacture of "12fpe" for the UK to deliver a rifle UNDER 12fpe as 12.1fpe would get you arrested instantly in that county so they come a bit under to be legally safe and leave it up to a shop ( who has the anti-tamper tools to work on UK rigs) .
Now those wild spikes you mention seem a problem. And that, depending on what it is might lower power?

A rubbing striker ?
Leaking transfer port?
Speed of trigger pull - some can drag if pulled slow compared to pulling very fast
Bit of crud - honestly could be, shouldn't be but could.
Chrony to rifle angle/distance ANY different, or lighting.

I only have a .22 maximus or I'd run a string for you.
It is the very lowest priced pre-charged made ( I just cant count the wf-fi /10-77 thang ), tons of mods! Most ( NOT all) Benjamin Discovery and or 22xx parts and mods work.

Personally IF I could find a major defect I would send it back for warranty otherwise I would be "playing" with the spring(s) rate , transfer port, maybe even a regulator just trying to keep how ever many shots it could with an E.S. of 20fps.


Keep us posted.
John

 

[travelbike]

Instead of shipping it back, decided to open the Maximus to see what was wrong. The transfer port has a larger hole on the side that faces the valve. Smaller on the barrell side. Attached are pictures (sorry if not too good). First thing I noticed is that the o ring on the side on the valve side was kinda squished. I thought it was not there as shown in the schematics. I might try to slighly oversize the hole on the barrell side just a tad. Will try to measure the hole diameters next time I go back to farm.

 

[John "spysir" Blount]

Looks normal. open the TP if you want more power.

And you've chronied on a bench - same agle & distance-
And it shoot exactly the same fps with a very fast trigger pull as it does if pulled Slowly, right?
You called crosman and "He said they design the gun to be UNDER 12 fpe – NOT 12 fpe ! "
Right.
You purchased a rifle made for a country with power restrictions that if violated will land a person in Jail. 
Darn hard to tune a pre-charged to 11.9fpe and be certain it cant go over that with any pellet especially w/out a regulator.
Yours doesn't suit you ( just drill the TP ) BUT it IS legal for the intended market.
It is good that crosman maintains quality control that will keep folks who must stay under 12fpe out of prison.

Want a lot of regulated shots at "12fpe" ( really mine is at 11.8fpe) and a vastly better trigger grab a QB769 & a ninja bottle.

John

 

[travelbike]

Finally drilled the transfer port. The stock hole was about .05". Enlarged it to about .079 using a 2mm drill bit. It's now at about 12 fpe. On the downside, the shot string is descending from 1750 psi. Ordered a power adjuster and a lighter hammer spring. Might do a Bstaley tune using washers between hammer and valve. Hopefully we can get a flatter string hopefully in the 11 fpe

For the price of the gun, it's a good platform to learn tuning. Pretty straightforward opening and reassembling. Polished the hammer and the part of tube it slides in. Will do a more extensive chrono once I put the spring and adjuster.