Tuning Maximus Tuning Question

A slightly lighter hammer spring, a slightly smaller transfer port or a hammer spring adjuster will help. You could actually shim the hammer spring for more power or cut it for less as well. The hammer spring adjuster is the best bet, if your gun does not already have one, as it is adjustable from the outside, and will help you tune for best accuracy. 

https://www.ebay.com/i/123851520326?rt=nc&_trkparms=https://www.ebay.com/itm/123851520326?_trkparms=aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D2%26asc%3D20160908110712%26meid%3D5d7fd6b36d484c03b6de6cc2c5f8a8e2%26pid%3D100677%26rk%3D13%26rkt%3D30%26sd%3D201940203407%26itm%3D123851520326%26pmt%3D1%26noa%3D1%26pg%3D2386202%26algv%3DDefaultOrganic%26brand%3DCrosman&_trksid=p2386202.c100677.m4598

I’m assuming a .177 based on the speeds you mentioned. To get to the 12 fpe range with 8.4 gr pellets try a power adjuster (hammer spring adjuster) with either a .038 or .042 hammer spring. Use somewhere in the .093-.096 transfer port. You can order either a Maximus Euro or a Challenger port to drill out. The Euro/Challenger port will be in the 8-10 fpe range but a long useable shot count. For me I have found the Maximus likes the 14-15 fpe range or the 8-9 fpe range. Both with 35-40 useable shot counts. In between requires some trail and error to find the sweet spot. A 10 gr pellet flattens the shot curve but slows the velocity and has more drop at 35+ yards. I’ve not had much luck with pellets lighter than 8.2 grain. There is about a 10 FPS difference between 8.2 vs 8.4 gr. I don’t have my notes available right now to check specifics but you should get in the 35 shot range between 1800-1100 psi with a 5% spread.

Following with great inetrest

Can I de-tune a Maximus????

My 2017 Max developed a slow leak a few months ago. I sent it in to be repaired (not to Crosman - they were booked). I got it back, and now it clocks higher speeds (855 vs 840), BUT the shot count is down from 22 decent shots to only about 15 decent shots. Accuracy also falls off now like it never did before. 

Any basic tuning suggestions are appreciated.

Thanks!

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MJS

If the only thingl your repair service did was search for air leaks, attempt to fix them, and reassemble; then,there should be no change in the good shot count.

Unless of course something is amiss in the way the gun was put back together

The good news is, these rifles are not too difficult to take apart & fix yourself.

And if you are willing to try, there is some good info on the web to guide you.

What got me over the hesitance to work on mine were 2 videos by Bill Baldyga, proprietor of Magnum Air Power

They are about the Discovery, but can be applied to the Maximus as well

https://www.youtube.com/watch?v=woiQMwBbVxs

https://www.youtube.com/watch?v=TqDrNnTGPY8



Other members may have links to more.

Hope this helps

Ed



PS

Do you know where the gun is leaking from?

Thanks Ed 

I'll watch that and see what I can do. However, at this point I'll probably just buy a new Max or Fortitude ll when I can fine one for sale.

When I sent the gun in for repair, I only asked them to fix the slow leak. I didn't specify "Don't do anything else to the gun.", but I thought that would be understood. 

I don't know where the leak occurs. Before I sent it in, I installed a new fill port assembly, put a new o-ring and yellow tape in the gauge, and a new breech o-ring. Still leaked, so I sent it in.

What really annoys me is that it was a frg'n terrific shooter before I sent it in. 

Hope someone else learns from this experience.

Thanks

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Have you considered contacting the repair shop and letting them know it still leaks.

During that polite conversation you could also ask if they changed anything about the gun?

Who knows?

You might get a straight answer



When you tried diagnosing the leak did you perform a balloon test?

Simply pump the gun to your usual max fill (1800-2000) and attach a balloon directly to the muzzle end of the barrel

(Remove moderator, if any, first, and make sure the bolt is closed)

Then let the gun sit for a few hours/overnight.

If the balloon shows any sign of inflation the likely culprit is the valve

Also

About being a frg'n terrific shooter before the repair

Is the accuracy issue that it no longer hits the point of aim on all shots,or that accuracy falls off as the velocity drops?

Are you shooting with open sights or with a scope?

Info like that can help the readers that are expert with PCPs help diagnose the issue.

(I'm not among that elite)

BTW

Did you ever say .177 or .22

Ed