Disco/Maximus tuning question

Forums PCP Airguns Disco/Maximus tuning question

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    Helimech
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    I’m in the middle of tuning my sons .177 Maximus and I’ve come across something interesting. I slapped a few o rings in front of the valve and I am in the middle of shooting my first string. The o rings dropped the velocity down from 1100 fps first shot to 774. The shot string is still at a steady decline in velocity, but much slower. I’ve taken 26 shots on this fill with a high of 780 (second shot) and a low of 721 (shot 26). The impressive thing is I’ve only used 200 psi of air for 26 shots. My son is more than happy with this power because he’ll get more shots per fill. My question is how can I reduce my extreme spread? The first 17 shots have a 20 fps spread with no curve and then they fall off. With this many shots using so little air, there has to be a way to get more shots per fill with a tighter extreme spread. I’ll finish shooting the string down to 1000 psi after I feed the animals (kids). 

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    ajshoots
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    You probably still have too much hammer spring tension. Try removing one of the orings and going with a lighter hammer spring or cut down the stock spring. In factory form playing with different hammer spring rates is your only tuning options. An SSG or adjustable hammer and preload like what is used on the challenger are a couple add on options that will allow you to fine tune.

    If you need any further help, feel free to get ahold of me. Would be glad to walk you thru tuning. 4192352515.

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    Helimech
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    Why thank you AJ. I do appreciate that. I’ve just started tuning it and I’m teaching my 11 year old son the ins and outs of tearing apart an air rifle. He watched me for days trying to tune my marauder and he kept saying “I would have given up by now”. He said that until I figured it out with the help of the  interwebs and then he said he wished he could have a project to figure out. He has it now and he’s determined to get this Maximus shooting the way he wants. We will try taking an o ring out and grinding off a coil. We are taking a break right now. We have 67 shots in this string now and have only consumed 750 psi of air. Our fingers are sore from cocking and single loading this thing 🙂 

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    ajshoots
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    Always cool to spend time with the kids and airguns!! That is awesome that he wants to tackle tuning his gun. Keep us posted on the tuning.

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    Dairyboy
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    Any updates to this? Have a .22 Maximus that I’m not happy with the accuracy exactly and a spare very accurate disco .177 barrel I’m going to throw on there. Just curious what your results were.

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    Helimech
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    We shot the Maximus this past weekend and couldn’t get a 1″ group at 20 yards with any pellet. The pellets were very hard to load, so I took the barrel off and found the transfer port hole has massive burrs from machining. Monday I’ll be contacting crosman to see if I can get a new one. 

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    Dairyboy
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    I just checked my .22 maximus barrel and the crown is terrible no wonder why it can’t group! Looks like I’m going to be learning how to do a crown but in the mean time putting in the .177 disco barrel in it and tuning it.

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    JimNM
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    I have a bone stock Maximus in .177.  FWIW my gun really likes the CPHP in 7.9g and does not like the pellets that came in the bundle pack (HWS 8.3??)  At 30 yards, the CPHP will print clover leaf patterns, and the others won’t group better than 2″.  I do not find any problems with machine finish on my model.

    Luck to ya’ – get ‘er tuned up and shoot it well

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