Tuning Maverick Upgrades

So it is time to start adding a few upgrades to my Maverick. I have started to shoot mainly slugs, but do still shoot JSB [email protected] and H&N 18gr. But I primarily shoot .217 23gr NSA slugs now. But I have also shot 22gr Varmint knockers. I tried the H&N .217 23 gr slugs but they load really hard into the breech....not sure why, but I have to exert a signifgantly larger force to load them and only used 1 mag so far.

I am looking on putting in a heavier hammer to be able to push my speeds up a bit more. Right now I am at 150/120, hammer spring maxed and at level 7 I am getting about 968 out of the 23gr slugs. I would like to start shooting heavier slugs (26gr and up) and know I will need the heavier hammer to go to higher pressures. Right now I am for sure going to get the dual transfer port from Huma Air. I want to stay with the regular probe and not switch to the adjustable pin probe since I still shoot pellets. I was looking to maybe order the heavier hammers directly from FX-USA but am unsure of the part numbers. I wouldn't mind ordering the dual transfer port from them as well. (My Mav is one of the early ones that shipped without it)

So my question comes to where have you guys ordered your parts, does anyone have the specific part numbers I am looking for. Or would you suggest getting the Maverick Slug Power Kit and the transfer port from Huma.

https://www.huma-air.com/High-Flow-V2-Dual-Hole-Transfer-Port-For-FX-Impact,-Dreamline,-Crown,-Maverick-and-Wildcat-MKIII

https://www.huma-air.com/FX-Maverick-And-Wildcat-MKIII-Slug-Probe-Power-Kit

Any thoughts on why those H&N slugs feed so hard would be appreciated as well. I have 3 full and 1 nearly full tin of them I would love to use.
 
I purchased the slug kit from Huma-Air because they had it in stock and I got the dual transfer port from Ernest Rowe. On the slug kit I went with the pin probe because I only shoot slugs; 28.5gr is the lowest weight I use. My typical slug is the 30gr VArmint Knockers or the 32gr boat tails from Griffin. 
Don't have any experience with H&N slugs so I really can't help you on that one. Hope this helps some for you. 
The 30gr are at 1025fps and the 32grBT are at 1010fps.
 
I'm in the process of working up the mav for slug shooting. It looks like 100 yds or so is the practical limit for good accuracy. I'm at 155/120 bar and just bumping to 125 bar, fps drops. 

Thanks for the info on 910 Airguns; I've got the ER port coming as well and was able to source the mav slug kit from Spaw airguns here in FL. I'm interested to see how much further I can go without having to get the hvy slug barrel (assuming I could find one.....).



Jim