Huben Huben GK1 tuning

Jgarret7 said:

Can anyone help me out with a basic starting point or tune for H&N 31Gr (.25cal). When I purchased the huben through airgun tactical it cam with 44gr heavies. They stated in the paperwork that the heavys required the screw to be all the way out at max to work properly. It runs flawless however i would like to experament with some lighter slugs and try and get my shot count up a bit. I have some H&N Grizzly 31GR on hand. I have a chrono but not with me and was wondering if i should just dial the screw in 1/2 a turn at a time until i loose functionality or what would be the best place to start without shooting for a specific chrono speed?

Click to expand...

IF it was me i would most likely screw in all the way and count by 1/2 turns . Then back out 1/2 way and count my shots and so on . this would be shooting the 31's . when you find the largest shot count then shoot for accuracy . The largest count would be the slowest speed i think .
Best i can offer.

Are you trying for an even number of full magazines out of it, or like 1 or 2 full mags and some number after that thats less than a full one, and are you starting from a full 5000 psi or a lower fill? I personally set mine up with the 46 grain slugs I make to have just enough air for 1 full magazine and end about 2 mpa above where minimum operating pressure of 12 mpa, so about 14ish, just to be safe.

Lower power until the groups start losing accuracy, then fine tune it back up in power until its accurate again. Poor groups were obvious at 5 yards.

May have to do some trial and error then, since you are starting from 4500ish, I would suspect that to get two full magazines from that point, you're talking maybe 1 to 1.5 turns out from closed ( lowest power)

In mine to get one full mag from 5000 psi and ending on 14 mpa, it is about 2.8 turns starting from closed, thats why I'm guessing 1 to 1.5 from closed for you, but I could be wrong. If you can spare the pellets, turn it as i advised, shoot a magazine, then reload and be sure to check your pressure every shot in the 2nd mag so you dont jam it by shooting below 12ish mpa. I would bet that 1 full turn out from closed will get you close to two full mags from that pressure, but I can't be certain. Also, I have a version 1, so there may also be minor differences with mine that dont directly translate to yours that I am unaware of if you have a later version