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Air Gun Home Forum Index » Airgun Smithing » hammerli 850
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hammerli 850 
PostPosted: Fri Mar 11, 2016 8:11 pm Reply with quote
le3045
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Joined: 28 Dec 2015
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Location: south carolina
hi ive been doing the mods and this is what i have i have a jdsairman 22ci reged at 1800 psi and i removed the pin and spring in the reg so it is open all the time thats hooked to a hollowed out as to pb adapter with the as end bored to 5/16" and chanfered to a 30 degree bevel as i said it is bored as large as the oring seat for the reg and has no pin in it in the valve i drilled the 3 holes but didnt bore the opening where the valve stem comes out i did the barrel mod exactly how its described on the 850 index also i added the 1250 dominator spring but with all this the velocity with 15.9 jsb is anywhere from 580 to 630 fps and i just dont understand why the velocity is so eratic and so low any help would be greatly appreciated oh and you can still cover 5 shots with a dime at 30 yards with a 4x scope so it shoots accurately even with the variance in velocity also i have the stock 850 valve spring and i noticed the part numbers for the 1250 and 850 are different so should i use a different valve spring and if so which one?

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PostPosted: Tue Mar 15, 2016 8:15 pm Reply with quote
AirGunEric
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Did you test things before you started cutting and removing parts?

If not, you have no baseline to judge anything. I would suggest getting a new, unmolested adapter and start there. Also, by removing the pin and spring from the regulator you may have affected things negatively- but I have no idea how jds sets up his regulators.

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Hope 
PostPosted: Wed Mar 16, 2016 6:36 am Reply with quote
le3045
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Posts: 22
Location: south carolina
Eric I think we may have it I think the regulator was bleeding up not given consistent pressures and yes i did shoot it with one cylinder of CO2 in velocity for very consistent

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PostPosted: Thu Mar 17, 2016 7:39 pm Reply with quote
AirGunEric
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If you were consistent with velocity- it must be the jds bottle/regulator. Try putting it back how you found it and see if things correct themselves.

The other issue you may have is that the rifle's valve may not be able to handle 1800psi so it's partially locking up- try 1200psi.

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hammerli 850 
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