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PostPosted: Thu Jan 09, 2020 10:35 pm 
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Joined: Wed Jan 05, 2011 12:35 pm
Posts: 6223
Location: P.G. B.C.
Ravenairgun wrote:
Todays chrony was 700 702 705 698 700 690 710 left the gun for 15 UNCOCKED minutes 670 650 648 i dont get it like ya its cold out but its not that cold like today was -5. Im starting to think it could be my piston maybe thats what i sanded to much. I have a regular spring piston can i use that with the gas ram? If not why?


You sanded the piston. Why, may I ask? Was it not the right one for the rifle?
That rifle is only producing the same power as my HW98 in .22.

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Daryl


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PostPosted: Fri Jan 10, 2020 1:43 am 
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Joined: Mon May 06, 2019 4:07 pm
Posts: 158
Well i sanded it and polished it for smoother cycling. And that was the correct one for the gas ram. Im told im suposed to get 710 fps tops which im ok with. I just dont get why its droping to 650. I have another piston... only it doesnt have that filled spot on the inside were the ram is supposed to connect when fired. The gas ram's piston has new seal and the seal wasnt sanded at all. So i dont understand howthe metal part of the piston could cause.compresion issues. Maybe its just the cold....i thought gas rams work better or dont have issues in cold weather which is part of the reason i purchased it.


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PostPosted: Fri Jan 10, 2020 6:42 am 
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Joined: Mon May 26, 2014 1:08 am
Posts: 486
Location: Thunder Bay
Advertisements often say that gas rams are unaffected by temperature. It's false advertising. (maybe they think +10C is cold) Any temperature below 0C is going to slow down the strut. What happens to the struts on the trunk/hatch on your car when it's cold?
Member Todd Cooper (tcooper) did a test on his Crosman Fury Nitro Piston.(there's a thread on here somewhere) His gun slowed significantly in subfreezing temperatures. My experience with gas rams find they slow down more in sub-zero temperatures than my spring guns do. The gas rams seem to take longer to warm up and return to normal velocities compared to my spring guns too.
When it's -20C, my spring guns start to slow down after about 20 shots or 10-15 minutes.
All the guns mentioned above are tuned and lightly lubed with traditional moly paste lubes.
In my opinion, your gun is delivering very tight shot strings with some fall off of velocities due to temperature. If you're happy with 700fps (I would be with a tight velocity spread like that) I would leave it alone and just enjoy shooting it.

Edit: IMHO, a tight velocity spread shows there's nothing wrong with your tune.

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12 springers and a couple of pumpers.
2 lathes and lots of scrap metal.

The difference between genius and stupidity? Genius has limits. -Albert Einstein.


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PostPosted: Fri Jan 10, 2020 2:34 pm 
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Joined: Mon Aug 26, 2013 12:19 pm
Posts: 110
Location: Alvinston, Ontario
Buy a good or the proper spring. This is the same as the other thread turned into.
Have about 10 springers ranging from 5k to 30k+ pellets through them. Have only needed to replace 1 piston seal on brand new Benjamin.
Only D350 is hold sensitive and pellet fussy.

Sent from my LG-H873 using Tapatalk


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PostPosted: Fri Jan 10, 2020 4:23 pm 
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Joined: Mon May 06, 2019 4:07 pm
Posts: 158
Ya the strings range from like 8fps tops not even like todày was 699 698 700 690 705 702 700 20 minutes later 680 678 670 tempreture was +4 like melting snow weather im going to try one more fhing and thats making a shim for the o ring in the breach seal. Thanks for the help and feed back...ill see if that might stop the velocity drop.


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