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 Post subject: Gas ram velocity range
PostPosted: Wed Jan 08, 2020 7:12 pm 
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Joined: Mon May 06, 2019 4:07 pm
Posts: 158
Just wondering how much should the velocity differ from shot to shot on a well tuned gas ram. Fresh breach seal, fresh piston seal, cleaned barrel and freshly cleaned and lubed internals. My last 10 shot chrony was 725, 720, 705, 704, 700,705,700,698,702 then 670?


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PostPosted: Wed Jan 08, 2020 7:25 pm 
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Location: Kingston, ON
Not that much. See if it settles down, it may have been dieseling.

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PostPosted: Wed Jan 08, 2020 7:46 pm 
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Location: Thunder Bay
Just a few suggestions.
Is the new breach seal correctly sealing? Some breach seals need a spacer underneath, or a few wraps of dental floss to raise the seal.
If you recently tuned the gun, you could be burning off assembly lubes for the first two shots.
It seems like your gun is shooting around 700 fps. Is that similar to the velocity you were achieving with the same pellet weight before the tune and reseal? What pellet weight/caliber are you shooting? 700fps for 14.3gr/.22 is a little slow, particularly for a gas ram.
If you exclude shots 1,2, and 10, you actually have a tight shot string for 7 shots from 698-705 fps.
Also, sometimes velocities may wander a bit until a new piston seal wears in.
Have you tried different pellets?
Gas rams usually just suddenly totally fail rather than slowing down.
Hope this helps!

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PostPosted: Wed Jan 08, 2020 10:03 pm 
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Posts: 158
Ya all pellets were 14
.3 gr maybe the piston seal needs to be broken in? How do i check if the breach seals or test the breach seal to see if its seeling properly? Looks like that may be the.problem


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PostPosted: Wed Jan 08, 2020 10:13 pm 
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Joined: Mon Aug 08, 2016 7:23 am
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Location: Somewheres near the Atlantic
Place a piece of tissue/toilet paper over. If it blows away/off, then you have a beech seal leak.

You can shim them with some dental floss. Wrap it around a pencil, or something the dia of the breech seal groove. Then slide it down, then put the seal back in.


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PostPosted: Wed Jan 08, 2020 10:14 pm 
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Location: Vancouver Island BC
now you have two post basically the same topic


topic84424.html


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PostPosted: Thu Jan 09, 2020 12:32 am 
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So if i.put a piece of paper towl over the transfer port and do what exactly?


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PostPosted: Thu Jan 09, 2020 12:48 am 
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Sorry this ones about velocity and finding out why its inconsistant


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PostPosted: Thu Jan 09, 2020 4:46 am 
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Location: Thunder Bay
Ravenairgun wrote:
So if i.put a piece of paper towl over the transfer port and do what exactly?

Place a piece of tissue (toilet paper works well) over the breach after you have cocked the gun and it's ready to fire. Just lay it over top of the hinged joint where the breach seal is located, then fire the gun. If the breach seal leaks, the escaping air pressure will blow the tissue off. If your breach seal is sealing properly, the tissue will slide around a little due to recoil, but it won't blow off.

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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: Thu Jan 09, 2020 3:23 pm 
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Ok i just seen a video of the test am.i suposed to shoot it with a pellet in it?


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PostPosted: Thu Jan 09, 2020 3:31 pm 
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Location: Kingston, ON
Ravenairgun wrote:
I dont fully understand sorry... i break the barrel put a piece of tissue over the transfer port? Close the barrel and shoot it? Sorry just confused.

Make sure you load a pellet otherwise a dry fire can make matters worse.
But no, all you are doing is testing for a leak, so cock the rifle, load it, put the small piece of tissue over the breach joint and then fire safely - I suggest a bench rested shot. Examine if the tissue got blown or just slid.
I doubt its a breach seal issue.

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PostPosted: Thu Jan 09, 2020 5:21 pm 
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Ravenairgun wrote:
Sorry this ones about velocity and finding out why its inconsistant

LOL ok but no more oh put a spring in it .....


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PostPosted: Thu Jan 09, 2020 6:19 pm 
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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?


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PostPosted: Thu Jan 09, 2020 6:20 pm 
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lauchlin wrote:
Ravenairgun wrote:
Sorry this ones about velocity and finding out why its inconsistant

LOL ok but no more oh put a spring in it .....

Ya im going to rebuild my springer adventualy so i got a gas ram and a springer


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PostPosted: Thu Jan 09, 2020 6:23 pm 
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Ya didnt even move for the tissue test and i mean the only parts left are the piston and gas ram


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