Marauder rifle / disco air blast from rear adjuster hole.
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Marauder rifle / disco air blast from rear adjuster hole.
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Topic: Marauder rifle / disco air blast from rear adjuster hole. (Read 191 times))
robs5230
Shooter
Posts: 62
yes
Real Name: Rob
Marauder rifle / disco air blast from rear adjuster hole.
«
on:
June 11, 2021, 11:31:29 AM »
I wasn't really sure what to call the rifle
Its a Disco base, running a multi shot breech, MRod trigger and PRod hammer.
Its regged and set at 95 bar (it was far too low at 85 and made poor power), so just made the reg adjustment.
I've had this totally apart to change the reg settings.
What I'm getting now, though with acceptable power, is a noticable blast of air from the rear adjuster hole.
To be fair, my .22 PRod does this but not as much, but my 1720 carbine doesnt.
What causes this rearward air blast?
Is it something I've done (like a misaligned tp seal or something)?
Thanks Rob
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PikeP
Banned Members
Sharp Shooter
Posts: 627
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Real Name: Matt
Re: Marauder rifle / disco air blast from rear adjuster hole.
«
Reply #1 on:
June 11, 2021, 12:02:55 PM »
In order of likeliness.
Could be due to non-fluted hammer...
Or air escaping the valve stem
Or air escaping the tp port.
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USA, Colorado Arvada
Pacman Pc/Mobile v1.5 (Pcp analysis and calculation manager. The included script is for weather data fetching)
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Ribbonstone
GTA Senior Contributor
Posts: 12030
Re: Marauder rifle / disco air blast from rear adjuster hole.
«
Reply #2 on:
June 11, 2021, 01:18:59 PM »
That about covers it.
Could be air compressed by the striker going forward. Are other vents in your rifle (cocking pin slot/sear slot). But they don’t irritate a shooter like a puff of air in the face.
The BOTTOM of the transfer port not sealing to the valve body. Possible it could just be leaking into the non-pressurized back end of the air tube (but usually it leaks out at the transfer port area too).
Could be a little leak around the valve stem. Some PCP’s use an o-ring seal on the valve stem, most don’t.
If plugging the end cap hole (maybe adding a spring adjuster) keeps it off your face and does NOT change the velocity...have fixed the symptom but not the cause. Have one Crosman like that, didn’t change the velocity, but swapped the “face puff” for a “trigger finger puff”.
Someday I’ll get around to hunting down what’s causing it and fix it (either the transfer port or the valve stem)….until I need to get in side, will just live with it.
Considering I’ve used the same valve body for something like 12 years (and maybe 4 valve stems), am betting it’s the fit of the valve stem to the valve.
Call it a “dynamic leak” (only happens when you shoot) rather than a “static leak” (happens when air is in storage).
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Louisiana
PikeP
Banned Members
Sharp Shooter
Posts: 627
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Real Name: Matt
Re: Marauder rifle / disco air blast from rear adjuster hole.
«
Reply #3 on:
June 11, 2021, 01:52:34 PM »
Air is bound to leak out of valve stems, even those with orings, after enough dynamic motion, will show wear, just in the case of the non o-ringed valve stem, objects in motion, wear and tear...we are at the age we have quite a bit of technology to reduce it, but you cannot nor will not eliminate atrophy in its entirety.
Many valve bodies are aluminum while most valve stems are some kind of steel, which only makes the issue appear faster.
Sure cars use aluminum heads ect, but the parts that see motion are constantly lubricated by oil, your valve stem is not...
Certainly an area to improve upon for most pcp's, by using higher quality materials that are subject to less galling / wear...
We don't have advanced oiling system that is filtered to keep those two sliding components protected, and most would advise against lubing the area because of this reason...I am sure there are some safe coatings you can apply to help minimize this wear over time.
If my current valve ever sees enough wear that the stem begins to leak, I would sleeve it with a higher quality, better suited material for its application.
A .004" (.1mm) leak could exhibit roughly 10 mg of air being ejected during the shot cycle of a typical pcp that is releasing 600 mg, which means wasted air, and less pressure in the transfer plenum during the shot cycle. Albeit not much, being only 1.66%...but being punched in the eye with 10 mg of air over and over ain't no fun.
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USA, Colorado Arvada
Pacman Pc/Mobile v1.5 (Pcp analysis and calculation manager. The included script is for weather data fetching)
(download / save copy) / work in progress
"Too many spend their time in the black and white, rather than in their grey."
robs5230
Shooter
Posts: 62
yes
Real Name: Rob
Re: Marauder rifle / disco air blast from rear adjuster hole.
«
Reply #4 on:
June 11, 2021, 02:15:40 PM »
Thanks all.
I've noticed a puff or air from the joint of the tube and breech so guessing a misaligned lower TP seal.
I'll shoot it empty and replace it. Luckily I have a new one spare
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Ribbonstone
GTA Senior Contributor
Posts: 12030
Re: Marauder rifle / disco air blast from rear adjuster hole.
«
Reply #5 on:
June 11, 2021, 02:40:45 PM »
Seems we crossed swords...not my intentions.
If it has a little consistent/uniform leak,….won; do a thing to harm accuracy….just a little bit of “wasted air”.
It it irritates you by blowing into your face, then redirect it.
If you gotta have that last little bit (and it is little) of power or shot count, then seal it.
If there was not a hole pointed back at your face, likely not have noticed it and lived happy….if you need that last foot pound of energy or the last good shot in a shot string, fix it.
Elected to NOT fix it until I had another reason to get all the way in there.
«
Last Edit: June 11, 2021, 03:00:34 PM by Ribbonstone
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Louisiana
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Marauder rifle / disco air blast from rear adjuster hole.