GTA
Airguns by Make and Model => Benjamin Airguns => Topic started by: Wheelman on November 20, 2018, 01:37:41 AM
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I'm new to the board and did a quick search but didn't find an answer to my question.
First off a little background, I recently (a couple weeks ago) purchased a Benjamin Prowler .22 from Walmart, hard to argue with $89.00 shipped to my door. :)
I did a bunch of research ahead of time (I'm the type that over researches everything) and came close to buying a Gamo Swarm Maxxim but ran across Kenny Kormendy's review of the Prowler and changed my mind. Another factor in the decision was I had the opportunity to shoot my son's Nitro Venom .177 this last summer and was pleasantly surprised at how nice it shot.
So, in my adventures around the interwebs I ran across some diagrams that showed the gas ram in the Benjamin Trail NP2 rifles reversed (the gas ram chamber is in the compression piston as opposed to at the back of the compression chamber. So, out of curiosity I took the stock off my Prowler to see how the gas piston was oriented in it. I found it is reversed just like the one in the NP2 rifle. I understand my Prowler does not have a Nitro 2 piston assembly so I was very surprised to find the gas piston oriented the same way.
Is this normal for the Prowler or did I end up with a unit that was assembled wrong?
It cocks and shoots fine and once I got it broke in (over 400 pellets through it) is pretty accurate considering I'm using the included Center Point 4x32 scope (which is junk if you ask me).
Wheelman
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It's funny you should ask this as I am contemplating the same questions.
I made a recent post about a Titan where the body of the gas spring is rubbing the inside of the piston causing a gritty feel.
Somone suggested I try reversing the gas spring.
I actually had it apart some time ago and when I put it back together I had put the gas spring in backwards (according to the exploded drawing) but it shot fine. But it bugged me so I took it apart again and put the gas spring in according to Crosman's drawing, now I have the scraping issue.
I hope to get it turned around AGAIN and do some chrony testing to see if it makes a difference!
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I got the gas spring turned around backwards to what Crosman's drawings show and did some before and after testing.
It now cocks much smoother, no more gritty sandpaper feel to it.
It actually picked up a few fps from an average of 745 to an average of 762. The deviation increased slightly to 4.94 from 3.1.
Some of that increase is due to a few other factors but I think it is safe to say it is fine to have the gas spring in 'backwards' :P
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UlteriorModem,
It's interesting that you were able to turn the ram around and it fits in the body of the piston, how tight is the fit?
I can't tell just by looking at mine and I hesitate to take it all apart just yet but it looks like the fit is snug.
At some point in the future I will take this Prowler apart and "tune" it by de-burring, polishing and lubing the moving parts, probably replace the plastic washers at the barrel pivot with brass or bronze thrust washers to tighten it up.
Based on what you've reported I'll definitely be leaving the ram oriented as it is now, makes sense that the FPS would rise a bit due to the elimination of the friction between the body of the ram and the internal surface of the piston.
Wheelman
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UlteriorModem,
It's interesting that you were able to turn the ram around and it fits in the body of the piston, how tight is the fit?
I can't tell just by looking at mine and I hesitate to take it all apart just yet but it looks like the fit is snug.
At some point in the future I will take this Prowler apart and "tune" it by de-burring, polishing and lubing the moving parts, probably replace the plastic washers at the barrel pivot with brass or bronze thrust washers to tighten it up.
Based on what you've reported I'll definitely be leaving the ram oriented as it is now, makes sense that the FPS would rise a bit due to the elimination of the friction between the body of the ram and the internal surface of the piston.
Wheelman
It slips right in, after all the original design, when cocked, the body of the gas spring went up into the piston.
If it is working don't fix it :D Famous last words.
I was able to get a bunch more rounds through it this afternoon, and it finally quit dieseling so much. I can tell you that the 'backwards' piston has not affected accuracy much if at all.
By the end of the day I was shooting 1 to 1 1/2" groups from 26 yards consistently (with the occasional flyer). That is an improvement for my rifle. But I have done a few other things.
Still have the original pivot washers, I need to get around to doing that upgrade soon. :D
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I understand my Prowler does not have a Nitro 2 piston assembly so I was very surprised to find the gas piston oriented the same way.
Is this normal for the Prowler or did I end up with a unit that was assembled wrong?
Hi, Wheelman. Here's the parts diagram link for the Prowler:
https://support.crosman.com/hc/en-us/articles/204787210-BPNP17X-TMP-Owner-s-Manual-EVP-2014-
Have fun!
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Thanks Dan.
Based on what the parts diagram shows the gas ram in my Prowler is installed backwards.
I assume it must've come from the factory that way, it was purchased from Walmart as a new item and needed several hundred pellets fired before it started to group.
I have no intention of "fixing" it any time soon if ever so it is what it is.
My curiosity as far as that aspect of this rifle is concerned has been satisfied, thanks for the input guys.
Wheelman