So pulling down my inaccurate, freshly tuned (by me), Crosman Storm -- new apex seal, JM lubes, using the CTD guide... much like many of you. I pulled it down because of the accuracy issue (see other posts), just to see if there was anything obvious that I missed.

Everything seemed ok, till I got to looking at the seal (see image). Nice nick on it right on top. The cause? Sharp edges left inside the tube.

I started following the path of the seal back into the chamber, really paying attention to what it had to pass over to get in and out, and I still felt sharp edges... trigger bolt hole, pin holes...

I was SO CAREFUL not to remove too much material, that I obviously did not remove enough, and sliced the seal.

Lesson: Go sloooow, pay attention to detail, do it right the first time, and double check all of the edges. I ended up using a small diamond file to bevel off inner edges of the tube, it will not happen again...

(now if those new seals will just get here!):thumb:

Oh, and for you non-newbs... I assume this is the likely cause of my inaccuracies? Opinions?

Don't worry - been there done that. Now what I do is after removing all the stock parts and deburring, I'll leave the stock seal in there for the time being and rotate it so a good spot of it rests against the cocking slot. I'll run the piston with the old seal like that a few times and feel for grabbing as well as examine it to see if I did good enough on my debur. Though the sides of the cocking slot is important, so is every hole/slot the seal will come in contact with going in and out. That includes the stop in hole as well - I've had that take a piece of my seal out before...

In your opinion, what would be the performance effects of a nick like that? loss of power, but inaccuracy too?

Velocity inconsistencies, wider standard deviaton,
lose of power, etc...

Hubster:

If the muzzle has not been checked for burrs using the Q-Tip trick, now might be a good time to do it. If any are found, a little polishing of the crown might help.

BTW, make sure the stock screws are good and snug once it's back together.

Amigo

What I do when installing the piston/seal....
Even on a deburd gun the seal can catch on the end of the cocking slot.
if the seal is a tight fit it will protrude in to the slot and catch
when it gets to the end
I have a lenth of plastic 4thou shimming 300long X 25wide.
I slide in in the tube over the cocking slot till its past the end of the slot
slide the piston/seal in till is past the slot end then hold the piston
in place and with draw the shim.
No chance of tagging the seal on the slot edges or slot end.

It helps to use a plastic Q-tip with the cotton removed.
You can help the seal past any edges by pushing down
on the seal's leading edge to let it slide past the holes
and slots in the compession tube easier without snaging
on said edges.

Thanks for all of the suggestions... oh, and keep them coming, there are many beginners lurking around that need to hear this stuff!!:cheers:

I do something similar but use a piece of wood, a little thinner than a popsicle stick and "help" the seal past the edges. You can probably use anything that'll fit as long as it won't damage the seal.

It helps to use a plastic Q-tip with the cotton removed.
You can help the seal past any edges by pushing down
on the seal's leading edge to let it slide past the holes
and slots in the compession tube easier without snaging
on said edges.

always buy extra seals, if you can afford one you can afford two.
i have a spare seal for every gun i own, if i decide to take er down i want er up same day.

always buy extra seals, if you can afford one you can afford two.
i have a spare seal for every gun i own, if i decide to take er down i want er up same day.

The funny? part is that I did buy an extra seal... and I have torn my shop and office apart looking for it! My memory just ain't what it used to be, and I am not careless... I put is somewhere that it would be safe and not get tossed out... it'll turn up sometime! I have to write just about everything down at work, where I used to keep it all upstairs -- ah to be young again!

So I got two on the way... :D

i think we all have been there lol,I have used a strip of film from a non-digital camera to put inbetween the piston seal and the slots in the sompression tube it worked pretty well

I am in a terrible predicament. I'm very very new to air rifles. For my b-day, my mom bought me a Benjamin Trail NPXL 1500 .177cal right before she passed away a month ago. I miss her so much...i'm sorry for being so soppy. I've read that its a good idea to take apart, debur, relube and check/replace seals etc, but I have no idea what any of the parts are called. The gas piston, that's obivous but the piston chamber or piston/spring guide, compression chamber? EEERRR!!! Plus if I am going to need moly or tar, i don't know anyone or place around here in Havre de Grace, Maryland, who shoots airguns or anyone who i can ask to borrow or give me some of it. I know my situation shouldn't affect others, but since my mom passed, my pop is really struggling with bills and to get a parttime job along w/his regular one. So I don't want to ask him to help me. I can't even get a pt job because of school during the day and watching my little brother at night. or I would buy my own stuff. What I am asking for from everyone is :

1.) can anyone send me the exact things in detail that I need to do to get the most beneficial usage,
power, accuracy and longevity out of my Trail NPXL 1500 .177cal. I would like the steps to be
numbered in numerical order and in exact and definetive details, with pictures, but a
beggar cannot be a chooser.

2.) If anyone has any spare moly, tar or whatever type of lubrication that I will need, and/or replacement
seals (that is if I am to replace the ones that I have on the Trail now).

3.) Any pellets that your rifles don't like. I read that I have to try a bunch of different types of pellets
to shoot to see what ones your gun likes. I only have 300 crosman premier hollow points 7.9gr.
and for 5bucks @ a yard sale, I got Beeman Silver Arrows that my Trail doesn't like, so whoever
wants to trade, I got about 200pellets from a 300 can that I can swap or if you really need it i'll
give them to you just for helping me.

4.) I know nothing in life is for free so I have stamps for the use of currency or trade if anyone needs it.

I really would greatly appreciate it if anyone can help me. If anyone is interested my email is jwsmith3rd@yahoo.com. Also, if there is anything that I can help anyone of you with, just ask me. I may be a kid, but one day I want to be an engineer so thats why, later this year, i'm going into the Marines, so they can pay for my college.

Respectfully,

Joshua

I might be able to send you a few pellets. I have no idea on the rest of it. One thing i recomend, is saving the $32 it costs to get the GRT III trigger.

PM me your addy.

Also if you are joining the corps next month, I would say just shoot the gun as much now, and worry about mods when you get back.

All you'll need is a tiny tiny blob of moly and a new seal, the piston doesn't really need a guide but there is one available if you do some searching that's supposed to work pretty well. Otherwise an easier and cheaper way would be to button your piston.

To start from the beginning, you'll need a spanner wrench, basically a handle with 2 little metal dowels that will fit in the 2 holes in the end cap. This unscrews and you need no spring compressor to open it or put it back together. Or if you're like me and can't wait a big vise-grip can be made to work.

Pull out the parts and lay them down in the order they came out just to be safe. Your seal may even be in good condition! You don't have to do anything with the seal for this. Cut out 2 or 3 pieces of plastic from a soda bottle, quarter inch squares will do, otherwise a hole punch makes nice circles.

Hold the piston as it would be in the gun, slot down. Now looking at the end of the piston opposite the seal, glue a "button" on at the 12 o'clock position, 4 o'clock, and 8 o'clock. I used Gorilla Glue and took clear packaging tape and wrapped the SHIT out of the end of the piston and left it for 24 hours. You'll probably have to sand down the "buttons" to size them to the inner diameter of your tube, otherwise just one at the 12 o'clock position will work. Obviously, you'll need to remove the tape before reassembly lol!!

If you can get some 600-800 grit wet/dry paper, it's a great idea to polish the contact points in your trigger mechanism. Saves you the 32 bucks on the GRTIII and is rewarding to feel your work.

PM me your address, I have to mail some pellets to igotit I promised him a while ago and need to get a CD of mine mailed to a buddy so I'll be hitting the post office very soon. I've got almost all of the moly I ordered when I tuned my Trail XL, and I've used it on that gun, my Quest about 3 times, all 3 of the B3's I've had the numerous times taking them apart, and my Sterling. So don't look at the tiny blob I send you and say, "What the f%^k is this?!?!" Keep in mind, a little bit goes a llloooooooooonnnnnnnnnngggggggggggg wwwwwwwwwwwaaaaaaaaaaaaaaaaayyyyyyyyyyyyyyyyyyyyyy yyyyy

Just a suggestion, since your gun will wail out normal weight pellets over the sound barrier try to keep your pellets close to 9 grains or above for optimal accuracy