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All Springer/NP/PCP Air Gun Discussion General => American/U.S. Air Gun Gates => Crosman-Benjamin Air Gun Gate => Topic started by: 1216bandit on December 05, 2012, 07:22:08 PM

Title: Optimus and phantom breech seals
Post by: 1216bandit on December 05, 2012, 07:22:08 PM
Are there rubber o rings  that can used instead of the hard nylon type for breech seals?  The optimus is .177 and the phantom is .22. 
Thanx...Dan
Title: Re: Optimus and phantom breech seals
Post by: LAalex on December 05, 2012, 07:45:38 PM
  I would think that there's an O-ring that would fit, but I can't say.  I've never measured the size of it.  If I remember tomorrow I'll put the calipers on mine and get a measurement.  I know that there is a plumbing O-ring that works for the Dianas, not sure if it's the same size. 

Scotty
Title: Re: Optimus and phantom breech seals
Post by: 1216bandit on December 05, 2012, 08:13:37 PM
No reason to go through the trouble Scotty, you may end up damaging your seal.  I can take a measurement also, and I am sure my seal is bad so no big deal if it gets buggered up.  I just thought someone may be using a rubber o ring and know what size fits best.
Title: Re: Optimus and phantom breech seals
Post by: john on December 08, 2012, 12:53:38 AM
how do you know your seal is bad...?...just curious. I removed one of two shims I had under a breech seal the other day and the velocity dropped 100fps so I put it back pronto.
Title: Re: Optimus and phantom breech seals
Post by: 1216bandit on December 08, 2012, 04:47:37 PM
Groups started to open up and when I looked at the seal it was pretty much just flush with the breech surface and was really low at the top.  With the amount of use this gun gets it sure cant hurt! 
Title: Re: Optimus and phantom breech seals
Post by: john on December 08, 2012, 04:55:59 PM
check this out:
http://www.gatewaytoairguns.org/GTA/index.php/topic,17738.msg153909.html#msg153909 (http://www.gatewaytoairguns.org/GTA/index.php/topic,17738.msg153909.html#msg153909)
Title: Re: Optimus and phantom breech seals
Post by: 1216bandit on December 08, 2012, 05:23:36 PM
Interesting read...thanx!
Title: Re: Optimus and phantom breech seals
Post by: john on December 09, 2012, 02:08:04 AM
What I wrote was about my Trail NP but I'm guessing it's the same for your guns. The first time I ordered a spare breech seal from Crosman, the seal they sent was same diameter but disappointingly short. ??? I thought they has made a mistake and ordered the taller version. Later on, I ordered a spare Trail barrel/breech and was surprised that the spare had a shallower circular channel, obviously designed to take the shorter version of the seal, but it does require two of the metal shims (also from Crosman). So life with Crosman is like that "box of chocolates." You never know what you're going to get. Not complaining...at least parts are available. For a long time I could not figure out how they machined a sloped channel...but now i realize they simply channel first and face off the breech second. Duh! ::)

When I eventually decided to replace that original taller seal (by then dark yellow with use), it was brittle, unlike the soft white new one...oh, maybe my velocity spread would narrow with a new one...?...wrong, no noticeable improvement of any kind...so the old brittle one was still doing its job. Actually not sure how the seal does its job. I assume the air blast expands the seal radially outward against the outer wall of the channel and ovals it so that it spreads out against the bottom of its channel and the against the face of the compression tube.

Oh, and the channel edges of the new barrel/breech face...very sharp, so sharp that the fresh seal got shaved when pressed in, so i ended up sanding those edges. Always learning with these guns.

Also if not sure you're going to like a new seal or o-ring, thread a short length of dental tape (its wider than floss) thru the seal before seating...leave it long enough to grab...the gun doesn't even know it's there while shooting...you can pull that seal out easily anytime.
Title: Re: Optimus and phantom breech seals
Post by: 1216bandit on December 09, 2012, 09:06:21 PM
Thanx again John for the tips, will be careful of the sharp breech edges!  All I can say for sure is what was once a very accurate rifle is not quite as accurate.  All the screws are good and tight and barrel pivot washers are brass so no play in that area.  The piston seal was changed when I installed the e3650 spring which was not that long ago, so I really hope the breech seal brings back the accuracy!