760 Crosman variant help

[wetland]

Hi i picked up a great 760 off if crags list. Styrene stock and styrene forearm. Looks to be a flat head / it has the nut in the part attached to the forearm. From what I've read It must be a variant of the first version though its not all wood? Any one else have one of these? Crosman  site must be wrong... Not wood im a bit confused...  It is heavy compared to my 1976 Coleman powermaster which i just rebuilt. Any ideas / experiance appreciated. Serial # starts 004.

From what i read this must be version # 2? Though no wood / all styrene . 

Thanks,

Brad

[mav72]

Welcome!

I can't make sense of the serial # but it's possibly a 1977-1980 and that's only if it's all original...  I'm no expert with these older 760s though... Maybe somebody switched out the stock and forearm making it harder to identify...? As for the serial number, O,6,8,9s can look like 0s also..

[wetland]

Hey mav,

Thanks for the reply.

Serial # 04446xxx. Now according to Crosman if this were produced after July 1975 the first three digits should identify it. I just don't see how 044 can identify it... Therefore I think it must be pre-75.

Also when you cock the gun / open the forearm turn the gun upside down and look closely at the gun I see a nut in the piston assembly therefore it must be version #1.

So i guess if you see the nut in the piston assembly that is one way to tell, and of course the other break it down.

[wetland]

Ok after watching zerofossilfuel video i can now confirm I have the exact same gun as in his video.

I read elsewhere that this is varent #2 / don't know how true that is? Now on to breaking it down.

[mav72]

Oh Ok I see... I was thinking, it may be a pre 75 because of the number and the adjustable nut on the piston... I get confused with the variations because a lot of them are so similar. I think the forearm and stock may have been switched out... I've seen wooden parts occasionally being sold out there, if you prefer a wooden stock like me....  Or if you are good at wood working, you can make your own....

If you notice anything different from your other 760, make sure to take pictures when braking down... It could save some trouble... Also take your time... I've lost parts when in a rush trying to stick to a schedule... Heck, I've had trouble putting airguns back together when in a hurry when it was easy as pie the previous day.

[wetland]

Yes i agree all the information out there makes things a bit confusing sometimes...

Yes i think you might be correct about the forearm stock being switched out.
Now i do have a nice piece of oak 4 x 4 laying here might give the forearm stock a go after i get her running again.

The pictures are an excellent idea.

Take your time reminds me of a story... The old bull and a young bull are standing on a hill over looking a pasture with a herd of cows way down at the bottom of the hill. The young bull looks at the old bull and says lets run down there and get us a piece of a#%. The old bull replying to the young bull says lets walk down and #@%& (have) them all.

I know what you mean.

[mav72]

Yes i agree all the information out there makes things a bit confusing sometimes...

Yes i think you might be correct about the forearm stock being switched out.
Now i do have a nice piece of oak 4 x 4 laying here might give the forearm stock a go after i get her running again.

The pictures are an excellent idea.

Take your time reminds me of a story... The old bull and a young bull are standing on a hill over looking a pasture with a herd of cows way down at the bottom of the hill. The young bull looks at the old bull and says lets run down there and get us a piece of a#%. The old bull replying to the young bull says lets walk down and #@%& (have) them all.

I know what you mean.

^^^ I haven't heard that one in a while... LOL

I know there are guys on this forum who are real geniuses when it comes to those older 760s... You just have to wait for them to pop in... I haven't been "IN" for a while since I no longer have a home range and can't really shoot much any more so I don't know who is an active 760 expert at the moment....

[egillman]

I don't remember where I got this, but it seems correct.

Model 760 Powermaster

First variant. Wood stock and grooved wood forearm, brass bolt, smooth bore 1966-1970 (These smooth-bores shoot really well with pellets.)

Second variant with styrene stock & forearm & scope mount groove, brass bolt. Checkering on forearm 1971-1974

Third variant, self-cocking w/styrene stock & smooth wood forearm. 1974-1975

Fourth variant w/ABS stock & forearm. 1975-1977

Fifth variant w/manual cocking. Brass handle for bolt smooth bore 1977-1980

Model 760XL Powermaster Pneumatic, BB repeater, .177 cal., single shot pellet. brass finish on receiver and fancier plastic stock, rifled barrel 1978-1980

Sixth variant w/plastic bolt. metal receiver, rifled barrel 1980-1983

Seventh variant w/plastic receivers & w/welded sights. 1983-1991

Model 760/20 Pneumatic, BB repeater, .177 cal., single shot pellet. 20th year commemorative metal receiver rifled barrel 1985

Model 760B Pneumatic, BB repeater, .177 cal. single shot pellet. (Model 760 w/ black stock & forearm) rifled barrel Rifle 1988-1991
Eighth variant w/shortened barrel w/pressed on sights. Rifled barrel 1991-?
Nineth variant w/fiber optic front sight and 5 shot manual clip. smooth bore. current

[wetland]

mav,

LOL... Thanks again.


Hi Erik,

Thanks for the reply. I did see something similar on another forum / your list is much more detailed.

I don't remember where I got this, but it seems correct.

Model 760 Powermaster


Second variant with styrene stock & forearm & scope mount groove, brass bolt. Checkering on forearm 1971-1974


Fourth variant w/ABS stock & forearm. 1975-1977

In my OP the fourth variant is the one i just rebuilt I purchased it new in 1976. Its good to have her back.

The other one is definitely variant two. I broke her down today cleaned her up and have her back together.

She will not hold air I can hear the air coming out of the barrel when I cock her. From what I've read this might be from the quattro o-ring not sealing on the inside of the brass cup that fits on the back of the valve? Does this sound right?

Also when I took the valve apart the white plastic part (cone on one end flat on the other) in the back of the valve looked a bit worn, and the spring has a flat spot or two on a couple of the coils about midway like it was rubbing on the inside of the valve. I did replace the other three o-rings.

So I think I need a new quattro o-ring is the exact size of this o-ring 008? I know people are using the round 008 as a replacement. Just don't see the size of the quattro o-ring mentioned anywhere?

A new spring.

A new white plastic part.

Any other suggestions?

Thanks,

Brad

[egillman]

There are 5 seals that usually need to be replaced on a 760 1st or 2nd variant:  the 4 o-rings that go on the valve, and the plastic "pump cup" that goes on the piston.  The o-ring that best replaces the "quad" o-ring is a metric 4mm x 2mm which I get at my local True Value hardware store.  The pump cup can be purchased from JG Airguns, among others.  See the attached link - the Crosman 140 used the same valve as the 760. 
Erik
http://anotherairgunblog.blogspot.com/search/label/crosman%20140

[egillman]

One other thing you might want to do when rebuilding the valve is remove the aluminum "spacer" that fills up about half of the volume of the valve.  That way, you can put more pumps into the gun.

[wetland]

OK I will disassemble again and replace the quad seal with a 4mm x 2mm o-ring. Do you have any pointers on the removal of the original quad seal. I did read your other post where you stated the you were able to pry the seal out with a small screw driver. I would assume it would be easier to remove with the end cap in a padded vice?

Also I will have to replace the spring as I know it is worn. I will get one the same size and another longer one so I can experiment with the chamber as you suggested.

I also found this information on another site: X ring dimensions are 1/16" thick 3/16" ID and 5/16" OD  seals the exhaust valve to the main body of the valve.

Brad

[egillman]

To remove the old quad seal, either use a small jewelers screwdriver or an exacto knife.  Try to get all the way behind the ring and then pry it out.  They sometimes break if they are brittle, so go slowly.  I have found longer springs of about the same tension at Ace or True Value stores. I have also used two 760 valve springs in series. Have fun!

[wetland]

I just broke her down again.  I have the quattro o-ring coming tomorrow (might have a few extra will see).

Ok so try to get behind the quattro o-ring I can see this should be accomplished by trying to go in from the top then down behind the quattro. Thanks for the tip.

Now to go spring hunting.

[wetland]

Success! I got her put back together and she works great.

I used a 1/8" wooden dowel rod ground to a point and dulled to manipulate the new quad ring into place.

Found a miscellaneous pack of springs at home depot seems to have a few that will work. I put the valve back together with the aluminum spacer and a new spring.

Hats off to mav, and Erik for their help.

Brad

[mav72]

Glad you got her working! I remember the grin on my face when I got my brothers Crosman 766 working again... My gun now... LOL

Better watch out... You're gonna start looking to buy other old guns to fix, then the modding starts... 

[wetland]

mav, Grin is ear to ear.

Give a man a puzzle then he figures it out (well you know). Give a man a another and he figures it out it becomes (what's next? where's the next puzzle?) I know I need another puzzle.

Looking at 1377 wow mod city i know what you mean... Could be addictive. Especially with all the knowledge of all the people on this great board. Also considering a tecforce 99 / 97 or a nitrogen powered rifle. Need more tools dam...

Next step is to remove the spacer in the flat top and see what she can do. Also the 4 x 4 piece of oak i mentioned is itching to be turned into a forearm stock (another puzzle).

[mav72]

mav, Grin is ear to ear.

Give a man a puzzle then he figures it out (well you know). Give a man a another and he figures it out it becomes (what's next? where's the next puzzle?) I know I need another puzzle.

Looking at 1377 wow mod city i know what you mean... Could be addictive. Especially with all the knowledge of all the people on this great board. Also considering a tecforce 99 / 97 or a nitrogen powered rifle. Need more tools dam...

Next step is to remove the spacer in the flat top and see what she can do. Also the 4 x 4 piece of oak i mentioned is itching to be turned into a forearm stock (another puzzle).

LOL I have lots of puzzles... I'm still trying to figure out how to seal the bolts of my late 760 and my AM77 (2100).  I mean I pretty much have the puzzle solved in my head but I don' know where to find or what size those little tiny "O" rings are that I always hear the "hard core" modders talking about... The first puzzle I had with my newer 760 was, how do I get it accurate. The simple answer was rifled barrel... I turned down part of a 7/16 barrel to fit the transfer port of a 760 with a drill, masking tape, and a file...

If you do get a 13XX type gun to mod, make sure you firmly decide on which one you want. I was all over the place with mine.. Truly what I really wanted was a 2289 BUT at that time the 1322 and 2289 were no longer being produced. So, I ended getting a late model 1377. (I also have an old rear cocker 1377 that I converted to a steel breech.) Well, I bought the 14" barrel and steel breech for the 1377. Then the 1322 gets reintroduced and then the 2289 gets reintroduced... So now I have two 1377s and a 2289... It's a good thing I waited and didn't buy the 1322.  It's maddening I tell you! Maddening! LOL

Good luck with the stock... Take some pics...  I plan on working on one myself but in plywood... You can thank airgunandy for that one... Have you ever seen the late 760 that he did in plywood? I was in awww with that one... That beautiful gun inspired me to mod mine, which I thought was a piece of junk at the time...

[wetland]

LOL I have lots of puzzles... I'm still trying to figure out how to seal the bolts of my late 760 and my AM77 (2100).  I mean I pretty much have the puzzle solved in my head but I don' know where to find or what size those little tiny "O" rings are that I always hear the "hard core" modders talking about... The first puzzle I had with my newer 760 was, how do I get it accurate. The simple answer was rifled barrel... I turned down part of a 7/16 barrel to fit the transfer port of a 760 with a drill, masking tape, and a file...

If you do get a 13XX type gun to mod, make sure you firmly decide on which one you want. I was all over the place with mine.. Truly what I really wanted was a 2289 BUT at that time the 1322 and 2289 were no longer being produced. So, I ended getting a late model 1377. (I also have an old rear cocker 1377 that I converted to a steel breech.) Well, I bought the 14" barrel and steel breech for the 1377. Then the 1322 gets reintroduced and then the 2289 gets reintroduced... So now I have two 1377s and a 2289... It's a good thing I waited and didn't buy the 1322.  It's maddening I tell you! Maddening! LOL

Good luck with the stock... Take some pics...  I plan on working on one myself but in plywood... You can thank airgunandy for that one... Have you ever seen the late 760 that he did in plywood? I was in awww with that one... That beautiful gun inspired me to mod mine, which I thought was a piece of junk at the time...

I did read about the O rings and bolt mods you mentioned this will be one to definitely look at in the future. So you chucked up the 7/16 barrel into a regular drill? And used the masking tape as a guide. No there some ingenuity!!

I know AG Depot had the reman 1377's for $36 I now see they are OOS. Have been looking on CL daily to see what I can find. I live in the state where they will not ship .22 cal pellet guns, so for the 2289 or any other .22 cal I would have to jump through the hoops and have a friend in another state receive the gun and then road trip time. I do have a FOID card however the transfer fee of $30 seems ridiculous for an air gun (what a pain in the ^&*). Maddening you say..I like you / know I will end up with several my self

Yes I do remember seeing airgunandy's plywood stock / now that was really cool.

I did do pictures with this one here are a couple of shots I took.

Before
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The TOP
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Break Out
[smg id=1861]

The Valve
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New Springs / Quad
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After
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Brad

[ezman604]

And there ARE other variants out there.
I bought mine in either 1967 or 68. It is a Revelation 760 sold by Western Auto. It sports the wood butt and grip but the grip is not slotted. Mine has just a single finger groove down the center (similar to the plastic ones later). Also, mine is a rifled barrel.