GTA
Airguns by Make and Model => Crosman Airguns => Topic started by: bustachip on June 26, 2018, 11:35:17 PM
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and I have a couple of questions for those in the "know". One, does the valve dump all the air "completely"
with one 10 pump shot, or will there be a little air left in the valve? Two, if so what do guys do to fix it, use
a stronger hammer spring or a lighter valve spring?
And three, in this parts diagram it shows a (#2200-037 breech sleeve) going in the valve first, then the
(#130-036 breech gasket) goes in on top. Is the (#2200-037 breech sleeve) needed, or do you guys just
use the (#130-036 breech gasket)? Reason I'm asking is, I don't remember my 766 having a (#2200-037
breech sleeve), but I ordered one anyway and it doesn't seem to fit like I think it's supposed too...lol. The
pic in the diagram doesn't really show how it's oriented?
(https://i.imgur.com/k1qntbbl.jpg?1)
Here's couple of pics of the part I received (#2200-037 breech sleeve)?
(https://i.imgur.com/HAcAFdEl.jpg)
(https://i.imgur.com/zKg86Iwl.jpg)
If anybody has any answers about this part, or the valve dumping all the air, I would appreciate it.
Thanks guys, TMurray
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The breech sleeve is orientated like in the second photo. The "cylinder" part of the sleeve goes inside the breech seal, and the metal "washer" side goes against the valve port. Make sure that the transfer port is properly lined up with the corresponding hole in the comp tube, or it'll leak air, when fired. It can be tweaked after the valve is in the tube. I use the back end of a proper sized drill bit. Just stick the bit in the transfer port hole, and gently move the port side to side, until it lines up.
The gun should dump 10 pumps. If it doesn't, use a lighter valve spring, versus a heavier hammer spring. Less wear and tear on the gun.
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PT# 037 is the front main valve body section. That port must be squarely aligned with the breech port hole as he said. The cut tube/metal breech gasket goes between them when all is oriented properly to bolt together. And 030 takes the place of the old metal cocking piston on the other end of the hammer spring. I used the upgraded hammer spring in my 160, as the original powder blue painted one looked a lil weak and squished a bit shorter from the bolt being closed all that time? Nice, crisp little double click when I pull the bolt back and cock it.
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The "cylinder" part of the sleeve goes inside the breech seal, and the metal "washer" side goes against the valve port.
First off, thanks for the replies guys.
As the quote up top says, this is how I was trying it as it only made sense to me that way, here's a pic of my
valve with the breech gasket installed....
(https://i.imgur.com/XHOtK3Ul.jpg)
Problem is, in my mind, the breech sleeve should go inside of the port hole on #766-112 barrel support,
otherwise whats the point of the breech sleeve to start with...lol. But that ain't happening because the port
hole diameter is .125" and the O.D. of the breech sleeve is .152", so without drilling the port hole larger
the breech sleeve just butts up against the port hole, which isn't any good. Right now I just have the breech gasket installed in the valve.
Also, over on the "Crosman Green Forum" I got a reply with this diagram that says you don't have to use the breech sleeve, lower left circled in red.....
(https://i.imgur.com/uRuVpYjl.jpg)
I know this is a newer diagram but it's probably still applicable.
My 766 will dump probably 90 to 95% of the air in the valve with 10 pumps, so I guess I'd have to find a
weaker valve spring, would you guys happen to know where I could find one that would work...lol??
I have an extra one, wonder if I could clip a coil or two to fix it?
Thanks for your help.
TMurray
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What the sleeve does is keep the seal from blowing out, from the high pressure blast of air. I'd still use it, if it were mine.
As far as a weaker spring, take the factory one to the hardware store, and match it up with one that is the same outside diameter, and length, roughly the same number of coils, and made with thinner wire.
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There are 3 versions of the 766.
The V1 combines the breech and valve. (no breech seal)
The V2 has the brass sleeve and seal.
The V3 just has the seal.
You should determine which version you have.
Since you stated you didn't recall the brass sleeve in your gun
I would think your gun is a V3.
What's the serial number?
https://support.crosman.com/hc/en-us/search?utf8=%E2%9C%93&category=200223634&query=766&commit=Search
Either way I would leave it out as it can seriously restricts power.
I have a jazzed up 2100 and it dumps 15 pumps at 900 FPS.
I used a lighter valve spring and a heavier hammer spring.
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What the sleeve does is keep the seal from blowing out, from the high pressure blast of air. I'd still use it, if it were mine.
As far as a weaker spring, take the factory one to the hardware store, and match it up with one that is the same outside diameter, and length, roughly the same number of coils, and made with thinner wire.
Well, if I were to use it I will have to drill the "barrel support" port hole at least .100" otherwise it's just pushing against the breech sleeve and not getting to the rubber gasket I don't think that's the best scenario. But it could be made to work.
Thanks for the spring info, I'll do some looking around for one.
TMurray
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There are 3 versions of the 766.
The V1 combines the breech and valve. (no breech seal)
The V2 has the brass sleeve and seal.
The V3 just has the seal.
You should determine which version you have.
Since you stated you didn't recall the brass sleeve in your gun
I would think your gun is a V3.
What's the serial number?
https://support.crosman.com/hc/en-us/search?utf8=%E2%9C%93&category=200223634&query=766&commit=Search
Either way I would leave it out as it can seriously restricts power.
I have a jazzed up 2100 and it dumps 15 pumps at 900 FPS.
I used a lighter valve spring and a heavier hammer spring.
900 fps....that thing is humming..lol. I chronied mine today with 7.33 jsb it avg 669 fps with 10 pumps and
whatever air is left in the valve.
My 766 is a phase II model with the tapered steel barrel shroud, model # starts with 1179 so it was
manufactured in November of 1979. I guess I'll be going back inside again...lol, I can put it together blind
folded now :o.
I just finished rebluing all the metal and screws, trigger blade...etc
(https://i.imgur.com/3WMxiidl.jpg)
Is your 2100 a 177cal, and what pellet are you shooting to get 900fps, and any mods to the valve?
TMurray
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The 766 V2 with the tapered barrel shroud is my favorite.
That bluing looks really nice. What product did you use?
My 2100 is .177 cal and all the tests were done with 7.9 CPHPs
An adjustable piston, valve mods and sealing the leaks are the major mods.
Lots of 2100/2200 (766) mods so here's a few links that spell it out.
https://www.gatewaytoairguns.org/GTA/index.php?topic=136879.msg1369809#msg1369809 (https://www.gatewaytoairguns.org/GTA/index.php?topic=136879.msg1369809#msg1369809)
https://www.gatewaytoairguns.org/GTA/index.php?topic=136474.msg1364572#msg1364572 (https://www.gatewaytoairguns.org/GTA/index.php?topic=136474.msg1364572#msg1364572)
One piece breech:
https://www.gatewaytoairguns.org/GTA/index.php?topic=132874.msg1347720#msg1347720 (https://www.gatewaytoairguns.org/GTA/index.php?topic=132874.msg1347720#msg1347720)
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Awesome work man..thanks for sharing, I guess there's more to do to my old 766...LOL My barrel shroud
had light rust and minor pitting in spots, I stripped it with 200 then 400 then 0000 steel wool, and minor
filing.
(https://i.imgur.com/IxXFpst.jpg)
(https://i.imgur.com/HhSwSgA.jpg)
(https://i.imgur.com/tKqQ2Av.jpg)
(https://i.imgur.com/2G5m6hS.jpg)
(https://i.imgur.com/znMKAEc.jpg)
I used brownells Dicropan T-4 "first",I applied 4 coats with 0000 steel wool in between coats, then lightly steel wooled with Remoil. A day later I applied 3 coats of Perma blue with 0000 steel wool in between coats, I did this to all the metal parts.
(these 2 pics were before I added the 3 additional coats of Perma blue, just using the Dicropan T-4 they were
much more black rather than blue).
(https://i.imgur.com/LvtBC7W.jpg)
(https://i.imgur.com/cpl4T5o.jpg)
Anyway, my brass valve stem blew the old white seal it had, so I found a o-ring to fit in there and that
is what is currently sealing it. What do you recommend for a good valve stem replacement. Did you buy
or make your own, I have delrin and a lathe...lol, but no mill. I see some delrin looking valve stems on
ebay?
Thanks, TMurray
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Thanks for the tips on bluing.
The best valve stem to use on a high power gun is the MRod valve stem.
It's designed to take 3K psi and made from what looks like Delrin.
P/N 1700-140, $1.68 a copy from Crosman.
I usually get several at that price.
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Thanks for the tips on bluing.
The best valve stem to use on a high power gun is the MRod valve stem.
It's designed to take 3K psi and made from what looks like Delrin.
P/N 1700-140, $1.68 a copy from Crosman.
I usually get several at that price
The stem you're talking about and use in your builds, is the sealing surface just flat and made of delrin,
or does it have some kind of sealing material on the surface, and flat or concave surface?
The valve stems look pretty easy to make from delrin.
Also what kind of results did you get with your o-ring probe mod in your pumpers, before and after?
You've given me a lot to think about...LOL.
TMurray
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Not sure what difference the probe seal made.
I made several mods at once when the gun was apart.
Here's the valve stems for comparison.
Same as the stock stem but made from Delrin.
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Thanks again Tack Driver 10.
TMurray
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Not sure what difference the probe seal made.
I made several mods at once when the gun was apart.
Here's the valve stems for comparison.
Same as the stock stem but made from Delrin.
Not exactly the same. Wouldn't work in my Crosmans. The Delrin collar is shorter than the brass one. I polished the brass one and the shaft. Reused it and it's great!
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Not exactly the same. Wouldn't work in my Crosmans. The Delrin collar is shorter than the brass one. I polished the brass one and the shaft. Reused it and it's great!
Thanks uniondr, I've got two stems coming one old brass type and a newer delrin type. Right now I've got a
small o-ring in my brass stem and it's holding at 669 fps, but I don't think it will last (temporary fix).
I'll check them out when they get here, I might make one myself out of delrin, donno yet, if so I can make it
the same as the brass one.
I've got some tinkering to do still.......
TMurray
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You're welcome. The valve stems are a lil different length too. Keep an eye on that to keep everything function within the set limits.
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I tried a few of Tack Drivers mods today, I decided not to use the breech sleeve and instead I turned the
nipple down on the barrel support and added a .251" brass sleeve for a tighter seal, I made it about .030"
longer so it would for sure be pressing in on the gasket.
Here's a couple of pics.....
(cleaned up nipple)
(https://i.imgur.com/aGWRCOLl.jpg)
(.251" sleeve added)
(https://i.imgur.com/cLkJTgyl.jpg)
I also added the extra weight on the hammer.....
(https://i.imgur.com/L1WzBM3l.jpg)
(https://i.imgur.com/gTOPxO0l.jpg)
I made a little longer probe tip....
(https://i.imgur.com/OVxrRRMl.jpg)
And the current valve stem "fix" I'm using till I get some new ones this week....
(https://i.imgur.com/8kmTh4ql.jpg)
I still haven't found the right springs to try and fix the valve, so it will dump all the air, hopefully I'll come
up with some this week. It's still shooting around 650 fps with jsb 7.33's with 10 pumps, but the bolt wants
to blow back a little, guess it needs some kinda seal in the barrel, or maybe a new bolt and spring?
If I hold the bolt shut when I shoot it, it will shoot over 700 fps with the 7.33's....lol.
So, still a work in progress, but I'm not giving up :D
TMurray
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Looks like it's coming along nicely.
I sealed the probe on my 2100 by cutting the breech end of the barrel
back about .040" and adding an o-ring between the breech and barrel.
Made the probe from brass to fit snug.
Also a pic of the MRod valve stem without the Delrin.
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Thanks for the tips again Tack Driver!
Question....are the probe tips threaded on, or drilled and pinned?
I thought about the o-ring in the breech and cutting the barrel to make up the difference, I also thought
about a o-ring on the probe? I haven't decided yet.
I'm hopeful a heavier hammer spring and or lighter valve spring will fix the valve dumping issue, that and
sealing the barrel from the probe end, "should hook it up".
I'll post back when I get some results.....
TMurray
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I thread the plastic bolt with a 8-32 thread then center drill and tap
a piece of 3/16" brass rod. So they screw on and can be changed out.
I cut the "door" off as it serves no purpose for me.
The MRod valve stem will help dump more air.
Since it's made of Delrin and fairly hard it releases very quickly.
A stock 2100 spring should dump 10 pumps.
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Nice, are those probes with the 0-ring on the end for a .22cal barrel?
I'll try the threaded deal.....
TMurray
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Nice, are those probes with the 0-ring on the end for a .22cal barrel?
I'll try the threaded deal.....
TMurray
The probes in the top picture are 17 cal and the lower picture shows the 22 cal probe.
They all work really well.
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Here's the hot setup.
Modified the bolt assembly and added a brass adapter so valve caps can be used.
Used a grenade in this example.
As can be seen here:
https://www.gatewaytoairguns.org/GTA/index.php?topic=144083.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=144083.0)
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"Here's the hot setup".
Modified the bolt assembly and added a brass adapter so valve caps can be used.
Used a grenade in this example.
You have some excellent mods, man. Where did you buy the valve caps....wally world...LOL?
Thanks for sharing...
Question on the o-ringed probe, are you using "just" the o-ring probe to seal the barrel, or a combination of
the o-ring behind the barrel with the barrel shortened. I'm thinking these are two different set-ups?
I also tried the white delrin valve stem yesterday, but it didn't seal, so I'll have to look more closely at this.
I wasn't using the factory spring so maybe there wasn't enough spring pressure, and or, completely nick
free surfaces....donno.
TMurray
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Most of the valve caps can be found on EBay.
Lots of options or make your own bolt.
Just one o-ring either on the probe or sandwiched between the barrel and breech.
I use the seal on the probe exclusively now.
Does your white Delrin valve stem look like the one below?
They are fairly soft and usually seal without a problem.
If the seat is good you can try spinning the stem in a drill or lathe installed in the back
part of the valve.
If I have trouble getting a stem to seal I cut a new seat using a stubby cobalt 135 degree drill bit.
Press a new Delrin head on the stem and turn the same angle on the lathe.
Cut the outside diameter of the stem head no more than .050" larger than the throat.
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Good point about using a 135 deg. bit, a steeper angle like from a 118 deg. bit will not flow as well until the poppet is further off the seat where a shallower seat angle begins meaningful flow sooner.
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Good point about using a 135 deg. bit, a steeper angle like from a 118 deg. bit will not flow as well until the poppet is further off the seat where a shallower seat angle begins meaningful flow sooner.
Right, and use a new 3/8" bit that is only used to cut valve seats.
Cut this seat back some.
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Most of the valve caps can be found on EBay.
Lots of options or make your own bolt.
Just one o-ring either on the probe or sandwiched between the barrel and breech.
I use the seal on the probe exclusively now.
Does your white Delrin valve stem look like the one below?
They are fairly soft and usually seal without a problem.
If the seat is good you can try spinning the stem in a drill or lathe installed in the back
part of the valve.
If I have trouble getting a stem to seal I cut a new seat using a stubby cobalt 135 degree drill bit.
Press a new Delrin head on the stem and turn the same angle on the lathe.
Cut the outside diameter of the stem head no more than .050" larger than the throat.
Great info Tack Driver, thanks for posting! I was working on it before I saw this latest post...lol. I did think
about re-cutting the seat, but I decided to try and lap it first to see if that would work. I turned a piece of
brass rod to fit in the valve fairly close, to hold it square to the seat. Then I super glued a piece of 2000 grit
paper on the end and chucked it in the lathe, then "lightly" held the valve against it while it was spinning.
BTW, both the seat and the valve stem had imperfections on the surfaces. Next I chucked the valve stem
and "lightly" cleaned the sealing face, then I put the stem in the valve and chucked the stem in the lathe and
held light pressure so the two surfaces would burnish together, and it worked pretty good :D
here's pic after....
(https://i.imgur.com/eucM9p7l.jpg)
Nice clean seat....
(https://i.imgur.com/J3sC8Hvl.jpg)
Back over the chrony with jsb 7.33's it shot 680 fps, and if I held the bolt closed it shot 724 fps.
Now it dumps pretty much all the air, compared to before. Next I need to build a probe with the o-ring
(I don't have one that small on hand) or use the o-ring behind the barrel. Next week I have a bolt assembly coming so I'll wait on that.
I did try a mod to seal the bottom of the barrel (not sure if it's needed..lol). I used some heat shrink tubing
and covered the end of the barrel with the TP hole, after shrinking I cut out the TP hole, then trimmed away
all but a small piece and super glued it to the barrel.
Here's a pic.....
(https://i.imgur.com/NdvSVlzl.jpg)
I ended it up cutting it into a circle just big enough to seal the hole against the barrel support, I did have to
polish out the inside of the barrel support, because it was too snug of a fit, but it worked. If you have to remove the barrel more than a couple of times it will come off though.
here's the barrel support after polishing the inside (BTW the rear surface where the barrel butts up against
was really rough) just in case I want to seal it there with a o-ring. But I'll probably try the probe first.
(https://i.imgur.com/lGPguUsl.jpg)
I'll see how this valve stem works out before I mess with the valve anymore, I've had it out many times now
:o ??? ::) :-X
TMurray
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Nice work on the valve seat.
Sealing all the leaks in the 766/2100/2200 can be challenging.
Before I got a lathe I used a drill collar to seal the barrel to breech.
With a lathe the seal can be cut captive in brass in a slot and be made smaller.
Also nipping the nose on the valve cap to match the cup helps.
My 2100 got 825 FPS on 10 strokes with 7.9 CPHPs with a cup piston seal.
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Here's another method to deal with the TP to breech seal.
I did this on a 22 cal Disco tube pumper that got 1034 FPS with 20 strokes.
For the 766 you'd cut off the nipple. :o
Then drill the TP 1/4" to the center.
A Delrin TP with a 5/16" radius on one end sits up against the barrel.
A press fit will seal it up nicely.
Another alternative would be to counterbore the breech and use square end Delrin.
Either way pinning the valve should be done.
The hot setup would be the one piece breech using a modified 766 V1 breech.
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For the 766 you'd cut off the nipple. :o
Then drill the TP 1/4" to the center.
A Delrin TP with a 5/16" radius on one end sits up against the barrel.
A press fit will seal it up nicely.
Another alternative would be to counterbore the breech and use square end Delrin.
Either way pinning the valve should be done.
The hot setup would be the one piece breech using a modified 766 V1 breech.
Hey, I'm interested in any of the mods you want to show...lol. I'm not familiar with the 766 V1, my 766
phase II is the only pumper I've ever had apart, I normally shoot HW springers.
I get the idea of your post, however, from the pic is the slotted opening in the barrel not going thru, It looks
like a radius on either side? And the delrin piece still has a small tp hole going thru it, or opened up?
The other end of the delrin is a press fit in the valve?
I think I'm sealed at the valve, the breech end of the barrel is where I'm probably getting blow out.
But at least there are alternatives to seal about everything.....lol....thanks.
TMurray
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The slotted opening is the TP in the barrel.
The circle around it is there to show the boundary of the TP.
The Delrin is center drilled to whatever port size is required.
Just wanted to show another option.
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Are you using a #004 o-ring on your probes for the 177cal barrel?
Thanks....
TMurray
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Are you using a #004 o-ring on your probes for the 177cal barrel?
Thanks....
TMurray
I found a 004 seal is too big and a standard 003 seal is too small.
I used a 003 duro 70 poly seal but cut the gland diameter .100".
Fine tune it with a needle file and test fit.
This stretched the 003 seal slightly and fit perfectly.
There's a metric seal that might work but cost $1 each with a minimum order of 100.
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I found a 004 seal is too big and a standard 003 seal is too small.
I used a 003 duro 70 poly seal but cut the gland diameter .100".
Fine tune it with a needle file and test fit.
This stretched the 003 seal slightly and fit perfectly.
There's a metric seal that might work but cost $1 each with a minimum order of 100.
Thanks, I was looking at the o-ring chart trying to figure out which one would work the best, and the #004
looked pretty close, that's why I was asking.
Is this similar to what your using?
https://www.mcmaster.com/#9558k49/=1dloa20 (https://www.mcmaster.com/#9558k49/=1dloa20)
TMurray
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Yes, those are the ones but $3 each is very high.
Here's where I get mine @ $.30 each.
https://www.theoringstore.com/index.php?main_page=product_info&cPath=367_1321_1323&products_id=27478&zenid=35e66116da30d2d4492506ca75066884 (https://www.theoringstore.com/index.php?main_page=product_info&cPath=367_1321_1323&products_id=27478&zenid=35e66116da30d2d4492506ca75066884)
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Yes, much cheaper...lol, I'll order couple of those and hopefully shipping won't be $10 :o
Thanks again.... ;)
TMurray
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Yes, much cheaper...lol, I'll order couple of those and hopefully shipping won't be $10 :o
Thanks again.... ;)
TMurray
Shipping is free if you buy $150+ of goods....LOL
Here's a close up of a 17 cal probe.
Sets the pellet deeper past the TP.
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Shipping is free if you buy $150+ of goods....LOL
Here's a close up of a 17 cal probe.
Sets the pellet deeper past the TP.
Looks Great, I hope to make one similar when I get the new bolt assembly. I did make the little probe ext
about .200" longer on my current bolt assembly to push the pellet in deeper.
I'll pay the $6 shipping on this order...lol, don't need $150 of o-rings :o :o ;D, but it's good to know of this
website for future o-rings. McMaster-Carr doesn't tell you the shipping cost until after the order is placed,
and most of the time it's $15 for a $2 item...lol.
TMurray
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(Probe update)
I received the new bolt assembly and finally got some time to work on the o-ring probe. I first made a test piece using my old bolt assembly to get the fit and dimensions right, just for giggles I threaded it M4 x.7, it
worked, but screwed together tight because of the major O.D., but the main reason was to get the o-ring in
the right place, because there's not much sealing area in there...LOL.
Next I threaded the "new" bolt assembly 10-32 like Tack Driver used and it worked much better, the major
diameter is closer (since the plastic bolt probe doesn't get turned to the correct diameter). Also the tiny
003 o-ring worked great, and I made the new probe about .253" longer for a deeper pellet seating.
So before the 766 was shooting around 680 fps and the bolt didn't stay completely shut. Now with the o-ring
probe it's shooting 708 fps and the bolt stays shut, so it picked up around 28 fps. This was using the JSB
7.33's and 10 pumps, just as before.
Here's few picks of the "Tack Driver" inspired o-ring probe....
(https://i.imgur.com/G2Fcp9il.jpg)
Tiny o-ring laying in front of the brass probe...
(https://i.imgur.com/SIRTvn5l.jpg)
Finished o-ring probe.....
(https://i.imgur.com/OVToc9ul.jpg)
(https://i.imgur.com/mU17tCil.jpg)
I'd say it's dumping about 98% of the air with 10 pumps, so I'm still going to try and find a slightly stiffer
hammer spring. I'm also going to try and seal the front of the barrel support, where the barrel goes in.
But all in all a big improvement in my 766 since I started the rebuild/reblue job.
Thanks to all that responded and big thanks to Tack Driver for his mods sharing. I will update this thread
when more work is done.
TMurray
BTW, my phase II tapered steel barrel 766 piston doesn't have any plastic on it, just a steel shaft with
a milled slot at the other end...
(https://i.imgur.com/YvJPhOTl.jpg)
:D
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Looks real good.
I used an 8-32 thread as 10-32 was too big for the 3/16" brass stock.
Like all things Crosman there's so many variations it's hard to keep track of them.
Below are some of the 766/2100 piston variations.
If you make an adjustable piston you'll make the biggest gains in velocity.
I have a 1377 that gets 725 FPS with 10 pumps using 7.9 grain CPHPs, 800 FPS with 15 pumps..
It uses a "Spin Tight" (patent pending...LOL) piston so the rubber cup threads into the piston.
Makes for a super tight fit that builds pressure like crazy.
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In your piston picture, mine is second from the left.
Does your "spin tight" use a factory pump cup and angled head valve, or is it a flat top valve with a custom
pump cup?
Also in the second picture what does the back half of the piston look like? And when adjusting, do you just
bottom the pump cup out on the valve with a small amount of clamping distance for the pump arm to
clamp shut at the bottom of the stroke?
I haven't measured my piston in the tube so I don't know how close it comes to the valve when pumping.
TMurray
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In your piston picture, mine is second from the left.
Does your "spin tight" use a factory pump cup and angled head valve, or is it a flat top valve with a custom
pump cup?
Also in the second picture what does the back half of the piston look like? And when adjusting, do you just
bottom the pump cup out on the valve with a small amount of clamping distance for the pump arm to
clamp shut at the bottom of the stroke?
I haven't measured my piston in the tube so I don't know how close it comes to the valve when pumping.
TMurray
The spin tight piston uses a stock pump cup.
The threads are 1/2" x 20 same as the threads between the valve.
Adjust it so the piston touches the valve with about 3/4" space between the pump arm and tube (aka cam over).
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Another update..lol
Today I made a small collar with 3mm set screws and a o-ring to seal the front of the barrel support
where the barrel goes in.....like this
(https://i.imgur.com/DZ6P3BZ.jpg)
I also made a hammer spring spacer to preload the spring (since I wasn't able to find a stiffer spring)
and it works good. Now my 766 is completely sealed, and shooting at 720 fps with 11 pumps using the
jsb 7.33's, I'm happy to report it's dumping 100% of the air with 10 pumps.
I'm going to take a break and shoot it a little...lol
TMurray
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:D Velocity update today....
still shooting the JSB 7.33's, I decided to try 15 pumps over the chrony and got 777.8 "high" fps and
775 "avg" fps. I bet with a BB it would be humming along pretty good...LOL.
That's 50+ fps over the 10 pumps before.
766 is shooting strong!
TMurray
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The new, properly-fitting bolt probe has to be the reason. Another guy made a ring land on his original to fit a small O-ring and got another 50FPS. Why I've been wanting a small lathe to make them myself. But look stock on the outside...that's the heart of restomodding!
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Any chance we can get the broken images in this thread updated?
Jon.