Beeman QB Chief .22 broke down

[OTmachine]

I use what fits.  In the case of Chief’s barrel o-rings, I use the American sized ones as they seal good.   In a 1/16” or 1.5mm  cross-section o-ring, I am looking for the o-ring being proud of the diameter by .005 - .007” inch per side for a good seal.
The Metric set will probably work fine.  It is just that you hardly ever get an exact replacement size due to all of the varying cross-sections available and what you get in a kit.

Perhaps Ribbonstone can load up an image of the rifle disassembled.
Keith

[BigBird]

 There's a poppet guy  on Ebay

Delrindepot-4

I see custom fit, I would assume you would send them the specs and have to fit your stem ?

https://www.ebay.com/sch/delrindepot-4/m.html?_nkw=&_armrs=1&_ipg=&_from=

Does he make poppets?  I know he has delrin and looks like 7075 too.

[Ribbonstone]

Not finding the photo file....might still be on the old computer....will look tomorrow.

[Ribbonstone]

May as well seat out all the Chief’s particulars I know (so far):

Have no idea what changes were made to a Chief II or Chief II plus repeater version.


Currently, running a miss-match of some parts from the first and some from the second.   Picked the .22 to work with for my uses, can top-swap the .177 barrel and breech, and have most of the parts from the 2nd rifle at hand.

Expensive way to go about things (a 2nd rifle for a parts supply)...many of the parts are likely to find their way into other projects...but I’m loyal to rifles that shoot real well.

Questions:

Early or late version? The early and late parts will interchange….so I guess they had no need to call it Gen.I and Gen.II.

Early version didn’t have an adjusting end cap...later versions do.

Early (skinny degassing hole):

DSCN1835 by Robert Dean, on Flickr

Late (wide adjusting hole):


DSCN1834 by Robert Dean, on Flickr


They increased the beveled the rear edge of the striker on the 2nd. 

Went to two o rings on the bolt probe. 

Some of the screw heads were changed...where one used a slotted screw, might find a hex.

Same-same stuff:

Heavy striker (like 77gr./2.7oz) in both.

No change to the fill system or gauge block that I can see.

Gauge is a long stemmed gauge, gauge block “dead ends” so can use a seal rather than tape.  Tube is about 2mm thick,,,,can’t judge strength by thickness, but that’s reasonably thick (and heavy).

What QB78 parts can be used? Trigger and sights….nothing else.




Mods (minimal...wasn’t looking to hot-rod it)...and not really mods as I was mostly fixing things that should have been done differently.

 No local source foe the (early version) the bolt probe o-ring.  Enlarged the o-ring seat to take the o-ring I did have a source for.


DSCN0438 by Robert Dean, on Flickr


A bit of polishing (not enlarging, just getting the rough high points out) the loading tray, barrel to breech insertion, and the hole for the gauge….just keeping it from eating o-rings when taken apart/put together.

As they came, no mods,  could be adjusted up a bit (more like 28-30 foot pounds for the .22,  20 for the .177).  2K fill limits the shot count severely.  For my use, adjusted the power down to where it made the best bell-curve I could find.

Did have to make a valve stem.  Getting it to seal is a PIA.  The seating face of the valve is pretty much dead flat, which makes getting the poppet to seal more difficult. 

The metal stem is longer than other valve stems in the parts box….can’t try every valve stem made, but it seems a unique part.

Both barrels checked out cleanly rifled and crowned...not perfection, but acceptable….and both shoot well. Probably a bit of luck in that, can’t swear they’ll all be as cooperative.

Both needed the barrel band…no free floating.

Did change out the valve retention screws, but still won’t fill past 2K.




A few guesses:

1. That 2.7oz. striker does what heavy strikers do: keep the valve dwell higher than needed. Cheap way to make power, but it gobbles air doing it...and makes down tuning more difficult.

2. The later adjustable end caps seem to have about 8 rotations from fist contact with the spring and coming off their threads.


3. Making a poppet:

DSCN2232 by Robert Dean, on Flickr

The original poppet material seems softer than Delrin and had a slight “cupped” (concave) face….which is likely because of the big flat valve seat.  A slightly “round” (convex ) shape in Delrin won’t help power (acts a bit like a bathtub plug), but is easier to get to seal.

3. O-Rings?  Everything but the bolt probe o-rings could be sourced locally (at least if you live in a city).

4. Do not over look the fill nipple’s “check”...they used a cheap o-ring that will get squished.

DSCN1856 by Robert Dean, on Flickr


That’s about it so far...other than that, I’m empty of Chief’s Lore.

[BigBird]

It the valve face like a QB78?  With the harder delrin I would think a poppet with a 45° face would work better but you may have to polish the valve throat face.  I don't think it would be harder to open.  Actually, with anaerodynamic poopet you might get more dwell which may be a bad thing considering the heavy hammer.

Something like this may be a little too much.

[wll2506]

Ribbonstone.

Great write up and a wealth in info, thank you very much !!

Also what is the outside diameter of the poppet valve and length  --- what is the hole diameter of the poppet rod and how long does it go in?


wll

[Ribbonstone]

QB valve has that ridge abound the valve's air passage, which I've found to be easier to get a  poppet seal on than the Chief's big flat valve seat.  Bit more of a PIA with the Chief, but if you keep trying can make one that works.

[Ribbonstone]

I'll get the valve out the "spare" and measure it as I can (tonite or tomorrow)...not doing me any good inside a spare tube that I'll likely never use.

[Ribbonstone]

OK...got the replacement valve stem out of the spare valve (am presently using an original to see how long it will last...still alive after 3 years, but suspect.

Remember, was NOT looking for power...so pretty well just made a close copy of the original in Delrin.  Are better shapes and diameters if power is a goal...this isn’t one of them.

DSCN0140 by Robert Dean, on Flickr


Metal stem is .125” ( a common size).

Needs to be  close to 1.53” long from the sealing face of the poppet to match the original.  Probably could fudge that a bit.

Made this one .40” (10mm)… original was blown...believe the original started life about that diameter)

Made the spring end .27”...but whatever slide fits into the inside diameter of the issue valve spring (.31”) would work.

The brass band doesn’t do much good (adds a bit more weight...which isn’t a help) and the length of the poppet really is up to you….I was just approximating the original.

 Some notes:

1. Sorry...ain’t making them unless I have to...lost most of the shop-gear (and the shed/shop...lightening strike).

2. IF someone was to make them, would likely want the rifle in order to be sure they sealed.

3. The poppet seat on the valve is dead flat...it’s not going to “lap in” like the valve faces with a raised seat. 

4. Don’t bother with the brass ring.

5. I made that one 10mm..which is close to the original, and you can find 10mm Delrin rods.

[wll2506]

OK...got the replacement valve stem out of the spare valve (am presently using an original to see how long it will last...still alive after 3 years, but suspect.

Remember, was NOT looking for power...so pretty well just made a close copy of the original in Delrin.  Are better shapes and diameters if power is a goal...this isn’t one of them.

DSCN0140 by Robert Dean, on Flickr


Metal stem is .125” ( a common size).

Needs to be  close to 1.53” long from the sealing face of the poppet to match the original.  Probably could fudge that a bit.

Made this one .40” (10mm)… original was blown...believe the original started life about that diameter)

Made the spring end .27”...but whatever slide fits into the inside diameter of the issue valve spring (.31”) would work.

The brass band doesn’t do much good (adds a bit more weight...which isn’t a help) and the length of the poppet really is up to you….I was just approximating the original.

 Some notes:

1. Sorry...ain’t making them unless I have to...lost most of the shop-gear (and the shed/shop...lightening strike).

2. IF someone was to make them, would likely want the rifle in order to be sure they sealed.

3. The poppet seat on the valve is dead flat...it’s not going to “lap in” like the valve faces with a raised seat. 

4. Don’t bother with the brass ring.

5. I made that one 10mm..which is close to the original, and you can find 10mm Delrin rods.

Ribbonstone, thank you for your effort, I may get some PEET and make a prototype.

If I do, I'll send it to you for testing :-)

wll

[Ribbonstone]

Nope....have enough trouble keeping my own stuff running.

[z_johnq]

Hello,

I was wrong about the poppet in my Chief was fine. Please check the pic attached. At least one crack is found and there is another one smaller.

John, you said you made a poppet with delrin. I don't have machine tool or a lathe. Not sure if possible to make it myself. If not, the gun will be worth nothing but being discarded.
Thanks.

[CableStop]

Hello,

I was wrong about the poppet in my Chief was fine. Please check the pic attached. At least one crack is found and there is another one smaller.

John, you said you made a poppet with delrin. I don't have machine tool or a lathe. Not sure if possible to make it myself. If not, the gun will be worth nothing but being discarded.
Thanks.

I can make you one off Ribbonstone's dimensions.

[wll2506]

I just ordered some PEEK. will see if I can make one, but have no Idea how deep the poppet hole should be.

I have made poppets for a Liberty  but they had leaks, getting that face smooth is tough !

wll

[CableStop]

I just ordered some PEEK. will see if I can make one, but have no Idea how deep the poppet hole should be.

I have made poppets for a Liberty  but they had leaks, getting that face smooth is tough !

wll

Delrin is generally better for a drop in poppet in my opinion, just easier to seal without lapping.

[BigBird]

I'm planning on taking mine apart.  It isn't shooting consistently.  You've also got me interested in the internals.

[wll2506]

I'm planning on taking mine apart.  It isn't shooting consistently.  You've also got me interested in the internals.

Mine is shooting so well I would HATE to take it apart !!

wll

[z_johnq]

Hey wll, if your Chief shoots well, there is no need to take apart for sure. I took it apart because it is totally broken: 2k psi air leaks to zero psi in about 10 mins. 1st time to dismantle a PCP. I worked on my RWS 54 before, like replacing breech seal, piston seal and so on. It was easier since there was no valve to take care of, and not so many o-rings to replace.

Tom, if you can make a poppet for me, that will be great! Just let me know what you need from my side and how you'd like me to pay for it.

Thanks a lot.

John

[CableStop]

Well here is the first attempt, anyone with first hand knowledge of the poppet have any input on the dimensions?  If people think it'll work I'll send it over, I'd just want to be reimbursed shipping.

[Bentong]

Well here is the first attempt, anyone with first hand knowledge of the poppet have any input on the dimensions?  If people think it'll work I'll send it over, I'd just want to be reimbursed shipping.

that should do it, if you get leak...just chuck it to a drill and slightly pull it away to get it seated. 👍