Sunday, February 22, 2009

Derrick's Beeman P17 Overhaul Finale

Back to the overhaul. Time to remove the compression chamber and the valve assembly. Using a 2mm allen wrench, loosen the setscrew bearing against the cross pin anchoring the chamber to the lower grip frame shown below.

It's unnecessary to remove the setscrew. About one full turn out is sufficient.

With the setscrew loose, drive the cross pin completely out with a drift.

The compression chamber lifts right out. At the bottom of the chamber there are 3 steel "fingers" held in slots by a small cross pin. Punch out the small pin and pull the "fingers" out of their slots. Note that the center "finger" is different at the base. The small tab at the bottom guides the sear through its travel pulling the hammer. It's not a bad idea to polish the bottom guiding edge of that center finger.

Here's the compression tube. The breech o-ring can be seen near the top, left side. The valve stem is sticking out on the top right. It's a pull open valve. The hammer pulls the stem downward releasing the trapped air through the transfer port at the breech.

A 13mm wrench removes the brass nut to access the valve.

Oops. Pulled the top o-ring off already. I'm ahead of myself. The o-ring fits on the end of the valve stem in the groove. It's a #006.

I took that #006 o-ring off so I could carefully hold that end of the valve in a padded vise. A 7mm wrench removes the black nut that the hammer pulls against. The stem is peened slightly so the nut won't come off in use. Removing the nut also removes the slight peen and allows for complete disassembly.

I polished the entire valve stem on the buffer and carefully cleaned off the buffing compound. I also found a higher quality replacement hnbr o-ring (the green colored o-ring) to seal the valve circumference. Note: this o-ring is the same size as the breech o-ring.

Buzzy's Slick Honey is a superb o-ring lube--especially for sliding fit parts that still need to air seal.

The threadlocker will replace the peening I removed.

Thought I'd also teflon tape the valve nut. You know...just in case.

The PTFE tape was too wide. I cut it in half lengthwise and gave it three full wraps.

Got all liberal with the Slick Honey. Seriously, this stuff is almost impossible to wipe off. It is incredibly thin and lasts dang near forever. It was first marketed years ago by a world renown suspension tuner, Arlo Englund, as a shock bushing grease. It was first called Englund Slick Honey. Be sure to at least lube the o-rings.

Here's the reassembled valve. I didn't have a hnbr o-ring small enough for the valve seat seal. WHAT? I know. It seems impossible to me, too.

She goes back in like this.

Holding the stem stationary while threading the brass nut back in will prevent damaging that #006 o-ring.

A dental pick lifts out the breech o-ring. If better sealing against the breech was required, this is where a small super thin shim would be placed, then the o-ring reseated.

Ah yes. My green 0-friend.

Did I mention that the black nut was installed with a thread locking agent? I don't want the nut to loosen at all in use, as the hammer pulls the black nut straight down to fire the gun.

Time to reassemble. Almost as an afterthought, I decided to quickly polish the main pivot pin for the upper assembly.

Polished out. This was the pin with the small e-clips from part one.
Please refer back to the earlier post's pictures for reassembly. Essentially it goes back together as follows: First, reinstall the barrel into the top cover. The compression tube was then pinned back in place in the lower grip frame. Don't install the piston yet.

Let's put this mess back together first.

This is actually very straightforward. About 11 individual parts, but only 3 assemblies. The hammer, sear and trigger group.

Here's the hammer assembly. I lightly greased all the parts with the Buzzy's Slick Honey, then assembled the parts onto the pivot pin.

Like this.

Then, put the hammer assembly onto the valve stem and rotate it forward on the stem and into place, pressing the pin into the hole. Notice, I did not attach the small coil spring onto the lever just yet. Then, I reinstalled the torsion spring into the bottom of the hammer assembly and set the center of the spring loop onto the post molded into the grip.

Don't seat the lower end of the torsion spring. Leave the tail end of the spring hanging out the rear of the grip as shown above. Now the sear assembly can be slid into location.

Here's the sear with it's small torsion spring oriented correctly. Not shown is the pivot pin. As an aside, I should mention that in my gun--and in buddy Jason's--the hammer and sear were about as hard as glass.

I've had best luck installing the pin just far enough to go through both the spring and the sear and then sliding the sear forward through the hammer assembly. Push the sear's pivot pin into it's hole. Don't tension the sear's torsion spring.
Now is a fine time to install the trigger and trigger axis pin. No pics necessary.

Using a small pair of needle-nosed pliers, reattach the small coil spring to the hole in the lever (part of the hammer assembly) and hook the bottom loop of the spring onto the post directly below. The coil spring is directly behind the trigger if you look at the above picture.

Here's another view of that coil spring. Finally, using the needle-nose pliers, tension both the sear and the hammer torsion springs by seating their ends into the grip frame. They bear directly on the inside plastic of the grip housing. Replace the right side grip panel--taking care to align all the pivot pins, and snug down the single grip bolt with a 2.5mm allen wrench.

Pin the top cover assembly (barrel housing) back together with the long cross pin, snapping the e-clip into place. Finally, it's time to install the piston. Is the piston's #116 o-ring in perfect condition? If not, replace it and lightly lube the o-ring so it forms a positive air seal. MOST of the P17 problems will be traced back to this single o-ring. Slide the piston into the compression tube, tap the pin back in and snug down the 2mm set screw.

With this setscrew, it's done.

Shooting the gun across the chrony with a wide variety of pellets gave the following numbers:

376.9, 376.1, 377.3, 379.8, 380.8, 380.6, 379.5, 379.2, 380.5, 381.5

374.5, 383.1, 378.2, 384.5, 381.0, 385.1, 381.8, 387.5, 386.1, 387.0

399.6, 399.4, 401.1, 405.3, 402.5, 403.9, 406.8, 401.3, 406.2, 411.6

And just for fun some weird ones,
388.2, 369.0, 388.6, 382.8, 376.5, 380.8, 393.1, 374.5, 378.7, 384.8

366.5, 373.8, 380.3, 385.1, 381.2, 379.6, 369.6, 392.1, 383.7, 371.7

A strange fact: While Beeman has sold this gun now for several years under 3 different model names, it's never been listed on their website.

Updated note:
I've gotten many questions about P17's dumping their air on the closing stroke. Mine started doing this the other day and I immediately assumed it was the air valve not seating. A rebuild of the air valve showed nothing was wrong and the problem continued. Close examination revealed that the sear wasn't catching the hammer consistently. Sometimes it worked fine, then--whoosh. Frustrating. It appears that the problem was the v-shaped hammer spring binding inside the grip frame. I'd put the rear end of the spring into the left grip panel on reassembly and that's not the way to do it. The tail end of the spring must be seated into the RIGHT grip panel or the spring will bind.


JavaGonzo said...

This blog has been such a help; THANK YOU! Great pics and descriptions.
Did you also use Buzzy's on the compression chamber? If not, what lube did you select?

derrick38 said...

Yep, I used the Buzzy's on anything that an o-ring has to touch. The easiest place to find Buzzy's Slick Honey in most locales is a well stocked bicycle shop. It's used on suspension forks to minimize stiction between fork uppers stanchion tubes and the wiper seals on the lower leg assemblies. Most good mechanics will use nothing else. If the local bike shop doesn't have it, they can easily order it from their QBP distributor in MN.

Anonymous said...

i am about 3 years late for this thread, but i am on the verge of taking on a "well used" p17 it is sucking in air around the front piston O ring. you know , think i might actually give repairing it a go. just a shout out to know that the U.K guys are finding this site a big help too .

milton keynes thanks you


Orlando said...

Derrick, in your update you said that sometimes the valve dumped the air on the closing stroke and that you solved it sitting the hammer spring on the right panel of the grip.

I think that problem is caused by the invert mounting of the spacer that goes inside the hammer assembly (the bended wire that aligns the hammer and sear parts).

The way the spacer appears on picture 21 (round part pointing toward the pistol) seems to be inverted. I assembled mine the same way and after that I had some failures. Pumping the pistol without the grip cover45 I could see the sear failing to catch the trigger. I inverted the spacer (as it was before I disassembled the thing, IIRC) and the problem was solved.

Anonymous said...

Hi, I know this is old but ill give it ago, I cannot get the lower chamber to come out I have done the two things that are required to take it out but it just won't life out and now it has completely stopped working ? HELP !!!!

Anonymous said...

If anyone wants to buy my broken P17 (releases air on closing stroke), I am willing to sell it for parts or for refurbishing.
Email me at

derrick38 said...

Orlando, the part is oriented correctly per the Weihrauch schematic. Part #SR161

Anonymous said...

When the gun is new, whenever you open the cylinder all the way you will hear a click sound
from the hammer or sear spring. This is due to the engagement of outer rods and inner rod with
hammer and sear. Without this sound you will not be able to successfully cock the gun and all the air inside the cylinder will be dumped by hammer at end of stroke.
So when the gun reaches 1 year old all the efforts are for keeping or bringing back this click sound by either adding some oil in hammer sear system or using washers to reduce hammer or sear tolerance etc..............

Anonymous said...

When your gun gets old and it develops hammer or sear problems such as air being dumped
by hammer at end of cylinder closing stroke. After you overhaul or made necessary adjustments to hammer sear system. Be sure to leave hammer spring end inside the Right
Grip Cover!!!

Anonymous said...

on trigger adj. I found the best results when I adj screw out till it does not engage then inanity it works. you have more play till you feel the trigger"stop" but the travel after the first stop till firing is shortened and more predictable. Some people thank that if you take all the play out of the free play out of the trigger that it improves trigger but it makes the travel after trigger engagement to fire is increased.

Vance said...

My P17 fell out of my gun bag, and hit the concrete pretty hard. After that, the gun would dump the air pressure on closing. I took the piston assembly apart, cleaned, inspected, and lubed with Englund's Slickoleum (Buzzy's Slick Honey in a different, cheaper package). Great stuff! Reassembled, but the gun still dumped right at the end. Figuring the drop jarred something in the trigger/sear mechanism, I pulled the grip off. Everything looked fine, except I noticed the end of the valve where it sits on the little plastic block looked off center. I wobbled it back and forth, then centered it on the block. Reinstalled the grip and cocked it. Works fine. I guess the hit it took must have cocked the valve stem just a bit, so the air pressure just blew past the o-ring?

Unknown said...

I have a second P17 now, which started acting up about 50 shots in. I didn't drop this one, though. It just wouldn't cock. When opening, a hiss could be heard, and when closing, it would begin to pump then suddenly release. I took the grip off, and took a look. When the grip was off, it would pump correctly and would fire. Putting the grip back on would cause it to dump air on closing.
I tried cocking it a couple of times with the grip off. Two out of six would dump air. I then noticed the middle finger (AK136 on the p3 diagram) which contacts the sear (SR164) and locks it over the hammer (SR162), was not hitting it on center and was sliding over it resulting in no latch onto SR162. This caused it to dump on cocking.
I tried a bunch of things and did a bunch of research on this and found several complaints about this condition. The AK136 finger and SR164 sear parts are very thin, and misalignment occurs easily. Some people were bending the middle finger for better alignment but most said it didn't work for long.
I cut a nylon bushing for a spacer (about 3/32 wide fitting snug inside the hole) and inserted it into the removable grip's boss, hoping it would push against the sear spring (CS387) coil, and remove any slop which might allow the SR164 sear to tilt and slip off the AK136 finger. It works so far. I hope this will correct this fault.
The manufacturer needs to thicken the sear and finger so the contact patch is more substantial and can't slip. I can't see any problem with doing this interference-wise.
I believe this is the real cause of failure for many who believe they have o-ring seal problems. Disassembly-reassembly may fix this slipping off condition for a while. I also think this is why the spring-end placement in the right grip is necessary. It helps keep the sear from tilting on the post.
I'm hoping that my bushing will cure the problem, but who knows? I may have it all wrong....

Vance said...

My p-17 is still cocking properly after some shooting. I was not real clear in my above comment about the bushing I used. It fits snugly into the plastic lip in the grip, and of course fits over the pin. It's about 3/32" thick. When the grip is reinstalled, it presses against the coil of the sear spring which in turn presses the sear flat against the plastic pin boss in the opposite grip. The idea is to try to keep the sear from tipping on the boss and allowing the cocking finger to slip over it instead of pushing it down and latching correctly. Time will tell.

Unknown said...

Wow..does anyone know if these defects have been addressed by the manufacturer ...for 2015/2016. ?

banyard said...

Theses guns need to be totally recalled, and money back, and taken of the shelves,there useless. every component in it from piston to tiger breaks, seals go , springs dislodge,
loss of power the list is endless . I should of brought a mercarno set and tryed to build my own air pistol ,there a joke . If your looking at this forum you probably under stand

Unknown said...

thank you so much. this was useful to me thanks and keep up the good work

Unknown said...

I have used this gun almost a year and everyday I put 60 or more pellets through it.
Yesterday the gun quit on me. I removed the valve stem and found out the end M006 o-ring was cracked so I replaced it with a new one. The gun works like a new
one now! So if you have any air leaking problem just check all 4 o-rings and replace
them if necessary.

Anonymous said...

....I wish somebody would address the installation of the safety slide......When I re-assembled my P17 (just now) , the ball&spring ended up laying in the frame under the compression tube....I now have no safety even tho' the gun works fine ....I oriented the safety slide correctly by viewing the "Chambers" exploded view, which notes the ball as the sear ball(?) .... (The safety slide fell out as I was struggling with the trigger pin, now it doesn't move and has no 'detent' )

Whiteleather said...

Derrick, Are you sure that the compression chamber lifts out after removing the cross pin? Mine won't come out.

After taking off the RH grip panel it looks as if the black nut is caught on the hammer. I would rather not disassemble all those springs to replace my valve rings. Is that really possible?


derrick38 said...

Kris, this is a continuation of the full tear down from an earlier post. You do need to remove the sear, hammer, etc from the grip frame first. Sorry that's not clear.

Fred said...

I wanted to take the compression chamber out of the P17 to get to the valve assembly underneath. It states that once the set screws are loosened and pins taken out ,it will lift right out.I can't seem to get it out,and don't want to damage anything by forcing it up and out.Am I missing something?

Fred said...

Ok read the previous blog and understand.Any pictures of the disassembly of the other parts that need to come out?