Author Topic: Beeman Chief - Merry Christmas to Me !!! (Read 21000 times))

rsterne · « **Reply #80 on:** January 05, 2018, 08:24:14 PM »

If you have been following this thread from the beginning, you may remember that the trigger when I first inspected it had a burr on the top of the sear.... I polished it out, and when I pulled the gun down to do some work on it today, the burr is back, and bigger than before.... I had noticed that the back bottom edge of the hammer had the corner ground off (by hand) as if to cure some issue.... Well, I just discovered what that issue is, and IMO Beeman have made a really sloppy attempt to "cure" what over time may become a serious issue.... Here are what the parts look like today....

You can see the damage on the top of the sear, it appears to have been impacted from the "top".... Well that something is the back corner of the hammer, right where they ground a bevel on it.... In the photo, on the back of the Chief hammer, you can actually see a matching shiny mark on the hammer, right where it passes over the sear.... When the gun fires, the sear rotates forward into a near horizontal position, with the point on the top of the sear facing forward, towards the valve.... When the hammer bounces, and is thrown back towards the sear by the closing valve, that ground off back corner is colliding with the sear, and doing it hard enough to roll over the edge and form a burr, actually both front and back but worse on the back (what you can see in the photo), right where it holds the cocked hammer.... So I went in search of a solution.... I happen to have hammers from a QB78D and an FD-PCP, both of which use the same QB trigger assembly.... Here are the three hammers, with the sear catch points all lined up.... You are looking at the bottom of the hammers.... Forward (the valve side) is to the left, and the rear (spring side) is to the right.... The ground off corner on the back bottom corner of the Chief hammer is plainly visible....

Note that on the left (front) all three hammers have a flat ground on them, which is to clear the front trigger mounting screw.... On the Chief, it is a milled channel.... On the back the FD-PCP hammer has the lower part of the OD machined completely away, nothing to hit the sear after the gun is fired.... On the QB hammer, there IS no large OD behind the ring the sear catches on.... This should mean that all I have to do is mill a flat on the back of the Chief hammer, to prevent it from hitting the sear when fired.... I'll let you know how it works....

Bob

rsterne · « **Reply #81 on:** January 05, 2018, 11:28:21 PM »

Well, when I tried to mill a slot in the bottom I quickly found out that the hammer is hardened, and ruined an end mill trying.... So, I had to use my bench grinder and just grind a flat on the bottom as in this photo....

When I reassembled the gun, the cocking was somewhat "gritty" just before the hammer engaged the sear, so I guess the hammer is cocking slightly in the tube because I removed metal right where the hammer is pressing on the tube from the location of the cocking pin on top.... I deburred both the sear slot and the cocking slot in the tube (should have done that anyways).... and I used a stone in a Dremel and rounded the sloped surface in front of the new flat, and smoothed it so that it can't dig in.... It now cocks as smoothly as before.... but a better solution would be a hammer with a narrower flat, more like the one in front of the sear notch, so that more of the circumference of the hammer would bear on the tube.... only removing material from the bottom center to prevent damage to the sear.... I repolished the sear to remove the burr, so I can tell in future if there is any problem remaining.... but if I properly diagnosed the problem there really can't be.... I hope....

I tested the gun and the velocities are almost identical to before, it will still hit the same 966 fps maximum at 2000 psi with the 25.4 gr. at maximum preload.... and it now takes about 5.5 turns out of preload to get my best bell-curve, instead of 6 turns out.... the extra bit of preload made necessary by the slightly lighter hammer, I would think.... However, the gun seems louder, and may have increased hammer bounce.... I suspect that the back of the original hammer (where Beeman rough ground that corner) was hitting the trigger sear hard enough to debounce the hammer somewhat.... So, in saving the sear from further damage, I'm pretty sure I have increased the air consumption....

I was planning on making an SSG for this gun anyways.... so this is an excuse to make a new and better (longer) hammer that is less likely to cock in the tube.... and with a hole through it for the spring instead of that guide pin.... I have a 10 mm x 1mm bolt that I can use for the gap adjuster for the SSG that will thread into the rear plug.... so that will be the next order of business....

Bob

oldpro · « **Reply #82 on:** January 05, 2018, 11:44:44 PM »

I cant believe the sear didnt break! Obvious issue I hope the Mod works.

rsterne · « **Reply #83 on:** January 05, 2018, 11:51:33 PM »

I can't believe I'm the only one with this problem.... The weird thing is that somebody at Beeman or their supplier obviously knows there is a problem, because they took the lower rear corner off the hammer with a grinder.... Maybe they were supposed to take off more, and mine is an anomaly, I don't know.... or they could all be like this, just in varying degrees....

It's the first obvious QC problem I have seen.... and I'm NOT impressed at the attempted "fix".... pretty shoddy, IMO....

Bob

Ribbonstone · « **Reply #84 on:** January 06, 2018, 01:09:25 PM »

Bob:

There are differences between old and newer Chief's (maybe when they instituted the "powewr adjuster"?).

took mine apart just to see...as what you were showing didn't seem what I saw, but not trusting my memory.

Striker is not quite like yours. It''s basically 100% round, no cuts other than the threaded hole for the cocking pin/screw.

With a large bevel at the back end:

Unmodded trigger...made for a good pull, so I didn't do anything to it but lube it....doesn't show any damages ( a little bright spot wear, but nothing unexpected):

Will give you that my mild tune may not be generting the "bounce" that you are seeing...so not the "dings".

Not real sure the "why" of that forward cut in the striker..."they" didn't deem it needed on this one, and can't (yet) see where it would improvew the life of the sear...then again, may be some other differences I'd not find without a side-by-side take down.

JUST TO BE SURE...as we take too much for granted....the bolt handle on yours is threaded and screws into place (with a QB type lock screw fixing it in place once screwwed down)?

The striker cocking pin is actually a screw that does screw innto the striker?

rsterne · « **Reply #85 on:** January 06, 2018, 02:01:06 PM »

I'm guessing that when they changed from the generous bevel on the back of your striker they saw a problem, and their "fix" was to roughly grind the bottom rear corner of the striker away on mine.... Maybe some got ground enough to not whack the sear... and some (like mine) didn't..... which is a QC issue.... Remember, that I took my trigger apart and noticed that burr on it before attempting any mods or tuning, so that occurred with a stock gun within the first few shots....

Perhaps they changed the striker because they noticed the front bottom portion was hitting the front trigger screw.... so they machined that groove there to clear it.... but forgot the required bevel in the back.... Just out of curiosity, does your front trigger screw appear to have been ground shorter to clear your striker?.... One can only hope that they combined the two striker designs and get it right on version three....

Yes, my bolt handle is threaded in, with a set-screw on the back ala QB style.... BTW, my bolt handle was tending to pop up on firing, so I took a Dremel to the "down" (locking) slot in the receiver, and deepened it slightly and ground out the back edge a bit, but leaving the very top corner untouched.... This means that when the bolt handle is rotated downwards, the back of the notch slopes forward from the contact point at the back center of the handle to where the corner is.... That completely prevents the handle from popping up.... Yes, the cocking pin is a shouldered stud, with a slot on the top, that threads into the striker....

Bob

Ribbonstone · « **Reply #86 on:** January 06, 2018, 02:14:04 PM »

Front trigger housing screw has a washer...which limits it's depth. Same basic "double metal" as a QB for thatforward trigger housing screw (looks like a piece of tubing tack welded in place, with the screw threads going though both thicknesses to increase thread depth). By visual/by feel, that screw does not "poke out" and need the clearance cut.

Considering the hardness (or at least surface harness) of the sear parts, would be more concerned with the pin it rotates on (and the alloy housing fixing it in place) than just the visual ding.

rsterne · « **Reply #87 on:** January 06, 2018, 02:43:04 PM »

Mine has no washer.... I guess the reduced the parts count by machining that groove in the striker....

.... More likely, they found out that if somebody forgot that washer (or lost it) the screw stuck through and the striker hit it.... but they forgot the rear bevel and created a worse problem.... I don't suppose your erratic velocities on the first string after you replaced the valve screws was because you forgot that washer?.... just a thought....

I hope people don't have a sear (or mounting pin) failure because of this problem.... as I said, it seems Beeman needs a version 3....

Bob

Ribbonstone · « **Reply #88 on:** January 06, 2018, 03:16:16 PM »

Don't remember doing that....but wouldn't put it past me.

Anyway, stoned the end of the screw to smooth...maybe reducing it's length every so slightly..and "warped" the little washer slightly to mgive me that "tight" feel with perhaps a little less thread depth.

Anyway...it works. Velcoity tests normal, accuracy as good as before, no stray scractches on the striker.

rsterne · « **Reply #89 on:** January 06, 2018, 08:36:21 PM »

I made a new hammer today.... I moved the sear catch point forward about 0.070" to increase the hammer stroke to a measured 3/4".... I can't believe how long it took to make this, about 5 hours....

The cocking pin is in the same relationship to the front of the hammer as before.... but of course is stops 0.070" further back in the cocking slot when the hammer is cocked.... There is still plenty of room at the back end of the slots in both tube and receiver to cock the gun, also at the back of the slot for the bolt handle.... but I did run into one of those problems you don't anticipate.... After the hammer is cocked, when you slide the bolt forward, It didn't QUITE go far enough to turn down and lock.... What was happening is that the section in the middle of the bolt that is milled down wasn't quite long enough at the back, so I had to machine that 0.070" further back as well.... Fortunately there was lots of material in front of the threaded hole for the bolt handle, or I would have been making another hammer....

The hammer looks a LOT different than the original.... First of all, it doesn't have an intergral spring guide at the back, instead it has a 3/8" hole drilled about 1.5" deep through the center from the back.... This removes some weight, and gives a place for the spring and guide when you cock the hammer.... There is a additional full diameter section at the back to keep the hammer straighter in the tube, which should make it cock easier.... The weight at the moment is actually 1 gram less than the original hammer with the flat ground on the bottom, and 4 grams lighter than stock.... The cocking pin is made from a 1/2" long 8-32 SHCS with a 3/16" spacer threaded onto it, and then the "head" turned down to fit inside the cocking slot.... The hammer is counterbored 5/8" diameter from the back 3/16" deep to clear the extension on the rear plug, and the hammer will cock with it in place without having to shorten or modify it.... just in case I want to return the hammer setup to stock....

Tomorrow I hope to have time to figure out and make the SSG.... The plan is to have the guide fixed, with a sliding collar driving the hammer.... I like this style because it doesn't have a moving guide sticking out the back of the tube, and doesn't waste any energy accelerating the guide.... At least, that's the plan....

Bob

rsterne · « **Reply #90 on:** January 10, 2018, 01:43:29 AM »

I made the SSG for the Chief yesterday, here is a photo of it....

The 10 mm x 1 mm hex head bolt is the gap adjuster.... It threads into the original rear plug, and I drilled it out and tapped it 10-32 for the spring guide, which will also adjust the preload on the spring by using the screwdriver slot in the outer end.... There is a short steel spacer that is small enough to fit inside the 10mm threads, and then has a small shoulder on it for the spring stop, that fits in the 10.5 mm drilled hole in the end plug, and acts as a stop (in a similar manner to the washer on the outer end of the spring in a stock gun) when it comes up against the threads.... That spacer also has a short spring seat on it that fits nicely inside the spring.... I used the "set" spring from the Chief (12 lb/in), and made a sliding black Delrin spring guide for the other end of the spring.... The "head" on the front end of the spring guide is a 10-32 nut, threaded on with Loctite 638 (green) and then turned down under 3/8" to fit inside the hole I drilled in the hammer.... There is a # 008 O-ring (70D) acting as a bumper between the sliding guide and the end stop, just to cushion it a bit when it comes to a halt....

The black Delrin spring guide is what actually drives the hammer.... It sits in a recess in the back end of the hammer, and when you cock the gun, the hammer and that Delrin guide moves back over the (fixed but adjustable) steel spring guide, which moves into the 3/8" hole in the hammer.... That hole has to be deep enough to allow the hammer to cock fully, throughout the entire range of adjustment.... I ended up drilling it to within 0.10" of the front of the hammer to get clearance when the SSG is adjusted to zero gap, and all preloads from zero to 1/2" (which would be 6 lbs. of preload).... The hammer ended up at 70 grams, about 15% lighter than stock.... It seemed to take forever to get the right combination of the hole depth in the hammer, the length of the Delrin spring guide, and the steel spacer, plus I had to drill the 10.5 mm hole in the rear plug deeper, before I was satisfied that I had enough adjustment.... Once I find the setting(s) I want to use, I will have way more adjustment than I actually will use, of course.... but the first time on a new gun I always err on more adjustment rather than less....

While I am talking about adjustments, you will remember that I moved the sear notch on the hammer forward 0.070" to increase the hammer travel to a full 3/4".... Boy, was that a mistake....

.... Although I measured the lengths of the cocking slots in the tube and receiver and they were fine, I had to end up making TWO additional changes to the bolt travel to allow me to cock the gun with the new hammer in place.... It turns out that the milled slot in the bolt, which I had to lengthen at the back to allow the bolt to move forward enough to lock.... was too far forward at the front to draw the cocking pin back far enough to cock the hammer.... This is because the cocking pin is 0.070" further back, relative to the sear notch, of course.... The solution was to mill the slot for the bolt handle longer at the back, to allow the bolt to move further and cock the new hammer.... Well, that ALMOST worked, except the rear of the bolt then hit the plug in the back of the receiver, so I had to shorten that as well.... although only about 0.020".... All this occurred because I tried to get an extra 0.070" of hammer stroke.... My guess is that I should have left the cocking pin in the same relationship to the sear notch, and only shortened the front of the hammer to get the increased stroke.... There is one good bit of news, however.... By doing what I did, there is now more room to load the pellet when the bolt is back in the cocked position.... even with the longer probe I made.... So, all turned out well in the end, it was just a lot more work than I intended....

This is a typical case of one mod. requires two more, and those two need a couple more each.... and pretty soon what should have been really simple ends up causing lots of work and stress....

Anyways, I assembled it tonight (for about the umpteenth time) and it looks like I finally have every working OK and tons of adjustment in the SSG.... With 0.40" of preload on the spring, and 1 turn of gap on the SSG (0.040") it shoots 900 fps.... At these settings I have 4.8 lbs. of preload, and the cocking force is just over 13 lbs.... quite acceptable.... I hope tomorrow to play with adjustments and shoot some strings....

Bob

skorec · « **Reply #91 on:** January 10, 2018, 05:35:31 AM »

Bob, nice 2h? work

Am I wrong if I am thinking that shorter and stronger hammer spring do the same or similar as SSG ?
Whit the shorter spring I reach also necessary idle gap between the hammer and valve stem.

rsterne · « **Reply #92 on:** January 10, 2018, 12:27:54 PM »

A short stiff hammer spring will be harder to cock for the same hammer energy.... It is the average force accelerating the hammer and the distance that works through (the active stroke) that determines the hammer strike.... My SSG starts at 4.8 lbs. and ends at 13.2 lbs, for an average force of 9 lbs.... To do that with the same travel (and the same "idle" gap of 0.040") would require a hammer spring that takes 18 lbs. to cock, since it starts at zero force.... I am using a 12 lb/in spring with an active stroke of 0.71".... To get the same hammer energy with a short stiff spring and no preload would require a 25 lb/in spring....

Additionally, the short stiff spring (with no preload) takes almost no force to be compressed initially by a rebounding hammer, so still has the potential of hammer bounce, although reduced compared to a standard spring preloaded against the hammer.... My SSG requires 4.8 lbs of force to move at all, which the rebounding hammer is unlikely to be able to overcomer.... If it has enough bounce to compress the SSG, it would have a much easier job compressing the short stiff spring to store energy and end up with bounce....

I tried a short stiff spring to get an idea of what spring I needed for the SSG.... It required a spring made from 0.055" wire instead of 0.046" wire, with a rate of 24 lb/in, to get to 900 fps with a gap.... confirming the theory above....

Bob

rsterne · « **Reply #93 on:** January 10, 2018, 06:07:46 PM »

I reassembled the Chief today, here is a photo of it with the SSG installed.... The distance that the threaded rod protrudes past the head of the gap adjusting bolt equals the amount of preload on the spring.... No reason it can't be shortened, now that I know about where it will be running.... but that makes it very easy to measure how much preload on the spring.... in this case 0.40"....

The only other external changes are both ends of the bolt slot are slightly longer/deeper to allow for the longer hammer travel, but those changes require close inspection to even see, and once I touch up the bluing will be invisible.... I set the preload to 0.40", and then tethered the gun at 1800 psi and adjusted the gap from 3 turns negative (actual preload on the hammer) to 7 turns of gap.... Each turn of the gap adjusting bolt is 1 mm, so that is a total range tested of 10 mm (just about 0.40").... Here are the results, with both 18.1 gr. Heavies and 25.4 gr. Monsters....

When I am tuning a PCP with an SSG installed, I try and get the preload to the point that the velocity goes up onto the plateau with just a small amount of preload present, with the heaviest pellets I intend to use.... That way, you are on the knee of the curve with just a very small gap.... You can see that with the 25.4 gr. pellets, the knee of the curve is right at 1 turn of gap (0.040").... Sometimes you can get a bit more efficiency by using a bit more preload and a bit more gap, to give the hammer just a bit more room to rattle around.... but the difference is usually small.... As is typical of a gun with an SSG installed, once you start adding preload the gun gets very loud.... That happened with just 1 turn of preload in from zero gap, as expected.... Also, as you back the gap adjuster out, at some point the gun gets significantly quieter, and that happened at about 4-5 turns out.... By that time the velocity is dropping fast.... and the gap is so large that you may even see differences in velocity shooting uphill or downhill, because the hammer is coasting a long ways, and gravity has longer to act with a big gap.... The gun may be very efficient at those wide gaps, but may also suffer from a large velocity SD.... so you are usually better off to reduce the preload on the spring, and reduce the gap back down to under 1/8" or so....

Once satisfied that I had the preload in the ballpark, I shot a string with the 25.4 gr. Monsters with 2 turns of gap, using a 2000 psi fill.... I repeated with the 18.1 gr. Heavies, but the velocity was over 1000 fps, so I backed the gap adjuster out another turn, and shot a string with the Heavies at 3 turns of gap.... The results are shown below.... Only shots with a 4% ES are shown....

I am very pleased with the shot count at the power levels achieved.... The ending pressure of the strings were 1320 psi for the 25.4 gr. pellets, and 1200 psi for the 18.1 gr. pellets.... so I am getting a useful pressure range of 700-800 psi, compared to the 500 psi of the stock gun.... Part of that is due to the harder PEEK poppet, and part to the lack of hammer bounce on the second half of the shot string from the SSG.... The efficiency isn't too bad at these power levels, and ends up the same with both pellets, at 1.17 FPE/CI.... The 25.4 gr. Monsters returned 11 shots averaging 873 fps (43.0 FPE).... while the 18.1 gr. Heavies gave 14 shots averaging 959 fps (37.0 FPE).... both within my standard 4% ES.... By comparison, my much modified .22 cal Disco, with a 3" longer barrel that the Chief, required a 2400 psi fill to equal that string with the 18.1 gr. pellets, at slightly less efficiency.... so I'm pretty happy with the results....

One other thing I should mention.... With the increased velocity, the groups I am shooting through the Chrony have tightened up further.... The 25.4 gr Monsters now rival the 18.1 gr. Heavies.... and I got some of the new Redesigned Monsters and shot a few of those as well.... They are tighter still, with a hole from 5 shots completely round, but not quite small enough to prevent a pellet from falling through.... Yeah, I know it's only 20 feet.... but when any gun or pellet shoots like that during Chrony testing inside.... I know it has a lot of potential....

Bob

Ribbonstone · « **Reply #94 on:** January 10, 2018, 07:08:22 PM »

HAd wondered if that new made striker was going to crowd you for room...evidently not...evened out nicely.

rsterne · « **Reply #95 on:** January 10, 2018, 07:18:11 PM »

Crowded for room YES.... but that can be overcome by changing enough things.... *LOL*.... If I had it to do over again, I might only shorten the front of the hammer, and leave the cocking pin in the same place, relative to the sear notch.... Then you would not need any changes to the bolt or bolt slot.... However, with the longer bolt probe, moving the bolt back and gaining the loading room is an nice extra.... though not strictly necessary....

If you wanted more stroke without changing the hammer, all you need to do is shorten the stock hammer at the front, no other changes.... Don't go too far, however, or the cocking pin could hit the front of the slots in tube or receiver (or maybe the bolt) before the front of the (shortened) hammer hits the steel backing block....

Bob

Ribbonstone · « **Reply #96 on:** January 10, 2018, 07:46:23 PM »

Don't think I'm going to be shortening an already short striker...just inviting tipping (after all, doesn't the sear catch the bottom...which pretty much off-centers the spring tension?)

Am pretty happy with mine now...but if I get the urge to change, will likely make one that extends the spring guide out of the rear end cap, thread the end of that, and use it as an external stop.

WyoMan · « **Reply #97 on:** January 11, 2018, 01:03:59 AM »

Quote from: rsterne on January 10, 2018, 12:27:54 PM

A short stiff hammer spring will be harder to cock for the same hammer energy.... It is the average force accelerating the hammer and the distance that works through (the active stroke) that determines the hammer strike.... My SSG starts at 4.8 lbs. and ends at 13.2 lbs, for an average force of 9 lbs.... To do that with the same travel (and the same "idle" gap of 0.040") would require a hammer spring that takes 18 lbs. to cock, since it starts at zero force.... I am using a 12 lb/in spring with an active stroke of 0.71".... To get the same hammer energy with a short stiff spring and no preload would require a 25 lb/in spring....

Additionally, the short stiff spring (with no preload) takes almost no force to be compressed initially by a rebounding hammer, so still has the potential of hammer bounce, although reduced compared to a standard spring preloaded against the hammer.... My SSG requires 4.8 lbs of force to move at all, which the rebounding hammer is unlikely to be able to overcomer.... If it has enough bounce to compress the SSG, it would have a much easier job compressing the short stiff spring to store energy and end up with bounce....

I tried a short stiff spring to get an idea of what spring I needed for the SSG.... It required a spring made from 0.055" wire instead of 0.046" wire, with a rate of 24 lb/in, to get to 900 fps with a gap.... confirming the theory above....

Bob

Hi Bob, I think the SSG works better (than the SSS) for arresting hammer energy because the hammer rebound strikes a mass (the spring guide assembly), and that would dissipate some of the energy that would otherwise compress the spring.

In theory, the hammer rebound energy should load different springs (spring rates, compression levels, etc.) with the same energy... i.e. stiffer springs compress less.
But the SSG, I think, is a complex system because of the initial impact on an object with mass. I've found that even putting a small top hat on a SSS will help dissipate more rebound energy. I'm not completely sure though... just a theory from some limited testing.

Your other point, I've found, is also very true. SSS setups aren't very friendly for cocking effort if you need a hard strike on the valve. I've used them successfully with Cothran valves running with normal CO2 pressure. You can imagine how easy those valve will open.

Remarkable work with that Chief... thanks for the details!

Wyo

Late edit: The o-ring buffer on the end is a nice addition I had overlooked and there's probably not much weight in the Delrin guide that would subtract from the hammer energy

skorec · « **Reply #98 on:** January 11, 2018, 12:04:24 PM »

Bob,
Shooting .22 Monsters at 873 FPS only whit 1500 PSI and 21,5” barrel gun is really nice. Much Better then UMAREX Gauntlet .

My .22 JKHAN shot them with the same speed with 23,5” barrel but need 2350 PSI.

But I am thinking that Monsters need more FPS for longer distances.
I will wait for test you at serious distances.

nervoustrigger · « **Reply #99 on:** January 11, 2018, 01:02:54 PM »

Quote

But I am thinking that Monsters need more FPS for longer distances.
…
I will wait for test you at serious distances.

You seem to be holding onto a notion that ~950fps is a magical number for the JSB Monsters. As Bob has previously explained, the two important stability criteria actually become slightly worse as you get into the transonic region. If a particular rifle were to group better at these velocities, it would in all likelihood be a result of harmonics…in which case there is no reason to expect any two rifles, even of the same model, to exhibit precisely the same preference for a particular velocity. So regardless of how well or how poorly the Monsters do at longer distances in Bob’s rifle, it does nothing to predict how well they might perform in yours. This reality holds true for any pellet. The only way to know is to test them yourself.

Thank you to our advertisers!

Beeman Chief - Merry Christmas to Me !!!

Author Topic: Beeman Chief - Merry Christmas to Me !!! (Read 21000 times))