FWB 124 low power, and seal questions

FWB 124 low power, and seal questions

Joined: January 24th, 2009, 5:47 pm

October 11th, 2017, 12:41 pm #1

I have a pristine San Rafael vintage 124 serial 38XXX that I bought from the original owner in 2010. The factory seal went right away, so I put in a JM Old School kit. This was in my earlier learning stages. The piston seal was very snug. I fitted a new breech seal at the time also.

I never got much velocity: 740 with Exacts and 770 with Express. I have maybe 1000-2000 shots through it now. Currently 730 with AA Fields. I checked the breech seal with tissue, and put the factory one back in with the same results.

After seeing all the posts of folks getting 800+, I opened it back up today. Actually, the tight piston seal wore in nicely, and is now just "snug", but no more so than most of my other guns.

OK, here is the question: When looking into the receiver tube, the face does not appear to be flat. There appears to be a raised center "plateau" that is perhaps dime size. It seems that the piston seal bottoms out on this center part and the outer lip of the seal never hits bottom. Indeed, my seal only shows signs of wear in the center part, and seems as if the lip never bottoms out.

I did get a long metal piece to feel along the face of the receiver, and it does seem that the center part is raised perhaps .010"-.015". Is this how this gun is made? No 'F" marks on gun, just standard Beeman marks. It would seem like to me that I am having lost air volume at this spot, and perhaps machining the center face of the piston seal down a bit would be the cure. I know that currently "cup" style seals do exactly that.
Quote
Share

Joined: August 7th, 2003, 12:59 pm

October 11th, 2017, 1:29 pm #2

Piece of old seal stuck to front of receiver maybe ? ?
Quote
Share

Joined: May 20th, 2013, 12:46 am

October 11th, 2017, 7:49 pm #3

I have a pristine San Rafael vintage 124 serial 38XXX that I bought from the original owner in 2010. The factory seal went right away, so I put in a JM Old School kit. This was in my earlier learning stages. The piston seal was very snug. I fitted a new breech seal at the time also.

I never got much velocity: 740 with Exacts and 770 with Express. I have maybe 1000-2000 shots through it now. Currently 730 with AA Fields. I checked the breech seal with tissue, and put the factory one back in with the same results.

After seeing all the posts of folks getting 800+, I opened it back up today. Actually, the tight piston seal wore in nicely, and is now just "snug", but no more so than most of my other guns.

OK, here is the question: When looking into the receiver tube, the face does not appear to be flat. There appears to be a raised center "plateau" that is perhaps dime size. It seems that the piston seal bottoms out on this center part and the outer lip of the seal never hits bottom. Indeed, my seal only shows signs of wear in the center part, and seems as if the lip never bottoms out.

I did get a long metal piece to feel along the face of the receiver, and it does seem that the center part is raised perhaps .010"-.015". Is this how this gun is made? No 'F" marks on gun, just standard Beeman marks. It would seem like to me that I am having lost air volume at this spot, and perhaps machining the center face of the piston seal down a bit would be the cure. I know that currently "cup" style seals do exactly that.
1. Your current velocity isn't really that much off the mark for other 124s out there, and it's good to keep in mind that there is some variance from one rifle to the next of the same make and model number. I'm trying to say that you could spend a lot of time chasing that last 30 fps and never get it. So, what's it worth to you? Is the lack of that 30 fps. keeping you from doing something you need to do? (Edit: Oops. It looks like it could actually be more like 60+ fps. lower than some others, so I can see your point. I misread it the first time--sorry).

2. What Mark said about some remaining old piston seal debris is often right on the money when it comes to the 124. Of all the air guns on the market, the 124 is notorious for having a piston seal that disintegrated and cluttered-up the compression chamber when it went bad. Seeing it, then removing it can be a daunting task. When I tuned a 124, almost all of them had a ring of old seal debris at the end of the compression chamber closest to the breech. The beige color of the factory seal material tended to blend in with the color of the chamber. Even using a Mini-Mag flashlight (which will nicely fit inside the tube), you might not see the debris that needs removed to get complete piston travel and thus full velocity. Sometimes I had to use one of those little fiber optic attachments on the Mini-Mag light (see link below) to focus all around the perimeter of the chamber to see what was there (or not there). Then it took using the right tools to get into the edge of the chamber and remove the debris, even when I saw it. As long as you have the rifle taken apart again anyway, I suggest you look for any such debris and remove it if it's present.

https://www.amazon.com/Nite-Ize-FPO-06- ... B00019H6BG


3. Your question about removing that little hump on the face of the seal has some merit as it pertains to velocity, but probably not by a lot. You can sand it to a flat surface and probably pick up a few fps. Just keep in mind that the original design of the seal (with the hump) might have added a little cushion to the shot cycle as the piston landed on the chamber wall at the end of its travel. How much? I don't know. I can tell you that the originally-designed piston seal for the R1 had the same hump on it, and when it was removed the velocity of the rifle increased but the shot cycle didn't become anymore harsh to a noticeable degree. Now, as far as to going further and cupping or concave-ing the face of the seal as you mentioned, you may be in some uncharted waters on the 124 with that. The piston seal on the 124 has a slotted-parachute design versus a non-slotted-parachute design and that could make a difference. I don't want to type all of the negative possibilities, but although it works well on some other air rifles, there could be some negative effects and you might actually lose some velocity and need to order another seal and start over.

I hope that helps. Best wishes on your project.
Quote
Share

Joined: January 24th, 2009, 5:47 pm

October 11th, 2017, 8:00 pm #4

Piece of old seal stuck to front of receiver maybe ? ?
Nope, no seal debris in there
Quote
Share

Joined: January 24th, 2009, 5:47 pm

October 11th, 2017, 8:02 pm #5

1. Your current velocity isn't really that much off the mark for other 124s out there, and it's good to keep in mind that there is some variance from one rifle to the next of the same make and model number. I'm trying to say that you could spend a lot of time chasing that last 30 fps and never get it. So, what's it worth to you? Is the lack of that 30 fps. keeping you from doing something you need to do? (Edit: Oops. It looks like it could actually be more like 60+ fps. lower than some others, so I can see your point. I misread it the first time--sorry).

2. What Mark said about some remaining old piston seal debris is often right on the money when it comes to the 124. Of all the air guns on the market, the 124 is notorious for having a piston seal that disintegrated and cluttered-up the compression chamber when it went bad. Seeing it, then removing it can be a daunting task. When I tuned a 124, almost all of them had a ring of old seal debris at the end of the compression chamber closest to the breech. The beige color of the factory seal material tended to blend in with the color of the chamber. Even using a Mini-Mag flashlight (which will nicely fit inside the tube), you might not see the debris that needs removed to get complete piston travel and thus full velocity. Sometimes I had to use one of those little fiber optic attachments on the Mini-Mag light (see link below) to focus all around the perimeter of the chamber to see what was there (or not there). Then it took using the right tools to get into the edge of the chamber and remove the debris, even when I saw it. As long as you have the rifle taken apart again anyway, I suggest you look for any such debris and remove it if it's present.

https://www.amazon.com/Nite-Ize-FPO-06- ... B00019H6BG


3. Your question about removing that little hump on the face of the seal has some merit as it pertains to velocity, but probably not by a lot. You can sand it to a flat surface and probably pick up a few fps. Just keep in mind that the original design of the seal (with the hump) might have added a little cushion to the shot cycle as the piston landed on the chamber wall at the end of its travel. How much? I don't know. I can tell you that the originally-designed piston seal for the R1 had the same hump on it, and when it was removed the velocity of the rifle increased but the shot cycle didn't become anymore harsh to a noticeable degree. Now, as far as to going further and cupping or concave-ing the face of the seal as you mentioned, you may be in some uncharted waters on the 124 with that. The piston seal on the 124 has a slotted-parachute design versus a non-slotted-parachute design and that could make a difference. I don't want to type all of the negative possibilities, but although it works well on some other air rifles, there could be some negative effects and you might actually lose some velocity and need to order another seal and start over.

I hope that helps. Best wishes on your project.
Thanks Ed, I will keep in mind
Quote
Share

Joined: January 24th, 2009, 5:47 pm

October 11th, 2017, 8:20 pm #6

I have a pristine San Rafael vintage 124 serial 38XXX that I bought from the original owner in 2010. The factory seal went right away, so I put in a JM Old School kit. This was in my earlier learning stages. The piston seal was very snug. I fitted a new breech seal at the time also.

I never got much velocity: 740 with Exacts and 770 with Express. I have maybe 1000-2000 shots through it now. Currently 730 with AA Fields. I checked the breech seal with tissue, and put the factory one back in with the same results.

After seeing all the posts of folks getting 800+, I opened it back up today. Actually, the tight piston seal wore in nicely, and is now just "snug", but no more so than most of my other guns.

OK, here is the question: When looking into the receiver tube, the face does not appear to be flat. There appears to be a raised center "plateau" that is perhaps dime size. It seems that the piston seal bottoms out on this center part and the outer lip of the seal never hits bottom. Indeed, my seal only shows signs of wear in the center part, and seems as if the lip never bottoms out.

I did get a long metal piece to feel along the face of the receiver, and it does seem that the center part is raised perhaps .010"-.015". Is this how this gun is made? No 'F" marks on gun, just standard Beeman marks. It would seem like to me that I am having lost air volume at this spot, and perhaps machining the center face of the piston seal down a bit would be the cure. I know that currently "cup" style seals do exactly that.
On closer examination, I notice some scratches on the breech face. I will have to check to see if that is causing the breech seal to not do it’s job
Quote
Share

Joined: January 28th, 2007, 2:14 am

October 11th, 2017, 11:42 pm #7

I have a pristine San Rafael vintage 124 serial 38XXX that I bought from the original owner in 2010. The factory seal went right away, so I put in a JM Old School kit. This was in my earlier learning stages. The piston seal was very snug. I fitted a new breech seal at the time also.

I never got much velocity: 740 with Exacts and 770 with Express. I have maybe 1000-2000 shots through it now. Currently 730 with AA Fields. I checked the breech seal with tissue, and put the factory one back in with the same results.

After seeing all the posts of folks getting 800+, I opened it back up today. Actually, the tight piston seal wore in nicely, and is now just "snug", but no more so than most of my other guns.

OK, here is the question: When looking into the receiver tube, the face does not appear to be flat. There appears to be a raised center "plateau" that is perhaps dime size. It seems that the piston seal bottoms out on this center part and the outer lip of the seal never hits bottom. Indeed, my seal only shows signs of wear in the center part, and seems as if the lip never bottoms out.

I did get a long metal piece to feel along the face of the receiver, and it does seem that the center part is raised perhaps .010"-.015". Is this how this gun is made? No 'F" marks on gun, just standard Beeman marks. It would seem like to me that I am having lost air volume at this spot, and perhaps machining the center face of the piston seal down a bit would be the cure. I know that currently "cup" style seals do exactly that.
730 with AAs is ~10 fpe, and yes, that's pitiful. No other way to put it.

The last JM spring I measured was 37 coils, 0.128 wire diameter. That boiled down to a 4.74" compressed length; not much, if any room left to space it up. That spring produced a titch over 12 fpe.

I have also run 33 coil springs (also .128 wire, a common diameter)that perform in the 12- 13 fpe range. I did not note whether I had spaced up the spring, but expect I would have.

I want to say the "Old School" kit was billed as "kitchen table installation", that is, much shorter spring than the stock unit. If you have room to do so, try spacing up. That will usually coax out more power. You've got at least 4.74" to fill.

By what you've written I expect you knew not to over goober the innards with tar -- that'll suck the life right out of 'er!
Quote
Share

Joined: September 2nd, 2006, 1:43 am

October 12th, 2017, 12:46 am #8

1. Your current velocity isn't really that much off the mark for other 124s out there, and it's good to keep in mind that there is some variance from one rifle to the next of the same make and model number. I'm trying to say that you could spend a lot of time chasing that last 30 fps and never get it. So, what's it worth to you? Is the lack of that 30 fps. keeping you from doing something you need to do? (Edit: Oops. It looks like it could actually be more like 60+ fps. lower than some others, so I can see your point. I misread it the first time--sorry).

2. What Mark said about some remaining old piston seal debris is often right on the money when it comes to the 124. Of all the air guns on the market, the 124 is notorious for having a piston seal that disintegrated and cluttered-up the compression chamber when it went bad. Seeing it, then removing it can be a daunting task. When I tuned a 124, almost all of them had a ring of old seal debris at the end of the compression chamber closest to the breech. The beige color of the factory seal material tended to blend in with the color of the chamber. Even using a Mini-Mag flashlight (which will nicely fit inside the tube), you might not see the debris that needs removed to get complete piston travel and thus full velocity. Sometimes I had to use one of those little fiber optic attachments on the Mini-Mag light (see link below) to focus all around the perimeter of the chamber to see what was there (or not there). Then it took using the right tools to get into the edge of the chamber and remove the debris, even when I saw it. As long as you have the rifle taken apart again anyway, I suggest you look for any such debris and remove it if it's present.

https://www.amazon.com/Nite-Ize-FPO-06- ... B00019H6BG


3. Your question about removing that little hump on the face of the seal has some merit as it pertains to velocity, but probably not by a lot. You can sand it to a flat surface and probably pick up a few fps. Just keep in mind that the original design of the seal (with the hump) might have added a little cushion to the shot cycle as the piston landed on the chamber wall at the end of its travel. How much? I don't know. I can tell you that the originally-designed piston seal for the R1 had the same hump on it, and when it was removed the velocity of the rifle increased but the shot cycle didn't become anymore harsh to a noticeable degree. Now, as far as to going further and cupping or concave-ing the face of the seal as you mentioned, you may be in some uncharted waters on the 124 with that. The piston seal on the 124 has a slotted-parachute design versus a non-slotted-parachute design and that could make a difference. I don't want to type all of the negative possibilities, but although it works well on some other air rifles, there could be some negative effects and you might actually lose some velocity and need to order another seal and start over.

I hope that helps. Best wishes on your project.
...using a patch puller for muzzle loaders; one look and you’ll see why there’s probably nothing better:

https://www.amazon.com/Traditions-Perfo ... tch+puller

Quote
Share

Joined: January 24th, 2009, 5:47 pm

October 12th, 2017, 2:03 am #9

730 with AAs is ~10 fpe, and yes, that's pitiful. No other way to put it.

The last JM spring I measured was 37 coils, 0.128 wire diameter. That boiled down to a 4.74" compressed length; not much, if any room left to space it up. That spring produced a titch over 12 fpe.

I have also run 33 coil springs (also .128 wire, a common diameter)that perform in the 12- 13 fpe range. I did not note whether I had spaced up the spring, but expect I would have.

I want to say the "Old School" kit was billed as "kitchen table installation", that is, much shorter spring than the stock unit. If you have room to do so, try spacing up. That will usually coax out more power. You've got at least 4.74" to fill.

By what you've written I expect you knew not to over goober the innards with tar -- that'll suck the life right out of 'er!
This kit came spaced up to nearly max. It is one of his "older" kits and has 29 coils of .128 wire and a delrin spacer of 1.16". Maxed out at 4.87. The easier installation is with the spacer rather than compressing more coils.

On another gun, I once thought the JM spring had weakened, when in fact the leather to synthetic piston head had loosened and unscrewed and caused a shorter stroke. I don't doubt the JM spring in this one is more than fine also.

I just took .020" off the seal face where the center was protruding a bit, it is now flat or perhaps .005" concave. The seal still had the annular mold lines around the outer ring, so it was obvious it never bottomed out except in the center.

As you said 10fpe is not great in this gun. I like the 8-12 fpe guns, but unless I make an effort to detune something, I like to know that my guns are performing properly, and THEN I can do what I wish. And yes, no loads of tar. In fact, I almost never use it in anything now.
Quote
Share

Joined: January 24th, 2009, 5:47 pm

October 12th, 2017, 2:31 am #10

I have a pristine San Rafael vintage 124 serial 38XXX that I bought from the original owner in 2010. The factory seal went right away, so I put in a JM Old School kit. This was in my earlier learning stages. The piston seal was very snug. I fitted a new breech seal at the time also.

I never got much velocity: 740 with Exacts and 770 with Express. I have maybe 1000-2000 shots through it now. Currently 730 with AA Fields. I checked the breech seal with tissue, and put the factory one back in with the same results.

After seeing all the posts of folks getting 800+, I opened it back up today. Actually, the tight piston seal wore in nicely, and is now just "snug", but no more so than most of my other guns.

OK, here is the question: When looking into the receiver tube, the face does not appear to be flat. There appears to be a raised center "plateau" that is perhaps dime size. It seems that the piston seal bottoms out on this center part and the outer lip of the seal never hits bottom. Indeed, my seal only shows signs of wear in the center part, and seems as if the lip never bottoms out.

I did get a long metal piece to feel along the face of the receiver, and it does seem that the center part is raised perhaps .010"-.015". Is this how this gun is made? No 'F" marks on gun, just standard Beeman marks. It would seem like to me that I am having lost air volume at this spot, and perhaps machining the center face of the piston seal down a bit would be the cure. I know that currently "cup" style seals do exactly that.
Just an aside to anyone interested and to hijack my own thread: the first year "short tube" variants of the Diana 34 series guns had the same 28X77 B&S measurements as the FWB 124. Perhaps they thought that was a good starting point. The early Dianas however, didn't make the same power. I think maybe it had to do with their transfer port which was long, bent, and quite large in diameter. That being said, one of these detuned to 10.5fpe is VERY pleasant.
Quote
Share