FWB Sport

[ChuckHunter]

Factory spring is .142 wire and the kit from Tom is .148 wire. A little stiffer but fits the piston better than the factory spring!
I did polish the end that goes in the piston and didn't use any washers! But I'm happy where the power ended up! Snappy shot cycle kinda reminds me of a HW35!
Did you get a Vac seal too?
Looking forward to your update when you get it all together!
James from Michigan

 

[jimk1963]

Factory spring is .142 wire and the kit from Tom is .148 wire. A little stiffer but fits the piston better than the factory spring!
I did polish the end that goes in the piston and didn't use any washers! But I'm happy where the power ended up! Snappy shot cycle kinda reminds me of a HW35!
Did you get a Vac seal too?
Looking forward to your update when you get it all together!
James from Michigan

Will definitely report back. Received two HW80 30mm vac seals today, had ordered these earlier. Holy cow it is super stiff, and the face is completely different than the FWB OEM and ARH seals. Pictured are the ARH and Vortek vac seals. The ARH & FWB seals are flat-faced with an annular relief “gutter” around the periphery. The Vortek vac seal face is concave, with an angled perimeter that drops down into the concave face. The Vortek seal, like the FWB seal, is just a few thousandths smaller than the slightly oversized ARH seal. Looking forward to giving it a try!

 

[jimk1963]

Will definitely report back. Received two HW80 30mm vac seals today, had ordered these earlier. Holy cow it is super stiff, and the face is completely different than the FWB OEM and ARH seals. Pictured are the ARH and Vortek vac seals. The ARH & FWB seals are flat-faced with an annular relief “gutter” around the periphery. The Vortek vac seal face is concave, with an angled perimeter that drops down into the concave face. The Vortek seal, like the FWB seal, is just a few thousandths smaller than the slightly oversized ARH seal. Looking forward to giving it a try!

Received new custom PG1-based kit from Tom at Vortek. The kit includes a solid metal guide with integral brass washer, 905148 spring with 28 turns, and optional brass washers (qty 2) for fitting inside the piston. To order the kit, Tom had me describe it as shown here:

"PG1-905148-28 (NO TOP HAT), Washers to fit piston top hat"

Below are a few pictures of the kit, alongside the original factory spring/guide. Like ChuckHunter noted, the Vortek spring is .006" thicker than the factory spring, but it's also shorter with fewer coils. Similarly, the ID of the spring guide ended up about 1/64" smaller than the original guide. This did not cause any interference issues but does make for a near-perfect fit. I may ream out that last 1/64" at some point, if my OCD takes charge.

Initial results:
0) Config: Vortek PG1 kit, Vortek 30mm "Vac Seal" (moly impregnated), Ultimox 226 lube on piston seal/piston rear/brass washer inside piston/bottom of spring guide)
1) Significantly more difficult to cock than factory spring - immediately it's clear to me I'll want to remove a coil or two to improve this
2) Twang is 100% gone - this spring fits the piston very well, and the custom guide eliminated the trigger-side rattling
3) Shot cycle is - well, kinda reminds me of my brother's old 30-30 lever action. It's a jolt! Not overpowering, but the gun is quite clearly oversprung, which is what I wanted so I could remove coil(s) to dial it in
4) Energy - it's shooting WAY over spec, numbers of 14 to 16 ft-lbs. I will be removing a coil (or two) to see if I can tame this. A few numbers below.

One thing that's really bugging me, that I haven't experienced with earlier builds, is a random, super high Air Chrony reading (1400 fps range). Maybe 1 out of 10 shots. Observing the barrel afterward, a small amount of darkening is observed. There's no flame or smoke, but obviously something is igniting to cause this kind of energy and residue. The receiver tube was cleaned with paint thinner, followed by multiple rags. I realize the paint thinner is volatile but (maybe stuipidly) thought it could be completely removed with basic cleaning. Even if paint thinner is the culprit, I've put over 200 rounds through the gun and it still happens... trying to understand how. My only other curiosity is whether my Ultimox 226 from Amazon is the real deal. I also have Krytox, may go back to that tube for next round.

 

[razor62]

Here's a video that I made regarding the FWB Sport before I tuned the gun.

Here's the follow up video detailing the tuning process that I employed.

 

[jimk1963]

Here's a video that I made regarding the FWB Sport before I tuned the gun.

Here's the follow up video detailing the tuning process that I employed.

Thanks Kevin, this is Jim K from the long thread with Marc on your YT video - hi again!

As you can see, I’ve made some recent progress but need to clean the gun again. I read another post recommending paint thinner, may have been bad advice as I’m thinking there are traces of mineral spirits left behind to cause this dieseling - even though I dried it thoroughly with numerous rags and forced air. Going back to my usual routine of acetone, which should be able to dissolve any spirits residue.

Re: your video, I’ll be following your procedure to cut the spring down. I gave up on making a custom guide, went with Tom’s custom offering as you can see. Also may be no room for a piston sleeve with Tom’s spring, has a .006” chubbier wire diameter and fills up the piston with nearly zero clearance. Will revisit that later if needed.

First things first, get rid of this dieseling…

 

[razor62]

Thanks Kevin, this is Jim K from the long thread with Marc on your YT video - hi again!

As you can see, I’ve made some recent progress but need to clean the gun again. I read another post recommending paint thinner, may have been bad advice as I’m thinking there are traces of mineral spirits left behind to cause this dieseling - even though I dried it thoroughly with numerous rags and forced air. Going back to my usual routine of acetone, which should be able to dissolve any spirits residue.

Re: your video, I’ll be following your procedure to cut the spring down. I gave up on making a custom guide, went with Tom’s custom offering as you can see. Also may be no room for a piston sleeve with Tom’s spring, has a .006” chubbier wire diameter and fills up the piston with nearly zero clearance. Will revisit that later if needed.

First things first, get rid of this dieseling…

Hi Jim!
I'll tell you what......You've got exponentially more patience than I've got. So, other than the dieseling how're they shooting? Were you able to solve your power output issues? Marc recommends 91% rubbing alcohol for degreasing. I've always used acetone myself but Marc knows his stuff.
I wasn't aware that Tom had a kit for the Sport. Had I known, I'd have most likely gone that route. Keep us posted on your progress. Good to hear from you my friend.
Kevin

 

[jimk1963]

Hi Jim!
I'll tell you what......You've got exponentially more patience than I've got. So, other than the dieseling how're they shooting? Were you able to solve your power output issues? Marc recommends 91% rubbing alcohol for degreasing. I've always used acetone myself but Marc knows his stuff.
I wasn't aware that Tom had a kit for the Sport. Had I known, I'd have most likely gone that route. Keep us posted on your progress. Good to hear from you my friend.
Kevin

Good to hear from you as well! Really enjoy your videos, your FWB Sport videos were the inspiration for this project. I describe the shot cycle as very short, tight (no twanging) but with an impressive jolt. I likened it to my brother's old 30-30 lever action, which didn't have much of a kick but had that snappy jolt. When it's not dieseling, the power output is really high - from 14 to 16 ft-lbs as shown in the chart. It's oversprung, and power is too high but that's the starting point I wanted - so I can trim down the spring coil by coil. Cocking force is noticeably higher with the Vortek spring, reminds me of cocking a nitro-piston. Going back to my previous build, after much fine sanding of the ARH piston seal, with factory spring and no other mods (no custom spring guide or piston sleeve), I got the gun back to 13 ft-lbs with its out-of-the-box cocking force. Of course, with no custom guide or sleeve, Mr. Twangy has returned to haunt the gun. So this led me to a custom order from Tom.

Re: this Vortek kit - it's not a standard offering. Tom wants more feedback from customers like myself to "fine tune" his offering. The feedback I sent him so far is: (1) take 1 or 2 coils off (not sure yet) and (2) the guide's ID is 1/64" smaller than the stock FWB guide (used 1/64" transfer punches to determine this tiny delta), so need to enlarge that ID just a hair. On this thread, ChuckHunter went with 2 fewer coils and loves his result. But he's down in the 11 ft-lb range, which is lower than I'm targeting. This gun should be in the 13's with a tight, snappy, twangless shot cycle - like yours! :-D Re: the guide ID, it's not causing interference with the piston rod but it's a super-close fit, maybe a little too close when tolerances of other guns are taken into account.

There is a 3rd observation as well - notice in the photo there's a brass washer added at the base of the spring guide. I don't know how this thing was assembled, but that guide and washer feel like they're welded in there - I can't move that assembly at all. But anyway, that washer effectively makes the spring guide base thicker, reducing the amount of piston rod that is exposed to the trigger sear. No big deal, it does work. The only quirk I ran into is that when it first arrived, there was a 1/16" gap between that brass washer and the base of the spring. Try as I might, I couldn't slide the spring down to seat onto the brass washer. Eventually, I just assembled the gun and slowly cocked it - near the end of the stroke, I heard a "CRACK!" which was that spring giving way and sliding down onto the brass washer. I disassembled the gun, confirmed the spring had indeed moved into position, and it's been fine ever since. Not sure why it was made with that gap, but I alerted Tom to what I found.

I'm having way too much fun learning what works, what doesn't, making dumb mistakes along the way. Experts like you make this all the more enjoyable, hope this info helps others down the road. More to follow!

 

[razor62]

Good to hear from you as well! Really enjoy your videos, your FWB Sport videos were the inspiration for this project. I describe the shot cycle as very short, tight (no twanging) but with an impressive jolt. I likened it to my brother's old 30-30 lever action, which didn't have much of a kick but had that snappy jolt. When it's not dieseling, the power output is really high - from 14 to 16 ft-lbs as shown in the chart. It's oversprung, and power is too high but that's the starting point I wanted - so I can trim down the spring coil by coil. Cocking force is noticeably higher with the Vortek spring, reminds me of cocking a nitro-piston. Going back to my previous build, after much fine sanding of the ARH piston seal, with factory spring and no other mods (no custom spring guide or piston sleeve), I got the gun back to 13 ft-lbs with its out-of-the-box cocking force. Of course, with no custom guide or sleeve, Mr. Twangy has returned to haunt the gun. So this led me to a custom order from Tom.

Re: this Vortek kit - it's not a standard offering. Tom wants more feedback from customers like myself to "fine tune" his offering. The feedback I sent him so far is: (1) take 1 or 2 coils off (not sure yet) and (2) the guide's ID is 1/64" smaller than the stock FWB guide (used 1/64" transfer punches to determine this tiny delta), so need to enlarge that ID just a hair. On this thread, ChuckHunter went with 2 fewer coils and loves his result. But he's down in the 11 ft-lb range, which is lower than I'm targeting. This gun should be in the 13's with a tight, snappy, twangless shot cycle - like yours! :-D Re: the guide ID, it's not causing interference with the piston rod but it's a super-close fit, maybe a little too close when tolerances of other guns are taken into account.

There is a 3rd observation as well - notice in the photo there's a brass washer added at the base of the spring guide. I don't know how this thing was assembled, but that guide and washer feel like they're welded in there - I can't move that assembly at all. But anyway, that washer effectively makes the spring guide base thicker, reducing the amount of piston rod that is exposed to the trigger sear. No big deal, it does work. The only quirk I ran into is that when it first arrived, there was a 1/16" gap between that brass washer and the base of the spring. Try as I might, I couldn't slide the spring down to seat onto the brass washer. Eventually, I just assembled the gun and slowly cocked it - near the end of the stroke, I heard a "CRACK!" which was that spring giving way and sliding down onto the brass washer. I disassembled the gun, confirmed the spring had indeed moved into position, and it's been fine ever since. Not sure why it was made with that gap, but I alerted Tom to what I found.

I'm having way too much fun learning what works, what doesn't, making dumb mistakes along the way. Experts like you make this all the more enjoyable, hope this info helps others down the road. More to follow!

So glad that you're nearing your end goal Jim. Sounds like you're almost there. I don't know how you got the impression that I'm some sort of expert but I'm far from it. LOL! From what you've been up to, I'd say that you're better informed than I am on this gun. I just got lucky on my first attempt. So glad to hear that you're enjoying the channel. Looking forward to future updates....

 

[jimk1963]

So glad that you're nearing your end goal Jim. Sounds like you're almost there. I don't know how you got the impression that I'm some sort of expert but I'm far from it. LOL! From what you've been up to, I'd say that you're better informed than I am on this gun. I just got lucky on my first attempt. So glad to hear that you're enjoying the channel. Looking forward to future updates....

Brief updates:

1) Supersonic velocities have stopped on their own, without taking the piston out for a cleaning. Probably from simply running more pellets through
2) Re-checked original factory spring, with Vortek seal. Energy is about on par with Kevin's reported data from his video, so it appears the Vortek seal has significantly improved velocities/energy
3) Removed one coil from the Vortek spring - still a beast! RWS R10 Match 8.2g are averaging 922fps, 15.5fpe... Still way too high. Curious thing is, ChuckHunter had 2 coils removed on his build, but he's down around 10.7fpe with an 8.4g. Hard to believe power will drop off that much with one more coil removed...
4) Will cut a little more off the Vortek spring, maybe 1/2 or 1 more full coil...

Still also hunting for a fitted guide for the factory mainspring. Have a lathe, did some experimenting with Delrin, it's a lot harder than I expected to make something precision... and I'm using a wood lathe with a two-axis vise, not ideal.

 

[jimk1963]

Brief updates:

1) Supersonic velocities have stopped on their own, without taking the piston out for a cleaning. Probably from simply running more pellets through
2) Re-checked original factory spring, with Vortek seal. Energy is about on par with Kevin's reported data from his video, so it appears the Vortek seal has significantly improved velocities/energy
3) Removed one coil from the Vortek spring - still a beast! RWS R10 Match 8.2g are averaging 922fps, 15.5fpe... Still way too high. Curious thing is, ChuckHunter had 2 coils removed on his build, but he's down around 10.7fpe with an 8.4g. Hard to believe power will drop off that much with one more coil removed...
4) Will cut a little more off the Vortek spring, maybe 1/2 or 1 more full coil...

Still also hunting for a fitted guide for the factory mainspring. Have a lathe, did some experimenting with Delrin, it's a lot harder than I expected to make something precision... and I'm using a wood lathe with a two-axis vise, not ideal.

Update on Vortek PG1 Custom Kit install:

1) Spring was shipped with 28 coils @ 0.148" wire diameter. Now down to 26.5 coils
2) Shot cycle vastly improved. Tight, fast progression. Buzz gone, a little bit of high-pitch ringing but some of it is environmental (garage, near a metal door)
3) Still a little overpowered, but now my numbers are same as what Kevin reported (@razor62). Basically, 14-14.5 fpe across a range from 7 to 8.64 grains
4) Think this will be my stopping point for this particular kit. I may cut off another 1/2 coil later on, but first more experimenting to do. Have 3 more kit configs to try out, more on that later
5) One huge factor - the Vortek 30mm "Vac Seal". The gun's power jumped up immediately with this seal installed, zero sanding/fussing. The feel of that seal as the piston goes in is just fantastic. Maybe got lucky on the fit, or maybe the moly-impregnated material really does make a difference. Whatever the case, performance is much better than the original seal or the ARH seals.
6) All lube is with Ultimox 226. As best as I could, fully removed Moly from the interior of the gun using acetone and a million rags

 

[Keene]

Following with great interest.

 

[jimk1963]

Following with great interest.

Thanks Keene, this gem is far from the most popular springers out there, that’s for sure. Those who have one do appreciate its great craftsmanship and accuracy, aside from the rattly internals. This is my third rebuild (Anschutz LG380, FWB 124), only began this summer so have been climbing quite the learning curve. The LG 380 was restored to factory performance after two months of trying ARH and Australian parts that just weren’t good for that gun, finally finding Waffencenter parts with completely different geometries that worked perfectly. Posted the entire journey on GTA if interested, it’s one of the very few LG380 posts anywhere so it’s easy to find. Still working on the FWB 124, I’ve installed the Maccari Pro Mac kit, and separately experimented with the Titan XS No. 1 mainspring. More to do there.

Re: the FWB Sport, have more tune kits coming:

1) TbT custom kit with fitted delrin rear guide, spring chosen by Nick Stanning (HW80 FAC spring possibly, or similar), and top collet in lieu of traditional top hat because the Sport piston has a built-in top hat. The collet is basically just a super thick washer, looks same as stacking 6 2mm washers together but in one solid part
2) TbT kit with fitted delrin rear guide, HW80 spring and collet. The idea here is to check the compatibility of HW80 components, as that gun is so widely supported, may help others struggling to find a kit like I did
3) Titan XS Mainspring No. 1, with Titan XS fitted delrin rear guide. The Titan XS springs are easy to purchase, while the Titan XS guide was purchased from Airgunspares/Countryshop in UK (only place I could find that carries this part). Same idea as HW… test a kit that’s easy to purchase online. With this kit, the spring dimensions are a little more challenging. The ID is smaller than the Sport spring, so may have to use the TbT collet in the piston because the Titan spring may not fit around the built-in top hat. Also just a random aside - if you shop the Countrystore, be aware that their top hats are loose-fitting. I traded emails with Mark Knibbs, he says they’re purposely loose as they don’t need to be a tight fit - only the rear guide needs to be a tight fit. This is counter to other kits I’ve received, where the top hats are tightly fitted. Loose fit seems like a bad idea to me, just one more area to rattle around. But what do I know, I’m still in my rookie season of rebuilds…

 

[Michigander]

Thanks Keene, this gem is far from the most popular springers out there, that’s for sure. Those who have one do appreciate its great craftsmanship and accuracy, aside from the rattly internals. This is my third rebuild (Anschutz LG380, FWB 124), only began this summer so have been climbing quite the learning curve. The LG 380 was restored to factory performance after two months of trying ARH and Australian parts that just weren’t good for that gun, finally finding Waffencenter parts with completely different geometries that worked perfectly. Posted the entire journey on GTA if interested, it’s one of the very few LG380 posts anywhere so it’s easy to find. Still working on the FWB 124, I’ve installed the Maccari Pro Mac kit, and separately experimented with the Titan XS No. 1 mainspring. More to do there.

Re: the FWB Sport, have more tune kits coming:

1) TbT custom kit with fitted delrin rear guide, spring chosen by Nick Stanning (HW80 FAC spring possibly, or similar), and top collet in lieu of traditional top hat because the Sport piston has a built-in top hat. The collet is basically just a super thick washer, looks same as stacking 6 2mm washers together but in one solid part
2) TbT kit with fitted delrin rear guide, HW80 spring and collet. The idea here is to check the compatibility of HW80 components, as that gun is so widely supported, may help others struggling to find a kit like I did
3) Titan XS Mainspring No. 1, with Titan XS fitted delrin rear guide. The Titan XS springs are easy to purchase, while the Titan XS guide was purchased from Airgunspares/Countryshop in UK (only place I could find that carries this part). Same idea as HW… test a kit that’s easy to purchase online. With this kit, the spring dimensions are a little more challenging. The ID is smaller than the Sport spring, so may have to use the TbT collet in the piston because the Titan spring may not fit around the built-in top hat. Also just a random aside - if you shop the Countrystore, be aware that their top hats are loose-fitting. I traded emails with Mark Knibbs, he says they’re purposely loose as they don’t need to be a tight fit - only the rear guide needs to be a tight fit. This is counter to other kits I’ve received, where the top hats are tightly fitted. Loose fit seems like a bad idea to me, just one more area to rattle around. But what do I know, I’m still in my rookie season of rebuilds…

Is that "collet" really solid, or is it a cup intended to center the spring on the piston ID? That's what I was considering if I ever get inside my Sport. If not a cup, how would the collet differ from a simple spring spacer?

 

[Michigander]

This is a great thread! Thanks to all who have contributed, a lot of great information being shared. Here is what I can add.

Pivot lock screw torque: I had to send my Sport in for trigger work. After getting it back, all seemed fine for a while, then I noticed the pivot had worked loose. I went through several rounds of readjustment, putting a little more torque on the lock screw each time, but the pivot kept working loose. After looking up the torque specs for a high grade M4 screw, I found that the screw should be able to handle 30 lb-in, which was considerably more than I had been using. Being a little nervous about applying that much torque to a relatively small fastener, I contacted FWB and was assured that the 30 lb-in would be fine. I went through one more round of adjustment tightening the lock screw to 30 lb-in and have had no more trouble since.

Scope mount slipping: After trying two piece rings unsuccessfully, I switched to single piece mounts from BKL and SportsMatch. The BKL mount has 6 screws and held well once the screws were firmly tightened. The SportsMatch mount has only 4 screws, and required near the max allowed torque of 55 lb-in to eliminate slipping. I used 50 lb-in.

Vortek washers: I think Vortek intends those brass washers to serve at least partially as thrust bearings in order to help isolate the rifle from the effects of spring torque. The ultimate solution was found in the FWB 300s which used a pair of left and right hand springs to provide a self cancelling effect within the spring assembly.

Piston seals: It is possible that FWB intended the loose piston seal to allow for self centering of the seal in the compression tube. Even though loose on the piston head, the base of the seal apparently cannot expand enough within the compression tube to allow it to slip off the piston under normal circumstances. That said, no other manufacturer finds this "feature" necessary, and I am skeptical as to its benefit. I do like the Vortek seals having had good luck using them even with minimal lubrication. I am glad to hear there is one available that fits the Sport.

Noise: Wow, Kevin's gun was terrible! Mine was never that bad, or even close. The most I had was a little seal honking and some mild spring buzz. And after getting it back from repair, most of that was gone, presumably because some fresh grease had been applied to the internals.

 

[Keene]

This is a great thread! Thanks to all who have contributed, a lot of great information being shared. Here is what I can add.

Pivot lock screw torque: I had to send my Sport in for trigger work. After getting it back, all seemed fine for a while, then I noticed the pivot had worked loose. I went through several rounds of readjustment, putting a little more torque on the lock screw each time, but the pivot kept working loose. After looking up the torque specs for a high grade M4 screw, I found that the screw should be able to handle 30 lb-in, which was considerably more than I had been using. Being a little nervous about applying that much torque to a relatively small fastener, I contacted FWB and was assured that the 30 lb-in would be fine. I went through one more round of adjustment tightening the lock screw to 30 lb-in and have had no more trouble since.

Scope mount slipping: After trying two piece rings unsuccessfully, I switched to single piece mounts from BKL and SportsMatch. The BKL mount has 6 screws and held well once the screws were firmly tightened. The SportsMatch mount has only 4 screws, and required near the max allowed torque of 55 lb-in to eliminate slipping. I used 50 lb-in.

Vortek washers: I think Vortek intends those brass washers to serve at least partially as thrust bearings in order to help isolate the rifle from the effects of spring torque. The ultimate solution was found in the FWB 300s which used a pair of left and right hand springs to provide a self cancelling effect within the spring assembly.

Piston seals: It is possible that FWB intended the loose piston seal to allow for self centering of the seal in the compression tube. Even though loose on the piston head, the base of the seal apparently cannot expand enough within the compression tube to allow it to slip off the piston under normal circumstances. That said, no other manufacturer finds this "feature" necessary, and I am skeptical as to its benefit. I do like the Vortek seals having had good luck using them even with minimal lubrication. I am glad to hear there is one available that fits the Sport.

Noise: Wow, Kevin's gun was terrible! Mine was never that bad, or even close. The most I had was a little seal honking and some mild spring buzz. And after getting it back from repair, most of that was gone, presumably because some fresh grease had been applied to the internals.

Mine was an ear banging, teeth rattling, jumpy, exhausting pain in the rear to shoot OOB. An AGN member was extraordinarily kind enough to make me a steel, tight fitting, rear guide that made all the difference in the world. Gone was the twanging and banging, and the shot cycle much much improved. I had initially installed a an ARH piston seal that was not sized. It robbed a bunch of power, 80+ FPS if I remember rightly, and the gun felt sluggish. I reinstalled the OEM seal and gained back most of the lost FPS. At the time I only had the original spring to reinstall which also had a bit of a cant. I've been wondering whether or not to replace it with an OEM spring, that would now be supported by a guide that fits well(the factory guide was ludicrously slack), or whether to wait for Vortek to take the bit and manufacture a drop in PG-FWB kit and seal. Looks like the wait may have been well worth it! I've not seen anything near the velocities that most seem to have seen out of this gun, even when brand new. It's currently making around 13.0 FPE with FTTs, which is about factory spec. On most days it a laser at 25 yds. Other days I must have skipped breakfast

Keep the posts coming jimk1963

 

[jimk1963]

Is that "collet" really solid, or is it a cup intended to center the spring on the piston ID? That's what I was considering if I ever get inside my Sport. If not a cup, how would the collet differ from a simple spring spacer?

Great question - right now all I have is the photo below, parts won't arrive for a while, probably end of next week. Two kits are identical, the third kit is a spare without the spring. The "collets" are the thick washers you see near the top hats. Those top hats are not designed for the Sport, but rather will work on other guns like the HW80. To put it another way, I asked Nick to include top hats as well as these "collets" so I'd have more to experiment with down the road. Re: spring-slap against the piston, afraid that collet won't do much, as you observed - other than slicken the surface between the spring-end and piston head. But for that purpose, I already have a 2mm thick brass washer up there (from Tom at Vortek) that seems to be doing a nice job. The springs Nick provided are 32 turns (if I counted right), so I expect some work will be needed to right-size one. He was supposed to send me the spring dimensions but haven't received it yet.

 

[jimk1963]

This is a great thread! Thanks to all who have contributed, a lot of great information being shared. Here is what I can add.

Pivot lock screw torque: I had to send my Sport in for trigger work. After getting it back, all seemed fine for a while, then I noticed the pivot had worked loose. I went through several rounds of readjustment, putting a little more torque on the lock screw each time, but the pivot kept working loose. After looking up the torque specs for a high grade M4 screw, I found that the screw should be able to handle 30 lb-in, which was considerably more than I had been using. Being a little nervous about applying that much torque to a relatively small fastener, I contacted FWB and was assured that the 30 lb-in would be fine. I went through one more round of adjustment tightening the lock screw to 30 lb-in and have had no more trouble since.

Scope mount slipping: After trying two piece rings unsuccessfully, I switched to single piece mounts from BKL and SportsMatch. The BKL mount has 6 screws and held well once the screws were firmly tightened. The SportsMatch mount has only 4 screws, and required near the max allowed torque of 55 lb-in to eliminate slipping. I used 50 lb-in.

Vortek washers: I think Vortek intends those brass washers to serve at least partially as thrust bearings in order to help isolate the rifle from the effects of spring torque. The ultimate solution was found in the FWB 300s which used a pair of left and right hand springs to provide a self cancelling effect within the spring assembly.

Piston seals: It is possible that FWB intended the loose piston seal to allow for self centering of the seal in the compression tube. Even though loose on the piston head, the base of the seal apparently cannot expand enough within the compression tube to allow it to slip off the piston under normal circumstances. That said, no other manufacturer finds this "feature" necessary, and I am skeptical as to its benefit. I do like the Vortek seals having had good luck using them even with minimal lubrication. I am glad to hear there is one available that fits the Sport.

Noise: Wow, Kevin's gun was terrible! Mine was never that bad, or even close. The most I had was a little seal honking and some mild spring buzz. And after getting it back from repair, most of that was gone, presumably because some fresh grease had been applied to the internals.

Thanks for this great input. I have been taking this gun apart from nearly Day 1, so haven't experienced the pivot lock screw issue (yet). WIll keep an eye out for it. Also haven't even mounted a scope yet, which is pretty funny after 2 months... good info. Agree with you, not a fan of FWB's piston seal choice. Even if they wanted some "slop" they didn't need to design the seal to be so easily removed. It worked, but the Vortek seal works significantly better in my experience so far. The ARH seals were a PITA, purposely oversized so velocity drops by 100fps, requiring multiple rounds of fine sanding to find the best outcome - which means a full disassembly/reassembly of the gun every single time. Maybe I got lucky with the Vortek seal dimension, but man it just worked and felt great going into the receiver tube with no mods whatsoever. Just a tiny bit of Ultimox around the edge. My gun had some of Kevin's issues, not quite as bad but not great either. Had some "bed spring" noise while cocking, and significant buzz on the shot cycle. Did not sound like a $600 factory-new gun, that's for sure.

 

[jimk1963]

Mine was an ear banging, teeth rattling, jumpy, exhausting pain in the rear to shoot OOB. An AGN member was extraordinarily kind enough to make me a steel, tight fitting, rear guide that made all the difference in the world. Gone was the twanging and banging, and the shot cycle much much improved. I had initially installed a an ARH piston seal that was not sized. It robbed a bunch of power, 80+ FPS if I remember rightly, and the gun felt sluggish. I reinstalled the OEM seal and gained back most of the lost FPS. At the time I only had the original spring to reinstall which also had a bit of a cant. I've been wondering whether or not to replace it with an OEM spring, that would now be supported by a guide that fits well(the factory guide was ludicrously slack), or whether to wait for Vortek to take the bit and manufacture a drop in PG-FWB kit and seal. Looks like the wait may have been well worth it! I've not seen anything near the velocities that most seem to have seen out of this gun, even when brand new. It's currently making around 13.0 FPE with FTTs, which is about factory spec. On most days it a laser at 25 yds. Other days I must have skipped breakfast

Keep the posts coming jimk1963

Same experience here. The ARH seals are purposely oversized, requiring a laborious disassembly/sanding/reassembly/disassembly/more sanding/reassembly/... And each time, you really have no idea if you got it "right" or not. The expert tuners on here who do this for a living can probably tell what's best just from the feel of things, but a hack like me has to go through this learning curve in the most painful way. I read varying accounts of that "feel" too, some say the piston should slowly fall out of the receiver when held vertically, others say a more snug fit is better, others say "it depends" on a bunch of other crap I can't control like receiver honing, etc. For me, best I could do with ARH was to get the gun roughly back to original performance with the original FWB Sport piston seal. Roughly - as in still about 20-40fps lower, depending on the pellet. On the other hand, with the Vortek seal, and the original FWB Sport spring, that twangy combo outperformed the original factory config by a good 20 fps - without doing a thing.

Meanwhile, I had also purchased two factory OEM springs from Pyramid Air. You guys may already know this, but I was surprised to learn that a brand new spring (in this case) was about 276mm, but once I put it in the gun, just for a short time (a day or less), when removing that new spring it's only 264mm. These springs take a permanent "set", something I didn't expect. I found exactly the same behavior with my FWB 124 and the Anschutz LG 380. In both of those rifles, springs removed from the gun will be shorter than their original length. And I'm talking about after only a day, not 10 years. Sorry if old/redundant news, was just new to me.

Lastly, I'd love to find someone to make a spring guide for me that fits the OEM spring, like was reported earlier in this or another FWB Sport thread where the dimensions were shown in a hand drawing. I have a wood lathe, started making an attempt to turn one myself, but I am not skilled on the lathe and in any event, seems a metal lathe would be a much more suitable tool than what I'm using. The nice thing about the factory OEM spring is the cocking force - it's sort of like the FWB 124, meaning FWB focused on keeping the cocking force as low as practical, which I appreciate. This Vortek spring, even cut down by 1.5 coils, isn't bad but noticeably harder to cock than the factory spring. Which makes sense, as it's 0.148" vs. factory spring of 0.142". It's a beast.

 

[Keene]

I think this is the drawing that you are referring to.

I kept a copy in case I could find a machinist to make one for me. In the end event that wasn't necessary.

 

[Bk480]

Feinwerkbau Sport.
I own a FWB Sport, didn't like the factory performance but i knew this rifle had great potential so i sent it to (a tuner), which i won't name. Rifle came back and STILL i did not appreciate the work he did. The rifle got back to me and it was still the same or even worse than before, so i shot it a little while thinking maybe it will take a few hundred shots to break in? Nope! I found Motorhead tuning on AGN, sent it to Scott, well the gun had another unanticipated issue which i was about ready to give up on and just shoot as is. I discussed with Scott if he would tackle the issue besides the tuning and service work, he agreed to it. Scott remedied the issue, tuned the rifle to perfection the action and trigger now i have a rifle I thought was possible. Today it can be difficult to find folks with integrity, professionalism and grit. Motorhead Airgun Tuning is all that and more. Great job! and thank you for your work, you guys are greatly appreciated.
BTW if you own a FWB Sport you would do well to talk to Scott and send it their way, what a superb work they did on mine.
Sincerely David in Colorado

is that Scott Blair