Vulcan mods to make the hammer/spring assembly consistent.
This mods were performed on Zonk .22 Vulcan. his issue was sudden change in pellet speed.
in my testing —–> it was consistent for 5-12 shots or so around 900fps then drop down to 840fps for about 2 to 6 shots then back up to 900fps keeps doing this for 4 fill and can’t complete a string without the speed dropping to 840fps.
So the 1st thing I did was tuned the reg down to 120b with some polishing and better orings, didn’t see anything wrong with the reg during dissemble.
When testing the tuned reg I still see the speed drop in every fill. So I know now it’s in the hammer assembly so heres the mods I done in the photo:
1. In the middle of the hammer spring there is no spring guide so the spring flex where less resistant (rainbow) so the spring end at the HSTA rub on the threads in the action for the HSTA. to prevent the spring drag I sanded and polish the coils that’s making contact with the action threads and that also was sanded and polish.
2.The hammer was given a high polish for less friction.
3. The brass bushing for the hammer spring has an edge that side in the hammer chamber—- sense the hammer has a loose clearance that edge hits the action 1st at times that prevent the full travel of the hammer spring—the fix I reduce the OD.
4. after the hammer open the fire valve it will slam back at the brass bushing guide so to prevent metallic noise and still have a clearance for a de bouncing device (hammer is free floating so the hammer isn’t pressing on the VS when uncock) i installed a nylon slim.
here is a photo of a delrine spring retainer with a longer spring guied to replace the brass spring retainer and hopefully will keep the hammer spring from binding out ward so the back end of the spring from rubbing on the threads and reduce the impact noise.
if you want one contact John.
After all this mods I got her shooting consistently after 200+ rounds here are 3 shot string with the reg set a 120b. with 18.1g pellet.
pressure 205b to 105b
String #1 string #2 string #3
#shots 65 65 62
high: 900fps 907fps 902fps
low: 892fps 895fps 895fps
ES: 8fps 12fps 7fps
Not every Vulcan will have this issue but some useful info for others.
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I’m trying to learn to do my own casting from the Lyman 257420 mold. BUT got some good good ones both Lyman and Noe from Doug Noble / Dyotat100. Lots of info in the topic Other Guns. Have ‘t got the .257 but Doug is in the final stages of tuning so it should ‘t be long. I’ve sized some to my .25 AF Condor but then the .22 Vulcan arrived. RJPorter and Knifemaker are also doing .257 casting and have been very helpful.
:thumb: 5 oz is good Ernest. Sounds like it’s a shooter now for sure.
Those of us that have some experience in troubleshooting will greatly appreciate the description of such a process. Those with little experience may be overwhelmed.
The end result will no doubt show that some steps were not necessary.
It’s really facinating to hear all the the process from the expert Ernest.
In my experience the greatest experts are those that share their knowledge freely as Ernest is sharing here in this forum.
THANK YOU ERNEST :thumb: :thumb: :thumb:
LURKER, I see you have a 257–what kind and where you get your slugs. have a “TJ” 257 barrel for the 9mm cricket but cant find the right one that fit right, even tried the .25 heavy 34g like only the skirt had a good fit but accuracy wasn’t there at 1000fps
From the looks of it I’d say a dive shop……
From the looks of it I’d say we’re all learning something from my bad Vulcan……Lets all chip in so I can pay Ernest. I may have to take out a second mortgage…………….YIKES!!!!
Silicone is use in so many ways—its just how its labeled for that applications—don’t worry I didn’t use it on you BP. its my personal use and testing, I really like it, when dry its not wet or greasy—dont even know its there till you touch it—supper slippery, I even use it on pellet lube with it its hard to over lube, but didn’t use it on high pressure application only on trigger linkage, hammer spring. its sold in ebay
its not about the money–its the enjoy working with AG, so actually I’m paying you for the learning experience. got your trigger down to 5oz want it 3oz still?
well tested your Vulcan without the brass spring de bouncing retainer, didn’t really try to match the same speed but close.
fill pressure 210-100b
#shots: 58
high 899
low 888
ES 11fps
I could go in the firing valve and tighten down the VS, but not worth it to increase the shot count because it didn’t quiet down the hammer slap and ping down when I removed the brass retainer just lost about 5 shots even though with the slower speed so I reinstalled the brass retainer.
[quote=”spinj”]Where did you get that Ernest? Are my eyes fooling me? When I clicked on the photo it says, “For wetsuits, drysuits, and booties.”[/
From the looks of it I’d say a dive shop……
From the looks of it I’d say we’re all learning something from my bad Vulcan……Lets all chip in so I can pay Ernest. I may have to take out a second mortgage…………….YIKES!!!!
Polishing parts is frequently employeed to troubleshoot a complex mass produced mechanism in order to verify the proper fit and eliminate whole areas from concern.
Those of us that have some experience in troubleshooting will greatly appreciate the description of such a process. Those with little experience may be overwhelmed.
The end result will no doubt show that some steps were not necessary.
It’s really facinating to hear all the the process from the expert Ernest.
In my experience the greatest experts are those that share their knowledge freely as Ernest is sharing here in this forum.
THANK YOU ERNEST :thumb: :thumb: :thumb:
I thought the Vulcan was closest to being perfect… guess I need to learn how to do polishing more.
Where did you get that Ernest? Are my eyes fooling me? When I clicked on the photo it says, “For wetsuits, drysuits, and booties.”
That’s one part you don’t want heavy lube, it will slow down the spring and add inconstancy in the speed
Actually, it didn’t. I only put just a light coat just to lessen the friction when it rides along the guide on the hammer spring guide.
I use this, not sticky and dry—but slippery as hell
here is a photo of a delrine spring retainer with a longer spring guide to replace the brass spring retainer and hopefully will keep the hammer spring from binding out ward so the back end of the spring from rubbing on the threads and reduce the impact noise.
if you want one contact John.
Does the delrin spring retainer replace the brass spring retainer?
This pic seems to show both of them in use…
Hoot:
yes, but it will work without it, just have to test and see if a longer spring is needed and how much shot count it will loose—but I think its going to be like the HB I tuned for you–hardly no hammer slap
That’s one part you don’t want heavy lube, it will slow down the spring and add inconstancy in the speed
Actually, it didn’t. I only put just a light coat just to lessen the friction when it rides along the guide on the hammer spring guide.
Next mod on the Vulcan is to replace that brass spring retainer with a delrine retainer with a long spring guide just like this one but no shoulder to slam on the action —– just straight to the valve stem, will post results
That’s one part you don’t want heavy lube, it will slow down the spring and add inconstancy in the speed
Although my Cricket didn’t need it, I put a bit of moly grease on the hammer spring, but it didn’t make much difference as it was already quiet as it was.
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machine a Delrin replacement for the brass part and it made a very noticeable reduction in sound. So much that the Vulcan “hammer slap” is no longer a reason to gripe about this outstanding bullpup! I will be doing some more testing to see if there may be any reliability issues, but I doubt it very much.
The part I made looks similar to the one Ernest showed in his post, and I made a couple of the features a bit thicker for added strength. No need for any nylon washers when using Delrin or a similar material for this part. I’ll keep the TAG posted on this topic.