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Author Topic: Regulated plenum vs reservoir volume .257 160fpe  (Read 1374 times))

Offline mackeral5

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Re: Regulated plenum vs reservoir volume .257 160fpe
« Reply #40 on: April 22, 2021, 09:08:06 PM »
Do try the 2mm stem, I'd really like to hear the results.

The 2mm stem has around 150 or so rounds through it, so far it is holding up. 
 
Putting things into perspective--with the 2mm stem and .270 throat at 3500 psi it maxes out around 1055fps with the Arsenal 257388 87gr .  The hammer is in .250" of FREE FLIGHT, zero preload!

Generally speaking, I believe a 2mm stemmed peek poppet is good for valves under .300" seat at pressures up to 3500psi.  Assuming no more than .300 unsupported stem protrusion, must be a straight line hammer vs hinged swinging hammer, etc.

Still testing various things.  Will get back to the unregulated Arsenal 257388 testing soon.
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Offline rkr

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Re: Regulated plenum vs reservoir volume .257 160fpe
« Reply #41 on: April 23, 2021, 01:31:14 AM »
Do try the 2mm stem, I'd really like to hear the results.

The 2mm stem has around 150 or so rounds through it, so far it is holding up. 
 
Putting things into perspective--with the 2mm stem and .270 throat at 3500 psi it maxes out around 1055fps with the Arsenal 257388 87gr .  The hammer is in .250" of FREE FLIGHT, zero preload!

Generally speaking, I believe a 2mm stemmed peek poppet is good for valves under .300" seat at pressures up to 3500psi.  Assuming no more than .300 unsupported stem protrusion, must be a straight line hammer vs hinged swinging hammer, etc.

Still testing various things.  Will get back to the unregulated Arsenal 257388 testing soon.

That sound extremely good! I would love to use a free flight hammer in my .257 and still being able to achieve 160 fpe. Reduced air usage, less harsh firing event and better trigger feel. Some results at 3000 psi and under would be nice when you do the unregulated tests. 
Huub Viking Mk2 .177/.22 bullpup - grab'n go gun
BSA Scorpion SE .177 - plinker/training gun
BSA Scorpion .25 - 100M BR gun at 60 fpe
BSA Scorpion .224 - 100M BR gun at 100 fpe
Evanix Blizzard .257/.357 - 150/230 fpe
Exanix Sniper X2 .357/.45 - 210/270 fpe silhouette gun
Drozd Blackbird HPA - 1200 rpm full auto fun gun / meat grinder
Evanix AR6 carbine/pistol
+ a couple of springers

Offline rkr

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Re: Regulated plenum vs reservoir volume .257 160fpe
« Reply #42 on: April 23, 2021, 11:49:14 AM »
A question, what did you use for the stem? I just measured a normal 2mm HSS drill bit and the non fluted part is too short to be a stem for my Evanix.
Huub Viking Mk2 .177/.22 bullpup - grab'n go gun
BSA Scorpion SE .177 - plinker/training gun
BSA Scorpion .25 - 100M BR gun at 60 fpe
BSA Scorpion .224 - 100M BR gun at 100 fpe
Evanix Blizzard .257/.357 - 150/230 fpe
Exanix Sniper X2 .357/.45 - 210/270 fpe silhouette gun
Drozd Blackbird HPA - 1200 rpm full auto fun gun / meat grinder
Evanix AR6 carbine/pistol
+ a couple of springers

Offline mackeral5

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Re: Regulated plenum vs reservoir volume .257 160fpe
« Reply #43 on: April 23, 2021, 02:21:05 PM »
A question, what did you use for the stem? I just measured a normal 2mm HSS drill bit and the non fluted part is too short to be a stem for my Evanix.

https://www.amazon.com/gp/product/B00R1ISUN8/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I cut it with side cutters, then polish the end on a vertical belt sander.  I do not harden the tips nor do anything special in attaching it to the peek poppet.  Drill a 1/16 hole in the peek, press it in with only an interference fit. 
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Offline rkr

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Re: Regulated plenum vs reservoir volume .257 160fpe
« Reply #44 on: April 24, 2021, 07:17:15 AM »
A question, what did you use for the stem? I just measured a normal 2mm HSS drill bit and the non fluted part is too short to be a stem for my Evanix.

https://www.amazon.com/gp/product/B00R1ISUN8/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I cut it with side cutters, then polish the end on a vertical belt sander.  I do not harden the tips nor do anything special in attaching it to the peek poppet.  Drill a 1/16 hole in the peek, press it in with only an interference fit. 

Thanks, ordered some. I was checking M2 grade 12.9 bolts but you can't get them long enough either. Bolts make great valve stems:

stem3 by abbababbaccc, on Flickr
Huub Viking Mk2 .177/.22 bullpup - grab'n go gun
BSA Scorpion SE .177 - plinker/training gun
BSA Scorpion .25 - 100M BR gun at 60 fpe
BSA Scorpion .224 - 100M BR gun at 100 fpe
Evanix Blizzard .257/.357 - 150/230 fpe
Exanix Sniper X2 .357/.45 - 210/270 fpe silhouette gun
Drozd Blackbird HPA - 1200 rpm full auto fun gun / meat grinder
Evanix AR6 carbine/pistol
+ a couple of springers

Offline mackeral5

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Re: Regulated plenum vs reservoir volume .257 160fpe
« Reply #45 on: April 24, 2021, 10:19:11 AM »
A question, what did you use for the stem? I just measured a normal 2mm HSS drill bit and the non fluted part is too short to be a stem for my Evanix.

https://www.amazon.com/gp/product/B00R1ISUN8/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I cut it with side cutters, then polish the end on a vertical belt sander.  I do not harden the tips nor do anything special in attaching it to the peek poppet.  Drill a 1/16 hole in the peek, press it in with only an interference fit. 

Thanks, ordered some. I was checking M2 grade 12.9 bolts but you can't get them long enough either. Bolts make great valve stems:

stem3 by abbababbaccc, on Flickr

You're welcome and agreed on bolts....   I used a long 4mm SHCS on my Extreme 457. 

Longer drill bits work as well, sometimes Amazon has great pricing on odd length drills. 

Here in the US it is amazing that you can often find 36 inches of drill rod from Grainger purchased via Amazon, for less than $10 including freight.

I am learning that my goal of having a dual caliber .257-.357 gun requires some compromise.  If one is only going to change barrel/bolt probe there are indeed compromises to be made.  In .257 it is much nicer to have the smooth, crisp shot cycle of the .270 valve throat and hammer in free-flight.    I haven't shot the .357 much with the smaller throat, but it basically performs like an OEM Bulldog (max~250fpe), albeit with much less hammer strike required vs the .375 throat.

I look forward to seeing how the smaller stem works for you.  I think it will do the things you want.
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Offline rkr

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Re: Regulated plenum vs reservoir volume .257 160fpe
« Reply #46 on: April 24, 2021, 11:09:48 AM »
I think I'll make a "cup" for the 2mm stem from a piece of 4mm steel rod. It gets glued over the stem end at the poppet end making it 4mm thick there and should prevent the stem from punching through the poppet thus allowing me to use PET-P as the poppet material.
Huub Viking Mk2 .177/.22 bullpup - grab'n go gun
BSA Scorpion SE .177 - plinker/training gun
BSA Scorpion .25 - 100M BR gun at 60 fpe
BSA Scorpion .224 - 100M BR gun at 100 fpe
Evanix Blizzard .257/.357 - 150/230 fpe
Exanix Sniper X2 .357/.45 - 210/270 fpe silhouette gun
Drozd Blackbird HPA - 1200 rpm full auto fun gun / meat grinder
Evanix AR6 carbine/pistol
+ a couple of springers

Offline mackeral5

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Re: Regulated plenum vs reservoir volume .257 160fpe
« Reply #47 on: April 24, 2021, 11:18:06 AM »
I think I'll make a "cup" for the 2mm stem from a piece of 4mm steel rod. It gets glued over the stem end at the poppet end making it 4mm thick there and should prevent the stem from punching through the poppet thus allowing me to use PET-P as the poppet material.

That should help, it is how Edgun poppets are made. 

I only use peek and in using peek have never driven a stem through a poppet.  There was one time where I didn't full press the stem in the 1/16 hole in the poppet---after a few shots the gun just went "click"....It had driven the stem into the poppet where there was no more stem protrusion.  Now I take careful measurements pre-pressing the stem and after to ensure the stem is bottomed out in the predrilled hole.  As long as the stem is full pressed into and bottomed out in the hole, it will not go any further in a peek poppet.

Edgun r3/r5 poppets ,showing a similar concept to what you describe.

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Offline mackeral5

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Re: Regulated plenum vs reservoir volume .257 160fpe
« Reply #48 on: April 27, 2021, 07:39:42 PM »
I think I'll make a "cup" for the 2mm stem from a piece of 4mm steel rod. It gets glued over the stem end at the poppet end making it 4mm thick there and should prevent the stem from punching through the poppet thus allowing me to use PET-P as the poppet material.

Quick update on the 2mm stem.  I have fired upwards of 100 rounds at over 3500-3800psi and max hammer strike without issue.  This occurred during a firelapping regimen (still chasing a barrel issue.)  I was using as-cast Arsenal 257388, which after embedding with lapping grit required max pressure to get them moving.  This was indeed a torture test of the 2mm stem peek poppet and as far as I am concerned it passed.

I need to cast up some more Arsenal 257388 so I can do more accuracy testing with them.  I do have an assortment of lighter ammo to test with, possibly tomorrow....
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Offline rkr

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Re: Regulated plenum vs reservoir volume .257 160fpe
« Reply #49 on: May 28, 2021, 05:33:11 AM »
I made a 2mm stem valve for my .224 BSA. Unfortunately it didn't make much difference. I was able to loosen up the hammer spring a bit but there was no big difference I was hoping for. The original stem was 3.2mm so the area was reduced by 60% which should have considerable effect on dwell and the force needed to keep the valve open. BSAs do have very stiff valve springs though, perhaps the valve spring is now the dominating thing in valve closing event?
Huub Viking Mk2 .177/.22 bullpup - grab'n go gun
BSA Scorpion SE .177 - plinker/training gun
BSA Scorpion .25 - 100M BR gun at 60 fpe
BSA Scorpion .224 - 100M BR gun at 100 fpe
Evanix Blizzard .257/.357 - 150/230 fpe
Exanix Sniper X2 .357/.45 - 210/270 fpe silhouette gun
Drozd Blackbird HPA - 1200 rpm full auto fun gun / meat grinder
Evanix AR6 carbine/pistol
+ a couple of springers

Offline mackeral5

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Re: Regulated plenum vs reservoir volume .257 160fpe
« Reply #50 on: May 28, 2021, 04:20:35 PM »
I made a 2mm stem valve for my .224 BSA. Unfortunately it didn't make much difference. I was able to loosen up the hammer spring a bit but there was no big difference I was hoping for. The original stem was 3.2mm so the area was reduced by 60% which should have considerable effect on dwell and the force needed to keep the valve open. BSAs do have very stiff valve springs though, perhaps the valve spring is now the dominating thing in valve closing event?

Interesting results.  Perhaps this means the throat isn't the primary restriction in porting?  I understand you were more thinking about the affect of closing force, but perhaps there is another part of the air path that is choking flow? 

I am letting my big bores (and my nitrogen supply!!) rest for a while.  Been enjoying 12-15fpe Prod based guns as of late....will get back to the big bores sometime between now and the fall.
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Offline rsterne

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Re: Regulated plenum vs reservoir volume .257 160fpe
« Reply #51 on: May 28, 2021, 05:40:03 PM »
Quote
BSAs do have very stiff valve springs though, perhaps the valve spring is now the dominating thing in valve closing event?

That would be my guess.... Where is the smallest port equivalent, both before and after the stem change?....

Bob
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Offline rkr

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Re: Regulated plenum vs reservoir volume .257 160fpe
« Reply #52 on: May 29, 2021, 05:09:44 AM »
Quote
BSAs do have very stiff valve springs though, perhaps the valve spring is now the dominating thing in valve closing event?

That would be my guess.... Where is the smallest port equivalent, both before and after the stem change?....

Bob

5.5mm ports and the valve tunnel was 6.4mm so bore size all the way. I need to dig up a BSA valve spring, any ideas how to measure the stiffness and compare it to the closing force of the valve stem? Or perhaps I should just ditch the spring and retest?
Huub Viking Mk2 .177/.22 bullpup - grab'n go gun
BSA Scorpion SE .177 - plinker/training gun
BSA Scorpion .25 - 100M BR gun at 60 fpe
BSA Scorpion .224 - 100M BR gun at 100 fpe
Evanix Blizzard .257/.357 - 150/230 fpe
Exanix Sniper X2 .357/.45 - 210/270 fpe silhouette gun
Drozd Blackbird HPA - 1200 rpm full auto fun gun / meat grinder
Evanix AR6 carbine/pistol
+ a couple of springers

Offline mackeral5

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Re: Regulated plenum vs reservoir volume .257 160fpe
« Reply #53 on: May 31, 2021, 04:03:31 PM »
I don't think there is anything to lose in ditching the spring, if only for testing.  I have a couple guns that do not run valve return springs at all.....
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Offline rkr

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Re: Regulated plenum vs reservoir volume .257 160fpe
« Reply #54 on: May 31, 2021, 10:01:29 PM »
I don't think there is anything to lose in ditching the spring, if only for testing.  I have a couple guns that do not run valve return springs at all.....

I tried with no spring and unfortunately self centering valve needs a spring to center, i.e. it didn't seal. It didn't seal with light spring either so I took off  some material from poppet to minimize spring tension with original spring and it held air. There was marginal reduction in cocking effort but not what I was hoping for. The problem is partly the Huma gauge/fill valve unit which does not allow quick burst of air in to the cylinder.
« Last Edit: May 31, 2021, 10:05:19 PM by rkr »
Huub Viking Mk2 .177/.22 bullpup - grab'n go gun
BSA Scorpion SE .177 - plinker/training gun
BSA Scorpion .25 - 100M BR gun at 60 fpe
BSA Scorpion .224 - 100M BR gun at 100 fpe
Evanix Blizzard .257/.357 - 150/230 fpe
Exanix Sniper X2 .357/.45 - 210/270 fpe silhouette gun
Drozd Blackbird HPA - 1200 rpm full auto fun gun / meat grinder
Evanix AR6 carbine/pistol
+ a couple of springers

Offline mackeral5

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Re: Regulated plenum vs reservoir volume .257 160fpe
« Reply #55 on: June 01, 2021, 03:42:45 PM »
I don't think there is anything to lose in ditching the spring, if only for testing.  I have a couple guns that do not run valve return springs at all.....

I tried with no spring and unfortunately self centering valve needs a spring to center, i.e. it didn't seal. It didn't seal with light spring either so I took off  some material from poppet to minimize spring tension with original spring and it held air. There was marginal reduction in cocking effort but not what I was hoping for. The problem is partly the Huma gauge/fill valve unit which does not allow quick burst of air in to the cylinder.

That is interesting about the self-centering valve, I am not familiar with BSA's nor how that valve design works.  At least you were able to make a slight reduction in cocking effort.  Thanks for testing and sharing.
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