Chokes and velocity

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Definition of insanity... got it all back together and STILL at the same velocity. Took the hammer weight out since it was causing spring bind, but it didn't make a difference with it in.

So I did notice that the bottle to drop block adapter piece has a center thru hole which I ported. It also has holes drilled around its threaded section, with a recessed groove with four holes around it. When it's threaded together and sealed via the o-ring, the center hole is almost blocked off by the block wall, and the grooved transfer ring area is still back in the threads, blocking them off somewhat. What a poor piss design they have here.

I guess I will leave it alone and shoot it for now. I may try and hunt down an African Air Ordinance valve/block since those will eliminate this design flaw. There is just no plenum room or anymore meat to carve out.

Might be why the 357 bighorn didn't sell too well. The 30 cals did better velocity. I may order a 30 cal bolt and barrel and just downsize, or throw the hole thing in the burn pit!




Just kidding!
 
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Increasing the internal valve volume can help but primarily only if there is restricted access to the larger reservoir's volume.

The 8mm throat and 6.35mm ports are plenty enough for an unregulated .357, assuming the porting is through and through from valve exit to barrel as well as from valve entrance to bottle.

This thing should be capable of making 130-150 FPE or 850-910 fps with relative ease at well under 300 bar/4250 psi.

For a choke to rob that much performance, it would definitely be felt and a struggle to push one through by hand with a cleaning rod, I'd also imagine seating the pellet would take significant force if break away friction were robbing significant power.

Hope you get this mystery solved, I'll be following!

-Matt
 
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Dr. Kralenstein said:
Definition of insanity... got it all back together and STILL at the same velocity. Took the hammer weight out since it was causing spring bind, but it didn't make a difference with it in.

So I did notice that the bottle to drop block adapter piece has a center thru hole which I ported. It also has holes drilled around its threaded section, with a recessed groove with four holes around it. When it's threaded together and sealed via the o-ring, the center hole is almost blocked off by the block wall, and the grooved transfer ring area is still back in the threads, blocking them off somewhat. What a poor piss design they have here.

I guess I will leave it alone and shoot it for now. I may try and hunt down an African Air Ordinance valve/block since those will eliminate this design flaw. There is just no plenum room or anymore meat to carve out.

Might be why the 357 bighorn didn't sell too well. The 30 cals did better velocity. I may order a 30 cal bolt and barrel and just downsize, or throw the hole thing in the burn pit!




Just kidding!
Click to expand...

Yea if you have restriction from valve entrance to bottle, that could be what is causing the power loss, acting like a plenum in a regulated rifle.

Bummer! I feel you at least sourced your issue..

-Matt
 
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Since I can't get enough air out to push these pellets down that 23" barrel, I wonder if I cut it down if my vepcity lwould stay roughly the same? I've done that with other guns that were maxed out on air and it kept the velocity close to what t was with extra barrel length.

Basically I'm thinking I don't have the air to push the 81 grains of lead down the barrel before it starts to lose power behind that pellet, meaning the extra length is causing drag.
 
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Dr. Kralenstein said:
Since I can't get enough air out to push these pellets down that 23" barrel, I wonder if I cut it down if my vepcity lwould stay roughly the same? I've done that with other guns that were maxed out on air and it kept the velocity close to what t was with extra barrel length.

Basically I'm thinking I don't have the air to push the 81 grains of lead down the barrel before it starts to lose power behind that pellet, meaning the extra length is causing drag.
Click to expand...

I'd personally brain storm a fix for the valve block to breathe better. You stand to gain so much more by correcting that issue (assuming we're right about it being an issue) opposed to reducing barrel drag or eliminating the choke. There is a good chance reducing barrel length won't reduce performance greatly but imo it won't improve it either so only if the gun is unwieldy and long would I consider that approach.

-Matt
 
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This is what it looks like.
1000006673.jpg


I might cut that front section off so it gives a cavity before the angled transfer area that goes up to the valve. Plenty of threads on the other side to bite. Then I could open up the adapter section to probably 3/8".
 
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Stubbers said:
I'd personally brain storm a fix for the valve block to breathe better. You stand to gain so much more by correcting that issue (assuming we're right about it being an issue) opposed to reducing barrel drag or eliminating the choke. There is a good chance reducing barrel length won't reduce performance greatly but imo it won't improve it either so only if the gun is unwieldy and long would I consider that approach.

-Matt
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It's 49", to me that's unwieldy! I'm only 5' 7" lol. It's a bench/hunting blind gun really.
 
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I think you guys figured out a major contributor to not making power. We know an unregulated gun uses its tube or bottle as a plenum. The restriction right here may not be able to be overcome. Or maybe the diameter of that port is adequate but it’s the distance from valve to bottle that’s messing with the available power on tap.

IMG_3493.jpeg
 
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Vetmx said:
I think you guys figured out a major contributor to not making power. We know an unregulated gun uses its tube or bottle as a plenum. The restriction right here may not be able to be overcome. Or maybe the diameter of that port is adequate but it’s the distance from valve to bottle that’s messing with the available power on tap.

View attachment 448461
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That looks like you came over to my house and drew on my napkin with a red marker!

I just cut off that silly like front part of the block/bottle adapter and ported it up to 3/8". I got it all back together and no leaks, walking the bottle over to the action, and the bottle to adapter o-ring blew out. Nearly soiled myself.

It was a limp noodle, guess going from zero psi to 300 BAR all in one fill overheated it. The Yong Heng is getting a workout today!
 
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Vetmx said:
Gonna draw on your napkin again. So you cut this off? And yes, full fill to 300b will generate some heat. Hopefully that’s what pushed that oring.

View attachment 448465
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Yep, that's what I cut off, so there is more space before the transfer tunnel area. I actually LOST power. It's now only in the 715 fps range. Checked the chrony, it's spot on with my other guns.

That transfer area has got to be the limiting factor here.
 
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Dr. Kralenstein said:
Yep, that's what I cut off, so there is more space before the transfer tunnel area. I actually LOST power. It's now only in the 715 fps range. Checked the chrony, it's spot on with my other guns.

That transfer area has got to be the limiting factor here.
Click to expand...

One possibility is that your valve now is fighting more pressure during the shot cycle opposed to the prior arrangement which experienced a ton of pressure drop, which means less hammer strike was needed. Can hammer strike be increased?

-Matt
 
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Vetmx said:
Gonna draw on your napkin again. So you cut this off? And yes, full fill to 300b will generate some heat. Hopefully that’s what pushed that oring.

View attachment 448465
Click to expand...
also it is angled straight lines instead of a curve . but i have no idea how to drill a curve .
 
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nervoustrig said:
Sounds like it's back to needing one or more of the following:
  1. heavier hammer
  2. more hammer stroke
  3. stronger hammer spring
  4. easier poppet to knock open
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It's gotta be the hammer weight. I do get better numbers with the weight added, but that takes up spring cup area and causes spring to bind sooner.

However, I am now getting a smoother and longer shot string. Before I was getting 730-750 fps on the first mag, and now it's hovering around 710 average over 35 shots before slowly dropping into the 690s.

I may have to resort to buying a bighorn hammer and adding a tube inside the rear of the stock for it so slide into. I have space between the action and stock I was planning on filling with a chunk of wood anyhow, I can just use that area for the extra length I need.

So Kral decided instead of making the valve system more open and efficient, they'd just bash the poop out of the valve with a bigger hammer.
 
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Trying to knock open a valve to make 130+ FPE that wasn't originally intended for this kind of dwell isn't necessarily easy.

My guess is you opening the block increased the pressure at the valve so now you need more hammer strike. A conventionally valved .357 cal definitely requires a lot of hammer weight and spring. A 150-200 gr hammer with 15-20 lbs of spring perhaps, although this is uncharted territory for myself so take those wild guesses with a grain of salt.

The best approaches to increase valve lift/dwell.

1) Balanced/piloted valve (Easier said than done when it comes to fabrication and setup/tune)
2) Smaller valve stem & sleeved valve stem bore (.125" down to .098) (Very easy to do if you can fabricate your own poppet, great time to switch to peek)
3) Heavier hammer / spring, increasing the hammer weight/spring rate by 33-50%. (Can add washers behind the hammer provided it's not limited in travel)
4) Increasing the hammer throw. (Would require custom fabrications, preventing the spring from going coil bound, so longer springs may be needed)
5) Poppet material such as Peek(This helps marginally but nothing compared to the above)

-Matt
 
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Dr. Kralenstein said:
It's gotta be the hammer weight. I do get better numbers with the weight added, but that takes up spring cup area and causes spring to bind sooner.

However, I am now getting a smoother and longer shot string. Before I was getting 730-750 fps on the first mag, and now it's hovering around 710 average over 35 shots before slowly dropping into the 690s.

I may have to resort to buying a bighorn hammer and adding a tube inside the rear of the stock for it so slide into. I have space between the action and stock I was planning on filling with a chunk of wood anyhow, I can just use that area for the extra length I need.

So Kral decided instead of making the valve system more open and efficient, they'd just bash the poop out of the valve with a bigger hammer.
Click to expand...
Take a picture of your spring and the adjustment screw. I might have an idea.
 
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Vetmx said:
Take a picture of your spring and the adjustment screw. I might have an idea.
Click to expand...
You talking about how you did the SSG on the jumbo inside the stock?

I was looking at my action and pics of the hammer on the bighorn. The issue of trying to use a bighorn hammer is they're longer but that also means the length of the hammer tube is longer before sear engages. Meaning longer travel, which that I won't be able to reproduce. The rear of the action block is longer so there is more room to cock the hammer as well. The trigger is further back on the Bighorn.
 
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