ADA: Ask Doc Anything!

[DavidBoren]

So, in a STBB, using a lightweight striker/bolt assembly, a mainspring sized/trimmed to provide no preload, and a relatively light valve spring should, in theory, be the most efficient (all else being equal)?

This efficiency is achieved by allowing the striker to be moved backwards from rest as easily as possible, via reduced mass/inertia and no spring tension at rest. The easier it is to send the striker assembly backwards, the less pressure you need to divert from the valve... this allows lower operating pressure (as a byproduct of efficiency).

Regardless of the valve, bolt, regulator... inertia is present no matter what, and must be overcome. The quickest and easiest way to do this is to reduce the mass.

[DocsMachine]

I don't think dwell time can be blamed entirely on the spring and hammer setup since you have the ram pulling the hammer off the valve stem shortly after firing.

-Possible, but unlikely. Typically the hammer cycles and the valve closes again in roughly 10-12 milliseconds, as evidenced by the occasional E-Blade user who has been able to push his setup near 20 BPS. In a mechanical setup, even top players have a hard time doing better than 14, and 10-12 is a LOT more common. That's roughly 70 to 100 milliseconds. The valve has closed and the hammer is mostly at rest by that point.

Doc.

[DocsMachine]

My point with both of these is that being LP is a part of the equation that makes it more efficient. You said LP is a side effect, I'm arguing it's one of the root causes of the increased efficiency.

-No, sorry, that's exactly backwards. Reduced op pressure is a result of improved efficiency, not the other way around.

It's like saying that a motorcycle is more fuel-efficient than a car, because it has two wheels. Therefore, if we take two wheels off a car, it, too, will be more fuel efficient. We can make all sorts of guns "low pressure". I could make a 007 shoot full velocity at 200 psi if I had to. But it'd be fabulously inefficient.

For someone building a gun with the intent of being efficient, it would be important of them to know that they need to start with an LP system, not HP.

-Again, explain the Phantom. Or my first Minicocker back in '94 or so. Before I could afford a decent- or any, really- inline reg, I set it up on unregged CO2, a small expansion chamber (one of those 3-section Pro-Lines) and an angled drop to help keep liquid out. Stock valve with some tweaks, one of the first custom bolts I ever made, and a homebrew Nelson kit because I literally couldn't afford to buy the real thing. Depending on how fast I shot it, I could get 1400-1500 shots per 20-ounce.

Just that the Shoebox is no longer near the top 20 lowest pressure guns.

-So? I never said it was. I said it was among the lowest pressure guns- and, it's worth noting, it was the first to dip below about 200. Arguably the first to dip below probably 400, really.

No, I'm just a stickler for this kind of stuff.

-Ditto. Which is why I'm saying you're doing it backwards if you shoot for low pressure first, then efficiency. Build for efficiency, and chances are you'll wind up- though not always- with a pretty low op pressure.

But I'm also an obsessive know-it-all, with cockers being my one true passion.

-Ditto, again. Keeping in mind I've been doing this as a day job for twenty-two years now, and that I wrote articles on hot to time 'Cockers and 'sweet spot' a reg on a 'Cocker, before Ravi did.

I've been around this particular block a time or two.

Generally speaking, most people will consider red maddmann springs heavy, blue springs medium, and green springs light. That being the case, most people would assume from your comment about heavy springs being more efficient that they should use red ("heavy") springs.

-Thing is, that's often exactly correct. Go back and re-read what I wrote about the spring length, as well as weight. Ideally, the spring should be minimally or completely unloaded when the hammer is forward. Again, so the valve closing doesn't have to ALSO overcome spring pressure in addition to hammer inertia in order to close.

One of my common tricks is to cut a couple coils off a heavy spring, in order to get the strength without the length.

But you're going against the wisdom of every other cocker tech out there.

-Hardly. Staring with Bud Orr himself with whom I discussed this exact topic at length, and (the late) Aaron Alexander of AKA, who actually spent a great deal of time researching and developing a way to get the valve to close basically as fast as possible.

Danny Love, who made the first ever upgrade valve for cockers specifically for efficiency, makes bolts with huge ports.

-Certainly. Because Love is a salesman as much as he is an airsmith. Customers ask for big, mongo bolts, because virtually everyone things "more airflow makes it more gooder!" I saw the same thing with the Fastback- I can't count the number of people over the years that tossed my "tiny, restrictive" bolt for a big open pipe.

Bob Long's modern guns (G6r), which he has video of getting something like 2700 shots out of using a 77ci IIRC (which would still be well over a case on a 68/45) has a massive bolt hole.

-Electros, in this case, definitely blur the line here a little, because the dwell can be controlled electronically. For the moment, we're still discussing essentially mechanical dwell, as varied by striker and spring weights.

Doc.

[russc]

I don't think dwell time can be blamed entirely on the spring and hammer setup since you have the ram pulling the hammer off the valve stem shortly after firing. That's why some gun setups sound great as cockers and then fart like mad as pumps. I'm sure a fast ram with a tight timing setup would help.

[DavidBoren]

There's a fight? My money is on the polar bear...

Honestly, this "fight" is akin to two encyclopedias arguing... so much information being tossed back and forth... we all win.

[lew]

In a 'Cocker, a heavier hammer, in my experience, almost always leads to reduced air efficiency.

My experience on two different Cockers (both Minis!) states otherwise. Shocktech Phat Hammer, stock WGP Valve, Maddman green hammer and blue (or WGP stock) valve spring, and an open-face Delrin bolt of your choice (Jackal, Slik, Eclipse). ~2400+ rounds out of a 90/4500. Operating pressure is just north of 300 psi. Stock valve, hammer, springs, and sweetspotting gets me slightly more than half of that.

I'm taking Magmoo's side in this fight.

[DavidBoren]

There's no high pressure markers getting a case per fill because they can't drink deep enough into the tank... not because they are inherently inefficient.

[MrKittyCatMeowFace]

Diary Cow vs Polar Bear

not a fair fight XD

[Magmoormaster]

-Er, that was actually my exact point. You don't tune the gun for low pressure- any idiot can do that (with a 'Cocker) just by slapping a heavy hammer and mongo springs in there, but at a cost of reducing efficiency. You tune the gun for improved efficiency, which generally has the side effect of allowing you to reduce the operating pressure.

-Er, yeah. Because those guns were designed to be efficient, not just "designed for low pressure". The shoebox was designed as it was,simply because the solenoids at the time were only good to about 120 psi. It was designed to run at that pressure, not designed for efficiency.

My point with both of these is that being LP is a part of the equation that makes it more efficient. You said LP is a side effect, I'm arguing it's one of the root causes of the increased efficiency. There isn't a single HP semi auto gun (meaning pumps don't count) that can reach a case on a 68/45. Everything that can is LP. Hence, one can infer that to really be as efficient as possible, it needs to be low pressure. That might still be arguing semantics, but I think it's a significant distinction. For someone building a gun with the intent of being efficient, it would be important of them to know that they need to start with an LP system, not HP.

-Okay, now you're just looking for things to argue about. I did, in fact, say "one of the lowest", which means, for those blinded by pedanty, among the lowest. 165 psi is, after all, only 30 psi away from 135 psi, as you noted for your CS1. Because of that, do we now start referring to shoeboxes as "high pressure" guns? Of course not.

This one is absolutely me being pedantic. I'm not saying Shoeboxes are high pressure guns. Just that the Shoebox is no longer near the top 20 lowest pressure guns. Arbitrary for sure.

-Oy. I feel you're combing my post for even the most quibbling little bit you can work up into an argument. Did I step on your dog or something, at some point, and you now feel a moral obligation to somehow 'prove me wrong'?

No, I'm just a stickler for this kind of stuff. I certainly have nothing against you, I've been a huge fan for years. But I'm also an obsessive know-it-all, with cockers being my one true passion.

Put it this way: Define "heavy" when it comes to 'Cocker springs. At what point does a spring stop being "light" and become "heavy"? Is whatever random cutoff point you come up with an actual industry guideline, or is it just your opinion?

Generally speaking, most people will consider red maddmann springs heavy, blue springs medium, and green springs light. That being the case, most people would assume from your comment about heavy springs being more efficient that they should use red ("heavy") springs. It's not about what my opinion is.

-Oy, again. You'll note, specifically, above, where I stated, I thought with some clarity, that we were speaking of general use, and that there are too many variables- valves, hammers, springs, bodies, tolerances, etc.- to say that any one part will work "the best" in any given combo.

...

Repeatable as the day is long. Original 'venturi' over the chrono, 280. Same paint, same pressure, same chrono, just swap the bolt to the "big" one, 250. Swap back to the 'venturi', 280. Big bolt, 250.

Yes, I fully agree that the Lightning is a very good bolt, but again, there's way to many variable to say it's anything like 'the best", let alone the best for all possible combinations.

(trimmed to make this comment not a million miles long)
Lots of variables, sure. Cannot argue that. But you're going against the wisdom of every other cocker tech out there. Danny Love, who made the first ever upgrade valve for cockers specifically for efficiency, makes bolts with huge ports. Same with AKA, whose guns are always touted as being the most efficient. Bob Long's modern guns (G6r), which he has video of getting something like 2700 shots out of using a 77ci IIRC (which would still be well over a case on a 68/45) has a massive bolt hole. I don't think any of them just said "well, a larger bolt hole will probably be better." I guarantee they tested others. It might have been the case with yours, I'm in no way trying to call you a liar. But the only time I've ever heard anyone say something similar is with 12g's, which I think we can both agree is a very different animal.

[DocsMachine]

I'm afraid you are incorrect here. Low pressure can be wildly inefficient when done poorly[...]

-Er, that was actually my exact point. You don't tune the gun for low pressure- any idiot can do that (with a 'Cocker) just by slapping a heavy hammer and mongo springs in there, but at a cost of reducing efficiency. You tune the gun for improved efficiency, which generally has the side effect of allowing you to reduce the operating pressure.

[B]ut literally all high efficiency semi auto guns run in the sub 200 PSI range. That's AKA cockers, AKA Viking/Excal, Bob Long G6r, etc[.]

-Er, yeah. Because those guns were designed to be efficient, not just "designed for low pressure". The shoebox was designed as it was,simply because the solenoids at the time were only good to about 120 psi. It was designed to run at that pressure, not designed for efficiency.

I would also like to point out (though this is totally irrelevant) that Shoebox Shockers, with an operating pressure of 160-170 PSI, is nowhere near being one of the lowest pressure guns[...

-Okay, now you're just looking for things to argue about. I did, in fact, say "one of the lowest", which means, for those blinded by pedanty, among the lowest. 165 psi is, after all, only 30 psi away from 135 psi, as you noted for your CS1. Because of that, do we now start referring to shoeboxes as "high pressure" guns? Of course not.

you implied it when you said that best efficiency comes from a light hammer and heavy springs, then touted a Tornado valve as being the most efficient. The AKA hammer weighs 30g, which is certainly on the lighter side (later WGP hammers were 40g). But like I said the springs aren't heavy at all.

-Oy. I feel you're combing my post for even the most quibbling little bit you can work up into an argument. Did I step on your dog or something, at some point, and you now feel a moral obligation to somehow 'prove me wrong'?

Put it this way: Define "heavy" when it comes to 'Cocker springs. At what point does a spring stop being "light" and become "heavy"? Is whatever random cutoff point you come up with an actual industry guideline, or is it just your opinion?

When I say "heavy", I don't necessarily mean "concrete truck axle springs". When I say 'heavy', I don't mean that it takes three men and a boy to cock the gun. The original Snipers used Sheridan-style springs, which were, compared to most any Nelson spring, considerably "heavy". So by that metric, any Nelson spring would be a "light" spring.

I like discussing, or even arguing, technical things, but really, this is more quibbling over pointless semantics.

I did a similar test just 2 weekends ago. [snip] I have yet to see a single bolt beat a Lightning bolt over the chrono. And until I do, I will consider it the most efficient.

-Oy, again. You'll note, specifically, above, where I stated, I thought with some clarity, that we were speaking of general use, and that there are too many variables- valves, hammers, springs, bodies, tolerances, etc.- to say that any one part will work "the best" in any given combo.

I've done similar tests. As I said above, when designing the Fastback, using a Tornado valve (which was the hot, happenin' mod at the time) my smaller bolt worked better than one with more of a Lightning-style profile. But, as more of those bodies got out into people's hands, using different hammers, springs and valves, more than a few came up with a combination where a different valve worked better for them. (As evidenced by the fellow earlier in this thread, who had an Impulse bolt in his Fasty.)

I have a photo somewhere in my archives, showing an early Belsales P-block "venturi" bolt, with six small holes. Customer sent that gun in for mods, and one of the things I did was cut a new bolt with basically the biggest port I could drill in it and still have a front O-ring. I was actually surprised to see that bolt reduced the velocity by an easy 30FPS.

Repeatable as the day is long. Original 'venturi' over the chrono, 280. Same paint, same pressure, same chrono, just swap the bolt to the "big" one, 250. Swap back to the 'venturi', 280. Big bolt, 250.

My current go-to "parts box" 'Cocker, a basically unmodified '04 Prostock body, Tornado, Eclipse frame, and old-style (and long out of hydro ) Max Flow, easily hits 290 at 170 psi on the gauge. Using a custom made solid delrin bolt with a .257" hole stem to stern. Change absolutely nothing but the bolt, over to a Lightning, and it loses 20FPS.

Yes, I fully agree that the Lightning is a very good bolt, but again, there's way to many variable to say it's anything like 'the best", let alone the best for all possible combinations.

In your case with the Fastback... Well, I worked on a Fastback for JunglePeanut last winter and noticed the upper tube bore was quite a bit larger than normal. I'd guess (obviously speculation) that the FPS increase you saw was due to the better fit of the bolt you made for it, not the design itself.

-Um... one, the Fasts were made internally to basically WGP spec. And two, this was back in the prototype stage. ALL the bolts I was trying in it, were fitted to the body. There were no aftermarket bolts I could fit to it at the time, even if I wanted to.

Since it only took a few minutes to whip up another bolt, as I recall, I tried a venturi style, a Lightning style conical bore, I think about three sizes of straight bore, and one with a flathead stainless screw in the center as a sort of "diffuser". The bottom line was that, with the exact same setup in the gun, the biggest straight bore gave the lowest velocity, the Lightning-style a little better, the venturi surprisingly better still, and finally the smallest straight bore gave the best.

It's worth noting that the overall spread was still only about 30 FPS.

Doc.

[Magmoormaster]

Nope, sorry. Low pressure is a side effect, not a goal. That is, making the gun efficient often allows you to lower the pressure. Very often, if you shoot specifically for LP, it makes it less efficient.

The classic example is the old 'shoebox' Shocker versus something like a Phantom. The shoebox is one of the lowest-operating-pressure markers ever made, usually running around 160 to 170 psi. It's also widely famous for being one of the least gas efficient markers ever made. On the other hand, the Phantom runs straight, unregulated CO2, about 850 psi, and is considered one of the most air-efficient guns made.

Yes, that's comparing apples to pomegranates, but it illustrates the point: just making it low pressure does not make it efficient. The only way simply forcing the op pressure down 'adds' to efficiency, is it lets you go 'deeper' into the tank. That is, if one gun runs at 450 psi, and another at 180 psi, the other can use that additional 270 psi before losing velocity.

In a 'Cocker, a heavier hammer, in my experience, almost always leads to reduced air efficiency. Again, it has to do with valve dwell- how quickly the valve can open and close. That was the whole point behind the Tornado- the poppet was a fair percentage lighter than in other valves, and the relatively large cup seal area added to the 'push' of the air pressure in the chamber to help close it.

I'm afraid you are incorrect here. Low pressure can be wildly inefficient when done poorly, as you noted with the Shoebox, but literally all high efficiency semi auto guns run in the sub 200 PSI range. That's AKA cockers, AKA Viking/Excal, Bob Long G6r, etc, all of which have been known to shoot a full case on one fill. I would also like to point out (though this is totally irrelevant) that Shoebox Shockers, with an operating pressure of 160-170 PSI, is nowhere near being one of the lowest pressure guns when every single modern spool valve runs in the sub-150 PSI range. My Planet Eclipse CS1 shoots at around 135 PSI, as do the 5 or so Gamma Core guns (Emek, Gtek, etc). The CS2 shoots at 110. The DYE M3 is at 110 as well, and I'm assuming the Luxe ICE is in a similar range since it ripped off the CS2 bolt.

I don't disagree with the heavier hammer part.

-Nobody ever said they were. What they were, were weighted about right for the average Tornado install. Made so you could buy a ready-to-go two spring kit, rather than an eight-spring suite and do a lot of tuning and testing.

you implied it when you said that best efficiency comes from a light hammer and heavy springs, then touted a Tornado valve as being the most efficient. The AKA hammer weighs 30g, which is certainly on the lighter side (later WGP hammers were 40g). But like I said the springs aren't heavy at all.

-Nope. They're good, yes, but still suffer from the standard problem- the port expands in volume as it extends towards the ball. That allows the gas column to expand before it hits the ball, and thus wastes some of it's energy.

The most efficient bolt is one that maintains the valve exhaust port size all the way from the valve to the surface of the ball. If the column of pressurized gas is only allowed to expand as little as possible before imparting it's energy on the ball, that uses the air as efficiently as possible.

I have actually done some research of my own on this. I just don't have it on YouTube because I did it before YouTube existed.

Back when I was playing with the Fastbacks, one of the things I did in fact develop for it was the bolt. Sergei wanted a huge open bolt because that's what everybody else was making. I tried a couple designs, and eventually went back to what Bud Orr told me personally, when he was up here for an APL tournament in 1998. Keep the hole through the bolt the same size as the valve port, to minimize how much energy is lost to expansion of the gas column.

I whipped up one of those for my prototype Fasty- which I still have, by the way- and immediately gained some 30 FPS over a more Lightning-style profile. (I have a Tornado in the prototype.)

I'm not going to say mine's the best ever, though. As I said, there's way too many variables, especially in 'Cocker builds. In some guns the bigger bolt does indeed add more velocity, in others it reduces it. But again, generally speaking, the best bolt is one that stays the same size all the way from the valve to the ball.

Doc.

I did a similar test just 2 weekends ago. I recently put together a Macdev Sonic autococker that came to me in pieces. The Macdev bolt is what you describe as being the most efficient design; small inlet hole, and stays small all the way until the last 1/8" where it ramps up to a larger diameter. It offered roughly equal chrono readings to a Check It bolt and a stock aluminum 2k bolt. The lightning bolt offered a 15-20 FPS increase. I have yet to see a single bolt beat a Lightning bolt over the chrono. And until I do, I will consider it the most efficient.

In your case with the Fastback... Well, I worked on a Fastback for JunglePeanut last winter and noticed the upper tube bore was quite a bit larger than normal. I'd guess (obviously speculation) that the FPS increase you saw was due to the better fit of the bolt you made for it, not the design itself.

[DocsMachine]

It gets really complicated when you consider heavier hammers and lighter springs really help get the pressure down, which in turn helps with efficiency.

Nope, sorry. Low pressure is a side effect, not a goal. That is, making the gun efficient often allows you to lower the pressure. Very often, if you shoot specifically for LP, it makes it less efficient.

The classic example is the old 'shoebox' Shocker versus something like a Phantom. The shoebox is one of the lowest-operating-pressure markers ever made, usually running around 160 to 170 psi. It's also widely famous for being one of the least gas efficient markers ever made. On the other hand, the Phantom runs straight, unregulated CO2, about 850 psi, and is considered one of the most air-efficient guns made.

Yes, that's comparing apples to pomegranates, but it illustrates the point: just making it low pressure does not make it efficient. The only way simply forcing the op pressure down 'adds' to efficiency, is it lets you go 'deeper' into the tank. That is, if one gun runs at 450 psi, and another at 180 psi, the other can use that additional 270 psi before losing velocity.

In a 'Cocker, a heavier hammer, in my experience, almost always leads to reduced air efficiency. Again, it has to do with valve dwell- how quickly the valve can open and close. That was the whole point behind the Tornado- the poppet was a fair percentage lighter than in other valves, and the relatively large cup seal area added to the 'push' of the air pressure in the chamber to help close it.

I would like to point out, however, that AKA springs are not all that heavy by comparison.

-Nobody ever said they were. What they were, were weighted about right for the average Tornado install. Made so you could buy a ready-to-go two spring kit, rather than an eight-spring suite and do a lot of tuning and testing.

I also must disagree with the statement about lightning bolts; at least when discussing cockers, lightning bolts are for sure the most efficient bolts ever made.

-Nope. They're good, yes, but still suffer from the standard problem- the port expands in volume as it extends towards the ball. That allows the gas column to expand before it hits the ball, and thus wastes some of it's energy.

The most efficient bolt is one that maintains the valve exhaust port size all the way from the valve to the surface of the ball. If the column of pressurized gas is only allowed to expand as little as possible before imparting it's energy on the ball, that uses the air as efficiently as possible.

I have actually done some research of my own on this. I just don't have it on YouTube because I did it before YouTube existed.

Back when I was playing with the Fastbacks, one of the things I did in fact develop for it was the bolt. Sergei wanted a huge open bolt because that's what everybody else was making. I tried a couple designs, and eventually went back to what Bud Orr told me personally, when he was up here for an APL tournament in 1998. Keep the hole through the bolt the same size as the valve port, to minimize how much energy is lost to expansion of the gas column.

I whipped up one of those for my prototype Fasty- which I still have, by the way- and immediately gained some 30 FPS over a more Lightning-style profile. (I have a Tornado in the prototype.)

I'm not going to say mine's the best ever, though. As I said, there's way too many variables, especially in 'Cocker builds. In some guns the bigger bolt does indeed add more velocity, in others it reduces it. But again, generally speaking, the best bolt is one that stays the same size all the way from the valve to the ball.

Doc.

[Magmoormaster]

It gets really complicated when you consider heavier hammers and lighter springs really help get the pressure down, which in turn helps with efficiency. And not to mention, heavy springing makes the gun shoot like ****. And like Doc said, super high efficient setups tend to be very finicky. I would like to point out, however, that AKA springs are not all that heavy by comparison. They're roughly equivalent of a blue valve spring and green hammer spring from maddmann kits. They're not SLPS springs but they're far from being heavy.

As a quick aside, it was Freeflow that made Tungsten hammers. Shocktech made (and still makes) brass-sleeved steel hammers that are only a few grams lighter than the later WGP hammers.

I also must disagree with the statement about lightning bolts; at least when discussing cockers, lightning bolts are for sure the most efficient bolts ever made. In every comparative text, AKA bolts have the highest chrono readings by at least 10 FPS, 20-30 when compared to the really low-efficiency bolts.

[DavidBoren]

Thank you. Very much so.

That puts a nail in the coffin pursuing custom brass strikers just to pretty much tinker with in an attempt to figure this all out on my own.

I'm glad I asked you first, before investing a bunch of money and energy to learn what is already known. I appreciate you taking the time to have this thread and share your knowledge.

I will have to go change some mainsprings around in a few of my STBB's... I was purposefully running light, but long, springs to provide pretty much constant preload on the striker. It was low tension, but definitely preloaded due to length. I thought that by eliminating the free flying fling at the end, I would be able to achieve a higher level of consistency. I figured that the uncontrolled flight would not be guaranteed the same each time.

The tension/preload is not enough to overcome an AKA valve spring, even degassed... I run light, light springs because I think the stock striker (even the skinny one) weighs A MILLION. And the preload helps me sleep at night, because I also secretly think that the mainspring is too light. Lol.

I have an Alamo City fatty, too... I just literally hate powerfeeds SO MUCH that I don't run my Classic. I might have to get over myself and fire that thing up...

[DocsMachine]

Is there any significant difference in efficiency between using a heavy striker and light springs, versus a light striker and heavy springs?

-Very much so, and an excellent question!

Now, of course there's a million combinations of valve, bolt, striker, etc. out there in a hundred different kinds of marker, so we can't give a definitive answer that covers every single thing. BUT, generally speaking, the light striker with a comparatively heavy spring should be more air efficient.

It has to do with dwell time- how long the valve is open, how long it takes to close. In a typical 'Cocker or blowback marker, the striker hits the valve and pushes it open, letting gas through to the bolt. After a certain period- a few milliseconds- the force of the valve spring and air pressure pushing on the cup seal, push the valve back closed, and push the striker back the other way.

A heavy striker has more inertia, and all else being equal, it takes longer for the valve spring/air pressure to overcome that inertia than it would were the striker lighter. And in the case of a blowback, it takes more air pressure- more energy- to push a heavier striker back to recock.

Now, the trick here, for both kinds of gun but specifically for the 'Cocker, is that if the spring is too long, the spring maintains force on the hammer even when all the way forward, which also increases dwell. So the ideal setup would be to have a relatively lightweight striker, and a spring with sufficient force to open the valve properly, but which does not apply significant pressure on the valve stem at rest.

Clear as mud, right? Simply put: when at rest, the hammer not cocked, but the gun pressurized, when the hammer is resting on the tip of the valve stem, the spring should be putting either very little or no pressure on it. That way, when fired, the spring 'flings' the hammer forward, which strikes and opens the valve, but then, the valve doesn't also have to overcome residual spring pressure in order to close again.

That way, all else being equal, that lets the valve close as quickly as possible, which is a big key towards gas efficiency.

Is it the opposite of strikers and springs when considering the mass/weight of the ram, and the pressure operating the ram? Not with Autocockers, but things like the Impulse or Intimidator (although I don't see much variation in Timmy ram mass).

-Inertia is inertia. The Intimidator may not use springs to drive the "hammer", but the principle is the same. The faster the striker can retract- at least to the point of allowing the valve to close, generally speaking the more efficient the system will be.

I have a hard time believing that they are equally efficient.

-They're not, and by a long shot in some cases. A good example would be to compare a Spyder clone to an old VM-68. The hammer in a VM is something like a pound, the striker in a typical Spyder clone is an ounce or two. The VM wastes a great deal of gas- energy- trying to force the hammer back and close the valve, compared to the far lighter clone striker.

In the 'Cocker world, we used to (and in some cases, still do) try to make heavier and heavier hammers, with I think Shocktech coming out with a Tungsten hammer. We'd smash the valve open with heavy hammers and springs, ironically often to make up for INefficient valves, bolts and barrels.

Modern setups like the Inception guns are not the most efficient possible, as that can tend to be pretty fiddly, taking a lot of fine-tuning for different conditions. But they are fairly well balanced, giving pretty good overall performance over a wider range of conditions.

I also don't like to think that the best compromise is somewhere in the middle... that just seems lazy to me. Surely, when using efficiency as the metric by which they are to be judged, one combination is going to be superior in both theory and practice.

-It is indeed. I once set up a 'Cocker body, using an early custom Bob Long body where they'd bored out the valve chamber (this was in the pre-2000 days) and capped it with brass, to bring it back down to the pre-2K front bolt size. I used pretty much a full AKA setup: Lightning bolt, Tornado valve and AKA springs, all capped off with an early Max Flow running about 165 psi.

With good paint and a good barrel fit (this was also pre-Freak) I got right around 1,600 shots per 68ci/3K fill.

And since we now know the Lightning was not the most efficient bolt, I'd bet with a little more experimenting, I could have gotten it maybe even a little better than that.

The problem with a setup like that, is that it's quite sensitive, especially to paint. The paint-to-barrel fit has to be very good- not too loose, not too tight, and also not too short (like a 5-1/4" freak insert.) That 1.6K above was using quality paint through a 14" .687" Long Shot barrel. Switching to a 12" .689" Autospirit dropped my velocity by something like 40FPS.

That sort of thing is fine for a tinker-freak (raises hand ) but for most players, they just want to pull the gun out of the bag and go play. And especially in these days of all-day-air and 4500 psi tanks, squeezing the last little bit of gas efficiency is not as important as it once was. So most manufacturers set it up a lot closer to the middle of the proverbial road. Maybe not as good as it possibly could be, but also not terrible, and as such, works under a wider range of conditions and setups.

Doc.