ADA: Ask Doc Anything!

[MrKittyCatMeowFace]

Whats the fastest loader?

[DocsMachine]

Are porting really important on freak barrel tip?

-Nope. In fact I'm going to spout more heresy here: NO barrel porting, of any kind, does anything but quiet the shot.

In most 2-piece barrels, the front half is oversized, usually around .700". Doesn't touch the ball at all, and leaves plenty of space around it for air to go whereever it likes. The porting does nothing at all except give that air a place to go, and slowly enough that it slows down the "pop" of the shot to more of a "phoot".

Depending on your marker setup and which barrel we're talking about, some 2-piecers will still give you a little more velocity with the tip than without, but that's usually minimal at best. I've bene told by many dozens of players- many of whom were surprised by it- that their favorite Freak combo shot just as well (accuracy and velocity wise) with one of my stubby Flashpoint tips, as it did with the original 12" or 14" tip. (Typically a little louder, though. )

I know it will be louder but could it affect ball spin when the air expand around the ball at the transition of the freak insert and the bigger bore freak front?

-Generally no, but not always.

It's been my experience that a 2-piece barrel, with minimal porting on the front, does not shoot bad paint as well as a solid bore. My theory on that one is the air charge behind the ball is constrained enough to want to escape past the ball, rather than just leaving the muzzle in all directions away from the ball.

This, I think, lets the air catch on imperfections (out of round, bad seams, etc.) and so has more influence on getting the ball to spin, twist or corkscrew.

It's not a huge effect, and also not always reproducible, but in this case, with a minimal short tip, if there is such an effect, it likely won't be significant.

Doc.

[DocsMachine]

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)?

-Generally speaking, yes. You don't necessarily need to go for zero preload, though. It's not usually an issue with a 'Cocker or blowback, but in a pump (Sniper, PMI, PGP, etc.) if the hammer is slightly "loose" at rest, as Russc notes, the gun can "fart", or "honk". That is, the hammer bounces back and forth against the mainspring, usually popping a little extra air. The MVP is wicked bad about this, and the old Brass Eagle Cobras would do it too. My old one would sound like a goose honking every time I fired it.

You also don't want to go too light on the valve spring, as getting the cup seal closed as quickly as possible is one of the major keys here.

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.

-Correct, but with an asterisk. As always, there's a balancing point. Too light a striker and too heavy a spring cause their own problems, among them being more sensitive to op pressure.

One of the hot mods back in the day for the VM-68 was called, I think, a Pro-Comp kit. It had a much lighter hammer and a considerably shorter spring- a 'Mag bolt spring, if I recall correctly. And it would literally double the gas efficiency of a VM, which illustrates how much energy was being wasted blowing that fourteen-pound hammer back.

Doc.

[Alexndl]

Probably an easier question here
Are porting really important on freak barrel tip?

I have a long Progressive freak tip that I dont use and want to cut it the to make a 3" front tip but it wont have any vent ports

I know it will be louder but could it affect ball spin when the air expand around the ball at the transition of the freak insert and the bigger bore freak front?

[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.