Atomic B2 or Scubapro Mk25/A700 Owners: Pro / Cons

[Angelo Farina]

Not an argument, just a curiosity, why would you prefer a Mark 10 and a G250V instead of just jumping to the Mark 25/17/19 and G260?

I find the G260 easier to achieve a very fine adjustment using the Micro-Adjust feature without resorting to my "assorted spring box" to find the perfect spring. The G260 is also outwardly noticeably more compact than the G250 or G250V. I also find that the G260 has a smoother transition from low to high Venturi effect. But saying those things, the G250V is basically a G260 without Micro-Adjust and a "vintage" looking case.





Just curious for educational purpose.

I prefer a small number of parts both for 1st and 2nd stages.
Scubapro added complexity with the MK25 and G260, for a minimal performance increase, which is of no value for recreational depths (which here is 50m max in air).
Finally, my MK10 is packed with silicon grease and fully sealed, which the MK25 isn't...

 

[Angelo Farina]

G260 has two points of tuning, orifice and micro adjuster. The G250V has only one point of tuning, the orifice. With a G250/V once lever is set what you get is what you get unless you have a bunch of springs to play with, with the G260 you can finely adjust spring pressure using micro adjuster allowing pin point cracking accuracy.

I would add that the G260 also has the second adjustment on the spring load: the knob!
Back to my belowed 109 (converted to BA), if you want it "hot tuned" you unscrew slightly the orifice to the point that the lever almost touches the diaphragm.
On all my 109s, except one, at that point the reg hisses slightly with the knob all out.
On a G260 you act on the micro adjuster for removing the hiss.
On a 109 / G250, you simply screw in the knob half a turn, until it stops free flowing.
If you watch the schematics posted here above, you see that the micro adjuster and the knob have exactly the same function, allowing to change the spring load.
It was a great idea to allow the diver to adjust it while diving...
People who learned to "hot tune" their 109 and G250 see no value in the micro adjuster, as the knob provides exactly the same effect, with no tools needed.
The micro adjuster can also cause problems: if the reg is tuned "too hot" and hisses slightly with knob all out, the owner of a G260 can think the reg is defective or improperly tuned, and brings it back to the shop or to his own benchwork for having the microadjuster retuned.
An owner of a 109 or a G250 is not concerned of that small hiss: the knob is there for fixing it on the fly...

 

[Nemrod]

Hmmm, maybe yes, maybe not exactly, well, I think we are just differing in semantics . With an A700 or a G260 with micro-adjust I would set up the orifice and lever height as always done with a G250 or 156 and no lever rattle. The adjustment knob should already be set fully out. With the micro-adjust, the knob would be set fully out also but the MA is protruding inward 2mm at a starting neutral position. Which means you can use that additional 2mm (G260) or 1mm (A700) to further compensate for spring variability. And it is a finer adjustment.

A700:




G250V:



And finally just for fun, the G260 (It is the Note in the instruction below that gives me a migraine):

 

[buddhasummer]

I would add that the G260 also has the second adjustment on the spring load: the knob!
Back to my belowed 109 (converted to BA), if you want it "hot tuned" you unscrew slightly the orifice to the point that the lever almost touches the diaphragm.
On all my 109s, except one, at that point the reg hisses slightly with the knob all out.
On a G260 you act on the micro adjuster for removing the hiss.
On a 109 / G250, you simply screw in the knob half a turn, until it stops free flowing.
If you watch the schematics posted here above, you see that the micro adjuster and the knob have exactly the same function, allowing to change the spring load.
It was a great idea to allow the diver to adjust it while diving...
People who learned to "hot tune" their 109 and G250 see no value in the micro adjuster, as the knob provides exactly the same effect, with no tools needed.
The micro adjuster can also cause problems: if the reg is tuned "too hot" and hisses slightly with knob all out, the owner of a G260 can think the reg is defective or improperly tuned, and brings it back to the shop or to his own benchwork for having the microadjuster retuned.
An owner of a 109 or a G250 is not concerned of that small hiss: the knob is there for fixing it on the fly...

Yes, but I don't use the knob to tune it per se.

 

[stuartv]

I'm in the market for a new reg and considering an Atomic B2 or Scubapro mK25/A700. What do you love or hate about yours? Or mildly like or dislike?

Short answer: Of the 2, get the Atomic B2.

Long answer:

I have Atomic M1, ScubaPro Mk 25 EVO/G260, Halcyon H75P/Halo, and have previously also owned Atomic Z2 and ScubaPro Mk 25 EVO/S620Ti.

The Atomics all breathe the same. They just have different materials and possibly a different feature here or there. Rather than buy Atomic B2, I would buy Atomic Z2. They are less expensive and the only differences are that the B2 2nd stage has some titanium bits and the ComfortSwivel. The Z2 2nd stage has zirconium instead of titanium. Just like what many (most?) of the other brands' 2nd stages have.

If you do any kind of reasonable rinsing on your regs, the B2 titanium is meaningless. And, to me, the ComfortSwivel is actually a negative. It comes on a 36", which is dumb. I want my hoses to be 22-24" and 40" for the primary and secondary. With the ComfortSwivel hose, the swivel is built in, so you can't easily change the length of the hose and keep the swivel. If you want to change to a different hose, you have to buy a jam nut from Atomic, lose the ComfortSwivel, and then you can put on a normal LP hose.

In contrast, the Z2 does not come with a ComfortSwivel. So, it's a lot less expensive and you can easily change to any length of LP hose that you like.

The Z2 also does not have a swivel turret like the B2 does, but I don't find a swivel useful for single tank. However, the Z2 DOES have a bottom port, which I DO use for single tank. And, you can add the swivel turret to a Z2, if you want. It's just a parts swap for the parts that are on the B2 1st stage, I believe.

Regarding the Mk25/A700, I simply do not like the A700. I don't like needing a small screwdriver just to remove the front cover, nor trying to not lose the 4 little screws if I needed to remove the cover under suboptimal conditions.

Also, I did ScubaPro Reg Tech training and was trained on how to service an A700. That was what really convinced me I never want one. Yes, the reg body is metal. But, it is SUPER thin metal. I am dubious that it is really any more resistant to damage than the polycarbonate body on the G260. Also, the air tube in the A700 is brazed into the body. Anybody that puts a wrench on that air tube thinking to remove it is very likely to destroy the whole reg body. AND, that reg body costs a couple of hundred bucks to replace. The body of a G260 is about $20 to replace, if it ever got damaged.

I have yet to try any reg that breathes better than the Mk 25 EVO/G260. But, the Atomics I have and have had all breathe just as well as that ScubaPro combo - which, for me, is better than the Mk 25 EVO/S620Ti regs I also owned at one point. And, I like the Atomic AFC feature. I've never had any trouble with mine and they save me from remembering to flip my Dive/Pre-dive switch back and forth, like I have to do with any other reg.

Of your options, I would go with Atomic Z2 with an extra Z2 2nd stage for your octo. Next choice would be any other Atomic. Next choice would be SP Mk 25 EVO/G260.

Also, with the Z2, I would order it Sealed. That adds about $30 to the price. If you choose to keep it sealed, it will cost a bit more at each service. If you decide you longer need it sealed, when you have it serviced, you can just tell them to leave it unsealed - at which point it will be just like the Mk 25. Being sealed is really not a big deal. Thus why I also have Mk 25s. But, the only downside to being sealed is a bit of extra cost when servicing the 1st stage. So, it's a small advantage, but I would still choose to have it sealed when it's an option.

Okay, for REAL, my top choice would be an Atomic TFX with an Atomic Ti2 2nd stage for my octo. I say that because I have recently ordered that exact setup through my shop, to be my new single tank rig. I have put my money where my mouth is. I admit it is stupid money and not for everyone... But, it will be the last single tank reg set I ever buy!

Yep, doing so is especially useful with primary donate setups since they have a longer hose.
View attachment 798770

This. I run my single tank setup almost exactly the same way. I run my AI transmitter where hose #4 is shown. And, for #1, I use a 40" hose. It loops under my right arm and the reg goes in a bungee loop octo holder on my right chest D-ring.

I like this setup way better than having my primary 2nd stage hose be 30-something inches long and making a huge loop out to my right. And way better than having my hose for my octo start off going straight out to the right from my 1st stage, then bending down to run under my right arm.

I think this setup results in better streamlining and less loops of hose sticking out (or not sticking out as far) to catch on stuff.

 

[Nemrod]

@stuartv, I am confused, are you running a long hose (donate) rig of 40 inches under your arm or a conventional (octopus) rig donation on a 40 inches hose under your arm?

My wife with her conventional rig, primary over shoulder on a 22/24 inches hoses, octopus secondary on a 36 inches hoses (she is only 5-4), and 24 inches spg hoses (she is little) and 22 inches inflator hose. She has a QR necklaced secondary, she sometimes secures it instead using a snorkel keeper to her right D ring, at least until I bought her a pink reg necklace (that needs to be shortened ):



Moving on. Regarding several comments about sealing piston regs, just in general, I really do not like the concept of semi-sealing a piston first stage with silicone grease which can (does) become diluted with salt water and very difficult to rinse out (like the Mark 10). I would rather have large, open ambient ports making rinsing easy (like the Mark 25 Evo).

 

[stuartv]

@stuartv, I am confused, are you running a long hose (donate) rig of 40 inches under your arm or a conventional (octopus) rig donation on a 40 inches hose under your arm?

I'm not sure what distinction you are making.

In the past, I would have a 70 degree swivel adapter on the 40" hose reg and I would run that under my right arm and up to my mouth. I would have my 22" hose reg on a bungee necklace under my chin. If I had to donate, I would donate the one in my mouth and switch to the other.

These days, I have the 70 degree swivel adapter on the 22" hose reg and that is what is in my mouth (maybe with a bungee necklace or maybe not). The 40" hose reg has no swivel on it at all and the mouthpiece from that is stuck through a bungee loop on my right chest D-ring. If I have to donate, I will donate that one that is attached to my chest.

So, either way, I'm donating the one on the 40" hose. All I have done is save myself the step of switching what reg I'm breathing off of.

For years, I drank the Tech Kool-Aid that I needed to make my primary reg be the one I donate. I have moved on to my own thinking on that subject and no longer see a need to use primary donate for recreational, single tank diving. As one of my good friends who is a much more experienced OW instructor than I am says, "why donate what's in your mouth? You've already got one OOA diver. Why make two?"

Also, 95% of my single tank diving is when I'm teaching Open Water. Every shop where I have taught has taught OW students to donate from the "octo holder" (not primary donate). So, running my rig the way I do now means I do it the same way outside of class as I do when I'm teaching OW.

Also, I have always had identical 2nd stages on my single tank rig. With my recent order of a TFX and Ti2, it will be the first time I've ever had non-identical regs. The TFX will go on a 22 -24" hose (I got a kit to shorten the stock hose, so I can keep the ComfortSwivel) and be my primary. The Ti2 will go on a 40" hose, be unused for 99.9% of its life, and be the one I donate in an emergency.

Does that answer your question?

 

[Nemrod]

I'm not sure what distinction you are making.

In the past, I would have a 70 degree swivel adapter on the 40" hose reg and I would run that under my right arm and up to my mouth. I would have my 22" hose reg on a bungee necklace under my chin. If I had to donate, I would donate the one in my mouth and switch to the other.

These days, I have the 70 degree swivel adapter on the 22" hose reg and that is what is in my mouth (maybe with a bungee necklace or maybe not). The 40" hose reg has no swivel on it at all and the mouthpiece from that is stuck through a bungee loop on my right chest D-ring. If I have to donate, I will donate that one that is attached to my chest.

So, either way, I'm donating the one on the 40" hose. All I have done is save myself the step of switching what reg I'm breathing off of.

For years, I drank the Tech Kool-Aid that I needed to make my primary reg be the one I donate. I have moved on to my own thinking on that subject and no longer see a need to use primary donate for recreational, single tank diving. As one of my good friends who is a much more experienced OW instructor than I am says, "why donate what's in your mouth? You've already got one OOA diver. Why make two?"

Also, 95% of my single tank diving is when I'm teaching Open Water. Every shop where I have taught has taught OW students to donate from the "octo holder" (not primary donate). So, running my rig the way I do now means I do it the same way outside of class as I do when I'm teaching OW.

Also, I have always had identical 2nd stages on my single tank rig. With my recent order of a TFX and Ti2, it will be the first time I've ever had non-identical regs. The TFX will go on a 22 -24" hose (I got a kit to shorten the stock hose, so I can keep the ComfortSwivel) and be my primary. The Ti2 will go on a 40" hose, be unused for 99.9% of its life, and be the one I donate in an emergency.

Does that answer your question?

The distinction I was asking is are you long hose primary donate or octopus secondary donate? I think I figured it out from your long answer .

I am with you, after this last trip I have become less than happy with the long hose (60 inches hoses) concept for open water recreational diving. I resisted (long hose primary donate) for the longest time and then about 15 years ago switched to long hose primary donate. But, as I said, I am now re-thinking the whole thing in the consideration of reducing my kit to the most minimal and simple and least fuss to get in and out of. And that may well be the new DGX Air thing and a G250 under my shoulder on a 40 inches hose as primary donate. Or just go back to a conventional secondary (octopus) donation.

I was just curious as to what you are doing because I am, it seems, considering similar. It is minimalism that is driving me to change. My new hypothesis, not acted upon just yet, is that the long hose primary donation concept for single tank open water diving, the advantages are a cliche based on dogma and anecdotal-isims.

 

[stuartv]

The distinction I was asking is are you long hose primary donate or octopus secondary donate? I think I figured it out from your long answer .

I am with you, after this last trip I have become less than happy with the long hose (60 inches hoses) concept for open water recreational diving. I resisted (long hose primary donate) for the longest time and then about 15 years ago switched to long hose primary donate. But, as I said, I am now re-thinking the whole thing in the consideration of reducing my kit to the most minimal and simple and least fuss to get in and out of. And that may well be the new DGX Air thing and a G250 under my shoulder on a 40 inches hose as primary donate. Or just go back to a conventional secondary (octopus) donation.

I was just curious as to what you are doing because I am, it seems, considering similar. It is minimalism that is driving me to change. My new hypothesis, not acted upon just yet, is that the long hose primary donation concept for single tank open water diving, the advantages are a cliche based on dogma and anecdotal-isims.

I think we are on the same page there.

I like minimalism. But, I rejected the Safe Second concept for that very reason.

I want my primary reg to be on the shortest hose that doesn't pull on the reg when I look full left. That means 22 - 24", with an angle adapter.

With the primary on a hose that short, I cannot donate it. So, the Safe Second option is out the window, since I can't donate that, either.

 

[Nemrod]

I think we are on the same page there.

I like minimalism. But, I rejected the Safe Second concept for that very reason.

I want my primary reg to be on the shortest hose that doesn't pull on the reg when I look full left. That means 22 - 24", with an angle adapter.

With the primary on a hose that short, I cannot donate it. So, the Safe Second option is out the window, since I can't donate that, either.

I think you mean Air 2 (type) combo inflator/regulator, not safe second? I am seriously considering this DGX BCI:

DGX Gears BCI Backup Regulator

Replacing both long-hose octo and BC power-inflator, the BCI regulator allows the diver to breathe normally as from any second stage, yet the diver can simultaneously and rapidly inflate the BC, as well as deflate or orally inflate, as you would on any standard inflator mechanism.

www.divegearexpress.com

And if so, I would still be primary long hose donate but the long hose under my arm would be 40 inches, not my current 60 inches and of course no necklaced secondary being replaced by the Air 2. But, a couple of summers now ago, I ran into the brick wall reality of a substandard pancake style octopus secondary was simply not up to the task (Oceanic pancake octopus) of supplying me air under duress and strenuous conditions. Therefore I am dubous of the Air 2 (type) combo regs as well for the same reason. But still considering it.

OP, sorry, off subject, blame me, but I think if you are still around your questions have been answered by one of us?