Calvin's Pro-Carbine shame spiral.

[FlightMedic938]

Calvin Are you using a Taso RVA? I noticed with one of my Taso RVAs that the adjustment range was a whole lot less than it should be because the adjuster is solid, not hollow. The spring guide is resting against the adjuster, not going inside.

What was happening was the adjuster, when adjusted too far, was pushing the guide pin out of the recess that would normally keep it secure. That caused all kinds of velocity problems. It’s like these old school RVAs were mainly designed to decrease spring tension, not increase it. The amount that it could actually increase spring tension without pushing the guide pin out is a really small amount.

Im not sure what the fix is for that to be honest.

[Calvin]

Now that I know the gun chronos more consistently with the stock adjustment screw, its a non issue for me. The gun is running great with a very light main spring, which is the key thing. Moving back to the stock back cap is just limiting complexity, which is alway a good thing. Of course, I am running the gun at high pressure. Im not sure if it behaves the same at the low pressures you are running at. Only the chrono can tell.

[Calvin]

Ok FlightMedic938.

I thought about this all day while working. What I settled on is the need to have a sliding sleeve in the back of the bolt. I used the back 6.5mm of the bolt to model a trapped inner sleeve. I used .3mm spacing between the trapped sleeve and the bottom of the inner bolt and .2mm spacing between the trapped sleeve sides and the inner bolt. These are pretty standard distances for easy release supports, so the trapped inner sleeve acts as a support while the two seperate pieces are printing.



I print these bolts with the ID a bit smaller than the drill bit I use to finish it with. That lets me use it as a mandrel to finish the outside before using the bit to finish the ID. I modelled the ID of the sleeve a smidge larger so it wouldnt bind on the bit. By the time I had the bolt finished, the sleeve went in and out with no force required and no binding.





It doesnt need an oring-like seal. It just needs to occlude that 3/32"ish gap between the back of the bolt and the front of the power tube momentarily at the full forward point in the cycle.


Newtons 1st law should make the sleeve extend as the bolt is accelerated forwards, and retract as it is blown backwards.

I will test it against the stock bolt for velocity in the morning since it is a known test control.

[FlightMedic938]

I’m having a difficult time comprehending this but it sounds very interesting. Basically it’s telescopic right? Or no? Man I hope it works because I want one

[Calvin]

Just a trapped inner sleeve. Bolt goes forward, it extends due to inertia. Bolt goes backwards, it retracts due to inertia. At the moment the bolt clears the power tube, it should still be fully extended. By the time the bolt starts going backwards, the sleeve will be going back into the bolt. The chrono will tell if it works.

[C26G]

Great work!

[Calvin]

This is the exploded view. The blue and the orange are merged back together into one piece with the sleeve printing inside it. The upper rim on the sleeve traps it inside.

[Calvin]

I decided to do the science this AM with extra science. Since I couldn't chrono outside on a Saturday (little next door neighbor kids are outside instead of in school), I decided to be extra controlled. I setup the indoor trashcan range. Instead of the usual mixed up pods of many game day's leftovers, I opened up a bag of Valken Grafitti purchased in Nov and regularly rotated through the winter. My method was 17 shots, dropping the highest and lowest shot. From that I calculated the avg FPS, and the deviation. I used the same CP .685 14" barrel, and left the velocity adjustment exactly where it had been, which is shown below:



There is still a couple turns of inward adjustment left, and alot of outward adjustment.

The results were surprising:



Stock bolt was: 302.60 FPS +/-9
New Bolt was: 283.93 FPS +/- 10
New Sleeved Bolt was: 273.66 FPS +/- 8

This jives with last weekend's use. I was running the stock bolt with the weaker silver spring, and getting 280 on the chrono in the approximate velocity adjustment position.

The sleeve is clearly detrimental, which is a bit weird. It cannot seal less well than the new bolt. It has to be some mechanical binding force that the sleeve exerts under load. Either way, I think I will use the current green spring and the new sleeveless bolt the next day I play. I will put the stock bolt and silver spring into the kit in case its needed. I would prefer to have the benefits of the detent cut and ball ramps, and the new bolt should provide that perfectly at field velocities.

edit: I already see a fuckup. Shoulda dropped 273 instead of 275 in the new bolt calculation. Oh well. I'm not a mathematician. I'm not a mechanical engineer either.

[FlightMedic938]

The bolts you created, do they have an o ring?

Very nice work your doing here Calvin! I really enjoy reading this stuff

[Calvin]

No orings. The detent cut precludes an outer one, and I dont think the an inner one would yield any benefit.

[FlightMedic938]

Maybe an O ring that’s located behind the ball latch cavity that seals in the breech could work. Or a C ring at the tip that doesn’t interfere with the latch or make one by cutting a O ring and super gluing it in a o ring groove. Or both.

You’d have partial sealing behind and in front of the latch channel

[FlightMedic938]

Calvin I was able to test the rear seal mod I did on the front bolt a minute ago. Same paint, operating pressure, and barrel. It was shooting 270-280 fps @ 550 psi with the occasional 250-260 fps shot which I just assumed was the Sidewinder breaking in.

Now it’s 290-300 fps with an occasional 310-315 fps shot. A 20-30 fps gain with an occasional hot shot. The hot shots have me confused.

I think instead of dropping the operating pressure down to get back to 270-280 fps I’m going to put in a lighter spring.

Edit- I got another real quick test in before I start adulting. I dropped the pressure to a smidge over 500psi and was getting 270-280fps but still getting an occasional hot shot of 280-293 fps (3 out of 11 shots were hot)

[Calvin]

Interesting findings. Those hotshots are an issue. My testing has led me to believe that the silver (weakest) spring and stock bolt combo is the way to go in my high pressure setup. It has proven dead reliable for me already. Thats really all I need out of the platform. I will just install a new detent every day of play so its at peak performance. I have a huge bag of em, so no loss there.

[Calvin]

I decided to try something different with the Pro Carbine, and spent the last month gathering parts. I printed a knurled sleeve to slide over the emptied out aluminum bodies of a Pop Enmey build reg that wouldn't hold air. I remounted the ASA backwards and placed the new grip there. I got a very nice High Pressure Smart Parts 4500 Max Flo on-bottle setup from mercpb, and have refurbed it. It now has a 60ci Bunker Kings tank on it. In terms of marker balance and feel, this is 10/10. The extra weight of the reg is all under your hand like a keel, and makes the whole setup very stable. Feels perfect against the shoulder too. Hoping to get to a field tomorrow to air it up and throw out some rounds from it. I already loved playing with it. If this setup holds air and works like I think it will, it will be one of my most used.

[Calvin]

The forward sweep is a more natural angle to hold with the off hand. Just feels right.

[FlightMedic938]

Looks really really good. Great job Calvin 👍

[FlightMedic938]

Calvin I just finished turning mine around reverse like you did. Kicking myself for not thinking of that.

[Calvin]

Three more weeks of failure has, I sincerely hope, yielded success.

The SP 4500 manifold mount reg was a complete bust. When I got to the field to fill the bottle and test it, I first filled it to 2800psi. The gun cycled just fine and the reg held air. I then filled it up to 4000, and it started to leak from the back of the reg. I cycled the gun a couple times, and it started leaking from the front of the reg too. I turned the air off and took it home. Inspection revealed that the piston seal oring had been blown in half. I took it apart and put in harder than spec orings in the rear plug and in the piston. Upon airing up, it blew the 90 Duro piston oring into bits. Then the on/off orings started to leak. I'm not sure why they called it the 4500, but the system sure doesn't like those pressures.

Knowing I was beaten, I pondered for a few days. I decided that I could remove the reg body from the manifold and mount it directly on an ASA under the grip using a 3/4" long steel pipe nipple. As a bonus, this would shed the chunk of metal that is the manifold. After rebuilding the reg again with spec orings I switched over to macroline to allow easier removal of the air fitting into the valve. I replaced the Chinesium 1000psi output valve onto the bottle and waited till I could get up to fill it. In the meantime, I purchased a pair of high output older series manifold mounted max-flos, and made one good one from the parts. I mounted that to the 2nd Pro-Carbine in the same manner. This weekend I finally got up to the field and got air into the tank to test with. Both markers were running robustly with the following setup:

Stock bolt
Stock Rear Cap
Lightest silver Techt mainspring
Very light spring from hardware store in valve
Power tube drilled open completely
Final version of the valve to power tube support
Cut down velocity adjuster screw with Oring on it to hold the power tube in place and seal the hole but place no constriction on air flow.

The one with a .685 16" CP barrel chronoed 280-290 at 785psi
The one with the brass .69x barrel chronoed 280-290 at 800psi

Both regs were very stable with no reg creep.

The one with the double trigger had snapped a seer spring when I used it last in May. I noticed while testing yesterday that the bolt would settle into a new position on the seer when I released the trigger after a shot. I think the TechT wide pin I was using to shorten the trigger stroke wasn't allowing the seer to engage the bolt properly. Upon coming home, I put in a new seer/spring combo from my parts stash, and moved from the middle pin I was using to the 2nd thinnest pin. That corrected the issue completely at the cost of a smidge more trigger travel.

Getting these two into exactly the kind of setup I had always wanted with one has been a crazy journey. Back in the mid 90s, I had mused that a pressure regulated Carbine would shoot better than the stock velocity screw adjusted version. There was no equipment back then that would allow me to accomplish that, and it became water under the bridge as time passed and new markers entered the collection. These two look a bit goofy with the reg by your hand, but you don't notice them at all when holding and shooting the marker. Service on the regs and the gun is also going to be much easier with this setup. Any hosing arrangement that I tried through the front ASA block was just too much of an angle and too hard to dissemble for valve removal. Now I am in the guts within 60 seconds of sitting down on the bench. With two of them, I don't anticipate ever working on one at the field. Bad happens, and the bottle moves straight to the backup marker.

Now that I have tested for reg creep and know the exact pressures involved, I plan on removing the gauges. I sure hope I have finally hit rock bottom.