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PostPosted: Fri Mar 16, 2018 9:55 pm 
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Location: 1/2 Way From Ottawa and Montreal,
I wish I had half your talent
and understanding.

I read all your post.

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Custom Design by ME PCP/HPA Air Carbine 10-50X60 Scope My 2018 FT Open


Last edited by FRANK on Fri Mar 16, 2018 11:32 pm, edited 1 time in total.

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PostPosted: Fri Mar 16, 2018 10:37 pm 
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You're far too serious, Bob. Lets face it - what we really want to know, since we're talking 6mm, is what happens when you load them with an airsoft BB. :shock: :lol:

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Daisy 953 * QB78D * Walther 1894 * Beretta CX4 & PX4 * Zoraki HP01 * Beeman P17 * Walther CP88 Comp. * Crosman 1377/2240/SA6/357-8
Swiss Arms P92 * Colt Commander 1911 * Walther PPK * P08 * Colt Python 357 * TW 1911/Limited * S&W M&P R8


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PostPosted: Fri Mar 16, 2018 11:12 pm 
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Yeah, I wondered about that.... Unfortunately, the airsoft BBs I have here are too small, and roll right down the pipe and across the floor.... :?

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Fri Mar 16, 2018 11:23 pm 
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rsterne wrote:
Yeah, I wondered about that.... Unfortunately, the airsoft BBs I have here are too small, and roll right down the pipe and across the floor.... :?

Bob

I just knew I wasn't the only one thinking this... like every time I read the 'subject' line of this thread.

I know nothing about airsoft, but I imagine all the BBs are the same size (but different weights). Hmm. Maybe a thin patch with the BB loaded from he muzzle end like a muzzleloader. Or place the target at a higher height so the gun is tilted up. Gad! I'm glad I'm not capable of doing the work you do - I'd be a danger to more than just myself. :roll:

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Daisy 953 * QB78D * Walther 1894 * Beretta CX4 & PX4 * Zoraki HP01 * Beeman P17 * Walther CP88 Comp. * Crosman 1377/2240/SA6/357-8
Swiss Arms P92 * Colt Commander 1911 * Walther PPK * P08 * Colt Python 357 * TW 1911/Limited * S&W M&P R8


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PostPosted: Fri Mar 16, 2018 11:33 pm 
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https://www.amazon.ca/Crosman-AirSoft-B ... B003QNELYE

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PostPosted: Sat Mar 17, 2018 11:05 am 
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FRANK, is the purpose of your link to tell me that those Airsoft BB's won't roll through a barrel measuring 0.236" land ad 0.243" groove ?....

lleader, I actually shot a tinfoil wrapped Airsoft from my 100 FPE .25 cal Disco, with no other changes.... and hit over 1750 fps....

http://airgunguild.com/ask-bob/1752-fps ... cal-disco/

Accuracy about 3" groups at 20 feet.... and LOUD !!!

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sat Mar 17, 2018 3:17 pm 
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Remember what I said about two steps forward, one step back?.... Well the all MDS hammer I made is too light to deliver maximum power with the valve with the 0.047" vent through the poppet.... Even with putting in a 14 lb/in spring, at 5 lbs. preload and zero gap on the SSG, I can't quite reach the plateau with the 61 gr. bullets, and I'm down about 10% on velocity (20% in FPE) with the 74 gr.... The good thing is that the shot cycle is a nice clean SNAP (although a loud one), with NO sign of hammer bounce.... However, the large vent, which is intended to make the valve more conventional in operation by eliminating (or reducing) the "blow-open" cycle is doing exactly that.... Basically the valve is operating like a conventional valve that is easier to crack, but that's all....

I have no doubt that by making a hammer that is in between the 32 grams I have now and the 59 grams I had before (both with the 11 gram cocking handle installed) I could find, somewhere, the perfect combination.... However, although not uncomfortable by any means, the cocking force is WAY greater with the light hammer, so I think I have gone too far on the (hard to change) vent size.... Before I pull the valve and make more changes, I am going to make an MDS hammer for the unregulated gun, which is working great except for having too large a gap in the SSG (about 5/16").... The valve in that gun has the original 0.032" vent through the poppet, so has a tendency to "blow open" but it looks like a lighter hammer will drastically reduce that tendency, so it may turn out that a light hammer with the small vent is the perfect combination....

It certainly makes sense to try that before deciding how to proceed with another round of changes on the valve in the regulated gun.... especially because changing out the hammer doesn't even require degassing the gun....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sat Mar 17, 2018 4:42 pm 
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Looking forward to your results! Quite the challenge finding what works best!

Sent from my LG-H812 using Tapatalk

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PostPosted: Sat Mar 17, 2018 6:59 pm 
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I made an MDS hammer for the .257 unregulated gun, and it works perfectly.... I was able to run a bit of preload on the 11 lb/in spring and reduce the SSG gap.... and every shot was crisp with no hammer bounce.... and I was able to push the gun right up to 185-190 FPE at 3800 psi, which is more than I would ever run it because it would use too much air at that power.... I backed the power down to 950 fps with the 82.5 gr. bullet (165 FPE) and ended up with 1 lb. of preload and 8 turns of gap on the SSG, which gives me a cocking force of just 9 lbs.... If I go to the 100 gr. bullet I need to reduce the gap a couple of turns, and if I drop back to the 73.4 gr. 257420 I have to increase the gap a couple of turns to keep it under 1000 fps.... Between the easy preload adjustment and gap adjustment, I can tune the gun from a "mild" 130 FPE up to about 180 FPE before it becomes an air hog....

With the gun set for the 82.5 gr. bullets I filled it to 3850 psi (all the pressure that was in my tank), with my digital gauge connected to the gun, shut off the tank and drained the inlet side of the gauge (it has a check valve for that purpose) and shot a 5-shot string as follows....

953
948
947
935
911

The ending pressure was 3350 psi (it used exactly 100 psi per shot from the 300 cc reservoir), and the first 4 shots were within a 2% ES.... I know that at 4000 psi at this setting the velocity is slightly lower, so I will have 5-6 shots within a 2% ES when off tether with a 4K fill.... and of course tons of shot when tethered to the regulator within a few fps of 950.... The 500 psi pressure drop over the 5 shots averaging 939 fps (162 FPE) works out to an excellent 1.28 FPE/CI, which I am more than pleased with at that power with a .257....

The combination of my version of the ART/SS valve and the lightweight MDS hammer is a real winner.... The gun is easy to cock, has tons of power, and when dialed back about 5% below the maximum is also very efficient.... I am sure setting the power lower would get VERY impressive efficiency numbers, but what's the point, this is a long range Varmint gun.... This valve has the original 1/32" vent through the poppet, which I am now confident is a better choice than the 3/64" I tried in the regulated gun.... Something in between, like the 0.040" vent I tried briefly, would increase the hammer strike, but now that I know the original setup works well when used with an MDS hammer I think I will just stay with the 1/32" vent.... I would like to get a couple of 8 lb/in hammer springs and run them with more preload, so that I can reduce the SSG gap a bit more.... but for now this setup will more than do the job....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sun Mar 18, 2018 4:05 pm 
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I just tried a couple of Airsoft BBs in the 6mm at 2800 psi.... 1944 & 1963 fps.... So much for the 1650 maximum.... *LOL*.... Next time I have the 6mm upper on the unregulated gun I will try a couple of shots at 3800 psi.... maybe even 4200.... :twisted:

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sun Mar 18, 2018 7:47 pm 
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rsterne wrote:
I just tried a couple of Airsoft BBs in the 6mm at 2800 psi.... 1944 & 1963 fps.... So much for the 1650 maximum.... *LOL*.... Next time I have the 6mm upper on the unregulated gun I will try a couple of shots at 3800 psi.... maybe even 4200.... :twisted:

:shock: :supz:

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Daisy 953 * QB78D * Walther 1894 * Beretta CX4 & PX4 * Zoraki HP01 * Beeman P17 * Walther CP88 Comp. * Crosman 1377/2240/SA6/357-8
Swiss Arms P92 * Colt Commander 1911 * Walther PPK * P08 * Colt Python 357 * TW 1911/Limited * S&W M&P R8


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PostPosted: Sun Mar 18, 2018 7:54 pm 
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Location: Montreal, Quebec
Really cool project. Love the use of AR15 stock and carbon fibre on the barrel.


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PostPosted: Mon Mar 19, 2018 5:53 pm 
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Location: Coalmont BC
I tried to glue up the 0.047" vent through the poppet and redrill it with no success, so today I made a new poppet for my SS Valve.... I am still using the 3/8" big end and 1/4" small end, but I added a thin (1 mm) O-ring inside against the shoulder of the poppet as a bump stop.... It should never touch, but if the valve was driven fully open (or blew fully open) the O-ring bumper would take the shock instead of either the shoulder on the poppet hitting the inside shoulder of the thimble, or the spring going coil-bound.... It was just a safety measure, but also a way to find out if the valve was opening that far.... As I expected, the O-ring made NO difference, which is proof that the valve is not trying to open more than the 0.19" travel before the O-ring hits.... This was a useful piece of information (and expected), and I plan on incorporating this feature into any future SS valves I make to insure they don't break from being overdriven, or from machine-gunning.... I used PEEK for the poppet, not because it was required, but just because I had some and wanted to try it, and it machines nicer than Delrin....

When I reassembled the 6 mm regulated gun I finally nailed it.... I used the 32 gr. MDS hammer, and the 11 lb/in spring with 1 lb. of preload on the SSG guide.... I was able to easily get to the plateau with all three bullets, and have to run 5 turns of SSG gap with the heaviest and 7 turns with the lightest to get about 3% below the plateau, where I want to operate to get reasonable efficiency.... Here is a graph of the velocity vs. SSG gap for all three bullets at 2800 psi....

Image

I am getting nearly 200 fps of adjustment before the valve falls off the cliff, which is plenty, I will never run it that low.... You will note that there is one additional line on the graph, the dotted black line.... I set the SSG gap at 6 turns, and using the 63.8 gr. bullets I tested the velocity adjuster on the back of the receiver that restricts how far the bolt retracts by moving a pin into the J-slot for the handle.... The reason for the slight increase in velocity when the adjuster is turned in 2 turns is that I had to shorten the nose of the bolt 1/16" because it was pushing the bullets too far forward, which made the 73.4 gr too hard to chamber.... This meant that with the bolt handle pulled all the way back in the J-slot it was creating more wasted volume in the chamber, behind the barrel port, which was dropping the velocity slightly.... It shows the importance of minimum wasted volume between the valve seat and the base of the bullet.... From the maximum velocity setting I have 8 turns of adjustment on the 8-32 screw, which moves the bolt nose from the back of the port to nearly obstructing it.... at which setting the velocity is below 500 fps.... The cool thing about this adjuster is that you can easily try different velocities, to find out if there is an optimum for accuracy.... Of course you should adjust the Harmonic Tuner at each velocity, just to make sure what you are seeing is a true velocity effect, not a change of accuracy due to barrel harmonics....

Once I am sure that there are no leaks, I will remove the "tiny tank" and replace it with my 500 cc CF bottle.... At that point I will be able to test the efficiency at various velocity settings.... These two guns are nearing the end of their development, which is a relief because it won't be long before the Motel gets busy and my shop time disappears once more....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Tue Mar 20, 2018 4:31 pm 
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The gun only lost about 100 psi overnight, so I figure that is "good enough" and I installed the 500 cc CF tank today, and attached the AR style stock.... Here is what it looks like....

Image

As shown it weighs 8.5 lbs., and without the Harmonic Tuner, exactly 8 lbs.... It balances right in the middle of the tank.... I'm very pleased with the way it came out....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Fri Mar 23, 2018 3:59 pm 
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Location: Coalmont BC
Well the 6 mm regulated gun has been sitting with the 500 cc bottle on it for a few days, and shows no visible drop in pressure after the initial post-fill cooling.... I topped it up from my SCBA tank, with the digital gauge in between, shut off and bled the tank valve, leaving the digital gauge connected to the gun with a microbore hose (there is a check valve on the "inlet" side of the gauge for this purpose).... I took a couple of shots until I noticed the digits dropping on the gauge, so I knew it was accurately reading the pressure in the 500 cc CF bottle, let it stabilize a couple of minutes, recorded the pressure, and shot 10 shots through the Chrony with the 63.8 gr. bullets, with the SSG gap set at 7 turns.... I recorded the average velocity (939 fps), the ES (11 fps) and the SD (2.8 ), and after a couple of minutes for the pressure to stabilize again (it rises slightly after the string as the tank warms back up to room temp) I recorded the pressure again.... The tank dropped 465 psi for the 10 shots (which averaged 124.9 FPE), which means I used 978 std. CI of air to produce 1249 FPE, which works out to 1.28 FPE/CI.... That should give me about 30 shots per fill (with the VanDerWaals correction), and I am very pleased with that.... I can dial the velocity up or down from there, which will lose or gain shots of course.... but I certainly have a good starting point for testing.... It shoots 982 fps with the 58.3 gr. Bowman HPs at this setting.... should be deadly on Varmints....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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