My Condor Builds

[dyotat100]

I was asked to start a topic on my condors.

I have .25, .257, and .308. All use TJ barrel liners.

.25 has a 24" TJ .25 auto barrel with 1:14 twist. It is set up with a modified etac-reg with a large chamber on a 62 ci tank.  Reg is set at 1800 psi and it gets 100+ shots starting in the 930's and ending in the 920's. I can change the TH setting with a shim and get anywhere from 890 to 960 fps.
Shroud is all aluminum and is 5 pieces that all screws together.




.257 has a 32" 1:14 TJ barrel. It runs one of my custom .257 valves in a tank adapter(etac but I make my own) in a 62 ci tank. .257 and .308 use a hammer cooking setup were the hammer clocks the gun instead of the breech.  Hammer is barrel riding and 150 gram. Breech is aluminum and is just a open and shut to load. Aluminum doesn't work on the breech if you have to cook the gun with it but works great now that there is no load on it. Shroud is same as .25 but just longer for the longer barrel. Here is some numbers

3300 psi fill gets shots in the 1080's with 74 gr lyman. With 102 gr slugs it is in the 960's.
3950 psi fill gets shots in the 1140's with 74 gr lyman. I got 1060's with 93 gr.  I didn't shoot the 102 gr on 3950 because all my tanks were low.




.308 has a custom 32" 4 groove 1:14 that I had made. It uses my custom .308 valve in a tank adapter in a 62 ci tank. Runs a barrel riding 150 gram hammer also. Right now I haven't made a shroud for it yet.

3300 psi gets 980's with 118 gr and 158 gr goes right around 900 fps. 171 gr are in the 880's.
4000 psi bumps things up a bit. 118 gr go in the 1040's
158 gr are in the up 950's.
171 gr is right around 930 fps.





I have to change my hammer springs to get back my bell curve on both guns. The .257 at one time would get 5 shots
1066 1070 1072 1065 1062 on 3300 psi.  On the HPA tank I can get a curve and was surprised how it was shooting during the crony testing.

I took all 3 out today to do a little shooting. .25 was struggling in the wind but was still able to hit a couple golf balls at 110 yds.

.257 shined in the wind. I was drilling the golf balls at 110 yds.  .308 needs a muzzle brake to calm the beast. It does great but it is a monster. I have a muzzle break that I will put on until l do a shroud.

Here is the one golf ball that I stuck in a fitting and couldn't go anywhere. This was shot standing shooting off a high table at 110 yds.

[dyotat100]

Here is the .257 build link.
http://talonairgun.com/forum/viewtopic.php?f=11&t=24826

Here is the .308 build link.
http://talonairgun.com/forum/viewtopic.php?f=11&t=21357

[CarsonRatSniper]

Is your # still the same as last year?

How about the same design setup as your .308 but with the .25 ACP barrel for shooting 52 grain slugs around 80-90 ft lbs?
I would need the last 4" of the muzzle turned to exactly .437" (unless you're aleady using that barrel diameter) - I have a 1.5" x 13" long Titanium Clague I could put on it........

Let me know....

[dyotat100]

Yes same number.  Why do you want it to shoot so slow? 900 fps is 93 fpe.

With my valve it could do 1050 fps at least.

[rsterne]

Very nice guns and impressive performance..... I'm still interested in the pressure range used to produce given shot strings so I can get an idea of the efficiency if you have that data....

Bob

[CarsonRatSniper]

I like to stay in the 950'ish range so I don't cross into the transonic region. The ranges I shoot at even 900 is just fine.
I want a fairly high shot count at that power level.
Right now I get 10 shots within 2.5% @ 80 ft lbs. out of 290cc's.
62 ci ought to be an entire day of pesting with no need to top off or bring a pump!

I will text you tomorrow after work...

[dyotat100]

Thanks

Here is all I have. .25 shooting 63 gr and .257 shooting 74 gr



Let me know what else you need or want.

[CarsonRatSniper]

*Edit*
I didn't see the bullet weights on top.........Thanks!

[rsterne]

Thanks for that, I assume they both are running 62 CI tanks, so I'll run the numbers....

.25 cal, 6 shots, FPE = 142, 142, 139, 137, 134, 134, total is 728 FPE
Pressure drop is 3122 - 2809 = 313 psi which is 313 / 14.5 = 21.6 bar times 62 CI = 1338 CI of air total at 1 bar
Efficiency = 728 / 1338 = 0.54 FPE/CI

.257 cal, 6 shots, FPE = 191, 191, 187, 185, 184, 181, total is 952 FPE
Pressure drop is 3205 - 2860 = 345 psi which is 345 / 14.5 = 23.8 bar x 62 CI = 1475 CI total at 1 bar
Efficiency = 952 / 1475 = 0.65 FPE/CI

Appreciate the data....

Bob

[CarsonRatSniper]

Bob, on the 25 I got the following: (I may have missed the 1 BAR addition for volume and just calculated space though)

1 ci = 16.387064 cc's - so 62 ci = 1016 cc's
Efficiency = .61
26.9 BAR/CC
135.8 ft lb Avg
52 psi/shot

I bet it would run closer to 1.0 in the 80-90 ft lb range. Just a TH adjustment could take care of that.

[dyotat100]

So what is good and what is bad?

I can do the .308 if you want tomorrow.

[CarsonRatSniper]

Bob is the Master on this subject, but basically you want an efficiency factor of 1.0 or higher.
Your numbers are typical for a high power big bore that isn't tuned for a good bell curve but is tuned for maximum output - unfortunately wasting a lot of air.
You could tune it down and only lose marginal power but gain a ton more shots.
I didn't understand any of that when I first strted following Bob's posts.
Now that I do, my guns are all tuned for the best compromise of power and shot count.
I'm sure he will explain finding the 'knee' of the bell curve and tuning to just below that.
You want the valve closed by the time the pellet hits the halfway mark down the barrel. Any longer of an opening duration and you're wasting air.

You would have to adjust your top hat down maybe .005" at a time and shoot a couple of shots over the chrony.
You will see where the velocity does not drop much at first then begins to drop suddenly - that is the 'knee'.
You want the gun tuned at or just below this point for maximum efficiency.

If your throughput in the top hat matches the bore diameter it will make it even easier.

[dyotat100]

I can get a bell curve. I just haven't adjusted to the new hammers in .257 and .308. I will have to change out the hammer springs in both. The .257 use to get a good curve. If I go up to 3600 psi I can get a good curve right now.

.25 numbers are from my .25 when it had a 24" LW barrel in it with my one off valve. That valve at one time did over 1000 fps with 70.5 gr. Yes the stem bore is .250" also. .257 is .280"

[CarsonRatSniper]

Upping the fill pressure to get a curve shows there is too much hammer spring (as you already stated).
I am using an 82 gram hammer I made in my 25 Challenger with a 10# hammer spring.
The only way I can tune my gun is by adjusting the hammer spring preload using my rear velocity adjuster.
The heavy hammer gives me a longer dwell = longer valve opening duration.
That is all I can readily control.

You on the other hand can control hammer spring preload just like me BUT you can also adjust how far the valve actually opens. That is something I really like about the Condors.
Hammer weight/spring preload can control duration (time on target). The heavier the hammer the longer (in milliseconds) it takes to reverse direction.
Top hat controls how far the valve opens - either adjust the top hat itself or add shims in the form of o rings or teflon washers behind it.

Because you can adjust those components you have way more control over tuning your rifles than I do.

I would love to have one of those to tinker with! 

[rsterne]

If you have the ability to raise your fill pressure safely, then that is the easiest way to get a good bell-curve.... HOWEVER, 62 CI tanks are usually rated at 3000 psi.... If that is the case WHAT are you doing filling them to 3600.... or as in your original post, 4000 psi .... Enlarged from your posted photo....



The GTA cannot condone these sort of practices, it is only a matter of time before somebody reading a thread that suggests it gets maimed or killed.... BTW, I noticed that in your build threads you talk about using Helium.... I assume the numbers you gave above were on air?....

Bob

[dyotat100]

That is my regulated .25 setup.

I haven't shot the .257 on helium yet. .308 did over 400 fpe on 3000 psi of helium in the very early stages of my valve. It should do over 500 fpe now.


I have a 70 ci 4500 psi bottle I use.  The highest I fill is 3300 on the 3000 psi bottles.



I'm in the process of figuring out a 45 ci 4500 psi bottle setup with a small chamber. They are to short so I'm going to build a 2" OD × 3" long chamber to add more volume and length. Bottle will be offset on the chamber to drop the bottle down.

I'm going to build a 1:10  7 mm and it will be a 4000 psi gun.

[rsterne]

All the photos you have above show the same tanks, a 62 CI, which is 3000 psi.... A 10% overfill is not recommended, the 3000 psi stamped on the tank is there for a reason.... it is the Maximum Safe Working Pressure (MSWP).... I assume the strings you posted were with those tanks, if you were using a 70 CI tank, then the efficiency calculations I did were 13% better than you actually got if you used the larger tank.... CarsonRatSniper's comment about 1.0 FPE/CI being "OK" is about right for a .25 to .30 cal that is shooting a proper bell-curve with a 4% ES (ie starting about 4% below peak and ending there), but not stellar performance by any means.... The kind of numbers you have (~0.6 FPE/CI) are about what I would expect for a gun tuned as per your strings, where you are basically getting a few shots right at the top of the curve, the first two being equal in velocity.... I've certainly seen Big Bores with a lot worse efficiency, my DAQ .308 Exile only got 3 shots as delivered, 186 FPE (118 gr.) at 0.38 FPE/CI.... With just a simple reduction in hammer spring it now gets twice the shots at a higher average velocity at 0.88 FPE/CI from a 3200 psi fill....

I've never used Helium, always been curious about it, and realize it's in a class of it's own FPE-wise.... What wall thickness and material are you building your pre-chamber from?....

Bob

[dyotat100]

I never leave a tank with more than 3000 psi in it. 

Shot strings were done with 62 ci.


Chamber will probably be out of 1144 shock proof.  Has a strength of 125,000 psi. Comes in bar and I will bore it.  Would have  .120" thick walls and OF would be 2"

I also have 7075 aluminum bar but I have to look up the strength. What material would you use for a chamber good for 4500 psi?

[rsterne]

My info on 1144 is 108K yield and 125K tensile, but even at the lower figure, at 4500 psi the safety margin is ample at 3.3:1 for a 2" OD with a 0.120" wall.... My usual choice is normallized CrMoly, but at 63K yield and 97K burst it would require a thicker wall to have sufficient safety margin at yield, although at burst it would be nearly 3:1.... You can use 7075 with sufficient wall thickness, but I don't have the data for that.... Lloyd Sikes would be the guy to ask, you can pm him at lloyd-ss here on the GTA.... I guess the nice thing about boring a piece of bar stock is that you can machine in one end and not have to install a plug with fittings, O-rings, etc....

You might want to check out the "Geek Gate" as we call it here on the GTA.... http://www.gatewaytoairguns.org/GTA/index.php?board=164.0

Bob

[zerodrop]

is there a smith that will build that .257 .
those numbers are amazing, think id buy one if they came stock like that....would make an amazing coyote rifle round here