.458 big bore mule test bed project (video added)

[lloyd-ss]

This is the start of a thread about my big bore mule test bed.  It's been around for a long time, in a lot of configurations, and done a lot of things.  I just put a  .458 barrel on it, but its had everything from .25 to .510 on it . The hope is to optimize that barrel and bullets for this gun.  It's a process i have never really been through, and it will take a while.
This first entry will just have some basic info.

The barrel, which is actually a chrome moly barrel liner from Mike Sayers,  is .458 groove dia, .450 land dia, 5 grooves, .065 land width, .220 groove width,    1 in 18 twist, 36" long. It's O.D. is 5/8", and it is sleeved and tensioned in a 1" O.D x 3/4" I.D. aluminum tube.

To begin establishing some sort of baseline, I took a number of low pressure, low power shots across the chrony to get a feel for where the gun was at.  That data will be forth coming.

I then took 4 low powered shots with 143 gn .457 dia round balls at a cardboard box set at 38 yards. All the round balls measured .457 on the average, but were terribly egg-shaped from .453 dia to .460.  I'm sure that did not help accuracy.  The target is a cheesy setup because I didn't think it was going to be a keeper.  The shots were all done at 1200 psi, the dwell time was set fairly low to hold the velocity to about  650 fps.   The 4 shot group measured 1.50" C to C, so there is lots of room for improvement, but not terrible for a first time out.

More to come.
Lloyd

38 yd target. Lots of room for improvement.


Backside of the same target to get a better idea of the group.


The mule with the 36" .458 barrel. She's all business, and had a rough life.
6X A.O. Leapers Bug Buster.  279cc tank


The brains

[Guam Airgun Shooter]

Nice work, gratz. Whats next? larger air res? higher operating pressures? keep them coming.

[rsterne]

I will be following the thread with interest.... Lloyd has recently prodded me into considering a .458 barrel for my Hayabusa project eventually....

Bob

[dk1677]

Looking good Lloyd!

[melloroadman]

Lloyd so I have a clear understanding and can follow this correctly . Can you give some more info on the rifle . From what you have said I believe the psi can be set electronically . And the dwell on the valve as well . Is the dwell time totally capable of not being affected by the weight or friction increase or decrease of the bullet ? Is it capable of measuring the consumed amount of air per shot as well?Also is there any control over the port size or is it fixed ? Marvin

[lloyd-ss]

Marvin,
Wow, you want me to give away the farm.  LOL, just joking.  Please ask away and I'll say what I can and let you know what I can't say. And what I am saying applies only to what I am working with right now.  This thing has been through all sorts of changes, back and forth, some good, some bad, and some very task specific.

In the configuration I have set up now, the tank pressure dumps directly thru the transfer port to the back of the bullet.  There is no regulator to vary that pressure, and doesn't really need to be.  That way you can run the tank from full pressure all the way to below 800 psi.  There is a pressure transducer in the tank that monitors the pressure with a resolution of one psi and an accuracy of maybe 2 or 3 psi.  The trigger is electronic, and the force is adjustable from a gnats breath to too hard to fire. The valve is dwell is electronically controlled and can either be set to a specific value by the user, or it can adjust automatically within the programming with the varying tank pressure to maintain a  constant energy output.   The weight of the bullet has to be know, too, for the proper amount of air to be metered.   Think of big cams and carburetors vs EFI and variable spark control. Its a new application of what is now standard technology.

The valve and transfer port I have in it right now are for the big booms, but it is also controllable on the low end. The transfer port is a full .500 I.D.  to work well with the big calibers.   A couple of last thing that folks keep bringing up in various places and guessing erroneously about: 1) This is totally different from the Daystate controls.  Daystate has a beautiful system that uses a solenoind driven hammer to strike a relatively conventional knock-open valve.  The coil that drives the hammer is big and is probably good for maybe 75 fpe, not an absurd amount more.  2)This gun has no hammer at all.  Someone somewhere else was talking about hammer bounce and debounce.  Nope.

I hope to have time to post some low end numbers as a first pass with this long barrel tonight.  Might not be til tomorrow morning, though.
Lloyd

[melloroadman]

Let me restate this one . With a standard BB the valve dwell time is effected by the weight or the diameter of the bullet . Will this valve over ride these effects or can the dwell time still be affected by the bullet ?Marvin

[lloyd-ss]

The dwell time is independent and goes by the clock.
lloyd

Edit added at noon, 6/10/11   
Let me clarify a little more.  Even if a bullet were lodged in the bore, the valve would stay open for the programmed dwell time, whether air was flowing past it or not.
Lloyd

[Rescue35]

Sweet set up Lloyd. Keep us updated.

[cfxlongshot]

Is it me or does everyone have to pull out a machinists dictionary when Mellroadman and lloyd get to talking?  LOL!!!

[lloyd-ss]

Here's the first set of data to take a look at.  I had my laptop hooked up to the gun to record the various outputs.  The pressure transducer is very nice because it allows you to see exactly how the air is being used and then to calculate the efficiencies and other characteristics.

Please note that for this series of shots, I put a wooden plug in the reservoir to cut the tank volume down to 95cc.
That is smaller than the tank on a disco, and I wanted to see where it ran out of air.  

All these shots were made at a very low 1100 psi +/-, and I added whatever air I needed to between shots.  Just feeling it out and looking at the bottom end performance with the undersize tank.  I started with the dwell very low, and ramped it up to shot 7, and  then shots 8,9, and 10 were all at the same dwell.  (dwell times are relative, with 'a' being shorter than 'b', etc.) You  can see it running out of breath at the higher settings with the tiny 95cc tank.  Also, in shot 8, you can see the serious blow-by from the undersize round balls. Similar situation with shot 8 and 9. I calculated the efficiencies two different popular ways.  In the first column, a bigger number is better, and in the second, a smaller number is better.

The 143 gn shots were .457 round ball, 170 gn was an Air Venturi lead HP, and the 405gn was a 45-70 RN-FP lead.  The bore on this barrel is about .458, and I feel that that everything I currently have to shoot is too small in dia.  I will remedy that.  Also, at these low pressures, I feel the barrel length is too long, and has not come into its real performance zone yet.
Just for comparison, I put a column at the end that calculates how much air would have been used if this setup had a 500 cc tank.

For a first pass with a 95cc tank, and undersize bullets, pretty decent, I think.  260fpe at 1100psi seems ok. I have to get to the dive shop and get my tanks filled.
Lloyd


Low pressure try-out.
This shows the versatility of adjusting the valve dwell.
Notes-
Undersize ammo and tiny 95cc tank.
This shot string  shows how increasing the dwell time with each shot increased the power level of each shot.
  The power level was basically manually,"dialed in," by adjusting the dwell in the electronics.
The last 3 shots were all taken at the same, higher dwell setting. You can tell that by the air usage.
The 143 gn round ball is undersize for the barrel and air leakage might keep it from going any faster.


edited 6-11-12- added more notes to pic. lloyd

[Rescue35]

Wow! Those are some very respectable numbers. Especially since you are starting at such a low PSI. I can't wait to see what happens once you have a full tank.

[lloyd-ss]

Wow! Those are some very respectable numbers. Especially since you are starting at such a low PSI. I can't wait to see what happens once you have a full tank.

Rescue,
I am hoping to get some decent shot string, too.
Lloyd

[lloyd-ss]

Here's some fresh data using 2500 psi.

Most of the shots are with 230 gn bullets, but I also have a couple of 170 gn and 400 gn shots in there too.
I'm still playing with the dwell times.  You can see how the air usage starts to climb pretty rapidly as the high end of the power levels are approached.

Shots 1, 2, and 3 are pretty efficient with the air usage.  Most of the other shots use a  lot more air for the amount of gain you in power you get.
But, if you are a power freak, you gotta love shots 9 and 10.



I'll have a shot string to post in the next several days as I work more with this set-up.  3500 psi is coming eventually.  

Lloyd

[dpricenator]

WOW, is all I have to say about this thread.  I have no idea of what you are talking about except that 500+ FPE is over kill for a squirrel or bunny.  That gun looks bad A, but I would need to go back to school to understand how to use it effectively.  Can I get a dummy proof big bore? 

[jetmangd]

LLoyd-SS,
              Super impressive Self Engineered Air Rifle you are in the process of developing there LLoyd. The Test figures are
              Quite Respectful with some very solid Performance. Wow, 525 FPE with a 404 Grain Projectile Traveling at 765 FPS.
              That is Amazing LLoyd, No Doubt you are quite an Engineer and Designer. It is also so Cool to be able to follow your
              Progression on this thread. Wow, Again and Keep up the astonishing work and developments.



                                                                             Jetman.
           

[lloyd-ss]

Thanks guys, glad you are enjoying the info.  I am doing some more work with it and hope to get a video of it this weekend.
I also plan on having it up  a full load of 3500psi.
Lloyd

[lloyd-ss]

Finally, some high pressure shots!
Its a shame when work and other things in life get in the way of your airgunning habit.   I finally have had some time to work on this project some more and made a few changes and fixed a few things.  It still has the same basic arrangement with the 36" long .458 barrel with 5 grooves and narrow rifling.  I improved the sealing on the breech block and worked on the barrel some. 

One thing I have been experimenting with is reservoir size, because my valve allows air flow directly from the reservoir without going through a pre-valve holding chamber.  I put the plug back in the reservoir to cut the volume from 279cc down to 105cc.  The gun uses fewer bar-cc/fpe than with the bigger reservoir. It sounds counter-intuitive, but I checked it many ways and that's the case.  I wonder if a partition with a tiny hole in it, put into some of the big air-hungry guns might do anything good?

So these are just a few shots taken with the 105 cc reservoir.  I had to hand pump from 2300 to 3600 psi so I don't have too many at the real high pressure.  But I like the results!


This table shows 9 shots where the valve dwell times for the shots were varied to get different velocities.
The reservoir was refilled as needed.
Max power was the goal with shots 5, 6, 8, and 9.
The far left column shows the equivalent air usage (in psi per shot) if it had a 500cc tank.





Chart 1 shows what's happening in the barrel during shot number 9.
There are 2 vertical scales and they might be a little confusing.
It shows barrel PSI and FPS  on the right hand vertical scale (blue and green lines)
and it shows FPE on the left hand vertical scale ( red line).
The scale along the bottom is the bullet travel in the barrel in inches.





Chart 2 shows what's happening in the barrel during the same shot number 9.
It shows FPS again on the right hand vertical scale (green line).
It shows the bullet acceleration in g's inside the barrel on the left hand vertical scale (purple line).





Chart 3 shows what's happening in the barrel during shot number 1.
It shows barrel PSI and FPS  on the right hand vertical scale (blue and green lines)
and it shows FPE on the left hand vertical scale ( red line).





Chart 4 shows what's happening in the barrel during the same shot number 1.
It shows FPS again on the right hand vertical scale (green line).
It shows the bullet acceleration in g's inside the barrel on the left hand vertical scale (purple line).





Even though both bullets leave the barrel at approximately the same velocity, the graphs have a lot of information
about what is happening differently in the barrel for each shot.  Little bumps and humps and such. 
You can see how the valve has to close a lot
later for the 405 gn bullet for it to get the same velocity as the 230 gn bullet.

I think the graphs are pretty cool.  I hope you enjoy them.

Lloyd

[melloroadman]

Interesting for sure . I have a mind like yours so bare with me .  How is this being calculated ? Sensor at points in the barrel ? And is there a way to covert the G forces if that is the proper term or a term I can use to psi ?Marvin

[rsterne]

Lloyd.... There is sure a wealth of information in those graphs.... and over 700 FPE.... all I can say is WOW !!!

Crazy that the gun is more efficient with the smaller reservoir volume.... I sure wish I could understand WHY that is happening....

Bob