Can we discuss mid-barrel tuners yet?

Mike

Contrary to what many believe, shooting a Rail Gun is not as easy as one might think at first glance. There are all sorts of avenues for weird vibrations to be set up. Since the demands placed upon the Rifle and the shooter are so great, (the aggs can get REALLY small), you have be very careful the way you handle the Gun.
My idea behind this mid barrel "device' is to interupt any induced vibrations, such as those produced when the top goes against the stop. Also, I am attempting to "tame the barrel' when shooting really fast.
I have no theory on this. The "device" is machined from a very hard rubber like material that we use to make small rudder bushings. It is very 'dead", if you know what I mean. It is bored to fit tyhe barrel very close, and lightly clamped with a split and three 10-32 Allen Head Capscrews.
the fact that my Rail Gun shot quite well last week end says something, but then, it always shoots pretty good........jackie
 
jackie schmidt said:
Contrary to what many believe, shooting a Rail Gun is not as easy as one might think at first glance. There are all sorts of avenues for weird vibrations to be set up. Since the demands placed upon the Rifle and the shooter are so great, (the aggs can get REALLY small), you have be very careful the way you handle the Gun.
My idea behind this mid barrel "device' is to interupt any induced vibrations, such as those produced when the top goes against the stop. Also, I am attempting to "tame the barrel' when shooting really fast.
I have no theory on this. The "device" is machined from a very hard rubber like material that we use to make small rudder bushings. It is very 'dead", if you know what I mean. It is bored to fit tyhe barrel very close, and lightly clamped with a split and three 10-32 Allen Head Capscrews.
the fact that my Rail Gun shot quite well last week end says something, but then, it always shoots pretty good........jackie
Click to expand...

Jackie, it seems that with my gun the accuracy node is very wide and forgiving. I think this is attributable to likely more than any one thing alone. That said, I think that it got better in that respect with the ring. Would you say the same is true in your gun? I hope to find out that the accuracy node per se, is consistantly wider in most any gun using a mid barrel tuner. Hopefully Al will have some good info for us on this later but I believe that the muzzle will be more "still"(ha ha) with it and this may well explain the wide tuning window. It may then come down to weight and placement to precisely tune a barrel to a wide range of loads. Hopefully.---Mike
 
Mike

Since I installed that thing just the week end before the Gulf Coast Region Championship. I did not have time to play around with it. What I will do the next time I have it at the range is slide it to different positions, and see if I can tell any difference.
This is a tall order. The Rail Gun will shoot 5-shot "zeros", and 10- shot mid ones with this particular barrel. I don't know if I can ascertain any improvement. In all honesty, I doubt the rest of the combination is capable of producing groups much better.
Besides, with the accuracy that one can achieve with a good Rail Gun, (when sitting down and taking ones time), the increments of improvement can be so small as to be barely noticed.
In short, the Rail Shoots pretty good with the "thing" on there, so I will probably keep it there.......jackie
 
Varmint Al said:
Here are the results of the Keyboard Expert shooting the FEA model of Esten's 6PPC Rifle in a Digital Tunnel with Zero Wind and the scope Numerically Locked with a Perfect Hold. The Forced Deformations were calculated and the Projection of the Muzzle is shown with the Bare Barrel compared to the same barrel with a 3.46 oz Brass Mid-Weight attached. For this study, no powder was burned, no fumes were created, no lead pollution was caused, and no animals were harmed in any way. Puns intended. Some of us need to have fun sometimes.

esten-rifle-midring.png

Here is a picture of the FEA model with the Brass Mid-Weight bonded to the barrel with the front face of the Mid-Weight 6.5" behind the muzzle. A muzzle velocity of 3350 fps was selected for the calculation.

midring.png

The Muzzle Projection Curve shows the bullet exits near the peak in the curve, but the peak has a lower amplitude than with the bare barrel. The high frequency jitter on the MPC results from the gas pressure traveling up the barrel in 1/4" increments. I have talked to Esten about this and it effect. He said that since he can hit tune points in moving his tuner a small incremental amount, the high frequency is actually present in a "Real Rifle". For the Mid-Weight, the calculation shows that the bullet exit time is NOT at an UPWARD SLOPE of the MPC. This configuration appears to not compensate for small variations in muzzle velocity.

BTW, if anyone is interested in doing FEA calculations on other variations, I will happily give them the input file for Esten's Rifle. There is a free (one month) Demo Version of the LS-DYNA software at: http://www.lstc.com
They also give classes in how to use the software and how to interpret the results. But, I have to admit, it is not an easy liberal arts course.

Good Hunting... from Keyboard Expert Varmint Al
coyotel.gif
Click to expand...

Thank you Al! Would I be correct in saying that the muzzle has about 25% less movement with the ring than without it?---Mike
 
Al

If at all possible, could you, instead of using a brass ring, substitue a piece of material that has no vibration characteristics, or in lay terms, is "dead", such as I have on my Rail Guns Barrel .
Also, without the piece in place, you can tap the barrel, and it still has a certain "ring" to it, even though it is mounted in a non-metalic isolator sleeve. (How's that for describing a nylon bushing).:D When I place the ring on the barrel, 1/2 way between the muzzle and the barrel block, it looses the majority of this "resonance".
Anything to this, or am I just full of it??:cool:.........jackie
 
Amplitude

For the short BR game, it would seem to me that reducing the maximum amplitude would be worthwhile. How much weight and or position change would be projected to reduce it by half?
 
Jerry H said:
For the short BR game, it would seem to me that reducing the maximum amplitude would be worthwhile. How much weight and or position change would be projected to reduce it by half?
Click to expand...

I simply don't know,yet. Hopefully we are on the path to answering that very question.---Mike
 
Jackie, MWezel

How did you attach the mid barrel weight..? Press fit, glue or screws..
How does the nylon mid-barrel bushing compare in weight to brass..?
If brass, and nylon both dampen barrel vibration, and weight is not critical, could a hydraulic (liquid filled collar) improve dampening..?
 
eww1350 said:
How did you attach the mid barrel weight..? Press fit, glue or screws..
How does the nylon mid-barrel bushing compare in weight to brass..?
If brass, and nylon both dampen barrel vibration, and weight is not critical, could a hydraulic (liquid filled collar) improve dampening..?
Click to expand...

I cut the i.d. of the ring with a taper that matches that of my barrel and simply slid it on. As I said before, I really expected it to fall off after a few shots like this but that was about 500 rounds ago without any problem with it trying to shoot loose. I just wanted to see what it did to my groups and immediately saw them get smaller so I've left it alone. I would like to think that you may be on to something with the idea of a fluid filled dampener. I think that length and placement will make a difference. I'll do some testing with it in the next few days.---Mike Ezell
 
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