100 yd shooting tunnel

The tunnel

Hi Guys,
About 8 years ago I visited a ranch in outback Australia. It wasn't that far from the opal mining town of Cooberpedy. There was no mine there but the rock strata was the same. The owner Morry Wilkes tunnelled into a hill. Put a large exhaust fan from a mine behind the target which was turned off when shooting. It also had a shutter over the hole to keep stuff from coming in.

There was about thirty feet of rock on three sides of the tunnel and the bench was about 40 feet inside the opening. Irrespective of the time of year it was 70f in there. A bank of fluorescent lights illuminated the target. He rode a push bike out to the target. With the fan turned off after the fumes were extracted those flags didn't move. If there was any mirage I couldn't see it very well. He wasn't a bench rest shooter he just wanted a good place to sight in his rifles.

Andy.
 
Appendix E in "Rifle Accuracy Facts" by Harold Vaughn is about a shooting tunnel he built. Well worth reading.

I would think that having insulation on the outside of the tunnel would help to reduce the mirage. Building one out of concrete pipe with 4 to 6" of direct burial rated foam insulation on the outside of it might work. (I have that kind of foam around the edges and under the outer 4' of my shop floor.) The idea of the insulation on the tunnel being to have the floor, walls, and ceiling at air temperature. If it was going to be heated it would have to have the heat on 24/7.
I suspect the reason the Houston Wearhouse worked so well was it's size.

Fitch
 
The fire that they had at Nosler bullets that burned the plant up started In the under ground tunnel. One of the employees didn't turn on the exhaust fan. Max
 
The tunnel that Vaughn built was on top of the ground but covered with dirt which I think has significant advantages over one built underground. Under ground would have a lot of issues to deal with - drainage being one, collection of heavier than air gasses (like propane) being another.

Fitch
 
Gentlemen let us not forget the arched path to the target will require a little more height then what some things might allow.
 
Vern said:
Gentlemen let us not forget the arched path to the target will require a little more height then what some things might allow.
Click to expand...

100 yards? Not much arc except for a slingshot. Probably 3" max from muzzle to top of trajectory. I think there are problems with tunnels smaller than 4' or so in diameter related to interaction between the bullet and the tunnel, but trajectory isn't an issue for any practical tunnel and rifle cartridges.

Fitch
 
Fitch the comment was mainly intended for the one who was thinking about using tires but still something for all to think about.
 
Al

They are pretty cheap if you look around. Just ask for "no longer certifiable" boxs. We batted the idea around last year down by the coast (i have an excavator) but drainage was a huge issue, figured i would come back to it flooded. If you get serious, let me know, Ill come up and give you a hand on a weekend.

Ethan
 
Well, I've got the perfect spot. I've designed two concrete underground ranges and I work with drainage issues every day.

I'll start looking.
 
Pete Wass: Franklin Mann in his book "The bullet's flight" show's a tunnel like that.
 
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