I live in Kentucky and the Fish and Wildlife people have many public ranges throughout the state. Its nice and free and no range officers but-- they have these used sewer pipes that you are required to shoot through. I guess its a safety issue but I have a question. Does anyone here have any experience shooting through pipes? By the way these pipes are about 30 feet long and allow you to shoot 25 35 50 and 100 yds. They also have a slanted steel piece extending down a little on the top end of the tube so as to deflect any skyward shots so you have about a foot and three quarter to shoot through. I get good groups out to 100 yds with say a 223 or 3006 but heres the problem. Low velosity loads like a pc9 9ml subsonic loads seem to vary. If I set a few targets up and down a 2 and a half footpiece of cardboard the top target groups group high while the lower targets group low. This is the old Ruger 9ml rifle not a pistol on a bench rest. at 50 yds. I finally got a good group by aiming at the same target at the same low side of the cardboard. Will the blast gasses beat the bullet on a subsonic load? any suggestions?

Maybe the lighting inside the tube is screwing you up and you can't see very well? I doubt the expansion gases are the problem. The bullet has mass; the gases have very little mass and will negatively accelerate far faster than the bullet. How do you stabilize the gun? Is the pistol shot from a rest or offhand? Maybe you can try some handloaded ammo so you know what you have...

Ranges with these safety limiters are more common these days. I shoot at a Missouri Conservation Dept Range near Kansas City, that is limited to 100 yards. There are large composite walls downrange, suspended over the shooting lanes, so that a skyward shot will hit the wall (this is necessary because of the massive overdevelopment of the area around the range and north of the city). Because of this "armor-piercing" and ammo that "contains steel" is prohibited; so much for surplus rifle ammo. Oh, as usual, they also prohibit human silhouette targets and anything oval-shaped. At least it's a place to shoot, for $3 an hour. At least I don't have to shoot through pipes.

Back in the early 1960's, the US Air Force Rifle Team at Lackland AFB, Texas, tried such tubes for testing rifles for accuracy. They were too small and accuracy wasn't good. Same rifles and ammo used on 100 yard outdoor ranges did great. So they stopped testing in their tube.

Some years ago, I had use of a friends 100 yard underground range. Built with concrete blocks, it used a 5-foot diameter tube with a track for the target carrier to ride on. The chronograph room in front of the shooting room was 15 feet long, 8 feet wide and 8 feet tall. No muzzle blast effect on accuracy could be seen. The huge volume of space in the chronograph room was probably why. Neat place to shoot on cold December nights.

Our club has a 100-yard long 5-foot sewer pipe for an underground range. It has pre-set target stops with lights at 50 feet, 25 yards, 40 yards, 50 yards and 100 yards. An electric motor runs the target carrier with automatic stops and return. The concrete bench is set up a few feet from the mouth of the sewer pipe. It works very well, but the high speed exhaust fans can affect small bore bullets at the 100 yard range setting. The shooting room itself is pretty large - probably 400 square feet or so.

The problem I found with pipes was that after a few rounds there was turbulence in the pipe .This bent the light waves so the accuracy dropped.Just like the shimmering effect you get on a hot day with heat coming off the ground.

I would think any low volume fan on the target end pulling air through the pipe would be helpful to remove powder fumes and turbulence.

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100 yard underground range.

One of these in Martinsburg, WV at a place called Sharp's, or something like that. Right off I-81 at Exit 12, just south of the exit...