DocHeb,
I am a gunowner, shooter, and an NRA certified firearms instructor. I can usually be counted on to come down on the side of a gunowner or shooter. But not in this situation. Your neighbor is putting you and your family at risk along with whoever is further downrange. I do not see this as a rural vs city issue, this is a safe vs unsafe issue.
The walls and windows of your home will not protect you and your family from a stray high power round at 350 feet.
It is unusual to shoot a high-power rifle at a target less than 100 yards away so virtually any club range which permits high-power rifles will have a 100 yard target position. (600 to 1000 yard matches test the skill of a shooter.)
You can demonstrate this if you have a friend from work who is a shooter (and a member of a safe range). Construct a mock-up of your wall, vinyl siding, 1/2 inch plywood a 2*4 sized gap filled with a matt of fiberglass and a sheet of drywall. Set the wall mock up at 100 yards. Mark a target (aim point) and place a water jug (one gal. milk jug, distilled water jug ...) or watermelon on the back side in line with the aim point. Observe from a position behind the firing line and far enough to the side to see the jug. Have your friend from work shoot at the target with a high power round (30.06 or better any of the 'belted magnums").
The jug will explode and you will not be comfortable hearing the gun shots knowing where they come from and where they are directed. From your profession I am guessing that you will be able to interpret what you see in more depth than I am able to.
Another test is to shoot through a scrap window glass in place of the simulated wall section. The window will offer less of an obstacle than the wall section. If the bullet hits a 2*4 it may slow down and be deflected enough to miss the jug.
A one acre lot is not large enough to contain an outdoor rifle range.
There is no way that having a house 350 feet down range and 100 feet off the center-line of any rifle range is "safe".
There is no way that one (or more) bales of hay is an acceptable backstop for any firearm.
There are many issues you should be aware of. A few highlights are:
A bullet may be deflected to the side by hitting something. The thing deflecting a bullet does not have to be 'hard' Hitting a branch will deflect a bullet. The bullet is spin stabilized by the rifling in the barrel of the gun. This spin helps keep the bullet traveling in a repeatable path. The bullet may be cleanly deflected or start to tumble. The path of a tumbling bullet is harder to predict.
A bullet may hit a rock or piece of metal and ricochet. The angle of the backstop surface to the path of the bullet is critical to allow the bullet to enter the backstop berm and not ricochet.
A bullet may ricochet after hitting the ground at an oblique angle. This frequently happens with the shooter hitting the ground within 25 to 50 yards of the firing line. Think of skipping a stone across a pond. The downrange and side berms must be high enough to catch the bullets which ricochet off the ground between the shooter and the target.
A bullet may be accidentally be fired into the air by the shooter. A shooter may simply pull the trigger before he is lined up on the target, this is a common mistake for an inexperienced shooter with a light 'match' trigger Any shooter will have less control of successive shots fired in a rapid sequence. The muzzle is lifted by the recoil of the earlier shot and the shooter must force the gun back down to the target. Many ranges restrict fast fire when the backstop berm is marginal. (80 shots per hour is not rapid fire.) Overhead baffles at the firing line and several positions downrange catch (deflect in a controlled direction) shots which would otherwise pass over the top of the berm. While few ranges have overhead baffles today the development pressure are seeing in the eastern US will soon force all ranges to install berms or close.
From memory (its been a while since I studied the Range Design Handbook) a range needs a fan shaped safety zone about 1.5 miles downrange for a pistol range and 3.5 miles for a rifle range. The safety zone must be clear 20 degrees on each side or the center line in a range with side baffles and more without side baffles. Clear means without people or structures. 350 feet is practically in the firing line for a high power rifle.
Building a safe range is not a simple process. Berms are needed downrange and to the sides. Backstop berms should be a minimum of 15 feet tall with 25 feet recommended. Baffles are required to reduce the size (angle from the center line) of the downrange safety zone. Baffles to the side and overhead deflect bullets which would otherwise miss the backstop berm.
The NRA publishes a range design handbook
http://store.nrahq.org/nra/product.asp?dept%5Fid=115&pf%5Fid=AR+14860 )
For an online summery of the NRA range design criteria see http://www.rangeinfo.org has some papers on range design
There have been a message suggesting that he may have a metal plate in the straw bale. This is not necessarily sufficient. The design of a metal backstop is more difficult than just putting a metal plate in the bullets path. If the bullet huts a plate at a normal angle (90 degrees) a high power hunting round will penetrate a thick steel plate. I have seen a heavy 1/2 inch steel plate penetrated with a large hole from a 7mm Rem. Mag. bullet. This is a cartridge which would is used hunting Elk and large deer) Metal bullet traps are designed to deflect a bullet down into a sand box below the plate or through a spiral trap. In a spiral trap the bullet travels through a path like the inside of a Conch shell hitting the wall an ricocheting multiple times within the trap. The metal trap must be replaced when it becomes 'too dented to use'. Armor plate lasts longer than mild steel but costs far more. Metal traps are usually used for indoor pistol ranges.
Your neighbor expects far too much from you. Even if he could and does install side baffles to partially protect your house, he is basically making a fraction of your property unusable to you. You and your family will not even be able to build on or use the land downrange from his firing line. You can not even take a walk in your woods without confirmation that your neighbor will not come home, grab a rifle and open fire.
We have seen other threads on TBN talking about easements and neighbors. Your neighbor expects far more from you than the neighbors we have read about logging or building roads on neighbor's land.
There have been suggestions that you help your neighbor build berms. You should consult with your lawyer before you do anything that can be seen as endorsing the firing range on your property.
If I was in your situation I would talk to the neighbor and explain that he now has a neighbor and can no longer assume that your property is empty. I would insist that your neighbor bring his range up to the NRA range standards, without relying on your property as the unoccupied safety zone, before using it the next time. (He will not be able to meet the standards but may not realize this.) Depending on his personality it will be far harder for him to object to the NRA standards than to a group perceived as 'anti-gun' and shows that you are making for a reasonable request. The NRA offers reasonably priced consulting on range safety and design. This may be useful if you need someone to interpret the handbook for him.
If you don't close his range you might as well give him the deed to your property. Its not useful to you. I would not sit in any above ground room in your house with your neighbor firing a high-power rifle.
