Bench critique needed

T

tricrown

Guest
The club we shoot benchrest at is shared with a much more numerous and lucrative group of black powder silhouette shooters that voted unanimously against us laying down a cement slab. We average a couple dozen people a shoot. They get much better than double that.

We currently shoot off of wobbly wooden benches that rest on the stones that the black powder boys like to lay on. So as an alternative to a cement slab we’re thinking of making solid benches by auguring in 3 posts with a triangle made from 2x6s on top and a couple support boards running from the top and bottom of the rear post to the center of the front posts. On top would lay a pre-fabbed cement benchtop. The benchtop needs to be able to be moved some on a few of the benches to shoot at targets that’ll be at different angles down range. As in 200, 300, 400, 500, and 800+ meters. 10’ apart will easily get all 10 needed benches under the roof and leave 6’ or so for all 8 silhouette shooters to lay or stand in between them.

Does anyone have any experience with benches of a similar design? How big and deep are the posts. I’m thinking 4X4s 3 feet down here in PA for the front and a 4x6 for the back should easily hold a 200 lb slab benchtop steady. Am I off by a lot?

Thanks,
Bill
 
It depends on what you mean by steady. If you mean absolutely no reticle movement on the target, using a high magnification scope on your rifle, with you in contact with with the bench and your rifle....no way. Since the only concrete is the top, build one to try, I think that you will see what I mean. In a season, the wood will shrink a little leaving the fasteners loose enough for the bench to wiggle...more. Think steel...set in concrete, that is slightly below grade. On the other hand, you may be quite pleased with the improvement over what you are currently using. Good luck. Build a prototype or live with your mistakes times ten. You will pardon my passion about good benches. Years ago our club built 42 cast in place, monolithic, reinforced concrete. It took a crazy amount of work, but they don't move. I had months of time in the project. Seriously, I hope that your project is a huge success. I can give you a few tips about building forms.
 
Boyd, thank you for your input. What we have is a under roof shooting line that is raised 6’ or so above the surrounding area. It was built as a silhouette range. So the 500 meter target line is better than twice the length of the 200 or 300 lines and are all the way to the right side of the 500 not centered. What that gives us is a good amount of angle difference for some benches when shooting the different distances. Our shoots are at 200, then 300, then 500. So now guys just move the wobbly benches to line up. We will take your advice and build just bench 1 to start with. That’s the one with the biggest angle difference from 200 to 500.

Now another club that draws 60 up to 100 shooters for a Saturday match has the same benchtop we’re thinking on. But their benchtops are set on mortared together cinder blocks on top of a cement slab. I shoot there regular and do occasionally move my benchtop so I don’t have to have to lean across the top of the bench or have my front rest close to falling off the edge. I have noticed a small amount of reticule movement there. But as the numbers show, guys are either oblivious to the movement or consider it acceptable. I hear complaints about our benches every shoot. So I’m thinking if we can at least get that amount of stability on our new benches we’ll be OK.

I looked at the price of steel and it is way over what I think I could get the club to spring for. I’m thinking 4”- 5” or so OD would be the smallest pipe to use. It’d have to be a good thickness for the weather here in PA. The 7 year old basketball post in my driveway that I filled with cement is rusting pretty badly. Where as our 4x6 pressure treated swing posts that are the same age show no signs of giving up the ghost.

I know what you’re saying about wood warping. Three of the 8’ 4x6s I used to hold up the back porch roof have bent ugly bad. But I’m hoping that with just 3’ or so above ground the bench posts shouldn’t warp that much. I will be needing somebody with a good eye for lumber to help pick out the posts if we go that way. Lord knows I can’t tell what piece is going to warp from a good one. I thought about using plastic pipe and filling that with cement with a re-bar or 2 thrown in. But I’m thinking the plastic would be all busted up in no time and then we get into needing guys to mix a lot of cement or tying up a cement truck for a good amount of time. And the benchtop still will need to be moveable.
 
Hi,
What I was referring to was not warping. To be more clear, when the weather is damp, wood swells a little, but where steel fasteners go through it, it cannot, so the cell structure is slightly crushed, so that when weather is drier, and the wood shrinks, the joint gets loose. This is why wood tool handles loosen. As far as metal goes, a regular coat of suitable rust protective paint, properly applied, and renewed from time to time should make steel last just fine. To save money, you could use recycled material, from a scrap yard. The legs of your various benches don't have to match, as long as they are all sturdy enough. If you must work with wood, you might consider incorporating screwed plywood "shear panels" into the design. Fellows tend to look at the down forces on a bench and ignore the side forces that cause twisting and bending that lead to top movement.
Boyd
 
if steel legs

are what you choose try a local drilling company for old drill rods.
just a thought.bricks and cement are best
jmho.jim
 
You must log in or register to reply here.
Back
Top