Building A BackStop

[timlab55]

So today I started to build my backstop for my AR15 shooting 556/223 rounds. Of course until I get my silencer, the only rounds I will be shooting are the 223 subsonic rounds. After the silencer I guess everything goes. Okay, I have a 2x6 frame that is 6' tall x 4' wide. In order is the following: A sheet of 3/4" plywood, followed by a 3/4" horse mat, following my 12" of sand, followed by another 3/4" horse mat, and the end is 3/4" of plywood. I have found several video's of people testing these rounds and it seems like 6" of sand would do the trick. But I'm looking for other's who have done test like this. I'm sure the distances has to be added, so what was the distances tested?
Thanks

[zoomie]

After the silencer I guess everything goes.

Before you jump headfirst into this, do you have any experience with suppressors? Why does the suppressor change the ammo type you're going to use? Usually people switch TO subsonic - not from subsonic - after they get the can. Are you trying to be considerate of neighbors? It seems you might not have an accurate expectation of silencer performance.

[ammo.crafter]

Indoor or outdoor?
Distance of range
FMJ rounds?
....
There are many types of back stops. Rotating drum, angled steel into sand, etc.
Research the internet before starting project.

[Shadow9mm]

Originally Posted by zoomie

Before you jump headfirst into this, do you have any experience with suppressors? Why does the suppressor change the ammo type you're going to use? Usually people switch TO subsonic - not from subsonic - after they get the can. Are you trying to be considerate of neighbors? It seems you might not have an accurate expectation of silencer performance.

As i understand it the OP is looking to remove coyotes from his property. He found standard 223 to be too noisy for the neighbors and switched to subsonics. However they are not cycling his action and are not a good choice for coyotes. Got a suppressor on the way which should get him close to 22lr noise levels with full power ammo, which are fine on his property.

[Bob Willman]

I have no experience with any AR-xx ammo penetration, however I do with many other calibers concerning sand. My backstop was built in 1972. It is a number of railroad ties laid in a shallow cup shape and stacked similar to a split rail fence and backed up by 4 wooden utility poles set in the ground behind them. The face of this was covered with corrugated plastic sheets and then 2 dump truck loads of yellow sand was piled in front of that wall. At the target line the sand is 4 to 5 feet thick and about 6 to 7 feet wide. Yellow sand in this area is abundant, economical and does not contain rocks.

Many different firearms of various calibers have been shot into it over 50 years. A typical jacketed hunting bullet from a 30-06, from 90 yards, will penetrate 7 to 8 inches depending on type. FMJ ball will go deeper. I have found .45 caliber muzzle loader lead bullets, also from 90 yards, elbow deep in the sand.

As for maintenance, one time about 10 years ago, the sand had settled some and I had to shovel some from the front back up on top of the pile and replace the railroad tie that is below the target line that keeps the sand in place. Full disclosure the local woodchucks were responsible for much of the sand movement and they make interesting targets of opportunity.

If there is a possibility of upgrading your firearm collection, a foot of sand may be a problem. Plywood will not last long exposed to the elements, and after a bunch of holes it could be very difficult to replace easily.

NRA Benefactor

[44 AMP]

The indoor test fire range backstop at the Army Small Arms Repair course at Aberdeen Proving Grounds was a room with 6 feet of sand in front of a steel back stop. weapons were test fired through ports (about a foot square), and it handled everything military less than .50 cal, including AP. (.50BMG was not allowed on that range)

When the firing had dug a trench a foot or so deep in the sand, they would go in and "shift" the sand. This happened every few years.

[georgehwbush]

(Got a suppressor on the way which should get him close to 22lr noise levels with full power ammo,) ?

granted i have little experience with mufflers but the supersonic crack is well above that of normal 22lr in my testing. YMMV your mileage may vary

[Shadow9mm]

Originally Posted by georgehwbush

(Got a suppressor on the way which should get him close to 22lr noise levels with full power ammo,) ?

granted i have little experience with mufflers but the supersonic crack is well above that of normal 22lr in my testing. YMMV your mileage may vary

All i know for sure is i shot a 7in 223 ar with a 30cal suppressor on it, no ear protection, 55g at 2900fps, and it did not hurt or make my ears ring at all. To my ear it was pretty similar to supersonic 22lr unsuppressed. I don't own a suppressor yet, but i have a friend that does, and im planning to file my own paperwork in the near future.

[georgehwbush]

for the shooter YES the suppressor helps greatly, but for the neighbors .25 miles .5k away, there is presious little difference. just saying. and you may come to a different conclusion.

as one that has been down range. the supersonic crack of the projectile is the loud sound the blast of the propellant is the quiet part, and only orients one to the direction of the shooter. and as per the holywerd portrayal of the sounds generated by suppressed gun fire: it's not even close.

[georgehwbush]

and by the way, yes indeed; i believe all firearms should come with mufflers, it's a shame that the atf gets away with telling us that it's not a good idea...

and while i'm thinking about it, why do so many movies depict the sound of gunfire as making that buzzing his prior to the bullet reaching the victom/target i mean war movies and all kind of shoot-em-up flicks do that... the only way that happens is if that "sniper" is so far away that the bullet has already gone subsonic ten seconds before it got to the microphone... well maybe not exactly 10 seconds but long enough for the sound to "out run" the bullet quite a bit.

have they never heard of "crack thump" ?