HB 400 (or 450, or 500) plates for local shooting range 1

[kingnero]

Our local shooting range needs to renew the backstop plates. No info on the quality that was used previously, so no useful empirical data.
I tried googling but I didn't quite found what I am looking for.

Is there a known (empirically determined) relationship between calibers, distance, steel quality and thickness ?

More specifically, I am asked to write the tech spec for a steel detailer to provide a frame (with removable AR400 (or similar) plates that can be lifted out by 2 men).
This is a handgun range (no magnum ammo), with the backstop at 25 m or 80 ft). Hoping for a lifetime of at least 10 yrs.

Seeing the high steel prices, and the limited budget of this range, I'd try to avoid going overkill in quality and thickness.

Any tips or known data is much appreciated!

 

[DAVIDSTECKER]

I use this company for my Hadfield Manganese needs.
You may want to contact them and see if they have any customers with similar needs and see what they've been buying.

http://www.stulzsicklessteel.com/

 

[SwinnyGG]

Is there a known (empirically determined) relationship between calibers, distance, steel quality and thickness ?

Yes. Well, sort of.

Caliber basically doesn't matter at all - what matters is bullet velocity and energy at the target. Various grades and thicknesses are going to be rated for a certain amount of energy; keep in mind that's energy at the target, not muzzle energy.

For example, 1/4" AR500 is usually rated to be good for up to 700 ft-lbs of energy. That will cover most all pistol rounds, with the exception of 44 magnum at close range, and some .44 and .50 caliber wildcats. As long as shooters don't hit target edges, don't shoot ammo with any steel in it, and don't shoot crazy soft tip or hollow point hand loads, targets will last indefinitely below their rated energy.

 

[kingnero]

Thx to both of you - that's good info to know.
I have various reloading manuals (The Speer one probably being the most interesting), I have access to muzzle energies and speeds at 25 m (weight should be fairly constant until impact...). I can work with that.

Additional question: is it true that AR 500 is more aimed at abrasion (=> sliding rocks), and AR 400 has better impact resistance (=> falling rocks)?
Does this matter for this application, or does this matter enough to choose one over another?

 

[SwinnyGG]

AR400 vs AR500

I think if you're lining a dump truck bed or whatever, yes - AR400 is more resistant to impact.

But the primary damage mechanism for targets is localized melting due to extremely fast deformation when bullets hit; this is what causes targets to spall on the impact side. For that condition, AR500's higher hardness makes a huge difference.

My last sentence is 100% of my knowledge of the physics, but anecdotally (I shoot A LOT) I can tell you that AR500 targets are MUCH more durable than AR400 of the same thickness. 1/2" AR500 will handle high velocity boattail .308 hand loads at 100 yards easily. At 300+, the same loads don't just deform AR400 plates - they punch right through. Big, big difference.

For pistol calibers only, AR400 might still win if the cost vs. thickness equation balances out; AR400 was substantially cheaper than AR500 in the same plate thickness last I bought some.

 

[IRstuff]

MIL-A-12560H Armor Plate, Steel, Wrought, Homogeneous (for Use in Combat-Vehicles and for Ammunition Testing)
MIL-A-46099C ARMOR PLATE, STEEL, ROLL-BONDED, DNAL HARDNESS
MIL-A-46100D ARMOR, PLATE, STEEL, WROUGHT, HIGH-HARDNESS
MIl-DTL-46193A ARMOR PLATE, CONTROL ROLLED, STEEL, WROUGHT, HIGH STRENGTH, HIGH QUALITY


TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

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[SwinnyGG]

Yeah mil standard plate isn't even worth trying to find unless you have a van full of gold bars in your garage

 

[kingnero]

Swinny, if we were in Pat's pub, I'd offer you your poison of choice, and lots of it.
You've been of tremendous help. I know what to look for now.

 

[SwinnyGG]

You're welcome.

As a last bridge, couple things you can do to help maximize the life of range backing:

You want the plates angled toward the shooting line, so all debris and ricochets are angled down. This is pretty obvious, I'm assuming you picked up on this already

You want the plates 'hanging' as free as possible; not rigidly mounted, if you can help it. Even a tiny amount of movement, such as mounting the plates on a hinge at the top and resting them on a lower support, instead of bolts all around, will allows the plates to moved a tiny amount and dissipate some energy. Over the long haul this will increase durability a LOT. If they can move, they will be loud. Some places like this and some don't; it's common that the plates will be rubber mounted or even have rubber backing applied to them to help control noise.

If this is a situation where you're making a continuous backstop, you want to pay attention to where you put joints. Rounds hitting right on the edges of plates will spall them, regardless of grade; it's just physics. Ideally, you want your plate widths to be whatever your lane widths are, so that joints are as far from the line of aim as possible. A lot of shooters suck and will hit plate edges anyway; if budget allows, butt the edges of the main backstop plates together and then 'armor' them with a narrower strip (which can be a less expensive grade if you want, since it should be supported on the back side by the main backstop plating) a couple of inches wide.

Because it's narrow this joint 'armor' is going to take a beating, but replacing a 3" wide strip of 1/4" AR400 is a lot cheaper than replacing a 4' or 6' wide sheet of 5/8" AR500.

 

[kingnero]

Thanks for the additional information. Yes, the target holders are hanging freely on a rail with cables to enable them to move forward/backward.
These are the primary plates that will catch bullets.

The frame I am asking for, is a backstop. This will be rigidly mounted at the back of the range, to catch bullets that miss their primary targets. I know I can't count on that (I've seen shooters miss a 1.5 ft wide by 2 ft high plate at 5 meters), but I'm just giving this information to be complete.

The backstop though, will be mounted in a rigid frame. Good idea to provide smaller strips to protect the edges. This was not the case (old plates slid into C channels, and these C channels were replaced more or less frequently. These are standard steel, so apart from half a day work, the cost is nearly nil. The new system will be more or less similar (per their demand), but it's not a lot of work or additional cost to provide a small strip in front of the C channels to protect those.

Yes, the entire backstop will be angled downward by approx. 30 degrees.

But you've given me some ideas to improve the design. I like hanging the plates from a hinge. I understand the advantage that this gives towards lifetime. Providing thinner strips in front of the seams will certainly be incorporated. A bit of rubber where the hinged plates rest on the bottom, also is not difficult to implement.

Again, couple of drinks on me.

@ IRstuff, I'll ask for the materials you suggested, but I'm in Europe so chances are slim. We do have excellent availability of SSAB plates though. I'll get back to all of you.

 

[EdStainless]

The only range that I ever worked on up close was a private one at a firearms company.
Their plates were heavy (3/4") at 45deg. Deflecting down into the crushed rubber catch tray.
They were supported on "T" frames but not bolted anywhere.
There were continuous rubber pads between the "T" and the plates.
The rubber strips were just held in with some double stick tape.
The "T's" slotted into top and bottom frame rails.
They could be replaced more often. But these guys rarely missed.
They were mild steel and they had a large pile of them.


= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[WKTaylor]

The indoor range where I shoot, expressly prohibits steel and tungsten 'shot' and bullets, IE: ONLY lead and lead + copper-jacket is/are permitted.

The range/desk crew inspect all ammo before permitting access to the range... open the boxes and look at it... and also, all shotgun ammo must pass 'magnet-test'... no steel BBs or slugs. Tungsten alloys would likely slip thru this test, I think... but they also pay close attention to shooters by cameras [video]... and could stop [or at-least track] ammo-violators if damage to the back-plate [or ceiling or floor] was noted.

PS: I think even a BB-gun of any kind would be prohibited... even though it is low energy... simply because of the steel content... which complicates scrap metal recycling/reclamation... unless the range/area was specific to 'air' rifles/pistols.

PS: Why are they called 'BBs'? The answer should be pretty obvious to engineers... and is sorta 'ah-ha' [RE: marketing] too.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[SnTMan]

Balls, ballistic? That's all I got

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[SwinnyGG]

They're called 'BBs' because they are shot size BB. I don't think there's a sliver of marketing involved.

 

[WKTaylor]

Come'on guys... BBs [Daisy 'Golden BBs', etc]... sound so cute/harmless.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[EdStainless]

I have a carton of Cu platted Pb BBs here.
The only thing that I shoot anymore though is lead pellets.
I have 5 or 6 big spring guns.
Cheap and fun.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[WKTaylor]

And 'BB' is an abbreviation for...?

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[SwinnyGG]

.....it's not an abbreviation.

BBs are (nominally) .180" in diameter; shot size BB. If 'BB' stands for something, its a backronym.

 

[WKTaylor]

This is painful...

BB guns are 'safe and cute'...

Ball Bearing guns sound awfully dangerous.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[SwinnyGG]

BB sized shot has existed for 300 years. BB guns have not. I don't know what else to say.