Bullet penetration on steel

[oaken]

At the recent quarry shoot we had a surprisingly high number of steels fail, this time with holes rather than the usual fixings.

I am interested in your thoughts on various bullets ability to penetrate steel at relatively close range. There were expanding, target and mil surp ammo being used though with a strict HME limit.

The steels that we use are AR400 10mm hung at a slightly downward angle suspended on chains. To be fair they have taken a good pounding over the duration of the MQC shoots. Some of them must have had suffered thousands of hits at as little as 50yds so I am in no way complaining.

Normal damage is minor dents to the surface and a slight dishing of the plate. Oddly the small targets have suffered the most holes this time, possibly because they are positioned slightly closer.

To date we have noticed that the faster lighter expanding rounds (.243 & 22-250) do the most surface damage with .30cal barely leaving a mark. However there was an element of mil surp ammo being used this time.

We have considered moving to AR500 but being harder (more brittle?) there is the possibility that it will hole more readily.

Appreciate your thoughts and advice

Rup

[MJR]

Interesting. I wonder if the metal is work hardening with the repeated impacts and failing due to fatigue. Wonder if they could be retempered with a heat cycle? Probably not worth it on a cost basis so you may have to resort to running a simple 'target life' whereby you replace them after so much use? Either that or give AR500 a go.

[Tiff]

Hi Rup, any ideas on the 'caliber' of the holes?

 

A lot of the 5.56 FMJ surplus ammunition (+some 7.62) contains a steel 'penetrator', that would defeat already work harden/weakened steel plate and even cause some significant damage to new plates.

 

The other issue may be that the steel has been structurally weakened by continued use - but I'm more of a meteorologist than metallurgist I'm afraid.....

[John MH]

The thing that kills steel targets is velocity, light fast bullets will do far more damage that slow heavy ones. Anyone shooting milsurp 5.56mm with a steel penetrating core in the bullet will also accelerate the failure. The Targets I have loaned to Tiff for the RCC are AR500, some 1/2" and some 3/8" no decernable damage on the plates that a new coat of paint won't hide and the only deformation damage is from a low strike on the mild steel baseplate on on of the poppers.

[oaken]

Interesting. I wonder if the metal is work hardening with the repeated impacts and failing due to fatigue.

I don't doubt that metal fatigue is the main issue but to have so many fail together rather points to a particularly destructive round being used.

 

A lot of the 5.56 FMJ surplus ammunition (+some 7.62) contains a steel 'penetrator', that would defeat already work harden/weakened steel plate and even cause some significant damage to new plates.

Yes, the holes are quite small compared to the splash holes you get with mild steel. The harder steels will not splash though so could be misleading.

I suspect these steel penetrators may be the cause!

[SteveW]

The thing that kills steel targets is velocity, light fast bullets will do far more damage that slow heavy ones.

 

From my limited experience John is spot on.

The day I took my Hardox targets out for a play, we were shooting it with a 20 VT, 220 swift and a 6mm06, the 6mm shooting 70g Nosler BT's and 68g Bergers put holes through from the first shot @ 120 yards and when my father started laughing I noticed the holes, but there were already several holes Not happy.

[Missed]

Velocity is the killer. I did some testing on steel some time ago and found that at 100m 50g Vmax and 52g Amax in 5,56 did considerably more damage then 123g and 140g Amax out of a 6,5x55. The 6.5x55 were doing in the region of between 2600 to 2900fps whilst the 5.56 was rattling along at around 3300fps. I have the numbers somewhere, including the depth of penetration.

[mtb]

I also found the same my 6mm with 105 no damage yet my 17 rem with 25 grn vmax left small craters

[oaken]

John, you are right, speed kills the gongs.

Have you any experience of the steel penetrators hitting AR500 at closer ranges ie. 50/60yds?

I think we need to stump up the extra cost for AR500 and maybe go up to 12mm too, may be a worthwhile investment given our short distance CoF. Otherwise we may have to start restricting some ammo types!

How can you tell if the bullets have these steel penetrators ? Magnet?

 

Steve, what speed is the 6mm06 doing with the 70s? And the 22swift for that matter?

 

Just thinking out loud here ..... Wondering if imposing a speed as well as HME limit may be the answer.....

[John MH]

Easy check for penetrator is to used a magnet but it's most likely that if it's milslurp 5.56mm it will have the penetrator.

[tackb]

It's not my Amax

[Tiff]

Just thinking out loud here ..... Wondering if imposing a speed as well as HME limit may be the answer.....

Aside from a ban on FMJ rounds (steel cores/penetrators is why I impose it at the RRC shoots...), impact velocity is your problem and not really impact energy.

 

From tests I've done on 10mm & 12.5mm Hardox 400 & 500, the max. impact velocity must not exceed 2,700/2,800 fps & around 3,200 fps respectively. My .338 shooting 300gr SMK at 300 yards doesn't mark either hardness, yet a good light .243 bullet certainly will!

[brown dog]

Easy check for penetrator is to used a magnet but it's most likely that if it's milslurp 5.56mm it will have the penetrator.

 

Yup.

 

The 'steel penetrator' element of this thread is making me chuckle: The clue is in the name

 

To give a sense of scale to what it's designed to do: The tip is there to assure penetration of 3mm of mild steel (standard helmet or body armour equivalent) at 600m with sufficient remaining energy after penetration to defeat the target.

 

You'd be hard pushed to find post-M193 NATO ammo without a steel core or a steel tip ahead of the core.

[Orka Akinse]

John, you are right, speed kills the gongs.

Have you any experience of the steel penetrators hitting AR500 at closer ranges ie. 50/60yds?

Otherwise we may have to start restricting some ammo types!

Just thinking out loud here ..... Wondering if imposing a speed as well as HME limit may be the answer.....

Go for it Rup I have a target barrelled .22 which fires sub sonic 40g into the same hole........ ideal for the quarry

 

Saves steel too!!!!!

[SteveW]

I think we need to stump up the extra cost for AR500

 

Steve, what speed is the 6mm06 doing with the 70s? And the 22swift for that matter?

 

Rup, both are around 4000fps, the swift with a 52g Barts and the 6mm06 with 68g/70g bullets as stated previously.

 

I did exactly as you are thinking and upgraded to the AR500 targets, but to date I haven't shot anything pokey at them, need to grow some I guess So can't help there I'm afraid. ( The 6mm/06 is no more, now a 284 Win)