MIG welding AR400?

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New guy here, so please be patient.  I have done research, but still have questions.I plan on making a bullet trap as pictured below.  I plan on making it from 3/8" AR400 steel plate.  From what I understand, I should use er70s3 wire with CO2 gas (that't the only kind i have besides pure Ar for my tig).  I should preheat.  Will MAPP gas do the trick for preheating?Can I weld cold rolled steel to AR400?  To save money, i would like to use cold rolled steel for the sides.  Can cold rolled be welded with solid welds to the AR400?Thanks in advance.  And any advise you can offer on welding AR400 is appreciated.Pict of bullet trap i plan on making.
Reply:Hello Caspian, have you considered using a flux-cored gas shielded electrode (dual-shield)instead of solid wire? I say this because generally the flux-cored wire may have a bit more ductility to the weld, be less susceptable to cracking, and work a bit better for your application. Most E71T-1 electrodes designed for use with CO2 will work for this application. Also, I believe that you don't really need "cold rolled" material for the side plates, good old hot-rolled A-36 will work just fine and cost way less. Good luck and best regards, Allanaevald
Reply:using gas shielded flux core is definitely fine by me if it will work better.  what would you suggest?you're correct, i meant hot rolled.  Will hot rolled weld well to AR400?
Reply:Will the bullets enter by your ground clamp? And how big of a gun will you be shooting at this thing? If your just shooting hand guns and rimfire rifles I dont know why regular 3/8" mild steel wouldnt work, As far as Im aware there are very few factory loads (other than solids and armor piercing) that will go through 3/8". For big game rifles the A400 might be necessary.
Reply:Hello again Caspian, I'll throw a number of them out there: Hobart Excell Arc 71, Corex Versatile, Trimark Triple 7, Esab Dual Shield 7100 Ultra, Lincoln Outershield 71M, there are any number of different ones that would work. If you have a particular dual shield wire already look for the "C" in the AWS wire type designation. If it has a AWS E71T-1C as a part of the AWS designation number that indicates that it will work with CO2 shielding and you should be good to go. Although the AR is definitely "hard" you would want to use a wire such as the 71 series to provide the best resistance to cracking. A higher strength wire doesn't mean that it will be less prone to cracking. If you were fabricating the entire unit out of AR and it's intended purpose was to utilize all of the benefits of the alloy you might use a high strength wire that closer matches the AR's tensile strength. For your intended purpose the 71 series should work just fine and be very well suited. Pre-heat would be a good idea, not excessively, and Mapp gas would work just fine. You likely only need to preheat to around 200 to 250F or so. Good luck and best regards, AllanI too would like to hear a bit more about this project and in particular why you chose this design, just curious. Please include additional pics while you are completing it.aevald
Reply:I got the idea from here:http://castboolits.gunloads.com/showthread.php?t=99283The project I am working on requires about 7500 rounds of 12 gauge 7 1/2 bird shot shells to be fired in an afternoon.  So while it is not a particularly high power round, the volume requirement without failure is why I am going with AR 400. If I shoot 5000 rounds and it fails and i have to burn a day repairing it, it will cost me more than the initial cost of the metal.  I went to my supplier and I can get a 10 foot x 8 inch wide piece of 3/8" AR400 for $150.  The sides will cost an additional ~$50, so the entire project will cost $200 plus supplies.I made one from mild steel.  I tested it with 75 rounds and broke out one of the deflector plates.  I think that was more of an issue with the impact angle since I had too wide of potential entry port.  The plate dented and the next shot dented the back of the trap.  I don't want to risk another failure.
Reply:i'm curious why and who is going to fire 7500 rounds of 12g in 1 afternoon. did i miss something? what kind of shotgun?225NT bobcatAEAD200LEScott 125mm175, mm252 w 30A, PT225mm211, TA 181iHyper Therm 380, cut master 529100X & XX, Digital Elite6 Victor setssmith little torch, meco midget kalamazoo band sawsteel max saw evoulution circular saw
Reply:Saiga 12 gauge shotgun with 5 - 20 round drums, 12 - 10 round mags, and 4 - 12 round drums and a one or two full time loader topping off mags....and me with a pillow strapped to my shoulder.  The reason for it is a durability test of sorts.
Reply:lead shot wont give A36 much trouble.  Its soft and slow
Reply:Originally Posted by caspian  The reason for it is a durability test of sorts.
Reply:Originally Posted by caspianSaiga 12 gauge shotgun with 5 - 20 round drums, 12 - 10 round mags, and 4 - 12 round drums and a one or two full time loader topping off mags....and me with a pillow strapped to my shoulder.  The reason for it is a durability test of sorts.
Reply:If all this is every going to see is 7 1/2 shot, AR400 is incredibly overkill, which I have no problem with as long as you understand that you simply throwing money down the drain.  If that is of no consequence, then go ahead.  The volume of the shot wont really make a difference, the problem with most mild steel traps is that heavy rounds deform the plate and grab and twist the steel until its unusable.  Since shot will never do any damage in the first place, you've got nothing to worry about.  Use 1/2" if you want to be overly cautious.Have we all gone mad?
Reply:Originally Posted by DSWOf you or the gun? I've yet to see if you have a machine capable of doing this yet. suggestions are pretty pointless if you have a small 110v unit to work with. Straight CO2 makes me wonder if you have a small mig.
Reply:Pretty much what I thought. Kind of shows the importance of telling people what you have to work with from the start.A few things. the CO2 valve is different from the Argon/CO2 reg that comes with most migs. You will need to get an adapter to run 100% CO2 or a dedicated CO2 reg.As far as a mig, you will definitely need a 220v mig for this if you want it to hold up. I'd go with a 250 amp mig if you can get one, but a 200 amp mig would work if you cranked it up near max. Doing this with a small 110v mig is probably a big reason why the 1st one failed.Given you already need to get the wire as well as the reg adapter to run some of the suggestions above, plus the fact you need to borrow a 220v mig, I'd think about just running stick with your Dynasty. I'd probably go with 8018 off the top of my head, but I've got a PDF here some where with info on welding AR I'd dig up, The link to the PDF was posted up here in a past discussion on AR or T1 IIRC. Run the dynasty on 220v not 110v to do this. You will want the added power to burn in your welds..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:10-4 on the stick.  I have never arc welded, so i was apprehensive about that option.  However, I have time to practice so it sounds like the way to go.  Amperage isn't a problem with the Dynasty, I have it on a 30 amp 220 outlet.  I'll pick up some eletrodes on the way home and give it a shot tonight with some thicker steel and test the strength of my welds.
Reply:The design with the multiple flat plate decelerator encourages concentrated wear in certain points on each successive plate.  I have always liked the type of trap with a pipe decelerator mounted vertically (I built and use one of this type) or horizontally (many indoor large-volume shooting ranges use this type.)  If using a pipe horizontally, you just split the pipe and position the two halves slightly offset to each other - this gives both an entrance and exit.What you're building there is a horizontal decelerator, but if you're planning to follow those dimensions, you're going to have to be standing right in front of it to use a shotgun.  If that were my only option, I'd shoot into a dirt pile instead and get some distance.  My decelerator will spit the occasional shaving of lead back out the front, although the vast majority is collected in a cast iron pot I place under the discharge.The main problem with centrifugal decelerators (in terms of fabrication) is that the shallow-angled throat required to keep the bullet on track into the trap means it uses a LOT of steel to build out to an acceptable-sized targeting area.
Reply:I bought and cut the AR400 and mild steel (mild for sides, top and bottom, AR400 for strike plates, back and front).  It will be 32" long and 17" tall.  Here is the layout.I have ordered the 8018 for stick welding and am waiting for that.  In the mean time, I bought some cheap 6011 from Harbor Freight to practice stick welding with since i have never done that.I had some scrap AR400 that I welded to some scrap mild steel with my Dynasty 200DX set at 200 amps using the 6011.  I put the welded piece in my vise and pounded on it with a 3 lb. sledge hammer until the mild steel bent and my arm hurt.  The clamp was about 1 inch from the weld.   I had it clamped in this vise, so the weld would have broken before the vise.I will wait until the 8018 gets here to do the welding, but I am much more confident in this design than the previous one.Thanks for all your help and I will update with final picts.CaspianLast edited by caspian; 01-07-2012 at 07:34 PM.
Reply:8018 and 6011 will weld completely different. 7018 would be a similar practice rod. You also need to do some grinding on that plate to get rid of the rust I see. I know it will F up your layout, but you will want clean plate if you expect to get good welds.As far as your "test" a lot will depend on the way you welded up the joint and how you pound on it. If it's a fillet weld like it looks like your welds will be you bend TOWARDS the weld, not away like most people do and only weld the one side. Personally I'm not a big fan of a "hammer test" as it usually doesn't show much unless you weld really poorly.Last edited by DSW; 01-07-2012 at 09:12 PM..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Caspian,Centrifugal decelerators rely on a CONTROLLED projectile path while the projectile loses energy.  What exactly are you trying to accomplish by angling your plates that way?  Your shot is going to be impacting the corner at the 4" and 4.75" plate joint and spraying everywhere from there, including a certain percentage back out the intake opening and a larger percentage out of the false opening between the 5.5" and 6.5" plates at 11:00.  I'm assuming you're building a large box around the outer edge of the plate, so shot from the false opening won't be out of control, but it still defeats the purpose of a decelerator, which is for the projectiles to lose ALL of their energy inside of the decelerator, and then fall harmlessly out into the catch area by gravity.I'm sorry that no one else sees it (maybe they don't understand what the design is meant to accomplish), but you're asking for trouble here.  And I'm not one of the normal 'naysayers' on this site.And again, if you plan to use this with a shotgun, you're going to have to be standing right in front of it because of the small intake.  It is entirely possible to make a safe centrifugal trap, but I'm telling you, this one isn't.  You will have high-speed ricochets coming back out of the trap intake - this design guarantees it.I hope someone else with some experience with this design will pipe up so the OP doesn't think I'm crying "wolf" here.
Reply:I'm sort of in there with tbone550. Just due to the fact that you have to be so dang close to the inlet with a shot gun there are going to be some tremendous forces exerted into & to this device. Both the weight of the shot and muzzle blast are still going to be very concentrated for that short distance involved here. Then as many rounds as you need to fire. Wowzer. I'm not sure exactly what kind of device is the right one but this doesn't give me that warm fuzzy feeling. I dunno. The muzzle blast dissipates very rapidly with distance I know and the shot does too plus it spreads with distance. I'd rather shoot into a barrel of sand at ten feet than something like this."The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:If anyone is interested in seeing what a properly designed centrifugal decelerator looks like, here is a company that makes them, both in small and large scale.  Hopefully the pictures will help show what I was trying to explain in my first post about using a longitudinally split pipe for entry and exit.http://www.snailtraps.com/ourproducts/
Reply:The final design has the opening extending 3" forward of the trap.  There will also be a hinged 2" thick rubber plate in front of the opening with only a 2" circular opening to put the barrel through.  The idea is to put the muzzle of the shotgun through the hole, so the shooter isn't exposed to the opening.I agree that a centrifugal design is the best.  However it isn't the only design that works.  Pre 1991, other traps were out there and did work.  For the home builder without access to hydraulic presses/dies for making the centrifugal bends, alternative options need to be evaluated.With regard to the pressures exerted in blasting point blank, there will be a ventilation port that is in the back.  it will be in an area protected by the plates, to no projectiles will escape from it, just gas.Lastly, I welded on both sided of the plates.  I will be able to do the same on the final product with the exception of one of the sides when the final side plate goes on.regards,Caspian
Reply:FWIW, bullets have a very low angle of deflection.  Shooting at 30 degrees, it will deflect at 8 degrees or less.  Using this information, having multiple strike plates, the bullet will lose energy, destabilize, and slow down considerably.  The potential impact of the bullet is diagrammed below.  While the final velocity of the bullet won't be zero, by the time it has hit plates 4-5 times, even if it hits an opening in the strike plates, the bullet will have little to no effect on the mild 1/4" steel.  Also, the projectile hitting the strikeplate destabilized increases it's surface area and potential for penetration.This design HAS been tested and shot with 300 Win Mags with no splashback as discussed in the thread posted here: http://castboolits.gunloads.com/showthread.php?t=99283Last edited by caspian; 01-08-2012 at 10:48 AM.
Reply:Caspian, a 2" hole is plenty big enough for ricochets to get through, although the idea of the rubber mat with hole in it is a good one.  Also, if you change the muzzle angle just a little from your diagram when you're using this thing, you have a straight back deflection at the 4" and 4.75" junction, as I warned you before.  Your diagram just helps it be better visualized.Just because someone else on the internet once built one of these and had success, doesn't mean you will.  Your design shows less understanding of the physics involved than the original that you're copying.  And with lead shot, you have no need for a multiple AR-plate system - a pipe would be fine and would eliminate most of your internal deflection hazards.I just don't want you to get hurt, I'm not trying to be hard on you.  But I know that you're going to build this regardless of what I say.  I hope I'm wrong about it's safety.  Please wear thick leather when you use it.
Reply:physics and bullet deflection are two different things.  I have plenty of experience in bullet deflections and their results.  You are correct in that I will build it regardless.  Leather gloves will be worn, along with the typical safety equipment when shooting firearms.Also, in my line of work, i have been shooting into various bullet trap designs for 20 years.  I currently shoot into a Snail trap at work, but for personal use, can't afford it.  I am incorporating designs of the past to work and today to make this one.I am very glad you are excited about your tubular design.  However, it's not the only way to skin a cat.  I am not overly thrilled with the Snail benchtop model I have at work and have had impacts on my hands from fragments.  That has shown me that this design is not perfect either.If you have had truly ZERO splashback from your design at close range (as the benchtop is designed), then you should consider contacting Snail and letting them know how you did it.  The bottom line is, ANY point blank design is capable of some splashback.BTW, i shoot about 10 different guns per day into the Snail for the past 8 years or so, so i can speak on this with authority.caspianOriginally Posted by caspianphysics and bullet deflection are two different things.  I
Reply:Originally Posted by caspianIf you have had truly ZERO splashback from your design at close range (as the benchtop is designed), then you should consider contacting Snail and letting them know how you did it.  The bottom line is, ANY point blank design is capable of some splashback.
Reply:here it is.  gonna take it out on MLK day and test is with some 3" 12 gauge steel shot, slugs, .45, etc.the final product will have a vent port in the back to release gas pressure.  also, there will be a thick rubber gasket in the front preventing splash back.Glasses, gloves, leather coat, etc. will be worn in testing.Oh yeah, I also caught myself on fire using stick for the first time.  Whoda thunk that touching the stick to the frame when looking inside would arc. LOL.Last edited by caspian; 01-11-2012 at 07:48 PM.
Reply:I don't know about the design, but I would think you will be in some serious pain long before you reach 5000.
Reply:my uncles and i built one for test firing shotguns for one of their manufacturing buddies  and all we did was use 8' of 14" steel pipe lengthwise it has  one internal  deflector to deflect it into upper corner and a 22% bends in the discharge and a rubber flap set up over were the gun barrel sticks in to protect the shooter we had the discharge end over a dumpster and it would penetrate paper but not cardboard when fired it docent take much deflection to make a shotgun round safe last i heard they were filling up a 55 gallon barrel a month with leadDo not argue with an idiot. He will drag you down to his level and beat you with experience.