Hi all, my 12ga falling block action showed up today. I rockwell tested it and it is 65 on the B scale. Sounds pretty soft to me. Did anyone ever respond with how to get the steel analized to see what the composition is so it can be heat treated? I ordered my barrel from Shaw and will have them cut a 3" chamber in it. I'll play with that then decide if I want to go to a 3.8" chamber later.

Lar--Maybe find a good place that heat treats and perhaps they can test for composition.Ed.

I found a place online that says they've been in the heat treating bussiness for over 100 years. I emailed them about it. I also contacted PTG like Rob suggested. The barrel shank hole is 1.095" and about 1.75" long. The action tapers at the front but is thicker back towards the breach. The only thing I'm worried about is getting a functional stock made for it. If the action turns out to not be heat treatable, I'll just use it in the proper pressure range.

Please be careful.

No problem there, I'll be sure to pull the trigger with a long string the first several times.

I took measurements and calculated strength on the action today. The hardness convereted to about 120 Brinell, so HBx500= tensil strength of about 60ksi. Looking on the charts seems real close to cold rolled 1020. So assuming hot rolled 1020 just to be safe with a yield strength of 38ksi and shear of 24ksi. case body diameter of .8" for thrust. The breach block side rails have a max shear yield of 38.4ksi chamber pressure. The action would have a max tension yield of 40ksi chamber pressure. I did the thin wall pressure vessel calculation on the barrel, 4140 23.56ksi, action 6.96ksi and 50BMG case 5.27ksi. I'm not sure if these add together or fractionaly. So about 35ksi max chamber pressure? In all my classes they never did go over the yield on threads. How is that calculated? I'm just thinking that it might be the thickness of halfway up the peak of the threads. So PIx diameter of median threadx 1/2 shank length?

So if I allow 100% saftey factor then I could have a safe chamber pressure of 17.5ksi?

Then if it will heat treat to a greater hardness I can go higher.

Thoughts?



We have a small furnace in the School Engineering lab that I could use to heat and oil quench, then temper. If the Steel isn't hardenable, then would it hurt it to try? I don't think that it would.

LAR--To figure the force to pull the sides apart you
should use the tensile strength.How thick are the sides,
and how tall, in the thinnest part of the sides? Ed.

I went back and reviewed my Materials text book. If it's steel even a low carbon then it's hardenable. To what degree is the question.

The walls are .15"x2.2" That's not includeing the web at the bottom of the action.

I need to take a trip to the library to find a book that gives specific hardenablility charts for different alloys and compositions. Anybody know of an online site that has that or similar? I think that I should use the yield stress for a max allowable force before it deforms, not comes apart. From looking at the charts for 1020-1040 I should be able to harden this to atleast twice the strength of what it is now. That would give me a safe working pressure of 30ksi which would put me beyond 700NE performance.



I don't think that the breach block will be a problem. If it does experience some setback, then it will just come in contact with a much larger surface area. I will probably case harden it for wear resistance.

Lar-That is thicker than my Greener is now, thicker than
thin sided Win 1885, thicker than Gibbs Farquarson.So if it can be treated say to a 80,000 lbs yield strength,
the cross section at .66 sq in, using the thickness and height figures, would be rated at 52,000
lbs of thrust.A case of .800 dia base with a 36,000 psi
load as an example, will put 13,000 lbs of thrust against breech.That gives a 4 to 1 safety margin.Most bolt rifle designers for big cases, at high pressure,
try to get a 3 times safety factor.And if it could be treated to higher levels, you would have that much more
strength.That is why due to design, Ruger #1s have 2-4
times the strength of regular size bolt actions.Ed.

I think what I'll have to do is heat and quench in the engineering lab under controlled conditions, then check the hardness and compare to various hardenability curves to try and get an idea of what composition it is. The only thing that I've seen in my engineering books is from analizeing a powdered sample, but I don't really want to do that.

Now I just have to learn how to make a stock.

Lar-Getting a stock on there that doesn't split will be

a real engineering feat.If it was mine, as I want lot

of weight,I'd have stock out of aluminum.Wouldn't

break..Ed.

Maybe an anodized Aluminum core with Walnut laminates on the sides

Lar- Possibility. Even glue on a woodgrain or camo
covering.I figure on the over grown Greener when I get it built that Aluminum is the way to go, and less hassle than doing wood, putting in weight, and hoping it don't break.Ed.

I shaved off a sliver from under the tang to send to Rothschild in AK for him to do an analysis of it. Then I'll have a better idea of how to heat treat it. Assumeing 1018 It looks like I can water quench and temper to get 30% more yield strength and 12% more ductilty out of it. I have an old Mauser stock that I cut in half to see what it looks like and see where I want the comb and stuff.



I was haveing a thought. This action was made to be a takedown with a cross bolt holding the barrel in. Maybe I could lap the threads to be hand tight, then cut a groove for the cross bolt and keep it a take down. I was thinking that I could get a 50BMG barrel and cut the chamber .1" short, then put a rim on and have a low pressure 50 express on the same action to easily equal 500NE. I'll have to work on the stock while I'm waiting for the barrel to show up.



Here's what an original looks like. My action is slightly different though.

Lar45- A word of caution. Once you know the actual steel composition, I'd really suggest you send it to someone with experience hardening and tempering machined pieces. A HUGE amount of warpage can occur ruining your action completely. I've had this happen even by heat-treaters who know what they are doing and have carefully packed the work in steel wool!Trying to do it yourself even with a lab oven could cause irreversible damage.

The barrel diameter is also pretty small. Not much more steel than a Encore 12 Ga! Do you have enough metal to bore it out more and then properly thread it? The 12Ga FH barrels will have a 1.5" shank.-Rob

There is not enough room to bore it out for a larger shank. Thin wall analysis of the barrel chamber shows 23.56ksi chamber pressure for yield stress for the barrel alone. I'm not looking for 12ga FH pressure, just 12bore express. Just by looking at 1018 steel for the action, then quenching and tempering should get me 30% more yield strength plus add more ductility also. I do have a couple of emails out to heat treat places but no responces yet.