Powder coating and Heat Treating.

[Rockydoc]

With the proper alloys, e.g., one with antimony and a little arsenic, one can heat treat to achieve BHNs up to 30. This is done by heat soaking the bullets in a convection oven for an hour at temps that can vary from 400* to 460* depending on the BHN desired, then quenching in water.

It seems to me that if you PC after heat treating that 1/2 hour in the oven at 400* would anneal your bullets back to a softer alloy.

What would happen if you size and add gas check, apply powder and bake for an hour at temps up to 430* and higher, then quench? Would that much heat for that long ruin the powder coat material?
Rocky

 

[Brad]

COULD burn the PC.
It is a combination of temp, time, and coating that determines what happens.
Certainly worth a trial run to see.
I believe Ian has done some testing where he baked PC bullets for a full hour.

 

[popper]

I use smoke's PC, coat, cook for hour and then into ice water. Never a problem, works fine in 308W & BO. Above 2% Sb H.T. works good. Add As to get the BHN up FASTER.

 

[CWLONGSHOT]

I advise a sheet of foil on top if bullets. I also advise that they be stood not laid on there sides. Yes 100% on ICE WATER!

As for the PC, they will survive the bakE if the heat is indirect. (That's what foul does)

I have never seen 30, I hesitate to say ya cant... But I have t reached that. But 25 ish sure!

CW

 

[waco]

One of the benefits of PC is being able to achieve speeds with a less BHN alloy than one using a lubed bullet can. I hope Ian chimes in. He did some real good testing and great results in his .308
If memory serves, he was getting something like 22-2300fps with just over 1 moa accuracy with something like 9-10 bhn alloy.
The polymer “jacket” allows for things bare lead just can’t hold up to.

 

[Ian]

One of the benefits of PC is being able to achieve speeds with a less BHN alloy than one using a lubed bullet can.

THIS^^^^^^^^^^^^^^^^^^^

Forget 30 BHN if you powder coat.

The only time anything harder than air cooled wheelweights was any help at all was one time in a 5.56x45mm at over 2,900 fps. Since then I've pushed a different .22 bullet (thanks, Walter for the mould) over 3,000 fps with MOA accuracy.....and the bullets were wheelweights that hadn't even fully aged after coating and air quenching.

You can get within about 80% of uncoated quench hardness by doing the same routine. The coating insulates somewhat and limits the quench hardness somewhat. 400⁰F for 20 minutes is plenty to soften to as-cast hardness but it takes a minimum of 45-50 minutes to loosen the molecules enough for a good quench hardening. Quenching after 20-40 minutes won't do squat.

 

[Ian]

These were from my M1A pencil-barrel, 50/50 alloy, first rounds I ever shot PC'd for rifle, as I recall that was about 2250 fps.



My LR-308 prefers a little more tough at 13-14 BHN, but with its 18" barrel I'm running right up against 50,000 PSI to get 2,464 average fps:

 

[Ian]

these were air cooled wheelweight .22s at over 3K FPS. All these and the ithers except the first M1A group on the left were shot at 100 yards.

 

[fiver]

when I want to do both I step up the heat.
350-375 400, 20 minutes each [and closer to 25 for the first 2 steps] this doesn't hurt the powder and I get a full hour of heat sink time.
I turn off the oven and wait about 2 minutes [until the heat starts dropping off] then pull the tray and dump everything into cold water.
I don't think I get much more BHN than water dropping from the mold, but I've never really measured either.

 

[popper]

This was from BO carbine, 2% Cu added to 50/50 & WD, 145gr PB HiTek ~2k fps. No leading. Don't know BHN but tested one against superhard ingot in vice. Dented the superhard! Hard works but NOT really needed. IIRC S.H. is >36 BHN.

 

[Rockydoc]

Thank you to all for your excellent responses. I don’t need anywhere near 30 BHN, that was only a demonstration of what is possible. I want 15 to 16 BHN.

So, size and gas check; shake powder and stand on end in a pan, cover with foil, bake for proper time and temperature for the BHN desired, carefully dump into ice water, and voila. Powder coated heat treated hardened bullets.

Thank you gentlemen.

 

[Rockydoc]

After thinking about Ian’s post, I think that COWW + 1% tin air cooled and PCed in a normal way should satisfy a requirement for 15-16 BHN.

Am I correct, Ian?

 

[popper]

Depends on what your load is. Using 50/50 H.T. in BO now, 50/50 AC in 30/30 - both work fine. H.T. low Sb alloy cause I'm cheap and it works. Been tinkering with alloy over the years, IMHO just hard enough for accuracy at the pressure/fps you want. PC will easily take temp above the slump temp of the alloy. When I remelt coated bullets in the pot, ~650 the coating starts to shrivel. Doesn't turn brown till 700+. Like Fiver says, start at 300-350 first to get the PC to flow, then up temp for an hour if going to WD. Just 15-20 min total for AC. I cook 100 at a time on hot plate standing - cover with a high temp plastic pan she gave me. Don't take the AR rifle upper very often but clocked 2700 fps 165gr GC PC in it, close to COWW H.T. alloy. Posted here someplace, AR308W @ 200 steel target, would have probably been MOA (just over 2" 3 shot group) but I'm sitting on a stool in the middle of sunflower field. Alloy was roto high Sb with some Cu added and HF PC loaded at least a year prior.

 

[Ian]

After thinking about Ian’s post, I think that COWW + 1% tin air cooled and PCed in a normal way should satisfy a requirement for 15-16 BHN.

Am I correct, Ian?

Sounds to me like you're getting wrapped around the BHN axle. Can we back up a minute and examine why you think you need 16 bhn?

 

[Rockydoc]

I estimate I would need 15-16 BHN for 30-30 Win 175 gr bullet @ ~1900-2000 FPS.

 

[JWFilips]

PC coating gives you a lot more speed potential even with low BHN bullets Try them as baked.... Bet you do not get leading!

 

[Rockydoc]

PC coating gives you a lot more speed potential even with low BHN bullets Try them as baked.... Bet you do not get leading!

So just "shake, dump, bake" as usual and they will be fine without bothering with heat treating (which is a pita )?

 

[popper]

Depending on powder used, yup. 185gr GC 50/50 AC runs 1950 from my marlin with LeverE load. Upper right.

 

[Ian]

100 yard group, Lee group buy 311041 copy, powder-coated, gas-checked, air cooled wheelweights at about 1850 fps from my old 336 Texan:



Something like 12.5 bhn, and they didn't need to be as hard as that, that's just how they turned out. You'll get further by spending your time actually shooting than you will reading the theories of Richard Lee.

 

[fiver]

you don't need the BHN without the coating.
the 30-30 is sooo easy to get good results from without a lot of foofarah it's not even worth trying all the baloney.

now, trying a couple of different diameters and one smaller than you normally would use when coating is worth the effort.
even slightly smaller jacketed bullets will generally do better than over sized ones.
not always depending on the rifling type etc. but in a good straight barrel they will.