couple of cooking pc questions

[ryokox3]

Hi all,

For those of you who know better than me, can PC be over heated (aside from melting the lead) ? If the instructions are 400 for 15 min, will going to say 450 for 15 mess it up? I'm thinking I'd like to add a buffer as my oven tends to wander during the baking session and I don't want to risk an under temp cook. I also want to stop having to fiddle with the temp during the bake.

Ty all

[popper]

I've gone to 425F before, no problems with Smoke's black (1 hr bake). It seems to flow a tad more at the high temp.
I'm H.T.ing to shoot in 308W @ 2700. Smoke's black does NOT get brittle at that temp. Loaded a bunch done @ 425 (PID) yesterday, no problem, same as ones @ 400. I load the convection oven, turn it on, ~10 min to get to temp & let it run for an hour. Dump in cold water.

[fredj338]

At some temp point you are softening the bullet. Whether the PC holds up or not, probably depends on the PC. Put an oven therm in, check it against the setting & try to stay as close to 400 as possible IMO. I am a newb at this though. I set my oven using the oven therm. The dial reads 425, but the therm says 400 after 15m preheating. I only bake 12-13min total time.

[Smoke4320]

Yes you can go over temp and end up brittle coating. Every color will be slightly different as to what that temp will be

[edctexas]

I use a PID to control oven temp. The TC sensor is attached to the metal sheet that the boolits sit on. Just this weekend I double checked the setup. I measured the boolits with an IR thermometer. Quick peak with the door open and shoot two boolit temps. Wait several minute and check a different 2 or 3 boolits. The result was that sensing air temp seemed to give a lower boolit temp than sensing the plate temp. Results were that the IR boolit temp for Smoke's orange brown and red are about 10 degrees below the oven setting. My cheap $5 oven does not have convection fans. The temp on the boolits checked in various locations indicated about +/- 15 degrees from front to back. Side to side was less. The oven has a heater in the bottom and the top running side to side in the center.

I have tried times from 10 minutes to 30 minutes at a 400F setpoint. The timing is from the indicated temp reaching 390F. This is after the coating is visually slick. Longer seemed better in terms of cleaner barrels (NO Lead). Shorter times took 4-5 patches with solvent. 20 minutes and 30 minutes cleaned with two patches. 50 rounds fired for each baked test run in S&W 66 357mag.

Ed C

[ryokox3]

Thank you all for the replies. I do have a well rated oven temp gauge I grabbed a year or so back on amazon. Also my oven is convection thanks to a nice craigslist pickup. It works great and holds a temp until I turn my back and try to do something else. It is like that damn oven knows and then increases or drops the temp. Anyway I guess I just need to keep babysitting it. I often wonder if installing a pid and figuring how to set it up would be cheaper than just buying a more expensive oven.

-Ry

[bangerjim]

A digital controller is not a cure-all for a poor oven. I sell industrial quality controllers and T/C's and do not use any on my oven or lead pots. Not really needed.

I bought 2 junker ovens for $5 each very early on when we all were developing this fun hobby and had horrible bakes. Threw them away and bought a $100 or so QUALTY convection oven. Best buy I ever made. Temp is with 5 degrees of dial.....YES the dial! I lucked out. A good oven thermometer (not an IR) is needed to verify.

I never bake over 400F. Early on I found higher temps can cause brittleness and darkening of the coating. Why deviate from from the engineered spec's for the powder......400F. I have baked from as little as 6 min to 20 min.......not really any difference. Now I ALWAYS use 10 min AFTER the powder turns shiny on the boolits. All my bakes are perfect hammer test passers! And they shoot great.

My suggestion is stick with what the powder is designed for and not a longer time.

bangerjim

[mongoose33]

Yes, you can over-cook them. Here's an example from my first PC attempt:



This was how I learned my toaster oven, set at "400" was actually exceeding 550 degrees; the darned boolits melted!

You can see how the coating is brown; it should have been the red color of the boolit on the right, which I did at a thermometer-verified 400 degrees.

So--you can "burn" 'em. Don't.

[Boolit_Head]

That is actually kind of funny, it looks like the PC sort of contained the lead as it slumped/melted.

[popper]

Attachment 151704
ESPC Smoke's black on my lazy susan/golf tee rig, cooked 1 hr @ 425. Sized fine, not brittle at all. This is a modified BB and coating is great all the way to the hidden base. I used the 'trident' modified electrode, didn't even bother to recover any overspray as there was so little. Dust coating on base is from not cleaning the tee's completely between sprays.

[P Flados]

I am not sure, but my HF red and what I did may indicated that success can come from much less than the "standard"

I got a $5 oven with digital controls & a broke display. First try was with some culls where I just turned it on, set it for bake & cooked for 20 minutes total.

Results were great.

Some later batches I loaded in a cold oven, and just ran for a time interval. Good results again

Some time intervals were probably less than 20 minutes and still melted/cured great.

The above seemed neat in getting the job done with no pre-heat & less overall time.

I noted that my water dropped COWW bullets seem to stay just as hard as before. I scraped off the coating & used drafting pencil scratching to compare to uncooked bullets from the same batch.

Then I decided to check out the oven using the T/C from the PID setup I use for my Lee 10# dripmaster pot.

Drilled a 3/16 hole in the side and stuck the TC in. Powered up the PID and turned the oven on.

I had previously checked the PID T/C and knew that it reads 217 °F at 212 °F actual. All results below are "compensated".

As it was heating up I noted the "convection" button for the first time. I hit the button, and the fan started.

Temperature came up and settled into an up and down cycle of 340 ± 5 °F.

So, it looks like I was getting a good cure with the actual coating never hitting more than say 345 °F. And in say 20 minutes from oven turned on until oven turned off.

I know that not all coatings work the same & there is some amount of "lack of precision" in my un-intentional testing of "minimum heat/duration" needed for curing.

However, this would seem to indicate that we may be able to PC with little or no adverse impact on the "heat treat hardness" we get from water quenching.

I need to do some test runs in a more controlled sequence to increase my confidence in how low/short is good enough.

The whole "check the toaster oven" started out as I was thinking about trying to cure PC and heat treat the bullets in one step. Again, sounds like testing is in order.

[popper]

Haven't used HF red for a while but Smoke's black starts to shine/smell about 350F also. I drop on a towel when casting, then H.T. & bake coating once. No worries about loosing BHN that way.

[P Flados]

Got in two test batches.

Batch #1 (335 °F peak, 10 minutes above 320 °F) did not get enough time and/or temp.

Batch 2 (362 °F peak, 14 minutes above 320 °F) did great.



Flaking noted on batch #1 smash test



No flaking on batch #2 smash test

[bangerjim]

Sooooooooooo.......why are you messing around with 320 and 360F??????? The powders are engineered to bake at 400F!

Just bake at what we all know works. The manufacturers all tell us that.

banger

[Dragonheart]

The manufacture of the powders I use says 400 degrees for 10 minutes. I also understand they is a little wiggle room, but if you want consistently good coated bullets just cook for 10 minutes once the oven reached 400. If you have a glass door on your oven, as most do, jut buy a Taylor Glass Oven Thermometer and place it where you can see it through the door glass. When the oven gets to 400 set the timer a little extra time doesn't hurt the process, but going too high in temp can.

[popper]

I see absolutely NO sense in preheating the oven. When you put several pounds of lead in, the temp WILL drop a lot. Waste of time. The powders I've used do NOT get brittle when cooked above 400F, my guess they are good to 550F or so (most 'plastic' elec. insulation is good to 600F), from watching recycling in the melt pot. Thick plastic is harder to bend without breaking than the same thin plastic.

[bangerjim]

I too have gone to "seat-o-the-pants" simple oven temp control!

I use ONLY a convection oven for accurate oven temp profile
Put trays in
Set dial at 400F (pre-proven with accurate oven thermometer/digital meter) Your dial may vary.
Turn timer dial to ~15 minutes.
Watch thru the glass until the powder on ALL the boolits turns shiny
Set timer at 10 minutes
Go load some more on racks

Works every time for me. No Proportional/Integral/Derivative controllers needed at all. Just plain old common sense.

bangerjim

[P Flados]

Sooooooooooo.......why are you messing around with 320 and 360F??

I had no clue as to the temps on my first few tests and they worked great.

Later I found I was getting good cures at what I now know was real close to 335 °F peak. With enough time, the lower temp passed the smash test just fine.

I do not plan to keep cooking at this temp (335 °F Peak).

I tried out the lower temps for a couple of reasons. I want to know what is "reliably good enough" with minimum oven time and I want to understand my choices with respect to final boolit hardness. I like water quenching from the mold. However, unless I can get more reliable time intervals (boolits need to drop with one tap) I may switch over to oven heat treating to increase hardness.

Getting 362 °F peak should be repeatable, I did one push of the "temp +" button combinations on the oven (again, it is a digital oven with a broke display).

I will probably run a test at the 362 °F peak setting for a couple of minutes less.

I want to find "just good enough" so I can add say 2 minutes to provide a reasonable margin for reliable results.

I may try push the "temp +" button combination twice & see what it gives me.

Bottom line, unless I am trying to heat treat (with quench afterwards to increase hardness, or air cool to reduce hardness) I do not think it is helpful get the bullets hotter than required or to cook them for longer than required. If the coating adheres good enough for the smash test, I am confident that it has the mechanical properties to provide the protective coating we want.

Back when I started using PC, I was kind of surprised at first that I did not seem to be loosing hardness given what I read here. However, now I think I understand why and I understand that there is probably no need to "sacrifice" your water dropped hardness if you do not want to.

[Dragonheart]

Agreed, no need to preheat, in fact it is much easier to load a cold oven, since I cook three racks at a time.
Once you have done a few batches watching the thermometer and time you find a consistant time it takes to come to 400 plus 10+ minutes more to cook. Then you can just set your timer after the oven is loaded and go do something else and the oven will shut down. You can retrieve the bullets sometime later or the next day, all perfectly cooked.

[45cal]

At some temp point you are softening the bullet. Whether the PC holds up or not, probably depends on the PC. Put an oven therm in, check it against the setting & try to stay as close to 400 as possible IMO. I am a newb at this though. I set my oven using the oven therm. The dial reads 425, but the therm says 400 after 15m preheating. I only bake 12-13min total time.

This made me smile,got you hooked looks like