Bigslug
05-03-2014, 11:19 AM
I knew that when I got to the point of casting little bullets, there were going to be some challenges to getting enough heat energy into the mold to get it up to a working temperature. After deciding on NOE's five cavity 70 grain RNGC, it seemed that if there was a place for additional temperature control, this was it, so I added Swede's thermometer to the order and requested that the mold be drilled for it's probe.
The instructions for the thermometer weren't caliber, bullet weight or mold-material specific. They generically suggest starting the mold low (about 300F) and the pot high (700-750F) and finding the sweet spot from there - usually bringing the melt temperature down. Since these were going to be less than half the weight of anything I've previously cast, I figured to start low (650F) and work up to whatever state it is that these wee wittle buwwets require. I decided to use Lyman #2 as a starting point, simply to get a solid, known alloy baseline.
.22's need to be cast HOT. . .but you probably already knew that. With the lower lead temperatures and the mold pre-heated to about 315F, fillout was quite poor. I even had a few cases of the sprue solidifying on the plate with little or nothing making it into the cavities. That was WEIRD. Consistent drops of well-filled shiny bullets were arrived at with the lead approaching 750F, though the final - and happiest - setting of the PID was 775. The mold wanted to run at about 415-425F. Below 400F and fillout problems started to return. At the workable temperatures it seemed to take about 20 seconds for the sprue to frost over - so about 25-30 seconds from pour to cracking the mold open.
As to the use of the mold thermometer, where I found it most useful was in determining the pace I needed to cast at to maintain the mold temperature. With these little slugs and big aluminum mold, there is a fine line between adding a few degrees, losing a few degrees, or holding steady with each pour. Not having a readout on the mold is like running a race where you can't see and don't know the distance between you and the guy you're trying to catch. Having the readout puts that guy in your sight and you have a much clearer idea of how fast you need to run.
Do I now regard this thermometer as necessary for all bullets? Absolutely not. Stuff in the 200 grain ballpark ensures enough energy being dumped into the mold to make the process fairly trouble free. For these little guys however, it saved serious time on the learning curve. The thermometer and probe were $33 (one time), having the mold drilled for it was $2.50 (big whup), and the thermometer came with the drill bit to DIY molds you already have (for the bit and tap for a set screw hole, you're on your own). I think any NOE mold I order from here on out will get factory-tapped to take the probe, and I will jig up the press to drill and tap my existing ones (the hollowpoints anyway).
I figure even on the easy molds, I will run them with the thermometer at least once to quickly and definitively learn their temp settings and necessary cadences, and write all that down for the next time I use them. I'd rather not operate with a Walkman cable strung out of my molds if I can't help it, but for getting initial data on the mold, I don't think you can beat it. Not a mandatory tool, but a darned helpful one!
The instructions for the thermometer weren't caliber, bullet weight or mold-material specific. They generically suggest starting the mold low (about 300F) and the pot high (700-750F) and finding the sweet spot from there - usually bringing the melt temperature down. Since these were going to be less than half the weight of anything I've previously cast, I figured to start low (650F) and work up to whatever state it is that these wee wittle buwwets require. I decided to use Lyman #2 as a starting point, simply to get a solid, known alloy baseline.
.22's need to be cast HOT. . .but you probably already knew that. With the lower lead temperatures and the mold pre-heated to about 315F, fillout was quite poor. I even had a few cases of the sprue solidifying on the plate with little or nothing making it into the cavities. That was WEIRD. Consistent drops of well-filled shiny bullets were arrived at with the lead approaching 750F, though the final - and happiest - setting of the PID was 775. The mold wanted to run at about 415-425F. Below 400F and fillout problems started to return. At the workable temperatures it seemed to take about 20 seconds for the sprue to frost over - so about 25-30 seconds from pour to cracking the mold open.
As to the use of the mold thermometer, where I found it most useful was in determining the pace I needed to cast at to maintain the mold temperature. With these little slugs and big aluminum mold, there is a fine line between adding a few degrees, losing a few degrees, or holding steady with each pour. Not having a readout on the mold is like running a race where you can't see and don't know the distance between you and the guy you're trying to catch. Having the readout puts that guy in your sight and you have a much clearer idea of how fast you need to run.
Do I now regard this thermometer as necessary for all bullets? Absolutely not. Stuff in the 200 grain ballpark ensures enough energy being dumped into the mold to make the process fairly trouble free. For these little guys however, it saved serious time on the learning curve. The thermometer and probe were $33 (one time), having the mold drilled for it was $2.50 (big whup), and the thermometer came with the drill bit to DIY molds you already have (for the bit and tap for a set screw hole, you're on your own). I think any NOE mold I order from here on out will get factory-tapped to take the probe, and I will jig up the press to drill and tap my existing ones (the hollowpoints anyway).
I figure even on the easy molds, I will run them with the thermometer at least once to quickly and definitively learn their temp settings and necessary cadences, and write all that down for the next time I use them. I'd rather not operate with a Walkman cable strung out of my molds if I can't help it, but for getting initial data on the mold, I don't think you can beat it. Not a mandatory tool, but a darned helpful one!