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pauljames
I just purchased the 225-67 mold to cast for my AR. I’ve never cast a bullet this small and I’m having some problems. I’m sure it is operator error so I’m asking for guidance.
The mold was cleaned when received and heated and cooled twice on my hot plate before use. I did not smoke the mold.I cast 5lbs or so yesterday at my normal 700* setting after preheating the mold. My alloy is basically COWW with 2% tin added. I maintained a fairly quick pace and water dropped most of them. I had some “folds” along the sides of the bullets with pretty good nose fillout. A few of the bullets had some minor finning near the tip of the nose. Most went back into the pot.
Today I tried another batch, again about 5lbs. I added another .5lb of tin to the mix, raised the pot temp to 750* and tried to slow down the fill to each cavity. I had better success but still have some minor “folds” in the area of the lube grooves and still have some minor finning at the nose. I have some shootable bullets but I’m still not satisfied.
I plan to try again tomorrow and realize that in the past I have taken 2-3 sessions with a new mold to produce quality bullets. I have 50 years casting experience but most of that was with iron molds and this geezer has struggled to learn to use quality aluminum molds.
I would appreciate any guidance in my quest to learn to cast this tiny skinny bullet. Thanks!
pauljames
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adamsutherland
Those wee bullets don’t add much heat to the mould each cast, so everything needs to be run hot, alloy, mould and sprue plate.
I’d turn the alloy temp up to 750, ensure the mould is well warmed up, I like to get my mould very hot so at first casts they sprue will take a long time to solidify I find it easier to let the mould cool down to running temp that try to get it to temp by casting. also importantly ensure the sprue plate stays at the right temp by running the alloy over the sprue plate for a second or two after the cavities are filled.
AlvinYork
I second Dromia’s comments.
The finning is probably due, at least in my case, to not getting the blocks shut tight enough. I attribute it, in my case, to old fiingers not doing their job. So if I’m having that issue I use a small 1 1/2 clamp on the mould handles to really get a tight closing of the blocks. Then I just pop it off after the sprue has darkened enough and usually the problem has gone away.Is the fining on the nose round the nose ‘tween mould and sprue plate or is it on the mould seam?
If the latter I would check the alignment pins seating depth. If the former then I would check the sprue plate stop screw and the sprue plate retaining screw to ensure that the sprue plate lies flat and isn’t warped by too much or too little screw tension on the sprue plate. To far in a sprue plate stop pin can also resist the proper closure of the mould and give seam fining as well.
The finning I’m seeing is at the mold split line. I’ll try keep the mold handles tighter and will take a look at the alignment pins. I do run with the sprue plate quite loose. I might try tighten it up a bit. I’ll set the PID at 750* and get the mold hotter before I start on the next batch and build a bit more sprue, probably tomorrow.
Appreciate the input guys!!Update………….Cast for an hour yesterday after checking alignment pins and sprue plate closure. Tightened sprue plate a little, heated mold and sprue plate at high on my hot plate and set my PID at 750*. I tried to concentrate on holding the mold handles tighter. I finally have better fill out and more acceptable bullets.
This morning I tried again with the PID set at 775*. I cast for about 30 minutes and the sprue plate locked up open. Not sure if I may have warped it. I quit casting and everything is cooling. I’ll check the plate with a straight edge when cooled and call NOE if it is warped. The added 25* did not appear to improve my bullets.
adamsutherland
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