Cause of poor fillout at the base of bullet

[Possum]

What causes rounded ends in the base of the bullet? I have two molds that I have that problem with and they are both gas check molds. Is it improper temp of the mold? Where it is occuring is right under the sprue plate.

[S.R.Custom]

Two things: (1) Not enough head pressure in your bottom-pour pot (too slow to fill; make sure your pot is full and the snout is clear). But you're dipping you say? Pour faster. (2) Cold sprue plate. Don't leave your sprue plate open any more than necessary. Overall, run your melt and mould a bit hotter.

[Possum]

Thanks

[1Shirt]

Agree with Super Mag! The key is more heat: Mold needs to be hotter, Lead needs to be hotter, and get a casting speed that is consistant so that everything stays hot. You will be hot enough when you get frosting on the blt.
1Shirt!:coffee:

[Calamity Jake]

There could also be a venting problem. Using a small sharpening stone put a small bevel along the top of the blocks at the parting line being sure you don't roll a burr over into the cavities or on the inside faces or top. GO SLOWLY AND USE A LIGHT TOUCH!!!!!!

[sundog]

Yup, heat and venting.

Also, make sure the blocks are clean. One other thing to check is sprue hole size. Too small and what you describe will occur because the alloy will not flow optimally. If you need to enlarge a sprue hole, do it incrementally. Find a drill that just fits, then go to the next size. Enlarge the hole, chamfer from the top only (by hand), and stone the under side making sure there are no burrs - sprue plate FLAT on a good fine stone or fine grit paper on glass. Test cast. Redo procedure until bases fill correctly.

Thicker sprue plates tend to work better than thin ones.

Jake has one of the 'bestest' solutions by chamfering the block mating surfaces. Under the sprue plate you will get a new vent line. Go real easy!

[garandsrus]

Possum,

Make sure you have an adequate puddle of lead on top of the sprue plate also. When the boolit initially cools it shrinks slightly so you want it to pull lead from the sprue and not the side of the boolit.

John

[dromia]

Make sure your sprue plate isn't screwed down to tight, it should move freely without rattling around vertically.

[Sky C.]

Make sure your sprue plate isn't screwed down to tight, it should move freely without rattling around vertically.

Another wat to ensure proper venting.

I play with a fair number of moulds & have encountered the problem somewhat frequently. Once you have verified you are working with a clean mould and have tried a range of temps - and this can all be done pretty quickly... The next step for me is to improve the venting. After studying some of Rob Applegate's moulds (absolute gems!) I tried adding vent lines to the top of the blocks under the sprue plate like what he does on his designs. It can be done by using a carbide scribe and with a bit of pressure simply scribe a few lines from the base outwards. A few passes is usually enough and can turn a tempermental mould into a well behaved one pretty quickly. The same goes for a mould where a band somewhere may not be filling out well. Drag the scribe from the offending portion on the mould a couple times out to the edge of the blocks and it'll usually solve the problem.

Best regards-

Sky C.

[38 Super Auto]

What causes rounded ends in the base of the bullet?

I had this problem about a month ago with a Lee 255gr .45 mold. After the mold heated up, I started dropping bullets. The bullets from four of the cavities would consistantly not fill out on the bases.

Lee molds have a reputation for a number of issues. I suspected venting, so I cleaned the mold faces and scribed out the vent lines, and tried again.

This time, I only had one cavity that wouldn't fill out. I worked on it some more and could never get the last cavity to fill properly. The lead pot was running max temp.

I noticed that one of the alignment pins was loose, so I sent it back for a refund and ordered a Lyman mold. I've got six other Lee 6-cavs and they all drop good bullets (after I worked on them a little)

[725]

Yes to all the above. SkyC alluded to a clean mould. If some Bull plate lube migrated over to the cavity, it has caused a rounded edge on some of mine. Clean mould, clear vent lines and (my favorite) a forceful stream should give good results.
725

[Possum]

Wow....go to work and get a pile of answers when I get home. Now that's service. :-D

I am going to look at the venting. I cleaned the mold well and put the heat to it. It probably is the venting. The hole size may be a problem also. Seemed like the stream had a hard time going down into the hole easy. I tried another proven mold with the alloy I was using to make sure it wasn't contaminated or somthing and it turned out great bullets. I will figure it out with your suggestions. I want this one to cast. It is the 358627 from the group buy that just got delivered. The few I did get filled out look great.

[725]

Possum,
I worked with the GB 358627 today also and had a minor example of the same thing. One of the cavities was more to the rounded base and several castings finally fixed it. Had to run it hot and add a little linotype. It's a neat one.
725

[Possum]

Boiled the mold in dish detergent, cleaned it with acetone, then bored out the sprue plate holes. It started casting great. Went through a whole pot in no time. Great looking bullet. I hope this one shoots as good as it looks. Thanks for the help!