Raised sprue bump on boolits from base pour molds, how many remove it?

[Hang Fire]

Some (actually many) mold sprue cutter plates do not cut flush on boolit base but leave a residual bump. Years ago I got tired of it and started removing them, at first I filed them off, but that proved tedious and time consuming. So made little jigs to hold boolits snug in vertical position, then with 220 grit paper on a piece of heavy plate glass and using a figure 8 motion, just hand lap the boolit bases flat.

I have read where some say so long as it is on the boolit base, no big deal as won't affect accuracy. But seeing that bump off center struck me as possibly making the boolit unbalanced. And it sure makes it nice when seating gas checks to have them seated true flat.

But that is just me, so would like to hear from others as to the pros and cons.

[Springfield]

Cut when the bullet is hotter and the bumps usually go away. My bullets usually actually have a depression on the base, not a bump.

[HeavyMetal]

I've had the bump issue and tracked it down to a loose sprue plate.

Check that and adjust as needed and do like Springfield says and cut the sprue just a little hotter.

[MtGun44]

+1 on cut sprue sooner or run metal and mold hotter.

Besides, this is NOT an accy issue.

Try this - pick out the 5 worst base bumps you can find and then 5 with filed flat bases.

Load and shoot groups, compare. Weep for all the wasted time.

Of course, MAYBE your results will be different and you will have discovered a new way
to improve accy. I'd not bet on it, but sometimes I'm wrong.

Bill

[357maximum]

You are cutting your sprues while the alloy/mould is too cold. Run the alloy warmer and/or cut your sprues sooner.........a small consistent divet is better than a bump.

[ghh3rd]

I notice mine when gas checking - can't stand to see the bump prodding the middle of the check, and usually file the bump off before checking.

[ph4570]

As others have noted, cutting the sprue sooner addresses the bump issue as well as making it easier to do the cut. Use a suitable lube to eliminate lead smearing.

[mroliver77]

I have had molds that the sprue hole was not sharp at the bottom and actually looked to have a tiny countersink from the bottom. I have used a countersink to sharpen the hole (from the top) and then worked sprue plate flat with plate glass and emery paper. As has been said, cutting a bit sooner helps too.
Jay

[qajaq59]

If you are getting a bump, that sprue cutter would have to be either bending up because it is really dull, or loose. I'd cut them a little hotter rather then spend time filing them.

[Blackknight]

In addition to the above methods try this; swing the sprue plate with a gloved hand to cut the sprue, then back the plate up to cover the cut sprue and press it down to flatten the bump. Hold it there for just a second and you will have a flat base with hardly any sign of the cut left. Often the base of the bullet will have the impression of the machine marks of the sprue plate. Temp of the mold and metal will have a lot to do with the end product.

Regards,

Bob

[DLCTEX]

I cut the sprue with a gloved hand and apply downward pressure to keep the sprue plate from riding over the bump. +1 on cutting hotter.

[theperfessor]

The only time I ever get a bump is with a dull sprue hole or a loose sprue plate, both of which can be dealt with by using a little TLC and maintenance.

[prs]

Back when I was so foolish as to cast my own round pistol balls, my molds left a little spru teet exposed. I got into the habbit of putting that teet upward where the ball ram would mash it flush anyway. Did do so accuracy testing with them willy nilly as compared to all up and with my limited shooting ability it made no never-mind at all. The Lee six cavity molds I use now demand cutting spru while the alloy is still way hot and soft and like Springfield, I get a very slight torn depression. Some will tell you that is a flaw in technique, but it seems not to matter one itty bit.

prs

[grouch]

I vote with the guys cutting the sprue with a gloved hand and downward pressure. Beating it with a stick has almost always left a lump on my bullets. Cutting with the gloved hand has really improved it.
Grouch

[mooman76]

I was kind of thinking the opposite but hard to really say without pictures or a better discription of the bump. Sometimes when cutting to soon it pulls a little piece of lead up leaving a depression but also leaving a little lump of lead next to it. If the other ideas don't work try cutting a little bit later so it has solidified plenty.

[wallenba]

I get that too. If I run it hot or cut them too soon they smear and build up under the sprue plate. With some of my Lee molds, the screw will not budge and I've learned my lesson by forcing one once before, broke the screw off. I just let it be if it's a low speed target round. With my rifle boolits I have what is essentially a paper patch board. Just a piece of plywood with a kerf in it to rest the boolit. I then use a sharp wood plane blade to nudge the bump off. I would rather have lead flakes than dust from a file to deal with.

[zomby woof]

I cut the sprue with a gloved hand and apply downward pressure to keep the sprue plate from riding over the bump. +1 on cutting hotter.

I tried this method yesterday, it worked great.

I'm getting good at this!!

[Dollar Bill]

I tried this method yesterday, it worked great.

I'm getting good at this!!

I had to confess the errors of my ways on the CBA forum and swore to never abuse my molds again by beating on the sprue plate. Nothing but smooth bases ever since. [smilie=w: