mold won't fill up

[Catch]

I have a Lyman 35893 mold. It is a pointed 125 gr. gas check bullet. It refuses to fill up when I am casting. I have cleaned it repeatedly, boiled it, lapped it twice, cleaned the surface grooves, smoked it, filled it with different temp lead, used different mixes, varied the cut off height
(8 or 10 times) and even beagled it with one thickness of alum tape. It still won't fill and leaves voids around the top groove..............
Help! I'm upset, but not pissed off..........yet. Can someone give me some ideas please? My tenacity is heading towards stubborn but I am willing to try anything before I call it quits and turn the damn thing into a paperweight.......(old folks are like that)
Thanks for your help and ideas in advance...........Catch. [smilie=b:

[longbow]

My first two suggestions are:

- pre-heat the mould to just under casting temperature (if you already haven't)
- loosen up the sprue plate so it will almost swing under it's own weight ~ sometimes they fit so well air cannot escape

Since you have cleaned and lapped, I doubt there is any oil or anything else left in the cavities..

If pre-heating the mould doesn't work or you have done it then I suspect it is the sprue plate being too tight. That one is an easy check though and if loosening it works then what you want to do is take a very FINE file, like a jeweler's file, and VERY SLIGHTLY break the mould face edges where they meet under the sprue plate to form a V of just a few thou... barely visible ~ about like a vent line or even smaller.

Breaking that top edge has worked fore me on several moulds where base fillout was not good or inconsistent. It allows venting under the sprue plate as the mould fills the base band or gas check shank.

Longbow

[montana_charlie]

It still won't fill and leaves voids around the top groove..............
I take it that you are not talking about the base of the bullet ... right?
Is 'the top groove' the one nearest the tip of the bullet?

CM

[popper]

varied the cut off height (8 or 10 times)?

[leadman]

If an actual lapping compound was used to lap it this may be part of the problem. The compound I bought from Midway uses an oil that is extremely difficult to get cleaned out of the mold.
I don't understand what varying the cutoff height means.

[runfiverun]

venting.....
not sure what the top groove is but i'd bet it's the base band..
i'd go with breaking the edge of the mold back too.
before I done that I would loosen the sprue plate nut a quarter turn.

[MtGun44]

Agree with r5r, loosen the sprue plate a hair and also, add some tin to the melt.

Bill

[Bullshop]

This can be tough to diagnose sometimes because its hard to comunicate exactly what you know or dont know that some people take for granted and then sometimes there is just a terminology confusion.
It sounds to me like you know what your doing and you have pretty much done everything you can.
I am not sure about this but I have an idea that sometimes there are internal flaws in the mold block material that may be quite porous. Once penitration oils have found there way into these internal voids it can be quite dificult to get out or take a very long time for them to completely burn out to the point where they no longer give off gas when heated to casting temp.
I too have had a couple in the hundreds that I have used that were very stuborn in this reguard but in time they will finally relent and break in for lack of a better term.
For goodness sake when it does finally end your missouri dont put any oil on it again as a preservative.
I have in just a couple sevear cases added a vent line to the band that is refusing to fill out because it is a venting issue that is being caused by the trapped oil. The super heated oil is producing gas faster than it can be vented by the venting system in place, the factory vent lines
Whay I have done is to individually clamp each block half one at a time in a vice. Then clamp a metal straight edge to the block half the one edge of the straight edge in exact alignment with the offending band.
Gently using a small three corner file pressed against the ruler stroke accross the block. In a few light strokes you will have a good vent line exactly at the location that is causing the problem.
To be sure this is a last resort but in each case that I have resorted to it it solved the problem.
If done with care it will look as if done when the block was machined accept that it wont match the other vent lines for size or shape but it will adiquately vent the problem area.

[Walter Laich]

Is there a bit of open space when you pour lead in the mold? Try reducing the stream (diameter) of the pour so the air can escape out the spure plate. Kinda out in left field with this but something that doesn't cost anything to try. I had a mold with spure holes too small that was a bear to cast with. Opened up the holes and problems went away.

my guess,
walt

[Chicken Thief]

Heat!
Heat the snot out of the mould and cast it to temp. Within reason!!!!!!!!
A hotplate is a BIG must/bonus here.
A 2 or 4 banger i rest on the end and a Lee 6 banger on its bottom.
When i cast above 10-12 BHN alloys i strive for 6-8 seconds between the sprue sets and hardens (turns gray instead of a slight opaque/semi reflective).
You will find a rythm that suits you but moulds are like rifles, each prefers it's own.

[Chicken Thief]

Some moulds cast good faster than others.
I have had a RCBS cast perfect from get go. It was cleaned and heated.
Some (all of my iron) takes just a few casts to get perfect.
All of my Lee moulds has taken some casting to get good (20-50 castings with wrinkled boolits).

[captaint]

Other than the sprue plate being too tight, the only other thing I can think of is a stone cold
sprue plate. Or break those top edges a little. I've done that when I have base fillout problems.
It does work. Mike

[Catch]

I am talking about the groove nearest the top or point (in this case) of the bullet. It would be the first full diameter of the bullet entering the rifling. 8 or ten times means I changed the height of the sprue plate 8 or 10 times. I shimmed it, washer ed it, and even tried casting a few without it. Same result. I lapped the thing with Dutch cleanser, twice. Sprue plate wasn't stone cold after casting 50 bullets, and the problem persisted with 99% unusable......
I guess I am a little annoyed with the damn thing. Normally I boil my molds to solve this problem and it usually does. A touch of dishwash soap and a 10 minute boil is all it takes "usually". I think Walter may have something, and I am going to try enlarging the sprue plate hole and countersink. Thanks for all your help. I appreciate the feed back alot. I'll post the result when I get it or how far I threw the damn thing in Lake Hickory............

[Iowa Fox]

I would try some Zud or Comet on a tooth bush before anything to really scrub the cavity and bottom of sprue plate. Its what I use on all my Lyman molds when I first get them. Rinse and scrub with hot water and dry with a paper towel and cast. I have that mold in a single cav. Mine fills out OK but it is the darndest mold I own to get the bullet to drop. I only cast about 25 or so at a sitting which is about all I can tolerate. I load them with 1 grain of Bullseye in a 38 spec case for a big Super Colibri at the garden. Very quiet pest load. If you have Lyman dies get the seating stem as it keeps the point on that bullet pristine, also the correct top punch for the sizer.

[Beagle333]

Well, don't throw it in Lake Hickory just yet. I don't have a 35893.... send it to me (on my dime) and I'll play with it a bit, then I'll mail it back to you (again, my stamps) and then you can throw it in Lake Hickory! ;-)

[Catch]

Good idea Fox, I will try the tooth brush idea. Maybe it will be good for the more local problem area.
I guess I am too stubborn to throw it in the lake and just stupid enough to keep on screwing around with it. If I ever solve it I will feel smug enough to get back on here and tell you (all) what I did. Am hoping to meet with a member close to me and maybe two heads are better than one. W'ell have fun anyway. ,......Catch

[ken s]

old trick, especially for the larger 500 grain I cast. wiggle the mould when you pour. get it hot, pour the lead, then gently wiggle the mould a second or two. it allows the air to escape and you'll see the dimple on top go down as you do it. it becomes second nature after a while...Ken

[LAH]

I would check the vent lines in the area of the problem. Clean the lines well with a proper size scribe.

[badgeredd]

It might help to run a sharp blade thru each vent line on the faces of the mold blocks. I've had several older, used mold that had a slight burr in each of the vents and once cleaned out, they cast well. It sounds to me like you definitely have a venting problem.