35-200FN casting undersize

[Marlin Junky]

I've had a couple RCBS 35-200FN molds in the last couple of years and have sent them back to the dealer (probably Midway) because of flaws. One time it was because of sticking bullets that I couldn't rectify and the other time it was because of poorly cut vent lines. So I thought I'd give 35-200FN one last chance and I broke in another new mold last night. It casted well but I couldn't get a .359" bullet out it even with the MasterPot turned up all the way and while pouring from nearly an inch above the mold with my Rowell #1. Sure, I could send it to RCBS but I may get a replacement mold that has poorly cut vent lines as before. The nose is fine at .3495" but the fist driving band is straining to achieve .3580" and a lot of the bullets that actually look great and weight in at 211 (bare) measure .3575" on the front band.

Any suggestions?

MJ

P.S. I don't care to "Beagle" this mold... I want to shoot 35-200 at HV (2200+) and I'm looking for 1MOA at the same time.

[missionary5155]

Greetings What is your mix ? Pure lead casts small . Most BIG Name molds are "Engineered" to cast with the Lyman # mix...
WW cast about .003 fatter in my .427 mold than near pure lead.....

[oneokie]

Second missionary5155's question about what alloy you are using. Have you tried dropping the temp of the melt? Hotter melt=more shrinkage. If you have to run hot for fillout, try adding some tin.

[mainiac]

I just bought this mold in june of this year. Mine cast a .3585 boolit, out of 20-1 ww/babbit. They weigh 214 all lubed and checked. The front band measures .3575, and the rest .3585. 1 cavity sticks on me, and i havnt really investigated it yet.

[Larry Gibson]

Mine drop a WW + Lead (50/50) at .358 and WW/linotype (60/40) at .3595. Are you "smoking" the mould?

Larry Gibson

[NHlever]

Here is a link to an article that lists bullet sizes with different alloys, perhaps it will help.

http://www.lasc.us/CastBulletNotes.htm

[Marlin Junky]

Smoke a ferrous mold? What for??

Alloy: 50/50 and range scrap for a bit more Sb which gets me in the 25-30 BHN range when HT'd at 500F... addition of Sn not necessary because fillout is great and Sn would actually lower melt temp. When I have too much Sn in alloy the bullets will actually stick together after a 500F HT followed by an ice-water quench. This same alloy casts SAECO 352 at .3590" to .3595" at the same MasterPot setting (about 800F). I suppose RCBS could find an alloy that would cast bullets to spec in this mold and that's another reason I don't want to deal with them. I like my alloy... it's versatile and accurate... I'm not going to change it to suit the mold. I suppose I could try lapping the mold out .001"... uh oh :( If anyone has a good procedure for lapping molds, I'd like to read about it. Otherwise the mold's a keeper... I just wish I had a .358 Win with .356" to .357" grooves.

MJ

[Larry Gibson]

Marlin

Just thought I'd ask is all, you'd be amazed at those that do.

Sorry you've had the problem with RCBS molds. I've found they do cast close to the "nominal" size as stated in RCBS's manual. Mine is the only 35-200-FN I've had and it casts fine. I helped a freind cast some with his mould a few years back and they cast out fine also. Luck of the draw I guess.

Larry Gibson

[beagle]

Get one of these "mochinists" with a CNC vertical mill to set up and open the bands to about .361".

I've had that done on several of my favorite marginally undersize moulds that I use a lot and don't want to "beagle".

Several .44s opened to .433" and a couple of .457s opened to .462" and one .35 opened to .361". Sizing takes care of the slight overage and I'm noe first sizing anyway.

It's a pretty tricky op but a good machinst can do it. The resulting moulds seem to lose that out of roundness from factory moulds as well.

I'd expect better than that of RCBS too./beagle

[35remington]

Hmm.

I usually get from .359 to .3595" and about .351-.352" on the nose. Shoots really well in a Microgroove.

[PatMarlin]

How bout' casting a lino boolit. Drill it dead nuts center and epoxy a steel mandrel shaft in it. Then use lapping compound and a dremel, or drill and keep at it.

[Marlin Junky]

Hmm.

I usually get from .359 to .3595" and about .351-.352" on the nose. Shoots really well in a Microgroove.

12 or 16 groove?

MJ

[Marlin Junky]

Hotter melt=more shrinkage.

Stabilize and equalize your mold temp and you will see this is not true.

For the best fill-out with ferrous molds, sprues should remain liquid 2 to 3 seconds after the cavities overflow. This is accomplished a heck of a lot easier at 800F than 750F.

MJ

[sav300]

Marlin Junky,how do they shoot?

[runfiverun]

rcbs uses 10% tin to 90% lead ratio as their mix.
i am thinking their cherry is getting worn down.

[beagle]

That process will work but has it's drawbacks.

If you use only the band portion you'll be all right. If the nose is all right diameter wise, just use the band portion of the bullet.

The problem with this method of enlargement is that you increase dimensions in all directions and sometimes, that's not a good thing or desired.

But, it works and gets you a larget diameter./beagle


How bout' casting a lino boolit. Drill it dead nuts center and epoxy a steel mandrel shaft in it. Then use lapping compound and a dremel, or drill and keep at it.

[Trailblazer]

I bought a new RCBS 35-200 a few years ago that cast just like yours. I called RCBS and talked to their mold man. He offered to replace it so I sent it in. The replacement cast a little bigger but still not what I needed. I called again and was told the cherry was new and that was as big as they got so I Beagled it.

[Marlin Junky]

I'll play with it a bit more. If I can consistently get .3585" bullets out of it and all else is fine, then I probably won't bother contacting RCBS. Actually, I'm not sure it's quite broken in because the cavities aren't blue yet.

MJ

[NHlever]

Smoke a ferrous mold? What for??

I suppose I could try lapping the mold out .001"... uh oh :( If anyone has a good procedure for lapping molds, I'd like to read about it. Otherwise the mold's a keeper... I just wish I had a .358 Win with .356" to .357" grooves.

MJ

One of the members here pours a bullet through a 1/4-20 nut, and then he puts a little fine lapping compound on the bullet, and turns the nut with a wrench. He said that sometimes one breaks, but then he just uses the other for both cavities.

[leftiye]

MJ, It sounds like you might want to back off your temp on that heat treating maybe 25 degrees. If they stick together, they're partially melting. This will cause uniformity issues (deformation), even if it is not visible. They will still get about as hard too if HT'd somewhat cooler.

My experience with maximum size out of a mold is that it happens at a medium temperature. Really hot boolits shrink more (even though they were cast in a larger mold).

[Marlin Junky]

MJ, It sounds like you might want to back off your temp on that heat treating maybe 25 degrees. If they stick together, they're partially melting. This will cause uniformity issues (deformation), even if it is not visible. They will still get about as hard too if HT'd somewhat cooler.

I can reach BHN 28-29 with the right alloy using a 500F HT. Air-cooled hardness will be 11. My point was, if I add too much Sn, the melt point will be less... which is a bad thing.


My experience with maximum size out of a mold is that it happens at a medium temperature. Really hot boolits shrink more (even though they were cast in a larger mold).

What do you mean by medium temperature? I cast at approx. 800F (or a tad more for molds with bigger cavities) using my RCBS and SAECO molds and the cavities fill out great with no frosting. When I go to a Lyman mold that casts a bullet under about 200 grains, I'm almost always thrown a curve so I like to set the melt at approx. 760F. My last batch of SAECO 352's (about 300 bullets) all weighed between 247 and 248 grains (bare) and the diameters were very consistent. I know this is supposed to be a thread about currently manufactured RCBS 35-200FN molds, but I've got to get as many "plugs" in for SAECO 352 as possible 'cause I feel its the best .35 mold out there from the Big-3. The only thing it needs to be a GREAT design is a little more lube capacity.

MJ

[leftiye]

Medium, not hot, not cool. I'm referring to mold temperature here, not lead temp. If you use an infrared thermometer to measure mold temp, this is about 400 degrees F. Lowest temp that will cast well with my molds is about 327 degrees, and above 500 is probly gonna frost no matter what temp your lead is. Actually, lino will not solidify in that (500 degree)mold. I just "shoot" the side of the mold with the thermometer.

The alloys that I use would melt in your 500 degree oven, yours are starting to melt if they stick together. I get BHN 28 from HTing my alloys too (at 425 in my oven). There probly is more tin in my alloy.

[Marlin Junky]

My alloy is Cheeeeeeep stuff. :-D Free wheel weights, free lead and free range scrap. Although... I do have to drive to the sources sometimes. :mrgreen: I fill my MasterPot (the 40 pounder) to about an inch and a half from the top with my 50/50 (WW/Pb) mixture and then place a 2-1/4 pound ingot of range scrap on top to spice it up with Sb. Air cooled it comes out about 10-11 BHN.

MJ

[GabbyM]

Lapping a mold;

when lapping you won't get a cavity any larger than the lapping slug.
What I do is beagle the mold to cast larger boolits for the laps. If I want a larger nose I'll beagle the bottom of the mold to fatten up the nose and so on.

I use 220 grit compound. I have a wood screw with the head cut off to chuck in a drill. I simply use a drill pres to drill a pilot hole in the bullet. After center punching for the drill. Since I hold the bullet in the mold I don't want to risk the drill running of center. Then with a variable speed hand drill run the screw into the lap. I use the same bullet in both cavities and start with about three from the same cavity for the laps. I run them until they quit pulling resisting. Usually the third one doesn't do much and that's when I'm done. A drop of light oil will keep the compound flowing along. As in any grinding op.

Cavities will lap out concentric fairly fast. After that it takes a good bit of work to get anywhere. You should be able to get close to .001” you're looking for. More than that is optimistic.

I use a file to reduce the gas check shank on the laps so not ot over size the check shank portion. So try a gas check on first as you may want to open it up too.

I sent my 30-180-FN in to RCBS because I just couldn't get it right and the cavities wouldn't match up. I was a bit worried they'd say I hacked it but they sent a new replacement.

My Lyman 311299 I returned came back reworked. They called it reamed on the sheet but the used a cherry to “ream” it. It had one good bullet and one -.004”. Haven't tried it yet but looks like they did a good job.

[PatMarlin]

Great info Gabby.. :drinks:

MJ- what are the ID, and inside height dimemsions of your 40lb pot?