Mold tolerance standards/expectations

[DrB]

I just picked up a new rcbs 7mm 168 sp and a lyman 311284.

The rcbs drops a nice round bullet.

The lyman mold looks okay to the eye, but bullets are down around ~.3085 transverse to the parting lines and as much as ~.3135 just off the parting lines on both cavities. There is no noticeable flashing, and the dimensions are still large off the parting lines, so it appears the cavities are somewhat elliptic.

I've had one out of round lemon in maybe a dozen lee molds (promptly replaced on warranty), and never had a problem with any of my iron molds. It's not usually something I bother checking unless I'm troubleshooting based on non-uniform sizing, feel, or appearance.

What kind of tolerances do y'all expect your molds to produce, and what do you consider acceptable in a particular application before sizing (pistol, low velocity rifle, high velocity rifle)?

If any of the resident mold makers also want to chime in, their views would be greatly appreciated.

Best regards,
DrB

[Dale53]

I have Mihec moulds (four and six cavity) that produce bullets from the different cavities within .0002" (two ten thousandths! out of round) and the bullets weigh within .2 of a grain of each other. I have NEVER seen that amount of precision in any other makers moulds. These are all pistol moulds.

I have a recent Lee six cavity mould that is.002-.003" out of round. It is a 230gr Truncated Cone bullet for the .45 ACP. Those bullets weight plus or minus a couple of grains.

The Mihec moulded bullets shoot well under 1" at 25 yards off a rest (to the tune of 3/4" groups). However, the Lee, after sizing will shoot 1 1/4" groups at 25 yards. In a pistol, that is not much difference. I much prefer the Mihec moulds but frankly, the Lee is a keeper. The design allow rapid loading with full moon clips in my 625 Smith revolvers and with the flat meplat hits considerably harder than hardball.

When shooting 200 yards benchrest with my Schuetzen rifle, I NEED ½ minute groups (one inch at 200 yards). I get it with an "as cast" single cavity bullet mould produced by Jim Borton (Borton-Darr).

So, it all depends what the demands are. The Lee is perfectly ok for pistols but would NOT be ok for precision rifle. I shoot pretty dern good with handguns but "Let's be real"... needs are much less with handguns, in general, than rifles.

On the other hand, I have a couple of Thompson Center Contenders that will shoot cast bullets (scoped off a bench) at ½" at FIFTY yards. That is nice when you are trying to snipe a squirrel out of a tall tree with a head shot...

Dale53

[DrB]

Thanks, dale.

[Dale53]

The mould was custom made for me and my rifle by Jim Borton. I cast it out of 25/1 certified pure lead/tin. It is shot "as cast" and is breech seated. It will regularly deliver ½ minute groups in good conditions. Schuetzen regulations specify a plain base bullet. The "sweet" spot in velocity is 1400-1500 fps. The bullet is a .32 caliber 200 gr bullet. My acceptance standards for this bullet is +or- .2 gr. (two tenths of a grain). I believe it is necessary to weigh every bullet for this rifle to maintain that level of accuracy.

Dale53

[DrB]

Anyone else with any experience to share? Everyone always talks about diameter relative to throat (or groove), but what about roundness?

what's reasonable for a pistol mold? (my lee 6 cavity I sent back is used principally for 357 plinkers and was returned because the bullets were seriously oversized and lube grooves were getting swaged out, more on one side than the other).

What's reasonable for a hunting rifle mold?

A target rifle mold?

What say the professional mold makers?

[bhn22]

Even out of round bullets will uniformly end up the same size after a trip down the barrel, assuming they're larger in diameter than the bore to begin with. Is the smallest diameter smaller than your bore dimensions? Have you tried shooting any of the bullets? How did they work with your rifle?

[leadman]

My Lyman Snover is about .001" out of round. This is a 400gr .410" boolit for my Pedersoli Rolling Block in 40-65.
If I hand lube and time the boolit seating to the case, then the case to the chamber it will usually shoot about 2" to 3" at 200 yards.
If I size in the luber/sizer and I seat the boolit in the case wherever, but time the case in the chamber it shoots the same. If I time the boolit to the case it makes no difference.
I marked the nose portion of one half of the mold so I can line up the boolit to the case.

I have had other molds that drop a boolit that is more out of round and the more these are sized, seems there is a less desirable effect on accuracy.
So it really comes down to how well your firearm shoots with the boolit after you have sized it to the gun.

[DrB]

At some point though, don't you just say wth?

I mean, with reasonable care, how hard is it to hold .001 on roundness for a cavity?

That's an honest question.

At some point with worsening out of roundness, you are going to encounter problems such as shallow or no lube grooves on one side or such.... (I've only seen that so far on my lee tumble lube mold I returned, but .005 seems like a lot for a rifle bullet mold)

Also, aren't you going to expect the base of your bullet to tend to be not perpendicular to the bore with a sized really out of round bullet?

What's the most out of round mold you've ever gotten to shoot accurately in a rifle (say at least under 3 moa)?

[W.R.Buchanan]

I would like to see the set up they use on a mill to close the mould blocks on the cherry. I have been curious about this for along time. I have my own ideas about how this is done.

I am assuming, since I'm a toolmaker, that there is a fixture that holds both sides of the ground to size blank blocks in alignment and after the hole for the cavity is roughed out that the cherry is then put in the mill and the blocks repeatedly closed and opened to clear chips until the hole is finished. This must be done several times as there is very little room for chips in the cherries I have seen. In fact the cherries on Mihec's sight have the most clearance of any I have seen.

With loose spindle the cutter could "wallow" which would result in an oblong shaped hole. It could also be a tri-oblong which is another product of a loose spindle. I have an old Ideal 358 mould that drops bullets that are .006 out of round, probably for the above reason.

Using newer CNC machining centers I have seen shops literally do one side of a hole and then do the other side in a separate operation and then when connected the hole is actually round! This approach requires extra careful work as any misalignment whatsoever would result in junk.

The whole reason I am adding my .02 to this thread is that I just came in from trying to size some boolits I made a couple of months ago only to find that they are too small to size and they aren't round either.

This is a brand new RCBS .45-300GC 2 cav mould, and it has been used in three different casting sessions. Bullets as dropped are .458-.4592 and vary from round to out of round by .001. The nose punch they sent leaves a big ring on the nose of the bullet and it in fact sticks in the nose punch and has to be pryed out.

Not the level of precision I was looking for. Kinda expected these to drop at about .461-2.

I made about 300 boolits in this mould and half were water dropped and half were air cooled they are exactly the same size and I am using plain wheel weights. The A/C ones came out 13+-BHN and the water dropped ones are 22 BNH. All fall right to the bottom of a .459 size die.

Is this a normal occurance for RCBS moulds or is this just a out of tolerance mould. It pretty obvious that it needs to go back as it will not deliver any kind a accuracy.

Hell the Hornady Gas Checks wouldn't even stay on the base after going thru the sizer, they would just fall off.

IF they are wearing out cherries and are not keeping their products within very tight tolerances I really don't see how they can compete in todays market. It is just not that hard to make stuff right with the machines available today, or yesterday for that matter.

Randy

[Dale53]

Randy;
I have a number of custom single cavity moulds for my match rifles. They are well made in every way.

However, when Walt Melander (of NEI) was alive, I bought a four cavity mould from him for my BPCR Silhouette Rifle. It was made as specified and there were no unpleasant surprises. Considering the amount of ammo I used while holding down a full time job and raising a family, that four cavity match quality mould was a life saver.

I also had LBT make me a four cavity mould and it was also made well.

Since then, we have been introduced to the precision of Mihec's moulds and they are just flat unbelievable. Every time I think about another casting session with them, I get a smile on my face.

You, who are lucky enough to have some of these fine moulds, do know that you are spoiled for life? Well, you are, believe me!

Dale53

[theperfessor]

Might I point out that it is quite possible to get an oblong or oval bullet out of a perfectly round cavity? And that certain alloys will change size by aging? Not defending poor quality control but I've made test molds with perfectly round cylindrical holes and the slugs cast in them (despite my best efforts at temperature control, steady rhythm, etc.) vary as much as .0005" out of round and with a mean diameter variation of about .0006", and a slight amount of diameter difference at the ends and middle of the slug.

Of course the bullet, not the mold, is what we shoot, so if a mold doesn't give you what you need then you just got to deal with it. But it's often a matter of .001" or .002" between a great mold and a waste of money.

[bhn22]

The whole reason I am adding my .02 to this thread is that I just came in from trying to size some boolits I made a couple of months ago only to find that they are too small to size and they aren't round either.

This is a brand new RCBS .45-300GC 2 cav mould, and it has been used in three different casting sessions. Bullets as dropped are .458-.4592 and vary from round to out of round by .001. The nose punch they sent leaves a big ring on the nose of the bullet and it in fact sticks in the nose punch and has to be pryed out.

Not the level of precision I was looking for. Kinda expected these to drop at about .461-2.

I made about 300 boolits in this mould and half were water dropped and half were air cooled they are exactly the same size and I am using plain wheel weights. The A/C ones came out 13+-BHN and the water dropped ones are 22 BNH. All fall right to the bottom of a .459 size die.

Is this a normal occurance for RCBS moulds or is this just a out of tolerance mould. It pretty obvious that it needs to go back as it will not deliver any kind a accuracy.

Hell the Hornady Gas Checks wouldn't even stay on the base after going thru the sizer, they would just fall off.
Randy

We discussed similar issues with RCBS moulds in other threads. RCBS specs their moulds for use with linotype. Plain WWs would indeed cast a slightly smaller bullet.

[DrB]

Guys, thanks for the additional (thoughtful) replies. Always interested in others experiences for anyone else who wanders through this thread. I know most of you have checked the bullets dropping from your mold for dimensions, and probably roundness, too. Please share what you have found, and what is worth experimenting with vs what just needs to go back to the shop.

Best regards, DrB

[W.R.Buchanan]

Dale: definately spoiled. After my last session with the .44 Mihec I was getting prefect bullets with sharp bases every single cast as long as I didn't botch the actual drop. Perfect pentagonal HP's too.

His workmanship is the best in moulds I've seen, bar none. Believe me the trained eye can spot all the little pluses and fine points in his work.. He is good!

I have a Magma mould .44-190SWC that works the same way but no HP. Their tool maker is good too.

I bought the RCBS mould long before I ever came to this site. And probably will only buy from higher end sources now as opposed "production sources" Although I ahve great luck with my Lyman .44 mould too.

I will call RCBS Tuesday and question this mould and if it in fact is spec'd for Lino type it will get sold. I have 1/2 ton of Wheel Weights and have no plans to use Linotype for anything. Besides Lyman moulds are built around Wheel Weights and they have told me so when I asked. Also 1:20 is very close to WW so why would one make a mould for a 138 year old cartridge to be used with Linotype instead of softer alloys.? Makes no sense. I would expect RCBS to be smarter than that.

I see no need for the harder mixture in bullets loaded below 2000 fps especially with gas checks. And really especially for just shooting at targets and misc inaniment objects. Maybe for smaller calibers below .30, and I know alot of guys use linotype for .30 cal. But mainly to be ran at 2000 and above. I have seen some pretty impressive groups shot with .30 cal guns using Boolits made from WW.

If and when I get to go Elk hunting with my .45-70 it will be shooting 400gr ish Boolits cast by me from Wheel Weights at probably 1600-1800 fps with gas checks, maybe even less. And they will do exactly what I want them to do which is punch a 1/2"+ hole completely thru said critter.

I was hoping to use RCBS.45-405 GC for this purpose but will adjust my plan if the mould won't drop bullets that are big enough to be sized completely to .459. If the mould is set up the same as .45-300 GC Then I will buy something that does work right. Magma or Mihec.

Randy

[tommygirlMT]

-0.0000"/+0.005

That is what I consider "acceptable" tolerance on the stated size of the mold --- out of round or otherwise no matter where I measure it on any of the drive bands that are suppost to be full diameter --- I can handle oversize no problem just lube it and then size it down in a press mounted push through die after the grooves have been filled with lube --- but undersize --- you dont want this p*ssed off b*tch on your customer service line --- NEI and Lyman have both found that out the hard way

[bhn22]

I believe RCBS specs linotype because it is "repeatable". Lino is lino, and universally avavilable. Wheelweights vary in composition from manufacturer to manufacturer. SAECO specs with "Taracorp magnum alloy", whatever the hell that is. I've never purchased "store bought" bullet metal, and couldn't honestly tell you the makeup of my common use alloy. I just enrich it in various ways to suit my particular needs. I do have a hoard of virgin linotype, but never use it. I must be saving it up for something.

[duck hollow pete]

Fuel for thought MAYBE, if this is the first casting you my try re-cleaning , if you already have disregard this reply. Awhile back I set out to cast 700hunderd or so from my new RCBS 30-180 sp and 311299 LYMAN, LYMAN went fine. About 3/4 thru the session I hit the spruce to quick and got a lead smear, that was dumb , but I wasn't done yet I went to put a dab of lube on the smear and got alittle to much and ended with some in both cavities. I cast a few bad ones then they came out all nice, should have miked them, when I went to size at .310 the problem showed up. This mould gives me a good .311 plus if I'm casting right, but I clogged up the vents and ended up with under size along the seam only(.308-305). I was able to save about 80 at .308 the rest junk, the next session I gave it a toothbrush denatured alcohol cleaning and it was good to go.

[DrB]

Fuel for thought MAYBE, if this is the first casting you my try re-cleaning , if you already have disregard this reply. Awhile back I set out to cast 700hunderd or so from my new RCBS 30-180 sp and 311299 LYMAN, LYMAN went fine. About 3/4 thru the session I hit the spruce to quick and got a lead smear, that was dumb , but I wasn't done yet I went to put a dab of lube on the smear and got alittle to much and ended with some in both cavities. I cast a few bad ones then they came out all nice, should have miked them, when I went to size at .310 the problem showed up. This mould gives me a good .311 plus if I'm casting right, but I clogged up the vents and ended up with under size along the seam only(.308-305). I was able to save about 80 at .308 the rest junk, the next session I gave it a toothbrush denatured alcohol cleaning and it was good to go.

They didn't look bad like there were volatiles in the cavity, but I'll try that. It struck me as a little odd that they were widest at the parting line (and it wasn't from flashing). Thought maybe it was because the mold halves weren't closed completely on the cherry...

[Iron Mike Golf]

...SAECO specs with "Taracorp magnum alloy", whatever the hell that is. ...

92% Pb, 2% Sn, 6% Sb