Where does the extra 0.001" come from in cast bullets?

[kleeber]

I reload a lot of cast/coated bullets and have noticed that the measured diameter of most bullets is 1mil greater than the advertised diameter. E.g., a ".452" bullet will measure .453. This makes them harder to seat straight and exacerbates chambering issues when a bit of runout is present. I would really like to run .452 bullets, unless that causes leading for me.


First, let me note that my calipers are properly calibrated. I can measure jacketed bullets from a variety of manufacturers and they are dead-on the stated diameter.


I bought a Lyman lubrisizer and some sizing dies to re-form some commercial cast bullets to a true .452. I bought a .452 sizing die and to my surprise the sized bullets still came out close to .453! Here's my question for those of you experienced in casting/sizing your own bullets: is the extra 1mil from

A. The bullet compressing to .452 and springing back to .453 outside the sizer,

B. By some convention a nominally "452" sizer is actually .453,

C. Some combination of A and B, or

D. Something else I'm not considering?

I'm betting it is (B) because a measured .453 bullet runs through a "452" die with very little effort.

I resolved this issue by ordering a "451" sizer die and indeed it produces .452 bullets for me.

Thoughts?
Thanks

 

[StrawHat]

There could be some spring back after sizing. I used to cast my own stuff, and used a soft alloy. I do not recall spring back happening, but, I never looked for it.

If you are seating bullets crooked, it is not the size that is the problem. I would make sure your dies are properly set. I use a .454 sizing dies for all my ACP cast bullets. I have no problems seating them in the stubby ACP case.

Check your dies.

Kevin

 

[kleeber]

Good point, Kevin. I wish the expander on my Dillon powder die was a bit wider at the point before the flaring starts. More flare only gets you so far.

Thanks,
Kevin

 

[stansdds]

My guess is that the bullets are actually 0.452" diameter, but the coating is adding an extra 0.001".

 

[46er]

Not all products are to spec. I have NOE dies that size .0005+ larger than marked. Spring back? you would have to accurately measure the ID and try different alloys.

 

[kleeber]

I just tried forcing a 0.453 bullet into a "452" die and it went in with hand pressure, so I guess compression/springback is not the cause.

Measuring the internal diameter of the sizing die is difficult because it is tapered at the mouth.

I guess the above experiment answers my question: if a measured 0.453 bullet is a tight slip fit in the die (assuming the bullet is basically round), then the minimum internal diameter of die should 0.453, give or take a couple 0.1 mils.

 

[LoboGunLeather]

"Springback" in cast bullets is pretty common, but usually more pronounced with the harder alloys.

The basic reasons for slightly larger bullet diameter to;

1. To ensure the best seal within the chamber, forcing cone, and barrel. The bullet will be swaged under pressure to the required diameter for that particular firearm.

2. Manufacturing tolerances are common in firearms. SAAMI specifications are the commonly accepted norms, but variations will occur due to manufacturing processes and tool wear during production runs. A modern .44 caliber revolver may be spec'd for .429" groove diameter, forcing cone, cylinder throats, etc, but the actual finished dimensions may be anywhere from nominal .426" to .433" (perhaps greater variations may be encountered; these are from my own personal experiences).

A .453" cast bullet should be no problem in a modern .45 caliber handgun. However, there may be some firearms with chamber dimensions on the small end of the tolerance levels that could make it difficult or impossible to chamber that loaded cartridge and operate safely.

On the other hand, many older .45 caliber handguns will be found having .454" to .456" groove diameters with forcing cones and cylinder throats all over the charts.

Short version: It is usually possible to find a combination that will function properly and safely in your firearm, but not all combinations will be suitable for all firearms. Occasionally we will encounter firearms that display any conceivable combination of manufacturing tolerances in every detail, and the only corrective action will be repairs or modifications.

 

[mtgianni]

The larger size in commercial cast may just be to prevent leading. Blowby is much more common when sized to barrel rather than oversized. I have one 32 H&R that has cylinder throats measuring 0.314". I size to 0.315" and have no problem shooting them in 0.312" bores. IIWM. I would be happy with the larger size and shoot them. The over size bullets may raise pressure slightly, but not even approaching 100 cup IMO.

 

[Ivan the Butcher]

I have Lyman's "Cast Bullet Handbook" 3 Edition and several editions of Lyman Reloading Manual, Number 46 especially. Both have the same section on Casting, which goes into detail about casting and sizing characteristics of 4 different common alloys. Some shrink while cooling and some actually expand! Some stay at the sized diameter and some (Usually the harder ones) spring back. The charts also give the different weights of different alloys from the same mold, so you can work out the percentages per alloy (WARNING: math homework involved). Basic hardness is also listed.

Some things that cause batch to batch changes are #1) using scrap Lead and #2) using different temperatures while casting-just letting the pot "Cook" extra allows temperature to rise, and casting right after adding more alloy is cooler!

Last big influencer are QUINCHING and TEMPERING and when the bullets were sized in relationship to when cast, Hint: Things pretty much even out between 3 and 6 months for each alloy.

I pretty much use a scrap and wheelwright mix alloy of 50/50 so no real ratios. But for specific target BPRC loads I use a Certified Mix of 20:1 lead: tin (No antimony). The 20: 1 alloy casts very consistent. I weighed a batch 336 castings. Every bullet but one was within a window of 330.1grains and 330.4 grains. That is less than .3% variation! (Sierra match bullets aren't that good!) I sized and lubed (room temp lube) in a Lyman 4500 sizer I bought just for SPG Lube! They were sized at .376" and the 20 random samples stayed at .376 for over 14 years. This bullet is for my 2005 made 28" 1885 Winchester Low Wall in 38-55. After the load was zeroed with the Tang and Globe sights, a 20 shot group was shot off a rest at 100 yards, that group was covered by a Lincoln Penny! I have 16 molds for my 45-70 Shiloe Sharp's, none of them shoots that well!

For 38 Special, 9mm, 45 ACP &45 Colt, I use a scrap/WW mix that makes no difference in the 25-yard group size! For 32ACP, Shot or Long and 32-20 handgun I use the 20: 1 alloy sized .309, .311, & .314 inch, depending on the gun and intended use.

I tried 1 Lyman Mold in 22 Caliber. In 3 different 22 Centerfire Calibers, nothing I did got that bullet to shoot less that 1" @ 50 yards, and they are proven guns!

Ivan

 

[zeke]

even with some jacketed, the diameter printed on the box may not precisely correlate.

specs are one thing, what really matters is actual measurements.

Would not expect the bullet mold manufacturers to produce all new molds just because people started coating them. Even if they did, the bullet makers might not buy them.

 

[reddog81]

I wouldn’t worry about it too much. I size all my 45 ACP bullets to .453. Slightly larger shouldn’t be a problem unless the don’t chamber.

 

[243winxb]

Harder alloys spring back more.

https://www.thehighroad.org/index.php?media/weights-diameters-test.4081/full

 

[rwsmith]

I just had a capital idea.

I just tried forcing a 0.453 bullet into a "452" die and it went in with hand pressure, so I guess compression/springback is not the cause.

Measuring the internal diameter of the sizing die is difficult because it is tapered at the mouth.

I guess the above experiment answers my question: if a measured 0.453 bullet is a tight slip fit in the die (assuming the bullet is basically round), then the minimum internal diameter of die should 0.453, give or take a couple 0.1 mils.

Use the casting compound used to measure barrels, except in your sizer. Cheap solution!!!

 

[WR Moore]

Post #7 mentioned tolerances. 0.357, 0.429 and 0.452 are nominal groove diameters. There's generally a +/- 0.001 in tolerance. But, that can differ depending upon the manufacturer. Yes, the general practice was that lead bullets were a thousandth over jacketed. Remington 158 gr LRN 38s were pretty much all 0.360 (but those bulk bullets might have been culls). Still shot well.

Way back when I toured the Douglas Barrel plant, they were the source for the blanks that Clark used for their .45 match barrels. Per the plant manager, the nominal groove diameter spec was 0.451 in.

 

[Alk8944]

Bullet sizing dies are often not exactly the size marked on them, usually .001" oversized, sometimes more. Makes no difference what makers dies you use. With hard alloys the die body can actually stretch slightly when a bullet is pushed into it. That isn't the fabled "spring back", at least not of the bullet! This is why the same die can be observed to size to slightly different diameters, depending the lead alloy being used.

Since cast bullets should be sized .001 to .003" larger than groove diameter this is no issue. I have a very time believing a .001" oversize cast bullets is causing any problem with either loading ammunition or in a gun, it just doesn't happen. I have been casting and shooting cast bullets well over 60 years in nearly all calibers and many different cartridges. Many 100,000 bullets. I have to say the problems you are having, or think you are, are from a different source, not .001" bullet diameter!

There are many thousand shooters who buy commercial cast bullets. Very many of those bullets are 1 or more thousandths oversize and I recall very few comments or complaints like yours from anyone of them!