Cast Bullets Sized for Revolver Cylinder or Barrel?

[MaverickNH]

OK - I'll pick a novice topic for my first post as a novice caster.

Do I size cast bullets to fit the revolver barrel or the cylinder throat? I'm reading "From Ingot to Target" and think it says to size to cylinder throat, but others had me slug the barrel for sizing.

Thanks for the help!

[fryboy]

Slug both just so you know and size to the biggest chamber on the cylinder ,hopefully your barrel is smaller if not ... ,oh and size both ends of the barrel ( they sometimes have constrictions )

[Char-Gar]

OK - I'll pick a novice topic for my first post as a novice caster.

Do I size cast bullets to fit the revolver barrel or the cylinder throat? I'm reading "From Ingot to Target" and think it says to size to cylinder throat, but others had me slug the barrel for sizing.

Thanks for the help!

Follow Glen Fryxell's instructions to the letter and you will be happy. There is no need to slug the barrel.

[MaverickNH]

Slugging the barrel was complicated as my S&W R8 has 5 groves, so a micrometer wasn't going to set right. I have a home mini-machine shop (lathe and mill) but don't have a 5-flute V-Anvil micrometer, which might work fine if I had one. But I do have precision Pin Gauges in 0.001 increments (sized 0.0002 under each whole 0.001 increment). Will those work?

[Sorry - posted this while you were replying Char-Gar. I'll slug the cylinders. But would Pin Gauges work OK for cycliders and bores?

[Wolfer]

Your boolits need to fit your cyl throats. They need to be bigger than your groove.
For example a 45 colt with .452 throats and a .4515 groove diameter.

If your barrel is bigger than your throats you'll probably have leading issues. Easy fix, just ream your throats to the correct size and size your boolits accordingly.

Hope this helps.

[Outpost75]

Easiest way on a revolver is to remove the cylinder from the revolver, support it on a bench block, then drop SOFT, pure lead round balls in from the chamber end, then tap them through and out the front of the front of the cylinder to measure the balls with a micrometer to determine the diameter of the cylinder throats where the bullets exit.

Size bullets to fit the largest throat. If cylinder throats are smaller than barrel groove diameter and/or if there is more than 0.001" difference between cylinder throats, send your cylinder to DougGuy in NC to have them reamed to proper size and all alike. Very reasonable cost to do and quick turnaround. Makes a BIG difference!

[outdoorfan]

My understanding is that Ruger Blackhawks in .45 Colt used to (maybe still do) have undersized cylinder throats , and that caused real trouble when shooting lead. I'd imagine that S&W has their tolerances down better. Anyhow, as the others suggested, size to the throats. If there's a problem, then you'll have to start checking on other things.

[DougGuy]

Pin gages are the exact right thing to measure throats with. For gun work, you already have the correct class, Z minus, which are -.0002" but you need the half sizes as well.

I have not read all of Fryxell but what he says about the relationship between boolit and throat is correct. The only problem with that, and it's a big issue, is uneven throats. How are you expected to size to a cylinder that has as much as .0025" from the biggest throat to the smallest? Answer, you can't. You pin out the cylinder and find it's largest throat, and you can make all of them match the largest one, or you can round them all up to the nearest half thou, and size the boolit to the whole thou under that. The PROPER method for fitting throats and boolits, are you choose the size boolit you want to use, then size the throats .0005" over boolit diameter. This way you make the throats fit the boolits, BUT you are achieving the exact relationship that Fryxell is suggesting, and that is a cylinder throat that does not size the boolit as it is fired, nor is it oversize and allow powder gas to escape along the sides of the boolit as it is fired. THIS is what works. If and it is a big IF, your throats are all even, then yes you can size .0005" under throat diameter and arrive at the same thing. Problem nowdays, aren't very many cylinders made uniform enough to do this with anymore.

Ruger used to gang ream cylinders 3 throats at a time, index the cylinder over one hole and ream the other three. When their reamers wore, they would replace them as they wore, but they only replaced the worst worn one, and didn't replace all 3 at the same time. So now you have worn reamers which cut smaller holes of course, and a new reamer which cuts larger holes because it isn't worn. The outcome of this, is that you have tens of thousands of cylinders made in this fashion with 3 "pairs" of throats, each pair a different size than the others. For these to be even, and having the throats as even as you can from one to the other, you have to match them all to the largest throat, or take all the throats to the next size up reamer. Either way, you want to end up with 6 throats all within .0002" of each other. <<< THIS, IS THE MOST IMPORTANT PART of getting the cylinder throats correct. They all need to match. You can then size boolits to fit the throats.

[DougGuy]

Now for some real world numbers. I keep two .44 caliber reamers, .4315" and .4325" some .44 cylinders aren't too badly mismatched and if I can use the smaller reamer on them, the shooter can size to .431" and achieve proper fit. Throats at .4315" and .431" boolits. This makes for a light drag fit and sometimes you can stick 6 boolits into the throats of a newly reamed and honed cylinder and turn it up vertical, and the boolits will stay in the throats. This is about as perfect as you could want the fitment of boolit to throat. It doesn't get ANY better than that.

Many SBH cylinders will have throats that the smaller .4315" reamer just falls through. For these I have to use the .4325" and recommend the shooter size to .432" and I can arrive at the same light drag fit.

In 45 caliber I use only a .4525" reamer and advise the shooter to size to .452" (Or they send the cylinder and say they want to use .452" and would I ream the throats to accommodate this boolit diameter). Sometimes they will send a dummy or two and a funny thing happens. The customer *thought* they were sizing to .452" but when I mic the dummy, it may read .452" on one axis, and .4529" or .4535" across the other axis 90° opposed to the first reading. They are loading an oval shaped boolit and because it's larger than the reamer, and larger than the final honed throat, it has interference. I have found more than a couple of samples exhibit this characteristic. For these, rather than hone a throat to fit a wacko boolit, I just tell the customer he needs another sizing die or to check the die he has, and generally the problem will be found and fixed. Pretty much sizing a .45 cylinder to .4525" should fix any issues the shooter is having. I have also been asked to hone to fit a specific boolit which may be larger than the throat cut by the reamer. Takes a little extra time for this, but it is perfectly acceptable to get a request for this. Some guys want to shoot -as dropped- and if the boolit is a little bigger, I have to hone the throat a little more to bring it into spec.

Generally speaking, a .431" will be larger than most if not all production made .44 spl/mag revolver barrels. Groove diameter is normally .429" ~ .430" so there really isn't a need to slug the bore. Same with .45 caliber revolvers, unless you are dealing with an old Colt or wartime S&W, it will have a groove diameter nominally .451" so using a .452" boolit is acceptable as being larger than groove diameter.

[MaverickNH]

OK - a bit more data in on that S&W M&P R8 Revolver:

1. Removed and cleaned cylinder well, with solvent wash. Washed Pin Gauges with solvent.
2. A 0.358 (-0.0002) Pin Gauge does NOT pass cylinder throats on all 8 cylinder bores
3. A 0.357 (-0.0002) Pin Gauge DOES pass cylinder throats on all 8 cylinder bores.

Still need:

a) 1/2 size pin gauges
b) Slug both ends of the barrel
c) Slug the cylinder throats for precision micrometer reading

[DougGuy]

You can get the best deal on pin gages from Meyer gage. Their part number for the gage you need is ZM and then the size so you might want to start at ZM3565, ZM3575, ZM3585 etc. This would get you the half sizes. I think they have a $25 minimum order and the gage pins are about $3.xx each so if you can come up with 8 or so you would qualify. You can get individual gages from Enco and of course MSC but Meyer has the best price for a small order.

http://www.meyergage.com/

[MaverickNH]

Thanks DougGuy.

Using a short series (0.3565-0.3585) of such higher quality Minus Pin Gauges (than my cheaper Chinese set) I find:

0.3585 No Go on all 8 cylinder throats
0.3580 Go on cylinder throats 1, 2, 5, 6
0.3575 Go on all cylinder throats

SO it looks like at least 0.0005 variation in throats.

1. Would it be advisable to have have cylinders reamed?
2. Would S&W care, or their specs not be that tight, even for a $1000+ Custom Shop revolver?
2. As is, would sizing to 0.358 be right?

Thanks

[Char-Gar]

Oh jeeze another guy wants to reinvent the wheel. Smith and Wesson cylinder throats have been .3575 +- .0003 for generations. Just size you bullets .357 and stop with the numbers already.

[DougGuy]

Ths single most important thing about cylinder throats is that they are all even. I send them out of here within .0002" of each other. You can always size to a light drag fit in the throats which is what you want. If a .358" will go with a drag fit in 4 of 6 throats but not 6 of 6, then the other two throats need to be lapped until they have the same drag fit on either the .358" boolit or the .358" pin gage, it matters not which. I can assist you with that if you want to send me a PM.

[dubber123]

Thanks DougGuy.

Using a short series (0.3565-0.3585) of such higher quality Minus Pin Gauges (than my cheaper Chinese set) I find:

0.3585 No Go on all 8 cylinder throats
0.3580 Go on cylinder throats 1, 2, 5, 6
0.3575 Go on all cylinder throats

SO it looks like at least 0.0005 variation in throats.

1. Would it be advisable to have have cylinders reamed?
2. Would S&W care, or their specs not be that tight, even for a $1000+ Custom Shop revolver?
2. As is, would sizing to 0.358 be right?

Thanks

Even is best. It sounds like .3575" or .358" should work decently as is, with maybe a little improvement to be had. The next big thing to determine is whether the bore is smaller than this measurement, which I bet it will be, and nearly as importantly if there is a frame constriction.

I commend you for taking the time to make your gun all it can be, rather than being happy with tin can groups at 25 yds. No they aren't all "right" from the factory.

[bayhawk2]

Maverick-I'm not a novice,but not an expert either.I will give my mistake scenario and let you decide.
I was told Ruger Blackhawks have cylinders too small for lead cast bullets.I was told to ream
the cylinder throats,so I did.Big mistake.Sizing of the cylinders and barrel are now so unmatched that I now have issues.WHAT I SHOULD HAVE DONE:is simply bought a bullet sizing die a couple of thousandths over the cylinder throat size.In other words,I should have sized the bullets to the cylinder.Instead I sized the cylinder throats to the bullets.It may work for some,but to me it is bad judgement,bad advise, and can ruin a fine gun.As I did.My opinion.

[Wayne Smith]

Humm, maybe I'm a little simple. I'm loading for a new to me 32 Long - S&W. I don't have pin guages and don't trust my micrometer reading. The book says .313 - I have boolits sized in a .313 die for my 32-20's - they don't fit the cylinder - go less than half way in and stick. I don't have a .312 die, but have a .311 die - size a couple of boolits. They push through the chamber and out the throat with a little effort, not much. The boolit does not enter the barrel - it is an old Lee group buy Keith 32 boolit. It stops on the shoulder in the muzzle of the gun. I figure I'm good to go - I might get a .312 die just to have a complete set but don't think I need it for this gun.

[mdi]

If you're having trouble measuring a 5 groove slug, try just sizing to the cylinder throats and shoot a few. If you're not getting any leading, you're good to go.

One way to measure odd groove slugs is to wrap the bullet, tightly, with a piece of shim stock, .002"-.004". Measure the wrapped bullet and deduct two times the shim stock thickness to get the slug diameter. Pretty accurate. I've been working (and measuring) metal since I was 12 and I can get an accurate measurement of odd number groove slugs by slowly turning the slug between the spindle and anvil while slowly closing the spindle. With a good "feel" an accurate measurement can be achieved. Works for me...

[John Boy]

I shoot Ideal 454190 bullets in my CAS revolvers. The bullets are 0.454. The cylinder throats are all uniformly recut to 0.04545 (.0005 over bullet diameter)

[Doc Highwall]

Two important things about size is the groove diameter of the barrel has to be smaller then the cylinder throats, and the closer the cylinder throats are to one another the better. When the bullets are sized for the throats of the cylinder and the gun is fired, the bullets have enough room to pass through the throats of the cylinder blocking most of the powder gasses, and when they enter the forcing cone and into the barrel (the larger bullet) will seal the barrel preventing powder gasses from jetting by and leading the barrel.

Example: I just bought a Talo Toklat in 454 Casull with a 5" barrel. With my minus set of pin gages I got the following dimensions.
all the cylinder throats will accept a .456"minus pin with no noticeable difference in looseness of the cylinder plug, all of them are very close to the same size.

All of the cylinder chambers will accept a .480" minus cylinder plug and a .481" minus only goes half way in pretty much the same for all cylinders meaning it is pretty consistent in dimensions.

The barrel slugged at .4530" right on the money, and the greatest wall thickness that I have measured on the Starline brass is .0115" down where the base of the bullet will be seated.

As you can see with the barrel slugging at .4530" I need to shoot a .4540" bullet.
Now take the .0115" maximum case wall thickness and double it to .0230" and add that to the .4540" diameter bullet and you get .4770" or .0030" smaller than the cylinder chamber I.D. of .4800"

My only problem is finding a mould that will drop a .4540" diameter bullet which I have from Al at N.O.E. that weighs 350 grains. I have not cast with this mould yet but hope to do so soon.