Sizing for your cylinder

[Bret4207]

There is no advantage whatsoever for making a boolit over throat size.
Push through is good enough. I have never had a problem with smaller either.
When you think of all the boolit configurations, there are not that many that will enter the throats. Those that do must chamber.
Those boolits that will chamber if too fat for the throats will indeed shoot but the big question is why make them that fat? Oversize ideas have grown to the point of being silly, it is getting to the point of needing .452" boolits for the .44!
Sure, brass can lay in the chamber a little off center with large chambers but it seems that brass starts to expand starting at the rear as pressure rises in a flowing motion and necks will not expand until the boolit is out of the way. Brass does not "jump open" the entire length when ignition starts leaving the boolit hanging.
Years of testing by thousands of rifle shooters has shown most full length sized brass shoots as good as neck sized in normal rifles. So too in the revolver. Neck sizing might gain me 1/8" at 50 meters so all the work of holding brass in line might not be worth the trouble because after a few reloads, they need sized all the way again.
I bet that S&W will shoot from .430" to .432". Just how many shooters will ever tell the difference in accuracy? I sure can't!

Okay, I'm not exactly disagreeing, but!- what makes you think the brass expands from the rear forward? The rear of the brass contains the web, the thicker area. Plus, you seem to be saying the powder must burn from front to rear sort of throwing the pressure to the front, but in larger cases using small amounts of powder the powder may be laying in a line across the bottom length of the case, or it may be fully forward or rearward. I don't think there's any certain rule to how the case expands unless it's a case load of powder and even then I'm not it'll always expand exactly the same. I would think virgin brass expands a little differently than brass on it's 10th loading or freshly annealed brass.

In the end, it's just another variable we can't always control, isn't it?.

[EDK]

That will work fine.
There is no "taper" in throats, only a starting round off to get rid of a sharp edge. Call it a ball seat if you will but throats are the same diameter full length to the round off.

I purchased several of the first S&W 625-2 (45 ACP) in the Saint Louie area. They had to be cleaned after a dozen or so rounds because of the lead rings shaved off in the ball seat. IIRC, the S&W rep at the Masters Tournament at Barry IL said that they got new chambering reamers cut with a SQUARE edge by a new machinist...ended up calling a retiree to consult on the problems....corrected by putting a very small radius on the reamer. It only took a few minutes to correct the guns. It is the kind of thing that can happen when a gun maker gets taken over by accountants and other non-gun people.

Good story...maybe true....Jeff Cooper said, "if it isn't true, it should have been."

[MtGun44]

Bret makes a good point that assuming the brass expands at the back in a straight walled pistol
round is doing a lot of assuming.

I will bet that the case expands at the front first. The internal pressure is essentially uniform
(within the speed of sound) and the case wall thickness is not. It will expand at the thinnest area
first, assuming that the brass is all the same hardness - which it is NOT. It is softer at the mouth,
which will further bias it towards making it expand first at the front (but where the gas pressure can
reach, initially behind the boolit, but rapidly moving forward as the case expands away from the
boolit and gives access to the case by the gases.

Since the speed of sound is about 1100 ft per second, the pressure wave will travel the ~3/4 inch
from the rear of a .357 mag or .44 mag case to the base of the boolit at the speed of 13,200 inches
per second. The pressure wave will cover 3/4" in 0.000056 seconds or 56 millionths of a second.
Pretty quickly, fairly near to uniform pressure for me.

Bill

[kirb]

slugged my SBHH and the cylinder comes in around .432-.4325. Now I have read
somewhere on this forum that one needs to size .001 over cylinder size. Well, I
did, and it doesn't work that well.

What does the barrel slug at I alway size to .001 over the barrel size and hope for a push threw on the cyl. throat and open the throats to match the barrel size if barrel is larger than cyl.

Kirb

[63 Shiloh]

Some absolutely amazing info and advice fellers, great stuff!

As an experiment, I will size down by .001", that will be the only thing I will change. Shoot and see how it goes.

I have A4 folders for each calibre and rifle/ pistol, it allows me to keep a really good record of what I have done and how it has worked.

Jeez, when I was laying in bed; staring at the ceiling last night and thinking about the variables involved with cast boolits and revolvers... Its a bloody miracle that the boolits even hit the target!

Cheers Lads,

Mike

[44man]

Okay, I'm not exactly disagreeing, but!- what makes you think the brass expands from the rear forward? The rear of the brass contains the web, the thicker area. Plus, you seem to be saying the powder must burn from front to rear sort of throwing the pressure to the front, but in larger cases using small amounts of powder the powder may be laying in a line across the bottom length of the case, or it may be fully forward or rearward. I don't think there's any certain rule to how the case expands unless it's a case load of powder and even then I'm not it'll always expand exactly the same. I would think virgin brass expands a little differently than brass on it's 10th loading or freshly annealed brass.

In the end, it's just another variable we can't always control, isn't it?.

This is true that the case is thicker at the rear but that is where pressure starts to build first. That area WILL expand with enough pressure, it is only brass.
The point I was making is that the neck with a boolit in it will not just jump open. The brass behind it will form to the chamber and as the boolit leaves, the neck will expand behind it.
High pressure rifle loads can have gas move alongside the bullet some and start to break neck tension as the bullet moves but I do not believe it is a sudden neck opening for the full length unless gas flows past the bullet before it moves. (Not good.)
We just don't know! We don't know if initial case expansion helps center things up either.
How about case head thrust against the recoil plate or bolt face? Does that lift the case from the bottom of a loose chamber? Darned if I know! I have seen crooked cases fired from rifles with barrels screwed in crooked.
I have gone the full route with rifles and revolvers, neck sizing, neck turning, etc. I found bullet run out was more important. FL sized brass over neck sizing never showed enough difference to worry about.
Powder burns from the rear to the front, pressure builds from the rear to the front. Expansion should start at the rear to the front. I can't wrap my head around the whole case jumping to the chamber walls all at once.
In the past there were tubes in some cases that projected the fire to the front, they were failures.
We do not want gas going past a cast boolit before it obturates in the bore. If it did, every single boolit we shoot will show gas cutting. With thousands of recovered boolits that show zero gas cutting, I firmly believe the boolit has moved out before gas gets around it. There is no indication of gas between the brass and boolit.
We have to look at a pinch of very fast powder in a large case. It can be all burned up fast so there is nothing but gas in the case. That might be a reason for a boolit over size to the throats so it keeps that gas behind the boolit. Slow powders can act as a filler while the boolit transitions the throats and provide a seal. Gas has not reached the boolit base yet.
Think in SLOOOOW motion, not milliseconds!

[prs]

I hope Ruger has stopped supplying cylinder throats that are smaller than the barrel daimeter. I ran into that with several RBVs in 45Colt. Hard to hit a paper plate at 25 yards with a good rest that way, but all shoot well now that they have been reamed. I like a nice gradual downward progression from case to barrel.

prs

[Fugowii]

slugged my SBHH and the cylinder comes in around .432-.4325. Now I have read
somewhere on this forum that one needs to size .001 over cylinder size. Well, I
did, and it doesn't work that well.

What does the barrel slug at I alway size to .001 over the barrel size and hope for a push threw on the cyl. throat and open the throats to match the barrel size if barrel is larger than cyl.

Kirb

My barrel sizes out to .430-.4305

[MtGun44]

I am convinced that part of the reason that jacketed projectiles are popular is that they
are so forgiving of really screwed up dimensional setups on revolvers. Not that lead
can't shoot reasonably well from a messed up throat/forcing cone/bore combo, but it is
more difficult.

If your revolver has a (as prs says above) a smooth progression of sizes from the throat
forward, it is much more likely that you will succeed with boolits. I, too, wonder if Ruger
has sorted out their throat dimension issues. Of course, when 90+% of the ammo that
will be fired is jacketed, maybe they are right to not care a whole lot about getting the
throats exactly right. It has to cost more to tighten tolerances and my bet is that not
only will 90% of revolvers be fired with jacketed, but about 75% of the shooters can't
shoot tighter than 6" at 25 yds with ANY gun, so they would never know if the gun was
more or less accurate. Sad to say.

44 man - I think you are right in many places, but for partially filled cases of fast powders,
I think the internal pressure patterns are very different than with full cases of slower
powders. I think that the thin AND soft case mouth right behind the boolit will open first
in almost every situation, but possibly a bit less ahead of the rear portion of the case with
big bottlenecked cases.

We are both speculating, and there is no way to prove either without multiple pressure
probes and maybe a transparent chamber with high speed microphotography. My budget
won't support it. Fine discussion, and very glad everyone is agreeing and disagreeing
without getting disagreeable!

Bill

[David2011]

Commercial J-Words and my cast boolits all drop right through the throats on my Blackhawk in .45 Colt. The fit is very close but no shaving occurs when I drop them through. I don't know how old it is- bought it in the early 80s used at a gun show. Accuracy is not spectacular but is as good as you would expect from any quality revolver.

I wonder about another thing. A large pistol primer has plenty of punch to move the boolit into the barrel without gunpowder. Could the boolit be leaving the case or at least starting to move before the powder develops significant pressure? Hard to guess since we're talking about microseconds but if so, the brass would not have expanded significantly under just the pressure of a primer.

I've read that in autoloaders (significant because there's no cylinder gap) the thought is that the bullet jumps forward into the leade or into the barrel a short distance on the primer pressure and then sort of sits and waits until the powder pressure makes it start moving again. Having fired a squib (missed dumping the powder) on a .45ACP I found the cast boolit had gone 1.5-2" into the barrel, measured from the hood of the 1911 barrel. The primer alone has pretty fair pressure.

David

[mroliver77]

My preferred method is to size to a mild snug fit in the throats. If you can drop a bullet into the throats without them falling through but can be tapped through with the eraser end of a pencil it’s perfect. Any tighter than that will cause chambering difficulties, any looser and there could be blow by in high end loads.

This is how I size for my long range match revolver. When chambering rounds I usually need to give each round a light tap with the tip of a finger and they chamber fully.

Instead of sizing revolver bullets to a given number, IE .431” for 44 or .358” for 35 cal try sizing to a good fit in your cylinder throats regardless of what number is on the die. Your alloy will effect the final sized diameter with a good chance it will be different than marked die diameter anyway, plus there are mfg tolerances in each die.

In a perfect world the measured groove diameter of the bore will be at or just a touch smaller than measured throat diameters, with a good throat fit life is good.

Sizing larger than throat diameter will not only make chambering difficult but revolver throats are without doubt the world’s best bullet sizing die. No matter how fat you make them they will be throat diameter when they exit. I am of the school of thought that says in a revolver with a good match between groove diameter and throat diameters the less the bullet is sized up & down in the gun the better. All the better for accuracy and for not leading the cylinder or bore. They fit in the throats, are well lined up with the forcing cone and without molesting them they fit the groove diameter.

Rick

+1
Jay

[EDK]

I hope Ruger has stopped supplying cylinder throats that are smaller than the barrel daimeter. I ran into that with several RBVs in 45Colt. Hard to hit a paper plate at 25 yards with a good rest that way, but all shoot well now that they have been reamed. I like a nice gradual downward progression from case to barrel.

prs

The early guns in 45...and most COLTS and SMITH & WESSONS...had oversize throats, according to most sources. While I'd like .452 from the factory, you can correct if they are too small. If they are oversize, you got a problem to live with or spend a lot of money to correct!

I'm currently using H&G 503/LYMAN 429421 clones from a brass and an aluminum mould from MI-HEC as well as MMA10MM's modified version of 429421, sized to .432, in 12 different 44 magnum Original Size VAQUEROS I reload for/have access to and getting great accuracy. I'm too lazy to slug all of them, but the boolit will not slip through any of the chambers I've tried. The NOE lube groove/plain base clone of RANCH DOG'S TLC 432 265 has to be sized to .431, with good groups but I need to do some more load development.

Dropping from 14 down to 10 brinnel hardness eliminated most of the leading in the 44s also. The harder alloy worked perfectly in multiple 357 Original Size VAQUEROS and MARLIN 1894 Cowboy rifles, with 5.0 of TITEGROUP and LYMAN 358665/358429 and NOE 360 180 WFN....sized to .359 or .360 when possible.

I'll admit to be a mass production, generic reloader for pistol calibers; I shoot 48+ rounds daily if I can. The only caliber that I have one firearm in is my 50/90 SHILOH SHARPS....and reloading black powder in the BIG 50 is a whole different ball game.

[timbuck]

http://www.brushresearch.com/brush-types.php?c1=4

check these out for opening up cylinders.

[gunslinger20]

If the boolit has a large diameter forward driveing band close to the nose and your brass is a little long it pushes the driveing band further out into the cylinder throat. Trim your brass to the min. spec. for the caliber which allows a shorter C.O.L, also Lymans Cast Bullet Handbook 3rd edition page 58 has a chart showing the predicted as cast characteristics and predicted sized dimentions of different alloys.

[ColColt]

Many years ago when I had a 4" M29, I thought the proper diameter was .430" for ALL 44 Magnums and ordered a size die from Lyman with that spec. That was in the mid 70's.

About two months ago I bought a 6" S&W M29-3 and attempted to use that same size die I bought many years prior and got leading with any and all loads. Once I found out what was going on, courtesy of this fine forum, and checked the throat diameter, turns out in this gun they were .432". I didn't have one that size and Lyman doesn't make one so, I had a size die custom made...best thing I ever did for accuracy and leading. Also, my old 429421 mold wouldn't cast larger than .430-.4305" so off to Erik it went to be opened up. Now I can easily size about .002" off the as dropped boolit and achieve the .432" needed for this particular gun. I'm currently a happy camper in that there is no leading with any load I use and accuracy is better than before.

[Bret4207]

This is true that the case is thicker at the rear but that is where pressure starts to build first.No, that is what you want to say happens, but it's not necessarily accurate. That area WILL expand with enough pressure, it is only brass.
The point I was making is that the neck with a boolit in it will not just jump open. The brass behind it will form to the chamber and as the boolit leaves, the neck will expand behind it. Isn't it just as likely the neck is expanding as the boolit is moving?
High pressure rifle loads can have gas move alongside the bullet some and start to break neck tension as the bullet moves but I do not believe it is a sudden neck opening for the full length unless gas flows past the bullet before it moves. (Not good.) But you just said that doens't happen. proper fit should prevent it in rifles or pistols.
We just don't know! We don't know if initial case expansion helps center things up either. Which is why alignment is important.
How about case head thrust against the recoil plate or bolt face? Does that lift the case from the bottom of a loose chamber? Darned if I know! I have seen crooked cases fired from rifles with barrels screwed in crooked. I doubt it "lifts" the case. I've seen too many cases that are off centered after firing.
I have gone the full route with rifles and revolvers, neck sizing, neck turning, etc. I found bullet run out was more important. FL sized brass over neck sizing never showed enough difference to worry about.
Powder burns from the rear to the front, pressure builds from the rear to the front. Expansion should start at the rear to the front. I can't wrap my head around the whole case jumping to the chamber walls all at once. What is the difference between 15 millions of a second and "all at once"?
In the past there were tubes in some cases that projected the fire to the front, they were failures. No, they weren't "failures", they just didn't do what the guys thought they would do within the confines of the guns and powders available. The idea had merit, but we may not be able to apply it to our platforms.
We do not want gas going past a cast boolit before it obturates in the bore. If it's big enough to start with, no obturation is needed or wanted. If it did, every single boolit we shoot will show gas cutting. With thousands of recovered boolits that show zero gas cutting, I firmly believe the boolit has moved out before gas gets around it. There is no indication of gas between the brass and boolit.
We have to look at a pinch of very fast powder in a large case. It can be all burned up fast so there is nothing but gas in the case. That might be a reason for a boolit over size to the throats so it keeps that gas behind the boolit. Slow powders can act as a filler while the boolit transitions the throats and provide a seal. Gas has not reached the boolit base yet.
Think in SLOOOOW motion, not milliseconds!

I believe you have to think in milliseconds. But it's all just opinion in the end.

[Char-Gar]

My 2011 Ruger 45 Flatop has .452 cylinder throats.

[MtGun44]

Bret -

Even faster than milliseconds, microseconds and even millionths are important. The pressure
wave takes about 56 millionths of a second to travel the ~3/4" length from the front of
the flash hole to the base of the boolit in a .44 mag or .45 Colt.
Like I said before, we don't actually know, and MY budget won't support the required
hardware setup to test this.

Bottom line for the whole thread - MOST revolvers need a boolit that is "a close fit" to the
throats to work well. We can thrash around all week about .001 larger or right on, out of
round throats, missing tapers, out of round boolits, driving band length and diameters, etc.

ALL are variables that will affect the outcome. For a particular gun, the loader will have to
try out some different things to see how that particular gun works out.

I strongly believe that the basic concept of fitting the boolit to the throats (however you do
it!) is the key concept that is NEWS to a lot of loaders, and awareness that this is a key
point to be fiddling with (rather than ignoring) is critical to success if the gun is not happy
with .429 or .430 diam boolits. Opening up throats was unheard of a decade or two ago,
and with some of the super tight throats that have been found, it has been a major breakthru
in revolver accuracy.

Bill

[cbrick]

Very, very well said Bill.

Each revolver is an entity unto itself and regardless of how you acheive it fit in the particular gun is the single most important part of loading for it. More so than alloy or BHN unless your way off base for the load/gun.

Rick

[Char-Gar]

I had a 2" Smith and Wesson Model 10 with .356 throats opened up 25 years ago. Clark in Louisiana did it for me. It was not common, but was done back then. You have been able to buy chucking reamers in .001 increments for many, many years.

It was Ruger and their itty bitty throats on Blackhawk 45 Colt revolvers that brought the practice to the fore. I don't know what posses Ruger to make sixguns with undersized cylinder throats and hog wallow oversized charge holes.

On my Ruger Flatop 45 I got last week, Ruger has correct both these glaring problems. Better late than never.