Sizing for your cylinder

[Fugowii]

I 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. My boolits give me a hard time seating in the
cylinder which makes sense, at least to me. A boolit sized .433" being stuffed into
a hole that is .0005 to .001 smaller isn't going to necessarily fit all the time.

I guess that the obvious solution is to go down a step to .432".

[MtGun44]

The boolit does not sit in the throat, it sits in the forcing cone between the chamber
and the throat. You normally need a boolit at throat diam or .001 over for best results.

HOWEVER - some throats are so oversized that you cannot chamber a round with the
boolit the proper size for the throats. In this case, you minimize the problem by using
the largest boolit that will chamber.

Bill

[462]

A case of tolerance mis-match, I reckon: Throats cut on the plus side and chambers on the minus.

All my revolver boolits are sized .001" over throat dimension, and cartridges chamber without problems. Perhaps the revolver boolit-god has been nice to me...

[Fugowii]

The boolit does not sit in the throat, it sits in the forcing cone between the chamber
and the throat. You normally need a boolit at throat diam or .001 over for best results.

HOWEVER - some throats are so oversized that you cannot chamber a round with the
boolit the proper size for the throats. In this case, you minimize the problem by using
the largest boolit that will chamber.

Bill

The problem is when loading the cylinder the boolit is larger than the cylinder and that
prevents the boolit from completely seating. This in turn leaves the boolit base a
smidge out in space and prevents the cylinder from turning. I've measured the case
and the boolit and everything is fine dimensionally. My barrel sizes out to .430-.4305.

I have no idea what you mean when you say the boolit sits in the forcing cone.
The cylinder does not have a forcing cone (or at least, I don't think it has one). I
am confused by your explanation so if you could take it a little more slowly, I might
be able to catch on.

[462]

What type of boolit are you loading...Semi-wadcutter, wadcutter, round nose?

[Larry Gibson]

Fugowii

Obviously the driving band on the bullet is well into the throat of cylinders chambers. Since the bullet is oversize the cartridge won't chamber all the way. This is why the rule of "need to" doesn't always work. Depends on the bullet design a seating relationship to the throats.

I've a similar situation with the 429640; if sized at .430 it won't chamber in my Colt Anaconda but will in my Ruger BHFT. Not a practical situation. I just size them .429 and they chamber fine in both revolvers and my Contender Barrel. Can't tell any difference in accuracy in the Ruger with the .001" less bullet. Truthfully I've been shooting a lot of cast bullets sized .429 in numerous .44s over the years. I've gone to .430 and .431 sizes to better fit the throats but, again, it's hard to say which is more accurate. Not saying that proper fit to the cylinder's throat isn't important but I think that sometimes we over concern ourselves with such.

I would select a size that allows the bullet to be gently pushed through the throats of the cylinders chambers.

Larry Gibson

[swheeler]

I have no idea what you mean when you say the boolit sits in the forcing cone.
The cylinder does not have a forcing cone (or at least, I don't think it has one). I
am confused by your explanation so if you could take it a little more slowly, I might
be able to catch on.

You are indeed correct that the cylinder does not have a forcing cone, the forcing cone is part of the barrel in a revolver. Size your bullets small enough to just let a cartridge chamber with no resistance, a bullet with a lot of driving band infront of ther case mouith will have to be sized smaller to chamber.

[63 Shiloh]

OK Fellers, I am completely confused now??

I have a Smith 686 .357/ .38 with a 6" barrel.

Now, when using .38 Special cases with DEWC seated flush to the case mouth, it is not being supported by the cylinder throat at all.

I size to .358" and lube with BAC, I tried to push a boolit through my cylinder throat and it is( throat) too tight!

My accuracy has been not too bad, I am new to revolvers and I get no leading with the above mentioned load.

Is the fact that my boolits are too fat to push through the cylinder, from one end and out the throat end, a bad thing??

Mike

[Bret4207]

No Mike, if you are getting good grouping then you're okay, maybe not perfect, but okay.

When we talk about fit we're talking about more than simply boolit diameter vs groove diameter or throat diameter in a revolver. Fit is made up of a combination of factors such as the chamber, throat and groove sizes, brass thickness and fit, boolit shape, powder charge, alloy, seating depth, peak pressure, and a lot of little things I'm forgetting to add. Basic static fit involves finding a diameter that works in that gun, with that brass, in that alloy, with that design boolit. Change brass and you might be able to go a thou larger or have to go a thou smaller or work on changing the brass. A boolit design with a tapered front section will fit differently in every gun, maybe even in every chamber of a revolver and as the throat wears it'll change more. Change alloy and you change your fit- maybe- because each alloy sizes a little different. And then, when you pull the trigger and get into dynamic fit...whoa! Everything can come apart or come together there.

Huh! Got off on a tangent there. Sorry. Now that I've confused you even more I'll try to make it clearer. You say you're getting "not too bad" accuracy. Okay, IMO at least 85-90% of the guns out there will equal jacketed accuracy with cast IF you can figure them out. So were it me, I'd be thinking I want to at least match what that gun will do with average factory loads. So to work on fit you have a lot of places to play with. You can start with the obvious stuff like changing sizing dies and see what happens.ONLY CHANGE ONE THING AT A TIME AND WRITE IT DOWN!!! You can change seating depth, crimp or no crimp, you can pull some loaded rounds to make sure you aren't "squishing" the boolit when seating, you can change alloys too as each alloy will have a different "spring back" (although with lead alloys this is usually a very small amount), and you can clean your gun thoroughly to make sure copper fouling or powder fouling isn't an issue. Only change one thing at a time and use the same powder charge, change 2 things at once and you're back to square one. Don't forget to check your boolits after sizing to see if they are being uniformly sized (assuming home cast). An off center sizing issue has ruined more than one good group. And make sure you are seating them STRAIGHT. It's not all that hard to seat a WC off center and cockeyed. I'm somewhat convinced that's part of the reason home brewed WC couldn't watch factory WC for a long time- misalignment.

When you get into the dynamic end of things you have a zillion variables. Lube, seating depth, crimp, powder charges, etc. Check one thing at a time. What you want to watch for is indications of a trend in the right direction. FWIW, IME Smiths are cast friendly. You might find simply reducing the boolit a thou will tighten things up, or that a seating depth change will do it.

My only concern with your specific situation is "What is happening to the boolit on firing?". I shoot lots of boolits that are "too fat" by everyday gunwriter type opinion, but they work great. But what is happening when the boolit is swaged down going through the throats? Is it being swaged or is it being sheared? Are you finding a ring of lead in your cylinders? If so a reduction in size might be in order. If no ring, is it being swaged uniformly?

Sorry this is so long winded, I'll shut up now.

[44man]

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! :kidding:
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!

[41 mag fan]

Brett,

Very informative! Dont quit now, there's plenty of ppl on here or ppl who come across this thread on google who are/will be gleaning info from your post. Perfect example, ring of lead in your cylinders. I got a SBH that does that. Never thought of down sizing my boolits.

[atr]

I would select a size that allows the bullet to be gently pushed through the throats of the cylinders chambers.


I most certainly agree with Larry Gibson on this one.....

[Shuz]

The boolit does not sit in the throat, it sits in the forcing cone between the chamber
and the throat. You normally need a boolit at throat diam or .001 over for best results.

HOWEVER - some throats are so oversized that you cannot chamber a round with the
boolit the proper size for the throats. In this case, you minimize the problem by using
the largest boolit that will chamber.

Bill

I understand Bill's comment about "forcing cone" in his post, means that there is a "tapered area" in the cylinder before the cylinder throat, that the boolit sits in before being fired. In my experience, as long as the loaded cartridge fits all the way into the cylinder, and the boolit rests in the tapered area before the actual throat, and the boolit is at least THROAT diameter, you will get good accuracy and minimal leading. Here's an example from a couplea my Smiths: they have .4285" throats and I load cast boolits of Bhn 11 alloy at .431" and they shoot 1" 5 shot 25 yd. groups from a scoped bench rested gun with no leading.

[Char-Gar]

I am not into bench rest shooting with a handgun so my standards are lesser than some folks. I want my sixguns to shoot better than I can when they are hand held. I also have a number of sixguns in the same calibers and like to load ammo that can be used in any of them.

I size my bullets as large as I can and still have the loaded rounds chamber with ease. If they don't chamber with ease, I size down .001 or more if needed. I let the charge hole throats do the sizing. This works out to .454 (45 Colt and AR cal), 359 (38/357 cal) and .432 (44 Special and Magnum cal) Rounds with this size bullets have fit in every pistol I own or have owned.

I don't think there is any particular accuracy advantage to doing it my way. But it does give me ammo that shoots in any of my sixguns and delivers far more accuracy than I want or can use. I know several well known gun writers who do the same thing, when they are shooting for fun and pleasure. When they are loading for articles they often go for the finer stuff.

[fredj338]

I have a M629 that has 0.432 cyl throats. I size to just that to make sure they seat. There is no benefit in going larger, the cyl throat will swage it down as it passes along to the bbl. The groove dia is important though, that is where you want the bullet to be 0.001" larger.
I had a tight RBH w/ 0.451" groove dia & 0.450" cyl throats. It shot ok, leaded badly in the first 2" of bbl. I opened the throats up to 0.4515" & the leading pretty much went away & accuracy is about twice as good as before.

[Fugowii]

Thanks to all. Looks like I need to downsize to .432" at a minimum.

[44man]

Thanks to all. Looks like I need to downsize to .432" at a minimum.
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.

[MtGun44]

Between the large diameter of the chamber and the smaller diameter of the throat,
there is a tapered area. This tapered area has to allow the boolit to fit. If it is too short
and steep, and you have a lot of full diameter boolit forward of the brass, then there
can be interference, maybe enough to prevent fully chambering a round. This
all depends on diameters of the tapered area (which I called it a forcing cone,
maybe the wrong technical term - ball seat is OK) the diameter of the
boolit, the particular shape of the boolit, etc.

In my experience, many/most REAL boolits are measureably out of round. A boolit that
just slip fits the throats is fine IF IT IS REALLY ROUND, most are not. IME, you are
better off with a bit of interference fit to ensure sealing and good alignment. In a perfect
world with perfectly round throats and perfectly round boolits, slip fit is fine. I think that
many will have some issues with this approach in the real world out of round throats and
out of round boolits. +.001 will ensure a very slight sizing so that the boolit is an exact
fit to the throats, a plus in my view. An out of round boolit that is just slip fit on the large
measurement may permit gas leakage and slight boolit tipping. These may contribute
to leading and/or loss of accuracy.

If your method works to your satisfaction, it is good. I think that +.001 is a good, safe
and effective method that has worked for many people in extracting good accy with no
leading from most revolvers.

Bill

[cbrick]

Thanks to all. Looks like I need to downsize to .432" at a minimum.

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

[Bret4207]

Between the large diameter of the chamber and the smaller diameter of the throat,
there is a tapered area. This tapered area has to allow the boolit to fit. If it is too short
and steep, and you have a lot of full diameter boolit forward of the brass, then there
can be interference, maybe enough to prevent fully chambering a round. This
all depends on diameters of the tapered area (which I called it a forcing cone,
maybe the wrong technical term - ball seat is OK) the diameter of the
boolit, the particular shape of the boolit, etc.

In my experience, many/most REAL boolits are measureably out of round. A boolit that
just slip fits the throats is fine IF IT IS REALLY ROUND, most are not. IME, you are
better off with a bit of interference fit to ensure sealing and good alignment. In a perfect
world with perfectly round throats and perfectly round boolits, slip fit is fine. I think that
many will have some issues with this approach in the real world out of round throats and
out of round boolits. +.001 will ensure a very slight sizing so that the boolit is an exact
fit to the throats, a plus in my view. An out of round boolit that is just slip fit on the large
measurement may permit gas leakage and slight boolit tipping. These may contribute
to leading and/or loss of accuracy.

If your method works to your satisfaction, it is good. I think that +.001 is a good, safe
and effective method that has worked for many people in extracting good accy with no
leading from most revolvers.

Bill

Good point Bill. That's another variable we often forget to even consider. Same with checking to see what our sizer dies actually produce.

[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! :kidding:
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.

:Fire::cbpour::redneck:

[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.