Sizing to Cylinder Throats

[mattd]

After pushing a 432 sized bullet thru my SBH cylinder I measure anywhere from .4308 to .4314. This is measuring it after the first pass thru a single cylinder, and it's the same after pushing it thru all cylinders multiple times to reduce any spring back.

Some throats are just a bit easier to push it thru then others.

Barrel is .429.

With all other guns I size .001-.002 over bore size and I'm good to go. When I read size to the throats for a revolver, does that mean size to the exact size of the throats? Or go slightly over size, as with other guns?

Currently I size to .432. I get minor leading even with a gas checked 429244 bullet. And after many, many loads haven't found one I'm in love with.

Could the minor variations in throat diameter be an issue?

Thanks,

[DougGuy]

Yep they are an issue because it's the same as having some cases with more neck tension than others, some with more powder than others, some slightly shorter than others, all theses variables cause an equally predictive change in pressure. Cylinder throats are no different. The single most important thing about cylinder throats, is that they need to be *even* in diameter because that affects the recoil impulse which causes the gun to recoil differently in the shooter's hands from shot to shot, which predictably causes the boolits to shoot to varying points of impact. You can always size .0005" under throat diameter, and with a soft enough alloy over enough powder, the boolits will easily bump up to throat diameter so there is no question about fitment.

Now.. You can't get too accurate a measurement using a boolit, they all have springback, calipers introduce errors, even mics. You CAN however tell if a throat has a tighter or looser drag on the boolit being pushed through it with finger pressure, which would not give you any mathematical dimensions to write down, but you know you have a mechanically induced variable if the throats are uneven.

You need to send the cylinder and have it throated so all the throats are within .0002" of each other, and if one throat is .432" the rest of them need to be sized at least to the largest throat but the most trusted procedure is to ream all the throats because a reamer cuts a very true and round hole where factory cylinder throats are often oval or belled, very common to be able to put a pin gage in a factory throat and see light on one side or wiggle it one way but not the other way. Reaming and then honing leaves the throats very round and true, and all are even.

Now you have removed a significant variable from the gun, where no matter how consistent your loads are, or how good of a shooter you are, the throats when they are uneven shoot differently and this just serves to open groups. It will still take deer at 25yds all day long, but 50yd or longer shots can become iffy.

If you currently size to .432" the reason you are getting leading is that the boolits are only .432" when they are assembled, after passing through the throats, they are sized to throat diameter and delivered to the bore much smaller than the .432" you started with. In so many words, you are firing them through a 6-port sizing die..

[DougGuy]

When I read size to the throats for a revolver, does that mean size to the exact size of the throats?
Thanks,

In a perfect world, the boolit needs to be .001" to .002" over groove diameter, and the throats need to be .0005" to .001" over boolit diameter. This is the best dimensional arrangement for a Ruger revolver. The reason you might not want to size any closer to boolit diameter, or to throat diameter, is that as cast boolits "age harden" they will grow in diameter depending on how much antimony is in the alloy. A change in diameter of .0003" to .0006" is not uncommon.

This means that if you cast and size boolits to .432" and then size throats to a snug fit, 3 months later that same boolit will not go through the throats, and consequently loaded ammo may not even chamber fully in the cylinder. Ask me how I know THIS one...... << Been there did that, and learned that cast boolits NEED a little wiggle room in the throats when they are freshly cast and sized so that later, they will still fit in the cylinder..

[44man]

What can I add---NOTHING. Doug has a way to tell it. You don't want larger boolits then throats so get it fixed.
I question a .429" groove in a Ruger too.

[Char-Gar]

Size you bullets .430 and go shooting. I will bet your problems will go away.

[DougGuy]

Size you bullets .430 and go shooting. I will bet your problems will go away.

He's already sizing to throat diameter every time he pulls the trigger. How is sizing smaller going to fix uneven throats?
_____________________________

Let's consider something before this conversation goes any further. Ruger makes thousands of revolvers every week. They run hundreds of thousands of cylinders on the same multiple chuck machines every week. Tooling wears. They don't spend money on carbide reamers, they use HSS high speed steel tooling that gets smaller and smaller every time it cuts a hole. Once the cutter gets too small to use, they replace it with a new one. Now you got 3 reamers chucked up into the machine, one is new, the other two are in various stages of wear, but suffice it to say neither of the worn ones are anywhere near the size of the new one that just got replaced.

Here comes a boatload of cylinders, chuck one up and plunge three throats at a time. Each cutter does one hole. Each hole is reflective of the size of the reamer, which is of course three different sizes due to normal wear. Index the cylinder over one hole and plunge the other three. Bang that cylinder is done, and sent down the line. Here comes the next cylinder, same thing.

Ruger made hundreds of thousands of revolvers with cylinders having uneven throats, this is fine with their QA, they test fire them for proof, and before they are shipped, the test fire them to see that they are shooting to point of aim enough that they aren't a safety hazard and they box them up and ship them. As long as they will shoot factory produced ammo enough to stay on target, this is ALL the test that is required of the product.

We here on this forum tend to be a little more in the know about our firearms, and the mechanics behind what makes them shoot well or not at all. I take it as a benefit that the cylinders are uneven, they leave enough metal in there that guys like myself can carefully remove the excess and reveal a pristine round, straight, true cylinder throat that is exceedingly even all the way around.

We ALL know that fitment is KING. You wouldn't tear down an automobile engine and simply chuck in oversized rings to tighten up the fit in worn out bores, any shadetree mechanic knows that it's proper procedure to have the block bored and honed and pistons and rings fitted, and now you have given this tired old piece of automotive engineering new life, it will get better mileage, run smoother, quieter, and longer, because of not only the quality of the work done, but the accuracy of the work.

Revolver cylinders are no different. The more accurate they are made, or smithed, the better the results will come from shooting the gun.

[DougGuy]

Revolver cylinders are no different. The more accurate they are made, or smithed, the better the results will come from shooting the gun.

It won't be long that EDM electron discharge machining technology will be affordable enough to use on the kitchen table. I don't know if it will be in our lifetime or afterwards, but I suspect that Ruger and other manufacturers will adopt this technology because it will be cheaper than the HSS reamers they currently use. Once this happens, we can look for uniform and highly polished cylinder bores and throats. I may or may not have a job after this, depending on what final size they decide on.

If I could afford EDM for my shop I would use it now. I spent about $2k on the Sunnen hone and all the related tooling I currently use for finishing cylinders, EDM is not that much more of an investment. In 10 years, I likely couldn't give my Sunnen hone away. It will go the way of the dinosaur.

[Piedmont]

Doug is probably right but I remember reading in my gun magazines back in the early to mid 1990s (when I still subscribed) that CNC machines were going to make all our firearms better and more accurate. It seems somehow after that these manufacturers that had the machines turned out a bunch of substandard firearms. Garbage in, garbage out I guess. It makes you skeptical.

For example, why the heck can't revolver manufacturers get cylinder throats right? All it takes is paying attention and measuring. I guess that is too much to ask.

[telebasher]

These machines are just like the guns we agonize and scrutinize over. They are only as accurate as the operator! Fortunately, Doug and others like him have the skills to correct what should be from the factory. I guess Ruger and other manufacturers have a hard time finding dependable workers to manufacture the guns we so love to shoot.

[44man]

These machines are just like the guns we agonize and scrutinize over. They are only as accurate as the operator! Fortunately, Doug and others like him have the skills to correct what should be from the factory. I guess Ruger and other manufacturers have a hard time finding dependable workers to manufacture the guns we so love to shoot.
It is also EXPENSE, Reamers are COSTLY to replace for every gun. Hand work will sink a company since we will not pay for it.
A cherry for a boolit mold can cost a fortune so they sharpen them as many times as they can get away with. I seen one for $275 so I make my own.

[DougGuy]

Reamers are a consumable. There is NO practical way to make a cutter that will last and last through those chunks of terribly tough steel they use for cylinders. I have some HIGH DOLLAR high tech coated carbide throating reamers that I paid 4x over the cost of the Manson HSS reamers, and I can tell they are wearing by how tightly pin gages go in the throats after they are reamed.

Even CNC tooling has mechanical cutting inserts, and as long as you are cutting metal with metal, you will have wear. it's not that manufacturers CAN'T make cylinder throats nice and even, S&W does for the most part, I get a wonky one in the door now and then but for the most part, their .45 caliber cylinders are SLICK! PRETTY! And usually even! Too bad they are all .451" and not larger.

L@@K at the cost of the S&W compared to the Ruger! We should ALL be glad that Ruger chooses this "replace by attrition" policy with their expendable tooling. Considering that ANY other method they could use to cut cylinder throats is much more expensive.

Correcting their cylinder throat diameters is usually an easily affordable, one-time cost of ownership expense to have them corrected to the tenth of a thousandth according to *our* needs or requests. Not too bad of a deal really, considering the alternatives, and considering that if/when Ruger moves on to a better way to do it, the mfsr cost of each revolver will go up 2 or 3 times the cost of having the diameter of the cylinder throats professionally corrected by a guy like me.

[mozeppa]

get douguy to ream your cylinders....he did 11 for me.

all is good now!

[mattd]

At some point i'm sure I'll use Dougs services, but I'm still a long way from needing the polishing touches accuracy wise. When I can do 3-4 inches consistently at 25y will be a good mark.

But, sounds like I can eliminate varying throat size by shooting out of a single chamber only, for accuracy testing anyway.

Was traveling this week so I stopped by midway and picked up a .431 sizer. Loaded up 5 of the lee 430-310s lubed w 50/50, cast of 6 parts WW and 1 part Lino. The .431 sizer barely touched it. First Load was 21.5g of 296 and Rem standard primers. Had one failure to fire, and was only able to clock one round (it's raining) at 1255 from the 7.5 barrel. 2 shots hit the sheet of paper at 30y, about 5 inches apart.

[44man]

I don't even start at less then 50 yards and I want 1/2" to 1" max for 5 shots. The lee 310 will do it.
Maybe you don't have loading right and are using dies not capable. I have tossed dies that don't work. Most were made into other tools. Doug can make the gun better but you might not get loading to where the gun shoots. Sorry to be harsh but those that can make a revolver work can be counted on a finger. Nobody can solve it but you.

[mattd]

Second round, all thru the same chamber, was 22g of 296. Getting flattened primers, but a break in the rain let me get the chrono back out.....

1288
1308
1297
1301
1327

that seems pretty good, so I'll let the dies off the hook. Accuracy was a bit better, but they are hitting very high, which I know we all run into w this bullet and factory sights.

But primers getting flat and a lot more recoil then 21.5g. Not that I need the speed, but I read on other threads you guys are pushing this bullet to 1350 for the spin/stabilization. Dosent look like I'm getting there.

[mattd]

For the record, my original enquiry wasnt about accuracy, more about function. I always got leading and never had great accuracy. So was curious if my throats could be the issue. Today I shot 10 high power rounds and 5 w a 200g bullet and 9g of unique. Checked after every 5 and never had any leading. In fact it's cleaner then ever. Not a high volume, but it never took much.

I think the important change was going from pan lubing and a 432 push thru sizer, to a 431 in a Lyman 450. Really that's the only change. But it works. So I guess now it's up to me to get better.

[44man]

For a 310 Lee, 22 gr is too much, Groups will open. Yes, just 1/2 gr.
Next, leave the chrono home. Do NOT worry about velocity at all or funny numbers.
Case tension variance will shoot you in the foot first. The best dies ever have proven to be the Hornady New Dimension dies.
I have worked the .44 since 1956 and went through the "shoot one chamber at a time" stuff. What did I find if my rounds were loaded right? I found a slight change in POI ONLY. Groups from each chamber were small but YES, shoot them all and groups were larger. The more even chambers are the smaller the groups so Doug is correct there.
But a difference in case tension from loose to tight can be 10" POI. So if Doug fixes you might still never shoot until you load right.
You do not know the harm some dies do with the .44. I figured it out in 1980 or so and had collar BR dies made for the gun. The custom die maker understood my words and did what no other tried. It worked but they are hard to use so it led me to test dies. I will not buy RCBS, Lyman or Lee even though they work for some stuff. None get the .44 right. Redding and Bonanza make rifle stuff I love. The Hornady dies were cheap enough at the time and did the same as my custom dies.
Shooting all my life has always had Hornady bullets shoot the best so why not dies? Now I buy nothing else, rifle or revolver.
Leading is something else as is powder choice, pressure at what point, Alloys, slump, primers, Lube, all related. Do it yourself and look at years and years but you can read rags and posts that lead you in the wrong direction. "You need softer to obturate" Get real! Hard leads a barrel, get real! This powder or caliber NEEDS a magnum primer, get real. The things I have found wrong will fill the library of Congress.
It is all repeated over and over but from what source?176806 Do this at 50 yards 176807 then this at 100 with a revolver and some will listen. Others skip over me but those that know repeat me. It is what I want, to make you shoot better.
If someone tells you something, test it first. Most times it is wrong so sit and think.
Doug has found what I did right and repeats, great by me. Others found I was correct and repeat. Keep it up, you are the best bunch ever. You need help at times. Some will always dispute.

[W.R.Buchanan]

My two Rugers are completely different.. The SBH has chambers that look like 30 miles of bad road. The BH chambers look like they were honed. Obviously they came from different stages of the tool wear cycle.

Throats are close but not identical on either gun. Barrels are both dead on .430 and glass smooth as they were hammer forged.

There is a very good "Historical" article in the latest Handloader Mag by Elmer Keith, about the evolution of the .44 Magnum. He talks about every aspect of shooting the guns and the guns themselves and the Boolits. It is about 7-8 pages long and he does tend to go on about certain things.

He was a big proponent of the 429421 boolit (wonder why?) and considered it to be the only boolit to shoot in those guns, both Specials and Mags.

Not a big fan of gas checks either as they don't allow the boolit to bump up which is necessary for optimum fit and caused leading, (which was a surprise to me) He also talked about sizing to .429 for all his boolits. Now he didn't talk about the throat sizes of his guns, but since his first M29 was SN#001 I'm pretty sure it was perfect. And in fact most early guns had lots more hand work in them than they do today so we'd expect them to be better fit.

As far as EDMing chambers and such goes, S&W is currently EDMing rifling in barrels and the finish is far from glass smooth. And just to warn you guys,,, EDM Machines are not cheap at all. Decent sinker machines start at about $100K and wire machines are more like $250K and as such tend ot not lend themselves to home shop applications. I guess if you could find used ones? but the other rub is the cost of generating precise electrodes which takes the same equipment as a reamer outfit has.

I would think that the chamber reamers would include the throat portion of the hole as well. I know we've been trying to get Marlin to put a radius on the back edge of the chambers for some time and all it takes is a slight mod to the reamers.

The material these guns are made from is Chrome Moly Steel, I don't know exactly which one, but that material machines like ship and unless your cutters are perfectly sharp, they will drag material thru the cut and leave a bad finish behind.

All large companies make their own specialty cutting tools or farm them out to a trusted specialty grinding shop, and like Doug said they are a one way trip. However they can be resharpened to a smaller diameter like starting with a .45 cal. reamer and turning it into a .44 cal and so on.

I may have to have another look at mine to see what they are again. I measured them both when I got them and they appeared to be somewhat close but I have forgotten what they were and they may need the "Doug treatment." I know I couldn't hit anything with either one Saturday so maybe some attention to detail would be in order. I don't have a Sunnen Hone, but sometimes I wish I did, as I can make a sizing die but it would be nice to be able to finish the ID right. Kind of need a hone to do that right.

Randy

[DougGuy]

I -just- got in today's mail, some samples of borazon (powdered metal with imbedded abrasives throughout) stones for the Sunnen hone in I want to say 800 grit and 1200 grit. I can do from .32 to .480 with these. Long behind are the days of the slotted aluminum rod and the abrasive paper. Gone also are the Acro laps that I used for about a year to finish with after the reamers.

Since the arrival of the Sunnen hone, I have started retooling my reamers to cut smaller so it leaves some metal for the Sunnen hone to clean up and leave less reamer tool marks behind. The reamers *do* cut an exceedingly round hole, they will straigten up an oval or belled hole like nobody's business so I like using those but the steel that Ruger uses for cylinders is some TOUGH STUFF! It is granular in nature and wants to tear and pull out regardless of how sharp the reamer is or what cutting/honing oil one uses. And it is quite inconsistent! I never know from one cylinder to the next which ones will cut smooth and which ones will be a booger bear and have the reamer squawking while cutting with it. Horrible sound. Hate it. It just comes with the territory and there is nothing that can be done about it.

I will get tearout now and then and there is NO WAY around it. Some are enough that they leave some tiny remnants of this in the polished cylinder throats, and I won't hone oversize to go after them just for a smooth looking finish as they don't hurt anything and fill in quickly with powder residue and lube residue.

[44man]

True about Ruger steels. Most don't know that when Ruger went to stainless they had galling problems. They had to change alloys for each part and the hardening process for each part. The hammer is a different alloy then the frame, etc.
To go to stainless from Chrome moly was a chore. Takes better tools too.
I see it when I make molds with stainless sprue plates. A counter sink is smoke in seconds so I gave up and cut on a face plate to taper. I have aircraft counter sinks that will smoke. Speed or oils all fail. Imagine cutting a chamber!