Problem slugging my revolver

[Plaz]

I tried to slug my S&W 629, 44 magnum revolver, today for the first time. This was my first experience slugging any gun. I used a cast bullet and hammered it through the barrel with no problem,. However, when I tried to measure the diameter of the lower flats on the bullet I found that they were not 180 degrees apart. Therefore, there was no way that I was going to obtain the diameter of the applicable flats that you measure when you slug a gun.

Am I doing something wrong?.

[SL1]

creates the problem you encountered. Rifling with an odd number of grooves and lands that are about equal width make this a problem, because there is no point where a groove isn't opposite a land.

As you have probably already found out, it is hard to use calipers and almost impossible to use a micrometer to get an accurate measurement across the edges of the raised parts of the slug. Just a little rounding of the slug edges can result in a too-tight measurement of the groove diameter.

What I do with guns like that is use plug gages to get the bore diameter, and then calipers on the slug to get the bore plus ONE land. The difference between the bore and the bore-plus-one-land is the height of ONE land, and I add that to the caliper measurement to get a total of the bore plus TWO lands, which should be the groove diameter.

If you want measurements to ten-thousandths rather than thousandths, you could use a small UNIFORMLY flat piece of metal that fits into a land impression in your slug and get a measurement of the bore-plus-one-land-plus-flat-piece-of-metal and then subtract the thickness of the flat piece of metal.

If you don't have a set of plug gages, you could use a drill press or a lathe to carefully turn-down a piece of brass or soft iron rod until it JUST fits into your bore, thus making your own gage, and measure that.

Frankly, all of that is a PITA to do, so I hope somebody on this forum has a better idea that you and I can both learn.

SL1

[rattletrap1970]

I never like pounding things through my barrels, too much can go wrong. I picked up some of that low melting point CHAMBER CASTING ALLOY. Melts at around 160°F. I apply a very thin layer of oil in the barrel. I cut a disposable squishy ear plug in half and push it .750" down the muzzle end, then allow it to expand. Then I pour the melted alloy into the bore till it is flush with the end of the muzzle. I give it about 10 minutes to cool then smack it out with a sturdy cleaning rod from the receiver end.

I wait 1 hour for the alloy to normalize in size then measure with a digital Micrometer.

For Grooves and lands that ate 120° apart, I would take the slug and pass it through ring gauges. (Basically an accurate hole in a piece of metal).

[alland]

IIRC S&W revolvers are 5 groove barrels. Mitotoyo and I think Starret make V angle micrometers that will measure the slug correctly, but $$$.

http://www1.mscdirect.com/CGI/NNSRIT...51458&PMT4NO=0

[Mal H]

Measure the outer diameter of the bullet (this would be the barrel's groove diameter since the slug is a mirror image of the barrel). You can usually find an area where that is possible to do even with odd numbered grooves. Then turn the caliper lengthwise and measure from groove to land. Subtract that measurement from the first to get your land height.Subtracting 2 times the land height from the overall diameter gives you the barrel's land diameter.

[briandg]

Take it to a gunsmith and give him $15?

[Unclenick]

Plaz,

Be aware that a conventional cast bullet alloy will not give you an accurate reading (not to ten thousandths). They are too springy, and expand outward against the bore. That's why you can't feel constrictions with them. You need to use pure lead because it is, for practical purposes, inelastic. Hornady swaged lead balls for cap and ball revolvers are pure lead, and you can use them as-is or flatten them to eliminate chatter for locating a bore irregularity.

A blade micrometer may be able to get the bore diameter of your slugs if the lands on the 29 are narrower than the grooves? I forget whether that's the case or not? If you can get that number, then follow SL1's instructions to find the groove height reflected by the raised area of the slug. It's probably about 0.004", but "about" isn't what you want.

When I slugged my Smith K-frame .38, I cast a pure lead bullet to use. After slugging, I measured land to groove diameter per SL1's method, then chucked one end of the slug in my lathe and set up a dial indicator to show the height difference between lands and grooves. If you don't have a lathe, the dial indicator on a cartridge runout gauge can be used to give you the same information.

The problem can also be solved by placing the slug in a v-block so it is resting on the groove impressions then using a depth micrometer, but you need precision ground dowel pins to calibrate the depth readings with and to be able to do some trigonometry to work out the bullet diameter from the depths.

[SL1]

Unclenick's v-block+dial-indicator idea seems like a good one to get the difference between the land and groove part of the slug. You just need to make sure that there is a large-diameter part of the slug in contact with the face of the v-block on each side so that the axis of the slug doesn't change as you rotate the slug in the block to get the two dial readings.

Rattletrap1970's idea about using ring gages leaves me wondering if you can "try" a pure lead slug in a same-sized hole more than once without changing the reading by as much as a thousandths of an inch.

The casting method is usually a little less accurate than the slugging method. And, of course, it doesn't change where the lands and grooves fall on the part that you need to measure, whether it is a slug or a casting. The casting IS harder than the pure lead, so you may be able to try it a few times in a snug-fitting ring gage hole without altering its dimensions. But, be sure to follow the directions about WHEN to measure it, because that casting metal alloy is designed to shrink enough as it solidifies that it can get out of the chamber/bore, then swell again. So, it is undersized when it first comes out. It is about the size of whatever it solidified in at one hour after casting, and larger after that. There are tables available the give you correction factors as a function of time since casting.

SL1

[Plaz]

Additional information. The cast bullet fell clearly through each chamber of the cylinder. However, I had to hammer the bullet through the barrel.

[SL1]

Much better that way than the other way around. Means you can probably get good accuracy if you match the bullet diameter to the chamber THROATS of your cylinder.

And, if you are going to do that, then why worry about groove diameter of your barrel, anyway. You should be able to measure the chaber throat diameter(s) successfully. If they are not all the same, you might want to avoid the one that is off the most or have them machined to equal diameters if they are all over the place in their various sizes.

SL1

[Unclenick]

I once slugged a couple of barrels with cast bullets just to try it. It took firm pressure to get them started in, and firm pressure to push them all the way through. In the second instance I thought to put an index mark on the slug when it was half way into the muzzle and used that to line the slug up and sent it through the bore a second time. It was just as hard to push through on the second pass. Pure lead slugs rub lightly where the bore is tight and offer no resistance where a bore is looser than the last tight spot. On the second pass you barely feel it and then it only lightly at the tightest place. It's those tight places you want to identify for removal by lapping, as even a springy hard alloy will splatter lead just after going through one.

I remember years ago reading that Harry Pope had been asked to look at a military barrel making operation that was having problems. The first thing he did was fish a pure lead ball out of his pocket and tap it into the muzzle of a sample barrel, then pushed it out from the other end with a cleaning rod. He caught it in his hand, then measured it with a micrometer and pronounced the result.

The plant manager who watched this proceeding proclaimed that it couldn't work because the lead ball would be too elastic. He got the same barrel measured with a star gauge and it turned out to agree with Pope down to the ten thousandth. But the plant manager would have been right if it had been a cast bullet alloy like I used in my experiment. Half a thousandth error would be reasonable to expect.

Note that if you cast pure lead, you can use brass rods at either end and a plastic hammer to bump them up to a tight bore fit. Cerrosafe has to be tapped out at the right time, while its size is still small, and then be measured after a specific wait for it to become the full size of the bore.

[Jim Watson]

There was a gentleman, since deceased, who had an assortment of micrometers, gauges, and v blocks and would measure a slug from about any bore configuration if sent to him. I don't think anybody took over from him.

It would be instructive to read in Hatcher's Notebook about the 1903 Springfield and 1917 US Enfield. Both .30-06 and with .300" bores, the '03 having four grooves .004" deep for a .308" groove diameter, the '17 having five grooves .005" deep for a .310" groove diameter. And the 1917 is "tighter". Because its lands are the same width as the grooves and the '03s are narrower.

[FrankenMauser]

This is a job for trigonometry, if you want to be precise about it.

It's a matter of solving the "big" triangle, and a smaller one that the big triangle gives us angles and a measurement for.




Mark the center of one of the grooves (in the slug). {Black line}

Measure the distance to the approximate center of an adjacent land and mark the point. {Distance "D"}

Make the same mark on the opposite side of the groove. So you've marked a point the same distance on either side of the center of the groove {Distance "D" from the black line, each direction.
We'll call these Points "D".

Now, measure the distance between Points "D". This is Distance "C". It is not likely to be exactly what 2 x Distance "D" is, but will probably be close.

Now, on the opposite side of the slug take measurements from a single point, to both Points "D". {Distances "A" and "B"} Compare the measurements until both "A" and "B" are equal. Write the measurement down.

That's all that's needed:
1. Distance "A"/"B" (one is fine, but you need to make sure both are equal, before recording the measurement).
2. Distance "C".

I don't have time to explain how to solve the triangles at the moment, but I'll try to repost later. If you just want to post measurements, that's fine.

[SL1]

I don't see how measurements "A" "B" and "C" can be made accurately enough to get a solution for the diameter that is accurate to 0.001". The problem is that there are no opposing surfaces to use as a "hard stop" for separating the ends of the the measuring tools. So, getting the two ends of the measuring device (e.g., calipers) to sit on the two marks, each within 0.001", seems unlikely. I know that MY eyeballs aren't calibrated that accurately. I don't think I would even see a mark that is only 0.001" wide, much less keep two points of the same tool on two separate marks long enough to get them set to the distance between the two marks.

SL1

[Plaz]

SL1 - Quote:Much better that way than the other way around. Means you can probably get good accuracy if you match the bullet diameter to the chamber THROATS of your cylinder.

If I increase the diameter of my bullets to accommodate the larger cylinder chambers won't they jam up in the barrel when fired?

In a revolver are you supposed to size your bullets according to the cylinder chambers or the barrel? Or does the requirement change in different guns? You can see I am new at this.

[Mal H]

Actually, Plaz, it's not clear why you are slugging your revolver in the first place. A modern gun such as your 629 rarely needs that exercise. I would be surprised if your cylinders aren't .430" to .431" in diameter. You can safely use .429 jacketed bullets or .430 plated or lead bullets without worrying about it at all.

What is the size of the bullet you are currently using?

If I increase the diameter of my bullets to accommodate the larger cylinder chambers won't they jam up in the barrel when fired?

Not at all. If you use bullets that just exactly match the cylinders, they will work just fine under pressure in the barrel.

If you were working with a older .45 Colt, for example, then the slugging exercise might be necessary, but I truly feel you are worrying about a factor that you don't need to at this stage of your reloading experience.

[Plaz]

The confusion gets worse.

For example my mold is a 429 mold. The diameter of the bullets I make with that mold are 418-420 in diameter. These are the same bullets I used to hammer a slug through my revolver bnarrel which is a 44 magnum.

A box of cast lead bullets that I purchased are labled on the box as 430 inches in diameter but the bullets as measured are actually 422 inches in diameter.

I like the previous comment I received which suggested I do not need to slug my revolver.

However, I sure would like to know what I am supposed to do if I wanted to select a proper sized bullet for my gun and do I select a bullet by its actual dimension or the dimension stated for a new mold? If I select by the actual bullet dimension I will not know what that is until after I buy the mold and measure a cast bullet. I am trying to learn and would appreciate any responses.

The big question is can I use the cast bullets I made which are 418-420 in diameter?

[Mal H]

The answer is obvious - there is either something wrong with your caliper/micrometer or with your measuring technique.

If your bullets were truly .418", they would most likely just fall through the barrel without touching the lands.

Please describe your caliper, how you are zeroing it, and how you are measuring the bullets.

For the .44 Magnum, you select a bullet as I described in the third sentence of my first paragraph - it's that simple.

[SL1]

usually vary with the alloy used to cast bullets with the mold.

It used to be that molds were made very oversized, so that all alloys made bullets that were too large, and then the bullets were "sized" (and lubed) in a "lubrisizer" device. But, people trying for maximum accuracy with cast bullets learned that sizing them down more than a couple thousandths really affected accuracy. So, newer molds are usually closer to intended final size. And, a custom mold maker will ask you what alloy you intend to use, as well as the dimensions of your particular gun.

I mention all this because I don't know what mold you are using, and I wanted to give you the info you might need to figure-out what is going on in YOUR particular situation. But, I agree wth Mal H that the measurements you have posted seem to have some sort of error that is substantial. One way to test your technique is to measure some jacketed bullets of quality manufacture. Hornady jacketed .44 bullets are usually about 0.430" while Speer and Sierrra are more like 0.429". Molds usually drop bullets slightly larger.

With respect to not knowing what diameter bullet a particular mold will produce without buying it and testing it, that is unfortunately true. Custom mold makers may tell you they will make one that produces bullets of a particular diameter with an alloy that you specify. But, new, mass-produced molds used to vary a lot and still vary substantially. When buying used, the previous owner MIGHT be able to tell you the diameter of the bullet that a particular mold produces with a particular alloy, but these days, many sellers on GunBroker.com are not really the previous users, they are just resellers. Also, be advised that buying used molds may or may not give you problems with concentricity and other factors that are associated with wear as well as original quality.

SL1

[FrankenMauser]

For example my mold is a 429 mold. The diameter of the bullets I make with that mold are 418-420 in diameter.

A box of cast lead bullets that I purchased are labled on the box as 430 inches in diameter but the bullets as measured are actually 422 inches in diameter.

The big question is can I use the cast bullets I made which are 418-420 in diameter?

I completely agree with Mal H.

Your micrometer/calipers are completely screwed up, not calibrated, or not properly zeroed.

What are you using? Brand? Digital or Analog (dial)? How do you zero them? Where do you store them? How old are they? Have you ever dropped them?

[Edward429451]

Those mathmatical calculations sure are impressive and I know that you guys are correct in what you say, BUT! There are those of us that on our good days our math comprehension just isn't allowing us to follow all that mumbo jumbo so understanding enough of it to realize that size is important, but not enough of it to actually perform this stuff on our guns...here is what I did instead, no disrespect intended to those that actually understand how to measure triangles and such....

The problem was clear in the beginning, mediocre accuracy and leading left over for the most part. I want more accuracy and less leading without needing the college degree or a laboratory.

Very methodiaclly I simply increased the size of the bullets I was using by buying bigger sizing dies and starting over from start loads. This time with slighty greater accuracy and less leading for me.

Use your calipers more and soon you will develop a feel for if it is giving you a proper measurement or not. Analog calipers are much preferable to digital calipers. You also have to realize that most commercial cast nowadays is all on the small side, you may have to cast yourself to get the diameter you need.
I only needed to go up to a .430 for 44 mag but my 45/70 Marlin rifle still leaded like crazy at .459 so I had to get a custom size die for .460 and now it shoots most bullets very well.

[zippy13]

I like the simplicity of using a ring gauge; but, who has a selection of ring gauges... Then it hit me: Can a sizing die be used as a slug ring gauge?

[Plaz]

Mal H Quote: The answer is obvious - there is either something wrong with your caliper/micrometer or with your measuring technique.

If your bullets were truly .418", they would most likely just fall through the barrel without touching the lands.

Please describe your caliper, how you are zeroing it, and how you are measuring the bullets.

For the .44 Magnum, you select a bullet as I described in the third sentence of my first paragraph - it's that simple.

---------

You were right I was not reading my calipers properly. I failed to zero it out first.

[Plaz]

Now that I learned how to properly read my calipers I still would like to know if I can use the bullets I casted. These were made using a Lee 429 mold and are now covered with alox. They are measuring as follows for the six bullets which I measured:

423-427
426-429
430-432
427-429
423-426
425-427


I also want to take this opportunity to thank all of you folks on this forum for all of the oustanding help and guidance you have given this 85 year old man who is trying very hard to be young again with this wonderful reloading and shooting hobby. Thank you all so very much.

[SL1]

Plaz,

You certainly CAN shoot them, but the accuracy may not be what you are hoping for.

The range of variation in your measurements seems to indicate one or both of two issues. One is that you MGHT not have figured out how to make precise measurements in a repeatable manner, so the variation just LOOKS larger than expected. The other possibility is that the casting (and/or lubing?) technique is making bullets that ACTUALLY have unusually large variations.

The unusually large variation seems to occur in the range of diameters of INDIVIDUAL bullets as well as from bullet-to-bullet. One thing that can cause ACTUAL differences in various diameter measurements of an INDIVIDUAL bullet is the alignment of the mold block halves. (On SOME molds, the cavities themselves can be out-of-round, but I think Lee's molds are made on a lathe, with tends to avoid that problem.)

It would help us diagnose your particular issues if you would take and post several measurements of the SAME bullet across the SAME two points around its circumference. In other words, try to measure the same physical thing several times so that we can see how much variation in your results is coming from your measuring equipment and measurement technique. If those test measurements on a bullet still have a substantial range, then it would help to ALSO do the same thing with something that is likely to actually be pretty round. I would suggest something that is pretty hard, like a drill bit SHANK (NOT the fluted part) that has not been scuffed-up already in a drill.

SL1