Matching bullet to throat to bore?

[patrick_sween]

I just started loading and now casting for a Ruger Single Six in .32 H&R. I slugged and measured the bore and cylinder throats and got .3117-.3120 on the bore, as expected. The cylinder throats were smaller, at between .3113 and .3115. I have fired some commercial hard cast bullets at .314 and a few home cast at .315 and got decent but not great results. Should I look at reaming the cylinder throats out to match the bore? I haven't seen any leading, just not the accuracy I would like. I know I have some more load work to do anyway, but don't want to chase my tail and waste components if the gun would benefit from some work. Thanks,

Patrick

[9.3X62AL]

I'm not certain that a few tenths of backwardness is capable of affecting grouping in a significant way. 1 or 2 thousandths of backwardness might be a problem, but I would run some varying designs through the revolver for test drives before taking tools to the throats. FWIW, one bullet design actually shot very well in my Built Backwards BisHawk x 45 Colt--#454490, a GC SWC that did good things in spite of .448"-.449" throats and .452" grooves.

[Char-Gar]

If that were my handgun, I would shoot about 100 rounds of full snort jacketed ammo through it, clean it well and then go back to cast bullets.

I have noted some micro fine wire edges on the front of some cylinders left over from machining. These can give a false reading of the throat diameter. They will shoot off in time, but with cast bullets it will take allot longer. At any rate, your handgun needs a good break in period before making any decision and work needing to be done. It takes some shooting before most guns do their best.

Sometimes guns do need work, but not as often as folks think. Certainly not until the gun is well broken in.

[happie2shoot]

I would polish the largest chamber smooth with 400grit and measure
it and bring all the rest to that size, I use to do this for a living, if you
don't know what you are doing have someone that does.

For best results with cast, usually, the throats need to be a little bigger
than the grove dia, have seen throats that were .0025' bigger shoot 3
to 4'' at 100yds with cast, no problem.

I like the throats at .0002 to .0005 bigger than grove dia, that way it
works super with jacketed and cast.

You need a smooth straight barrel too, with all mentioned you may get
2'' at 100yds with best loads, best = LBT LFNs, others can also make super
molds too, NOE and others just as long they make then right.

One of my NOE lee copies of the .433 315gr PB has shot five in 1.25'' and all
six in 1 15/16 at 100yds.

[happie2shoot]

I discovered Veral Smith in 1987 in gunsmith school, get this book
and you will know what it takes to make your revolver shoot like
a rifle.

http://www.lbtmoulds.com/books.shtml






JACKETED PERFORMANCE WITH CAST BULLETS
By Veral Smith



This illustrated booklet is recommended reading for all bullet casters, especially beginners, but even for those with 40 years experience. It has information about cast bullets which you won’t find anywhere else, and covers every important factor about making and shooting let bullets. It explains how to do it, the scientific answer to things that can go wrong, why, and how to correct any problem. Has Veral's new formula on killing power which dispels the other theories and myths (unscientific and unprovable notions) relative to killing power, and explains what actually makes a bullet kill. You’ll know and can prove the whole book is fact, and learn that the author despises theory, on anything!



PRICE $25.00 Shipping cost is $6.00 if purchased separately, no additional charge if purchased with other items.









In the mid 80s and earlier I was happy with four inches at 100yds,
after I learned how good a revolver could shoot now 2 to 3'' is
expected and under 6'' at 200yds is mandatory.

[huntrick64]

Just for chits and giggles, number your cylinder chambers 1-6 starting at the proof mark and going clockwise. Then take one of your boolits and try it in each chamber until you find one that it fits tight in the throat but can still be pushed through with your hand and a pencil. Keep track of what chamber number that one is, and go and shoot 6 rounds through that one particular chamber. If groups improve then you could probably gain something by making all throats the exact same size. Use pin gauges to measure the throats, if you don't have any, borrow some. If you are going to keep buying revolvers buy an $80 set of cheap pin gauges from Enco. Of all of the tools I have bought to tinker with my guns, my pin gauges have been the biggest bank for the buck.

I like for all of my throats in a particular revolver to have the same level of friction on my boolits. Usually within .0005 of each other. The pressure difference alone from chamber to chamber with .002 difference in diameter is huge. That can significantly change impact in a handgun just due to change in recoil. Sometimes a .002 smaller throat is all that is needed to spike a "top-end" load way over the top.

Good luck

[DougGuy]

If you slug your barrel, and the slug won't then go into the front of the cylinder, the throats need to be reamed and honed. I would be glad to be of assistance in this effort if needed.

You can load .314" or .315" all day, but they are going to come out of the front of the cylinder whatever the throat diameter is. If you have tight throats it will size them right down.

Here you go huntrick http://castboolits.gunloads.com/showthread.php?264821-Revolver-Cylinder-Reaming&p=3080618&viewfull=1#post3080618

[huntrick64]

Doug,

Your link is a good detailed explanation of what I was touching on for throat consistency.

Thanks

[str8wal]

The throats should be slightly (about .001" or so) larger than the groove diameter of the barrel.

[Yellow Fang]

How about fire lapping?

[Hickok]

I agree with Char-Gar and 9.3x62. Shoot the revolver for awhile before doing anything. The dimensions you give are darn close. Try some different loads, and give it some workout and development first.

[ejcrist]

I just started loading and now casting for a Ruger Single Six in .32 H&R. I slugged and measured the bore and cylinder throats and got .3117-.3120 on the bore, as expected. The cylinder throats were smaller, at between .3113 and .3115. I have fired some commercial hard cast bullets at .314 and a few home cast at .315 and got decent but not great results. Should I look at reaming the cylinder throats out to match the bore? I haven't seen any leading, just not the accuracy I would like. I know I have some more load work to do anyway, but don't want to chase my tail and waste components if the gun would benefit from some work. Thanks,

Patrick

Pat,

I bought a used Single Six 32 H&R with 6 1/2" barrel a few months ago with dimensions extremely close to what you have. The throats were .3110-.3112 and the bore was .312. I ran into this situation before with a Ruger 45 Colt Bisley. In the case of the 32 I first tried various loads to see how it grouped and my best average at 25 yards off a rest was with 10.5 grains of H110 was 2.3" which I wasn't too impressed with. H110 had the highest average velocity of 1,341 fps and lowest extreme spread of 19 fps. The other powders tested were 2400, Unique, and 231, and the velocities where quite a bit slower. If I remember correctly 2400 had the next highest velocities at around 1,200 fps or thereabouts. I speculated the reason H110 did the best was because the bullets were being sized down by the throats and the bumped back up when they slammed into the forcing cone but I don't know for sure if this was the case.

So anyway, I ordered the Manson reamer and pilots for about $140 for everything and opened all the throats to .3135. I retested the same loads and all groups improved on average around 20%-25%. H110 came out on top again and produced an average 1.7" which I was much happier with. I further refined the load and got her down to about an inch and a half with 10.3 grains of H110 at an average of 1,310 fps.

So, the moral of the story is that opening the throats worked good in two of my Rugers and may for yours as well, but I recommend you try a few loads out first and see, if for no other reason than to know how much of an improvement if any the operation had. I'm not a gunsmith or machinist or anything, but opening the throats with a Manson reamer is extremely simple and only takes about 15 minutes if you take your time. If you decide to go this route, don't forget to order Brownell's Do-Drill oil at http://www.brownells.com/gunsmith-tools-supplies/general-gunsmith-tools/taps-dies/tapping-cutting-fluids/universal-do-drill-prod1120.aspx to lube the bit. Let me know how you make out.

Gene

[patrick_sween]

All good thoughts, I appreciate them all. As for the 'shoot it out' idea, the gun is used and appears to have a fair amount of rounds through it, so I don't think it needs breaking in. I agree the amount of difference between the throats and bore is small, but still the 'wrong' direction. I'm leaning toward reaming to about .313 and casting/sizing to .314 just to be sure I have everything going right before I start serious load work. I plan to ream them myself, I have bit of machining/tooling experience and believe I can do the job without messing anything up. I'm not at all shy about tinkering with my own guns, I don't own any that I haven't worked on in one way or another and I haven't wrecked one yet :) Thanks again,

Patrick

[DougGuy]

Patrick, if you are going to get the reamer, get one right from Dave Manson where you can ask him what the reamer will finish at, he will pick one out of their stock and mic it for you while you are on the phone with him. And get the pilots for it too. You only need one or two pilots, but you need a pin gage or a really carefully mic'ed soft lead ball to decide exactly which pilots to get. It is totally not out of the ordinary to need two and in rare occasions three pilots on a Ruger cylinder, I see it all the time. For best results and the most concentric throats, I like the pilot to fit where it almost needs force to seat it in the existing throat. I get them in half thou increments to cover all the possible throat sizes. I use Tap Magic to ream with, works great.

[patrick_sween]

Fed-Ex brought the reamer yesterday, and today my throats measure exactly 0.3130" as best I can measure with a good mic. Haven't shot it yet, and like I said earlier, it wasn't that bad before, but this gives me the peace of mind that comes from knowing I'm stacking the deck in my favor when it comes to consistency. Was a 15 minute job, so even if I don't see huge improvements in accuracy I won't feel like I wasted much time. Thanks for the advice, now to shoot it.

Patrick

[dubber123]

You owe it to yourself to try the RCBS 98 gr. 32-SWC, if you haven't already. My Single Six loves it. Groups from an improvised rest run around an inch at 25 yds., best was .46" for 6 shots. I never slugged mine, but got lucky with .313"+ throats right out of the box.

[9.3X62AL]

What Dubber said, concerning the RCBS 32-98-SWC in the 32 Magnum OR the 32 S&W Long. It has shot superbly in my S&W Model 16-4 x 6" from 700-1200 FPS, and does not care one bit if the powder is Bullseye--WW-296--or anything in between. It is like Lyman #358477 in 38s and 357s, it just wants to shoot.

[bob208]

how are you doing all of this fine measuring? half a thou. is fine

[patrick_sween]

Good quality 0-1" micrometer. I'm measuring a soft lead slug tapped into the area of concern and then tapped back out. If measurements in all directions agree, that's what I post, if they are different I posted the range. Can't imagine doing any serious gun related work without a good micrometer! Plus I'm just anal enough to want to know where in the 'half a thou' range my stuff is.

Patrick

[Ballistics in Scotland]

I don't think there is any doubt that perfection is chamber throats equaling the groove diameter, or that single thousandth of an inch larger. But a lot of people overestimate this problem. You are talking of a difference well under .001in. in the wrong direction, and a difference between cylinders of .0002in. I doubt very much if either of those could do measurable harm to accuracy, unless you were using the sort of jacketed bullet which is necessary for the most demanding rifle shooting. Even then there are people on the paper patching boards who could give you an argument.

I have measured a friend's Webley-Fosbery and one or two conventional Webleys, peacetime production of revolvers which unquestionably did achieve very good accuracy. They had .455 grooves and .448 cylinder throats. They were, of course, designed around a bullet with a large base cavity, which expanded on leaving the cylinder. I think the logic may be that they predated good fast pistol powders, and were intended to build up pressure in the cylinder.

But people do get presentable though not brilliant accuracy in these revolvers with solid base bullets, as long as they are soft. The only rational explanation is that even these do expand on leaving the cylinder. I think bullets would have to be freakishly hard not to give much better results in a Single Six as you have described.

There are other possible explanations for less than perfect accuracy. One is alignment. The hand, at the moment of firing, ought to be pushing one side of the cylinder notch up against the locking bolt. If production economy prevented perfection, there would be a bit of rotational play. Radial misalignment seems unlikely from Ruger. Another possibility that with cast bullets of about .003in. over throat diameter, they are finning at the rear. This is unlikely to be consistent all round the base.

[leftiye]

I'm not certain that a few tenths of backwardness is capable of affecting grouping in a significant way. 1 or 2 thousandths of backwardness might be a problem, but I would run some varying designs through the revolver for test drives before taking tools to the throats. FWIW, one bullet design actually shot very well in my Built Backwards BisHawk x 45 Colt--#454490, a GC SWC that did good things in spite of .448"-.449" throats and .452" grooves.

I agree that a couple of tenths might not pose a problem. On the other hand, that much (up to a thou) can be rectified with a dowel and sandpaper in a drill easily. Especially when only opening up only a tech like this, straightness isn't going to be much affected (shouldn't be a problem). About like polishing after reaming.

[patrick_sween]

I do agree that I probably wouldn't have had to do anything, but I'm an engineer first, and an amateur machinist second, so my guns get tinkered on whether they need it or not! If nothing else it makes me feel better that things are 'right' and confidence has a great effect on shooting.

Patrick