Cast bullets what size ???

K

KEYBEAR

New member
I shoot steel targets for fun and it is easy no set up plus no mess .
Once I use a paper target and think I may have a problem .

I have been buying my cast bullets from SNS Casting and have been happy until now . I shoot 44 Mag 240 gr. lead at 1000 FPS .using 10gr. of Unique .

About one in five will key hole and I am using two guns a Ruger Super Blackhawk 7.5 inch and a 5 inch BFR both key hole about one in five .

The 240 gr. bullets should be .430 but are a little less (429 give or take )
The bullets are advertised as .430
 
Sounds like their bullets are just too small for your gun barrels.
No doubt they have larger ones.
If not, try another source.
There's certainly no shortage of suppliers.
 
According to Alliant, you're using jacketed bullet data. 10 grains of Unique is over max for a cast 240.
Anyway, key holing is caused by undersized bullets, over sized barrel, low velocity and a lack of lube on a cast bullet. I doubt 1 thou will make any difference(Jacketed bullets are .429" anyway. There is no "give or take" on diameters though.) and 1,000 fps is not too slow. Isn't likely the barrel either. Might be the lube. Or your revolver may just need a bath and your powder thrower might need looking at.
 
set off the quoted portion

According to Alliant, you're using jacketed bullet data. 10 grains of Unique is over max for a cast 240.
Anyway, key holing is caused by undersized bullets, over sized barrel, low velocity and a lack of lube on a cast bullet. I doubt 1 thou will make any difference(Jacketed bullets are .429" anyway. There is no "give or take" on diameters though.) and 1,000 fps is not too slow. Isn't likely the barrel either. Might be the lube. Or your revolver may just need a bath and your powder thrower might need looking at.
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Data is out of the new Lyman cast bullet manual and not close to max. As for over sized barrel I am using two different guns a BFR and Ruger Super Blackhawk .
All bullets are coated . Both revolvers were are cleaned before shooting .
my powder thrower (RCBS) is throwing between 10 and 10.2(max is 11.7) and I keep it better than half full at all times .
Most bullets are over weight from 240 to 241.5
 
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Lyman specializes in cast bullet loading and their most recent data does indeed show 10 to 11.7 gr Unique with a 240 gr bullet for the .44 mag so you are well within the loading limits. Typically, under sized bullets do result in keyholing and most likely that is the cause of yours. All it takes sometimes is .001 under sized (particularly so it seems with lead rifle bullets).
 
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I am betting the barrel is oversize ?

I did state I have shot the same loaded rounds in two totally different guns .
The Ruger an old model Super Blackhawk has shot cast bullets for me very well for over 40 plus years ? I find it had to believe the barrel got bigger .

I will have some different 240 lead bullets next week some I have shot before .
 
A couple things that come to mind; If you can, measure the cylinder throats (or slug them all, both guns) you may have an undersize throat on each gun, not uncommon. Measure all the bullets, you may be getting an occasional .429" bullet, or shoot 5 or six shots from each chamber of the guns and note the results (key-holes from one chamber?). Another thought; Ruger in known for occasional barrel restrictions, right at the barrel frame junction, slug the barrel and see if this area is tighter. Are you getting any barrel leading?...

All of these can possibly produce undersize bullets and cause leading and key-holing.

Jes a thought...
 
As others have stated, it sounds like a mismatch between the internal dimensions of your revolvers and the diameter of the bullet you are using. One could say the bores are too big, or conversely, one could say the bullets are too small. Either way, they are not compatible.

For the revolver with the smaller chamber diameters, one could have them opened up or reamed by a gunsmith who knows revolvers. If you haven't done so, it is often helpful to slug your barrels, which as far as I know, is the only way to know for certain what the groove diameter is in your barrel.

Typically I have found that if the bullet is too small for the barrel, enough to keyhole like you are seeing, I also end up with a great deal of lead deposits in the bore from flame cutting. Especially with that hard lube that commercial casting concerns put in the grease grooves.
 
In the BFR a bullet can be pushed through not so in the SBH .
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Then the throats of the SBH are swaging your bullets down before they hit the cone and barrel...

My SBH will pass .430" with no effort, and .431" with slight pressure...
 
I noticed that SNS casts everything at BN 16-17 (generally a laudable nod to Lyman #2).
But at the relatively low pressures you're running (240gr/1,000fps),* that is likely too
hard if the bullet isn't perfectly sized to begin with.

Notwithstanding that the cylinder throats are apparently waaaaay too small in the Super
Blackhawk,** you may find that a much softer alloy (BN 6-8) is a lot more conducive
to bumping up satisfactorily in the BFR.

Softer is good. Soft and flat (not bevel) base is even better.




* I'm guesstimating ~20ksi from parallel weight/velocity experience w/ several 45 Colts

**Rugers are notorious for having a serious mismatch between cylinder throat
and barrel groove diameters. I've had to ream out three of their 45Colts as a result: a
standard Blackhawk, an Old Vaquero (essentially a Blackhawk), and a New Vaquero.

See HERE for a reamer that will do the job for your 44. Along with some NAPA
cutting oil, they are fairly idiot-proof (I'm living testimony there.) ;) :D
 
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For me, "push through", "easy push through", and "hard push through" mean very little and very subjective (to you hard or soft will prolly mean a lot different than my hard or soft). Take one of the bullets that won't "push through" and force it through the throat, measure it with micrometers. Then you'll know what that cylinder throat diameter really is (or pretty darn close). A larger slug (+.010") is better, but you could get by for that one chamber with a slightly large bullet...

When dealing with any "fit" issue, measure!
 
I took the two Cylinders to a tool maker to be Measured .
The Ruger Super Blackhawk numbers are Five holes are .430 and one a tad bigger . The BFR has five Chambers and all five measured the same .431 with zero measurable difference .

I know some will disagree with any measurement or how the measurement was done . I found all chambers ok and the BFR great .
The fact I have shot lead out of the SBH for years with no apparent problem makes me think it is the bullets . I am now cutting some bullets apart ? The SBH is an old three screw I bought new and shot thousands of lead bullets out of it . I have call Penn cast bullet and should get a call back .
 
Keybear,

I think the guys are on the right track. In general, you size bullets to fit the cylinder throats to pass through with a little drag. Actual clearance maybe half a thousandth or even equal size fit with the throat. On top of that, you ideally want the cylinder throats a couple thousandths over the groove diameter of your bore unless you only shoot jacketed bullets, in which case half a thousandth over groove is enough. So you really want bullets that are about 0.431", and throats that are 0.431-0.4315" in ID for a revolver. I've played with this some and every pistol I have likes lead bullets about 0.001" over groove diameter, and every revolver I have shoots more accurately with bullets about 0.002" over groove diameter. I'm not clear why, but when I got a copy of the Beartooth Bullets tech manual, the author had found the same thing to be true of a revolver he was testing. Both 0.001" over and 0.003" over shot bigger groups than 0.002" over groove. I've also found my Marlin 1895 prefers bullets 0.002" over groove. You just have to try these things and see what happens.

Ruger is known to make some tight revolver chamber throats at times. It comes from using a reamer that's being resharpened a few too many times. When a friend of mine's Redhawk would not hit the proverbial broad side of a barn, we returned the gun to Ruger who sent it back with note saying their shop had reamed the chambers out to maximum. It then shot just fine. And in that case, the poor shooting was with jacketed bullets, too. Very tight.

The BFR chambers, I don't know about. I've never measured one or slugged its bore, but Magnum Research generally holds tight tolerances, so you might just call them and ask what specs they make the chambers to, then buy bullets that size.
 
Keybear,

You posted while I was composing.

Your measurement on the BFR is just right. Get bullets that are 0.431" for it. The uneven chambers in the Ruger will likely not shoot to the exact same point. I would get them pilot reamed to 0.431". Having Ruger do it is maybe best, as it won't void your warranty and they'll make sure the finish matches. It would be nice if your two guns used the same bullets.

Next, you should slug the bores. I expect the BFR to be right on 0.429". However, anybody can create a bore constriction running a tight barrel and frame thread together. Those can be very hard on cast bullet accuracy until they are lapped out.
 
Having Ruger do it is maybe best, as it won't void your warranty
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Ruger has no warranty expressed or implied...

What it does have, is some of the best customer service in the business...

That said, if they mic the throats and they are 'in spec', they will not ream them...

People wanting to accurize guns and be able to shoot cast, ream their Rugers all the time...

Ruger's 'No Warranty' page found under Service Dept FAQ's:

Why No Warranty Card Has Been Packed With Your New Ruger Firearm?
The Magnuson-Moss Act (Public Law 93-637) does not require any seller or manufacturer of a consumer product to give a written warranty. It does provide that if a written warranty is given, it must be designated as "limited" or as "full" and sets minimum standards for a "full" warranty. Sturm, Ruger & Company, Inc. has elected not to provide any written warranty, either "limited" or "full", rather than to attempt to comply with the provisions of the Magnuson-Moss Act and the regulations issued thereunder. There are certain implied warranties under state law with respect to sales of consumer goods. As the extent and interpretation of these implied warranties varies from state to state, you should refer to your state statutes. Sturm, Ruger & Company wishes to assure its customers of its continued interest in providing service to owners of Ruger firearms.
 
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