Revolver Question

[RikyRacr]

I have only been reloading a couple of months and have been doing a ton of reading and have gotten a ton of help. Haven't done any casting yet but have purchased a couple of molds, (with more to come soon), and hope to get a melter ordered later this week. Anyway, my question:
Is the "throat" I have heard many make reference to the portion of the cylinder just in front of the boolit? I have a GP100 and want to make sure all is well with the firearm. Also have a Blackhawk .45LC/.45ACP on the way and will want to check it as well. In my reading I've noticed some folks having to "ream the throat" to get good accuracy using cast boolits. I have not "slugged" the barrel of my GP100 but have shot many cast boolits through it that have been sized to .358" without excessive leading. In fact the accuracy has been really good as near as I can tell, (still not a great marksman with a handgun).
Thanks you!

[rlb]

You got it right for the throat. When you get your new gun just try it with a couple of different diameters befor worrying about changing anything on it. It might be a shooter without changing anything.

[MtGun44]

Yes on where the throat is. Way too big or small can be problematic for accy or
leading or both.

Currently working with a friend, with a Python with .3555 groove diam and .359 throats.
Not easily changed, so we will try .358 and .359 in mag brass, seated out long.

I had to ream out a Ruger BH conv .45 due to extremely undersized throats.

Bill

[DrCaveman]

So, is the term 'barrel throat' incorrect then? I had always thought the portion of the barrel closest to the breech was the 'throat'. Guess I am wrong.

Is the un-rifled section I am referring to the 'leade'?

I think I am confusing terms between revolvers and auto loaders.

Thanks for starting this thread, always interesting to learn something you thought you knew!

[Outpost75]

724977249872499

IGNORE groove diameter of barrel, doesn't matter.

Ball seat, CYLINDER diameter ahead of case is what is important!

Old fart with aging eyeballs here!

72500

[MtGun44]

Throat in a rifle and throat in a revolver are in the same location relative to the chamber. . . . .
sorta.

Think about it a minute. The issue is that the revolver has, effectively, a lot of freebore
compared to most rifles. The basic concept of "fitting the boolit to the throat" remains true
for revolvers and rifles. Now - semiauto pistols often/usually have no real throat or a
VERY minimal one. But the location where it would be is the same, just in front of the
chamber. Revolvers actually have a conical transition to the throat proper that is a bit
non-standard, too.

The point of filling the throat is to guide the boolit out of the case and into the rifling
without letting it tip and get mangled in the process.

The problem is that these different designs all have different needs and often the terms
are not exactly used the same way, or different words are used. "Ball seat" is often used
for what would also be called the throat in a bottleneck cartridge rifle.

Hope this helps clarify, not muddy the waters.

Bill

[BACKTOSHOOTING]

IGNORE groove diameter of barrel, doesn't matter.

Ball seat, CYLINDER diameter ahead of case is what is important!

? Could you please elaborate

[birch]

I had an old model ruger vaquero in 45 colt that was the most inaccurate SOB I have ever had the misfortune of owning. Each cylinder was + or - .002. I eventually bought a reamer from a local tool and die shop and figured that would do the trick--nope. I have heard that the throat (the area immediatly ahead of the cylinder) is supposed to be set an 11 degree angle, but it seems that ruger sometimes uses their cherries (reamers) until the max out on their tolerances. It seems that some guns have wore out reamers and new reamers in the same cylinder. For this reason, I have sworn off all single action rugers. Others will chime in and say that rugers are the best thing since white bread and I am happy they found great shooting revolvers.

On the other hand, I have had a super redhawk that would drive tacks at 100 yards. My brother has a GP100 that is just as accurate as my 8" colt python. If your gun shoots, I wouldnt change a thing until you have set up multiple targets at different ranges. I have owned a couple of guns that would not stabalize a boolit/bullet past 25 yards. This results in keyholes which look exactly like the title says. They enter the target sideways instead of head on. This can be ammo related or gun related and it sounds like you have a couple of different molds to play with so the results should be interesting. Also, powder type is very important. I highly recommend bullseye or tightgroup for you 45 colt/acp loads. Titegroup required very little in a case, so be careful of double charging. You will be amazed at how many rounds you can load up on a 1lb can.

[Outpost75]

The cylindrical portion of the front end of the cylinder ahead the chambers is referred to in by the gun manufacturers as the "ball end" or "ball seat." In dimensioning a modern revolver cylinder intended to be used with JACKETED bullets the ball end gage diameter is toleranced at SAAMI Max. bullet diameter +0.0000/-0.0015 so that the bullet is positively guided during initial shot-start and will enter straight into the forcing cone. This tolerancing convention was standard with Ruger 9mm and .30 carbine revolvers, and law enforcement orders on .38/.357 when jacketed service ammunition was specified.

Traditional dimensioning used in black powder calibers was for the ball end gage to be at max. bullet diameter +0.0015/-0.0000, so it was normal for a .45 Colt revolver to have cylinder "throats" of .455-.456 for use with a bullet diameter of .454, and barrel groove diameters were nominally the same as bullet diameter.

If there is a mismatch of cylinder throat or ball end gage diameter vs. bullet diameter, the bullet may either yaw in the cylinder when transitioning out from the cylinder, entering the barrel forcing cone, or it may upset non-uniformly.

Ideally the bullet should fit the cylinder throats snugly enough that you can feel resistance inserting and pushing a lead bullet into the chambers, through the cylinder and out the front. If a bullet is small enough to fall through of its own weight, as when attempting to shoot .452" bullets in cylinder throats of .455", accuracy will be poor. If the bullet is excessively oversized, such as when shooting .454-.455" bullets in tighter cylinder throats of .451-.452, as occurs in new Rugers, accuracy is also effected.

Best accuracy will be obtained when bullets are sized to ball seat or cylinder throat diameter. If the ball seat diameter is smaller than barrel groove diameter, then gas cutting and leading will be experienced, unless the cylinder throats are reamed or honed to approximate groove diameter +0.0015/-0.0000.

If the ball seat diameter is substantially larger than groove diameter, say a .457" cylinder throat and a .450" groove diameter, as many early S&W Model 25s were, having to extrude and elongate the large bullet diameter necessary for accuracy will raise pressure significantly. This is mitigated by using milder loads of softer alloy, and by reaming the barrel forcing cone to a more gradual angle, such as 6 degrees, vs. the usual 11 or 18 degrees, to reduce extrusion force.



IGNORE groove diameter of barrel, doesn't matter.

Ball seat, CYLINDER diameter ahead of case is what is important!

? Could you please elaborate