tight fit vs. loose fit revolver chambers

[wilecoyote]

from the point of view of accuracy, and of the safety, of course, is there an optimum, in revolver cylinder chambers, and obviously all chambers equal width,
regarding width tolerances?
I mean tight fit vs. loose fit of the loaded .44 magnum ammo in the cylinder_
I know it seems like a silly question but, given the possibility of managing things in one direction or the opposite, in what terms would it be preferable to orient the loading?

[TurnipEaterDown]

In a cartridge with a bullet loaded that has a driving band outside of the casing, and long enough to place the front driving band in the throat itself (which a 44 in a revolver is capable of in most cases), the alignment of the bullet in the throat is controlled primarily by 2 things: (1) diameter of throat minus diameter of driving band (clearance in the "front"), and diameter of chamber base minus diameter of case base at expansion ring above the rim (clearance in the "rear").
Alignment of bullet to throat prior to firing is important to accuracy. Proven many times over.

However, In the case of a revolver, the alignment of the chamber to forcing cone (when cocked and at full lock up) is also critically important.

I used to "short size" my 44 brass to leave it as big as possible at the expansion ring to help in alignment with the chamber. Don't have records of group sizes comparing short and full length sizing, so don't remember if it helped, and can't show any numbers anyway.
I did Stop this practice after a brief period, so I suspect that to me it was of no benefit.
Doing something like this short sizing also hampers reliability, and to be honest, most any day my 44 is a100 yd gun anyway. So, another set of reasons I likely stopped short sizing.

[wilecoyote]

TurnipEaterDown, I believe that even more so in my case the human factor tends to eliminate the advantages of a particularly sophisticated loading technique, but I am comforted by a more qualified opinion in any case. thank you very much !

[shooting on a shoestring]

Wilecoyote, I think you’re asking about clearances and not tolerances. Clearance is how much space is between the cartridge and the chamber wall. Tolerance is how much variation in size is allowed.

We have to have some clearance between the cartridge and the chamber in order for the cartridge to slide into the chamber. If there is not any clearance, then we’d have to push very hard to overcome the friction of the cartridge dragging against the chamber. If the chamber is smaller than the cartridge (an interference fit) then we couldn’t load the revolver by hand.

We want some clearance for ease of loading the revolver but not so much that the ammo rattles around in the chambers.

TurnipEaterDown is right. We want our boolits to stick out of the case and hence get pushed into the chamber throats where there is very little or no clearance. If there is no clearance we have to use some thumb pressure to fully seat the ammo in the chamber. Ok for target shooting, maybe hunting, but bad for combat shooting. By having the boolit enter the throat when loading, the boolit is centered in the throat.

Revolver chambers should have some taper cut into them so the back of the chamber is about 0.001” bigger than the front of the chamber. This ensures easy extraction.

So how much clearance is too much? Depends on how good of a shot your are. The real answer is to shoot a group with very little clearance then re-shoot with lots of clearance and see if your group size changes. If there’s no difference then you’re not a good enough shot to worry about such details. If there is a discernible difference in group size, then your reloading just got more tedious.

Pretty much the same can be said of tolerances in chambers and tolerances in ammunition. Most folks don’t shoot good enough to worry how much variation is in their revolver chambers or variation in their ammunition. But quite a few people on this board do shoot good enough to notice a difference in throat dimension sizes and tolerances on those sizes. DougGuy has a bit of a business in minimizing throat tolerances (making the throats uniform, or all the same size). Couple that with making the throats the same diameter or slightly bigger than the groove diameter can shrink group sizes (for a capable shooter).

[wilecoyote]

Wilecoyote, I think you’re asking about clearances ...

you have perfectly translated and understood what I meant.
I don't think I can expect more comprehensive and detailed answers than what I have received here from you both.
Thank you very much !

[justindad]

More clearance is created by a larger diameter chamber. The larger chamber will stress the brass more, as it expands further to fill the chamber (deflection limited loading). However, the total pressure developed in a larger chamber should be less (I have not measured), because the volume of space pressurized is greater. But when you get to very slow powders and lighter bullets where peak pressures occur sometime after the bullet has fully exited the brass - pressures won’t be meaningfully affected. Just a guess.

[tazman]

TurnipEaterDown, I believe that even more so in my case the human factor tends to eliminate the advantages of a particularly sophisticated loading technique, but I am comforted by a more qualified opinion in any case. thank you very much !

I spent quite some time and effort developing loads for my S&W Target Masterpiece a few years ago. I sized some wadcutters to the exact dimensions of my cylinder throats. I loaded them long so the front portion of the wadcutter was a slight press fit into the cylinder throat when loaded into the revolver. All the brass had been previously fired in that same revolver and "neck sized" so that the only part that gripped the boolit was the crimp and a tiny bit of the case. I used match brass and weighed each charge.
This was the best ammunition I could build for that revolver and it was a pain to have to push each cartridge into the cylinder with my fingers because everything was so tight. The accuracy was significantly improved----from a bench rest.
With me shooting offhand the difference in group size was so insignificant that I gave up on the process. I am 71 years old and am not getting steadier as I age. I decided to spend more time shooting and less time reloading.
I my case and probably a lot of other people's the loose nut on the grips of the handgun was a bigger issue that the ammo.

[wilecoyote]

I spent quite some time and effort developing loads for my S&W Target Masterpiece a few years ago. I sized some wadcutters to the exact dimensions of my cylinder throats. I loaded them long so the front portion of the wadcutter was a slight press fit into the cylinder throat when loaded into the revolver. All the brass had been previously fired in that same revolver and "neck sized" so that the only part that gripped the boolit was the crimp and a tiny bit of the case. I used match brass and weighed each charge.
This was the best ammunition I could build for that revolver and it was a pain to have to push each cartridge into the cylinder with my fingers because everything was so tight. The accuracy was significantly improved----from a bench rest.
With me shooting offhand the difference in group size was so insignificant that I gave up on the process. I am 71 years old and am not getting steadier as I age. I decided to spend more time shooting and less time reloading.
I my case and probably a lot of other people's the loose nut on the grips of the handgun was a bigger issue that the ammo.

I understand your reasoning, and I can take advantage of your comments.
in parallel I wonder whether a tight fit in sixgun magnum calibers could result in greater stress directly transmitted to the the chamber walls, as the possibility of radial dilatation of the brass is reduced, or not, even if the question is probably purely academic...

[Dusty Bannister]

When you think about it, the force on the base of the bullet will expand the cast bullet body before it even begins to move. The more space between the sides of the bullet and the chamber would allow accelerated movement before it hits the walls of the cylinder. If one could actually measure it, more force might occur under that condition rather than with a snug slightly over sized bullet that has to begin moving before max chamber pressure is achieved.

But this might be considered logical, and with cast bullets, thinking in that manner is usually not factual.

[black mamba]

I have had two revolvers, one in 44 mag and the other in 45 Colt, with enlarged forcing cones. Both were .004" larger than bullet diameter, and both shot noticeably larger groups than others with forcing cones only .001" larger than bullet diameter. When I tried .454" bullets in the .456" 45 Colt cylinder, accuracy improved, but not a lot.

[DougGuy]

I have had two revolvers, one in 44 mag and the other in 45 Colt, with enlarged forcing cones. Both were .004" larger than bullet diameter, and both shot noticeably larger groups than others with forcing cones only .001" larger than bullet diameter. When I tried .454" bullets in the .456" 45 Colt cylinder, accuracy improved, but not a lot.

You are no doubt referring to cylinder throat diameters. The forcing cone is the tapered part of the barrel just in front of the cylinder.

And you SHOULD size to a light drag fit in the throats. Groups are usually in bad need of improvement when you are shooting boolits more than about .0025" smaller than the throats. The harder the alloy, the more you need to pay attention to this sizing operation as there is less obturation with a hard alloy.

The Uberti revolver you see in the avatar pic has .4565" throats. I size the 454190 cast in 50/50+2% to .456" with SPG for lube and it's quite accurate even though the barrel is .451" and no leading.

[tazman]

I understand your reasoning, and I can take advantage of your comments.
in parallel I wonder whether a tight fit in sixgun magnum calibers could result in greater stress directly transmitted to the the chamber walls, as the possibility of radial dilatation of the brass is reduced, or not, even if the question is probably purely academic...

If you try the process I described, please let me know how it worked out for you.

[wilecoyote]

If you try the process I described, please let me know how it worked out for you.

...certainly, because not giving up it's in the nature of the true W. Coyote :-),
but I doubt I can obtain more comforting results than yours_

[black mamba]

Thanks, Doug, yes it was cylinder throats I was referring to.