.45 Colt Chamber Dimensions?


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rWt
July 20, 2005, 07:19 PM
I am very confused about this subject. I have read that in 1982, S&W reduced chamber dimensions in the 25-5 from .488-.489 to .483, thus making the later guns more accurate shooters.

Likewise, I have heard that some Colt SSA's have loose chamber dimensions and don't make good shooters.

What is the scoop here? Are tighter chambers better, and, if so, why? And, by how much?

Are earlier S&W's ( or other makes with the larger chambers poor shooters?

Are there also differences in cylinder diameters that one should also be aware of?

Thanks. Dick

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Majic
July 20, 2005, 08:18 PM
While tighter, consistant chambers will restrict brass expansion for a more optimum burn, the fit of the bullet to the throat plays a big part in accuracy and the throats were also tightened when the chambers were tightened.
You can make the older guns with looser tolerances shoot better by finding a bullet that fits the throat. Now this applies to a lead bullet because it will obutrate under pressure. A jacketed bullet is at the mercy of it's jacket and it's diameter won't change much, but most will still shoot consistantly.

rWt
July 20, 2005, 09:37 PM
Thanks for that info.

Is there a way to estimate how much better a "tighter" gun will shoot jacketed bullets vs a "looser" one? If a newer one will shoot 3" groups at 25 yards, will a looser one shoot a 4"goup? 5"?

I'm trying to guage how much it matters.

Thanks.

Majic
July 21, 2005, 02:16 AM
I imagine there is a probability equation, but I have no idea where to find one. There would be so many other factors involved it most likely would be nothing but a good guess.

zeke
July 21, 2005, 07:28 AM
The following is just an opinion, and as always there may be exceptions. The tighter chambers are better (unless too tight)

1-more accurate, though not as much affect as throat-bullet fit.
2-less working of the brass (this can be overcome, but is a pain)
3-easier to seal against chamber with the lighter loads.
4-cleaner chambers for easier extraction (if chambers are smooth)

Recently bought a new Ruger stainless Bisley. Brass split after two firings of heavier loadings (not near max), with full length sized brass.

If using a pistol with the larger chambers and lighter loads just for that pistol, ya can just neck size the brass for several loadings.

DHart
July 21, 2005, 03:35 PM
The size of the chamber mouth is important to accuracy. Many of the earlier model 25's have oversized chamber mouths. I have a 625-7 in .45 Colt and the chamber mouths measure .451", which is, I believe, considered ideal, generally.

Vern Humphrey
July 21, 2005, 03:46 PM
The ideal chamber throat is dependent on the groove diameter. A revolver should get smaller as it goes forward -- the chamber throats should be slightly larger than groove diameter.

A .452 throat ought to shoot well with a .451 barrel, but not so well with a .454 barrel.

If you have problems with a .45 Colt revolver, slug the throats and barrel, and open up the throats if they are too small.

DHart
July 21, 2005, 04:09 PM
Vern... thanks for the additional detail and clarity!

rWt
July 21, 2005, 06:07 PM
Thanks, everyone.

Seems to me then that if I want a good shooter, I should plan to buy a post '82 vintage. Too bad, in a way, because I love the old pinned barrels.

Vern Humphrey
July 21, 2005, 06:20 PM
Seems to me then that if I want a good shooter, I should plan to buy a post '82 vintage.

As a general rule, earlier .45 Colts by any maker are supposed to be deficient. However, I have a Ruger Blackhawk made in the 200th year of American Independence (that would be 1976 for you public school graduates) and a Colt New Service made the year my father was born (1906) and both shoot very well.

rWt
July 21, 2005, 07:15 PM
Was 1982, then, a year when all manufacturers shrunk their chamber and throat dimensions? If so, what was the impetus?

Majic
July 22, 2005, 03:35 AM
Was 1982, then, a year when all manufacturers shrunk their chamber and throat dimensions?
No because Colt still has large chamber throats.

zeke
July 22, 2005, 07:08 AM
And a lot of Rugers still have the larger chamber dimension, tho to different degrees. Alot also depends on what bullets you're using. It seems the shorter lighter bullets are more dependent on chamber throat to barrel transition. Some jacketed bullets even transition quite well from smaller chamber throat to looser barrel. Again, there are always exceptions.

Malamute
July 23, 2005, 11:12 PM
I have an older Ruger 45 colt SA, and it will shoot cloverleaf groups at 25+yards. It has sloppy chambers, but shoots great. I see no need to change anything about it since it shoots so well. Brass doesn't last as long, but I can live with that. I think in this gun I average maybe 8 or 10 loads in a batch before I start to get some splits.

I wouldn't be concerned about an older Smith 25-5 because of it's chamber throats.

I believe some gunsmiths were chambering 45 Colts tighter, and the factories began the practice after results were shown to improve case life and everyone was asking about the tighter chambers. Velocity was believed to be slightly improved some too, but I don't know if it's a significant amount.

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