WebHobbit
Member
ThroatDoc - That all sounds very reasonable but I know from personal experience that too large chamber mouths can cause tumbling so evidently their purpose is atleast in part to guide the bullet into the forcing cone straight.
Chambers on Redhawk 45 Colt
- Thread starter munk
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WebHobbit
Member
I think we need an engineer to define "too large"!
WebHobbit
Member
LOL
True!
xtarheel
Member
Well gentelmen, I am an engineer and part of the problem is that we are not dealing with a set of constanants. The variable is the diameter of the bullet, therefore everything becomes somewhat of a compromise, so we eliminate the variables that we can.
To get consistancy in where the bullet lands on the target, each bullet should experience the same pressures, constrictions, etc as it exits the muzzle as it would if fired from a single shot or autoloader which deal with a single chamber, throat, forcing cone and barrel.
Opening the throats makes sure that the bullet upon leaving the forcing cone is not smaller than the groove diameter.
Making the throats a consistent size, assures that each bullet enters the barrel with the same amount of pressure behind it and at the same time in the recoil cycle.
And yes, too big of a throat can also cause problems as seen on some pre-war Colts. Although in the example I gave earlier, with the .451 FMJ, you would be very hard pressed to see any light between the bullet and the wall of the throat, so it cannot tumble.
One final thought, for the best groups it is important that the shooter keep his eyes open when he pulls the trigger!
To get consistancy in where the bullet lands on the target, each bullet should experience the same pressures, constrictions, etc as it exits the muzzle as it would if fired from a single shot or autoloader which deal with a single chamber, throat, forcing cone and barrel.
Opening the throats makes sure that the bullet upon leaving the forcing cone is not smaller than the groove diameter.
Making the throats a consistent size, assures that each bullet enters the barrel with the same amount of pressure behind it and at the same time in the recoil cycle.
And yes, too big of a throat can also cause problems as seen on some pre-war Colts. Although in the example I gave earlier, with the .451 FMJ, you would be very hard pressed to see any light between the bullet and the wall of the throat, so it cannot tumble.
One final thought, for the best groups it is important that the shooter keep his eyes open when he pulls the trigger!
Xtarheel,
The oversized throat will not case the bullet to tumble, but it will allow a bullet to cock slightly as it leaves the throat and hit the forcing cone at an angle. The bullet will straighten itself as that's one of the purposes of the forcing cone, but the initial hit of the bullet on just one side of the forcing cone creates a different harmonic in the barrel as opposed to a central hit in the forcing cone. That different harmonic can cause the bullet to be a flier.
The oversized throat will not case the bullet to tumble, but it will allow a bullet to cock slightly as it leaves the throat and hit the forcing cone at an angle. The bullet will straighten itself as that's one of the purposes of the forcing cone, but the initial hit of the bullet on just one side of the forcing cone creates a different harmonic in the barrel as opposed to a central hit in the forcing cone. That different harmonic can cause the bullet to be a flier.
WebHobbit
Member
Majic -- that all depends on the bullet. I had Federal Nyclad .38 hollow-points that would tumble hitting the target sideways due to a POS Taurus with over-sized chambers.
I for one am very glad Mr. McLeod has taken the time to answer our questions and explain some specifics.
The ideal size quoted is .4525 for 45 Colt throats. This is .0015 larger than a bullet of .451 and only .0005 larger than a bullet of .452 , representing the range of factory jacketed bullets.
I wonder if .41 would be best served by .4105 or .411 ?? A little narrower range because the bullets are more standardized.
munk
The ideal size quoted is .4525 for 45 Colt throats. This is .0015 larger than a bullet of .451 and only .0005 larger than a bullet of .452 , representing the range of factory jacketed bullets.
I wonder if .41 would be best served by .4105 or .411 ?? A little narrower range because the bullets are more standardized.
munk
WebHobbit
Member
Agreed!
Good info to have.
Tom C.
Member.
Oversized Chamber Throats
Everything is a compromise. The .4525" throat is a compromise for lead and jacketed bullets. With the older guns which can have larger throats, .454 to .456", in addition to allowing the bullet to hit the barrel forcing cone at an angle, they also allow more gas blow-by which can damage the base of the bullet. The bullet then leaves the barrel with reduced stabilization due to damaged rear end. This can cause the bullet to fly in a helix which can cause interesting accuracy problems.
In addition to tight, consistent chamber throats, a uniform forcing cone also helps. I cut mine a little deeper than recommended. Works for me.
Another thing to look for in Rugers is "choking" of the barrel where it is screwed into the frame. The barrel diameter is reduced due to screwing the thin walled tube through the frame. It can be .0005†to .0015â€. That will cause the bullet to be reduced below bore diameter just as it enters the barrel. Not good. You can remove it by “fire lapping†or, just shoot it a lot and it will probably be peened out. I tend to cut most of it out by deeply cutting the barrel forcing cone.
I have been opening my cylinders to .4515". A little tight, perhaps, but it seems to work.
Everything is a compromise. The .4525" throat is a compromise for lead and jacketed bullets. With the older guns which can have larger throats, .454 to .456", in addition to allowing the bullet to hit the barrel forcing cone at an angle, they also allow more gas blow-by which can damage the base of the bullet. The bullet then leaves the barrel with reduced stabilization due to damaged rear end. This can cause the bullet to fly in a helix which can cause interesting accuracy problems.
In addition to tight, consistent chamber throats, a uniform forcing cone also helps. I cut mine a little deeper than recommended. Works for me.
Another thing to look for in Rugers is "choking" of the barrel where it is screwed into the frame. The barrel diameter is reduced due to screwing the thin walled tube through the frame. It can be .0005†to .0015â€. That will cause the bullet to be reduced below bore diameter just as it enters the barrel. Not good. You can remove it by “fire lapping†or, just shoot it a lot and it will probably be peened out. I tend to cut most of it out by deeply cutting the barrel forcing cone.
I have been opening my cylinders to .4515". A little tight, perhaps, but it seems to work.
Tom C.
Member.
Throat Enlargement
Reamers are available from the vendors in any desired size, but the standard reamer from Brownell's is .4525". I use a chamber polishing brush, also from Brownell's. It probably doesn't do as good a job as the reamer, but I am satisfied. I check the diameter with an appropriate bullet that I measure with a good mike.
Someday, if I am feeling flush with cash, I may invest in a reamer myself.
Reamers are available from the vendors in any desired size, but the standard reamer from Brownell's is .4525". I use a chamber polishing brush, also from Brownell's. It probably doesn't do as good a job as the reamer, but I am satisfied. I check the diameter with an appropriate bullet that I measure with a good mike.
Someday, if I am feeling flush with cash, I may invest in a reamer myself.
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