Cyl throat and boolit design

[LeadThrower]

Assuming everything's right with boolit and revolver dimensions (boolit, throat, bore), does anyone have any comment regarding boolit fit/position in the cylinder prior to pulling the trigger? Im just thinking to myself that I've read lots of "just touch the lands" or "a thou or two off the lands" in rifle loading, but I don't recall any equivalent discussion with regard to revolvers: just touching the throat, a thou off the throat, etc.

My guess is that it doesn't matter, or the answer is "ask Prof. Gun" since there are so many tales of accuracy with so many different revolvers and boolit profiles.

Any thoughts?

[Dale53]

Elmer Keith designed his bullets with a full diameter front band. That helped immensely to line up the bullet for a good, in line, start when the light goes off.

The problem is, revolver throats vary in diameter. The ideal set up is to have proper diameter throats to begin with (if they are too small they are relatively easy to correct by a simple hand reaming) then size the bullets to fit.

As an example, my S&W 625's (.45 ACP) have proper cylinder throats (right at .4525"). So, I size my bullets at .452", the bullets get a great start when the big light goes off and they shoot extremely well. My heavy bullet is the Lyman 452664, a 250 gr round flat bullet with a full diameter front band. Sized .452" I can feel the front band seat in the throat when inserting the cartridges. This is as ideal a situation as can be had. I have checked three friends' late model 625's and they are "spot on", also.

My .44 Special revolvers use Keith bullets and they are sized correctly to match the cylinder throats and shoot EXTREMELY well. This applies, also, to my .44 Magnums.

My .45 Colt Ruger Bisley Vaquero had slightly tight throats and I reamed them to .4525". They are now as good as I can make them and the targets reflect that.

FWIW
Dale53

[LeadThrower]

As far as fit to throat, I'm right there with you, Dale. What I'm really trying to get at is bullet position with respect to the throat. To use the example of your .44 special revolvers loaded with the Keith style bullet: where is that full dia front band with respect to the throat? Is it just inside, just at, or a few thousandths behind the throat?

Let me ask another way... if I had a WC soup-can that was sized perfectly for my perfect throats (and perfect bore), should I expect any different accuracy by seating the slug so that it fills the throat, half-fills the throat, or is fully inside the case and must make the small jump before entering the throat, assuming all other things are equal? Granted, powder burn will vary markedly by such changes in seating depth, but let's assume we can deal with that and make the differences negligible.

My hunch is that being well supported by the throat would allow for the greatest (if detectable) improvements in accuracy.

[Dale53]

I am not in a position to check ALL of my revolvers but recently DID check the 625's (my two and three others of my friends). The #68 H&G 200 gr SWC shoulder is somewhat off the cylinder throat (accuracy well under 1" at 25 yards). In the same revolvers, the Lyman 452664 has a full diameter band in front of the case. I can actually feel this full diameter front band enter the throat (with some resisitance) so I KNOW that it is perfectly aligned. Both bullets shoot at NRA Bullseye levels. I would expect that the Lyman 452664, being a longer bullet with more sectional density, would be accurate at a greater distance. However, I have not proved that, as yet, as I have not shot my 625's further than fifty yards.

However, others on this forum, who have great experience at 200 yards and beyond have stated that the distance traveled after the big light goes off in the cylinder is not nearly so important as having the bullet the correct diameter to match correct diameter throats. I believe that...

Dale53

[44man]

Assuming everything's right with boolit and revolver dimensions (boolit, throat, bore), does anyone have any comment regarding boolit fit/position in the cylinder prior to pulling the trigger? Im just thinking to myself that I've read lots of "just touch the lands" or "a thou or two off the lands" in rifle loading, but I don't recall any equivalent discussion with regard to revolvers: just touching the throat, a thou off the throat, etc.

My guess is that it doesn't matter, or the answer is "ask Prof. Gun" since there are so many tales of accuracy with so many different revolvers and boolit profiles.

Any thoughts?
I have found it just does not matter how far the boolit has to go before hitting the forcing cone.
Dead soft lead even goes to pot if a boolit is right at the end on the cylinder but the right alloy can run a long way first.
I have very few boolits that are anywhere near the end of the throats. You need a flashlight to see some of them! :mrgreen:

[44man]

OK now, if you use short brass like .44 spec in magnum revolvers, accuracy will suffer where the same velocity from the longer brass will shoot good even if the boolit does not enter the throats.
This is one thing I never figured out and gave up on. It might be a difference in pressure for the same velocity. Even 30 BHN boolits will not work.

[S.R.Custom]

... To use the example of your .44 special revolvers loaded with the Keith style bullet: where is that full dia front band with respect to the throat? Is it just inside, just at, or a few thousandths behind the throat?

Assuming that the front driving band is .001" (or more) larger than the throat diameter, I try to seat the bullet in the case such that it's just kissing the throat with the rim of the case securely against the cylinder. Any more than that (the rim held off the face of the cylinder), and you risk a 'soft hit' on the primer, or a bind in the cylinder rotation due to insufficient headspace.

Also-- if you're seating to that level of precision, make damn sure your crimps don't allow any movement of bullets from recoil. Easy enough to do in a .38, but more difficult to accomplish in a hard recoiling .44.

But you're on the right track. One of the secrets to accuracy in a revolver is consistent pressures and velocities from hole to hole. The best way to accomplish that? Seal the leaks. :-D

[LeadThrower]

Dale, 44man, SuperMag,
Thanks for your commentary! I'm a little surprised, but pleasantly so, to hear 44man say the distance traveled doesn't matter (within reason). I wouldn't have thought it to be so but I don't doubt the information, given the source. SuperMag, you bring up an excellent point about the recoil. There's certainly no tolerance for bullet pull if your slugs are over throat diameter and you're operating at the limit. Dale, it's great to have positive confirmation of the front band entering the throat with your Lyman (and your H&G info is in line with 44man's observations).

Awesome, thank you! :drinks: