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Dans Club
February 22, 2009
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With revolvers, much the same as many rifles, the longer the cartridge OAL, the better. The importance in "bullet jump" is overrated IMO. Particularly with longer boolits, the front of the projectile has started entering the forcing cone before the backend leaves the cylinder throat. The critical step is to get the correct size bullet and get it started straight in the throat/ forcing cone/ bore. With a revolver that is aligned properly, this is best accomplished by seating the bullet as far into the throat as possible, while still securing it in the case to protect from moving under recoil. That's why I always shrug at folks shooting 38 Specials in a .357... in that case, the bullet may be shaved by the throat before it even gets out of the chamber. It would even be worse in the maximum's chamber.
Anyway- probably the most important factor in revolver accuracy is its dimensions. Measurements should be greatest at the throat and least at the muzzle, with no swings back up in any part of the bore. A funnel of sorts from the rear to the front. This is why some of my Roogars needed a bit of work on the bore. The frame fitting process often leaves a tight spot that needs worked out by lapping (fire or hand).
I could now go into a diatribe about lead bullets and the importance of lube, bhn, obturation and so forth but that's already somewhere in the DWF pages of history... anyway- that's what I think I know.
Even with a "One Dollar" gap, the bullet is entering the bore before leaving the throat:
Technically, the glass is always full; half liquid, half air....
DWF Supporters
April 9, 2015
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Thanks for this explanation. Now I can't wait to reload the next batch of .357 super mags and seat the 180 grain Hornady XTPs to the longer cannelure.
“We cannot but pity the boy who has never fired a gun; he is no more
humane, while his education has been sadly neglected.”
-Henry David Thoreau
“When some of my friends have asked me anxiously about their boys, whether
they should let them hunt, I have answered, yes – remembering that it was
one of the best parts of my education – *make* them hunters.”
-Henry David Thoreau
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June 25, 2013
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Agreed Ron. That why I have decided to load ony the mag cartridges. There is no problem working up a load that mimics a 38 special or a 22 if that's what your after. The right powder and bullet makes it fun for the kids and the gentler folks amongst us.
Then you get to the point where you can feel by the recoil how the combination works together. With Dan's the the ability to swap barrel lengths toss in another facet to powders you can use.
Endeavor to persevere,
Press on regardless.
Need little, want less, love more.
Dans Club
DWF Supporters
April 17, 2015
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Very nice explanation, concise and straight forward. Now if someone could explain the concept of "one tooth off" regarding car distributors as clearly as you explained bullet jump, I would be all set.
Regards,
-d
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June 25, 2013
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Real life example, I had a squib once where the bullet ended up in the forcing cone and the cylinder. Lucky it was a Dan.
Just removed the barrel and shroud and cleared.
Endeavor to persevere,
Press on regardless.
Need little, want less, love more.
December 15, 2008
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Isn't this the same in reloading semi-automatics? Measure head space and then load right up to the max length?
Saddle Sore in Plano, Texas
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Dans Club
February 22, 2009
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Just a little difference: In pistols, the cartridge isn't fired until the breach is closed and the round is supported in the barrel's chamber vs fired in a cylinder. So, magazine space is the limiting factor in cartridge OAL. When loading heavy-for-caliber bullets, I try to make the semi-auto cartridges as long as possible to have as much room as possible for powder. And, FWIW, loading long doesn't always guarantee accuracy- it's just another factor to tinker with.
Technically, the glass is always full; half liquid, half air....
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June 25, 2013
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shooter 715 said
Isn't this the same in reloading semi-automatics? Measure head space and then load right up to the max length?
Now you got me looking. So I got out the calipers and stuff.
On this ruger 9mm the head space for the brass I have is .75". The mouth of the case is where the brass is supported in the barrel chamber. The case will fall out on it own from the chamber.
Now using the cartridge and a bullet lightly seated, I inserted the cartridge into the barrel chamber and it came into contact with the lands. At this time the cartridge will not fall out on it's own. I seated the bullet to the point where the brass finally made contact with the case mouth stop in the chamber. Now this measured 1.25 OAL using 115gr FMJRN. This is too long for the magazine.
A good guesstimate for the freebore is .33".
So .75"+ .33"= 1.08" to bullet ogive contact with lands.
Endeavor to persevere,
Press on regardless.
Need little, want less, love more.
December 15, 2008
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Well, I don't usually admit to being stupid but I will go ahead and tell on myself. Once I had just finished loading some 124 gr. round nose at 1.15 OAL for 9mm.
I had 250 Xtreme 124 gr Flat Nose that I decided to run right behind the round nose. I loaded them up and took them to the range. I took 3 different brands of 9mm pistols with me. Loaded up 2 mags for each brand and got ready to have a little fun. Popped a mag in the first pistol and the rounds would not go into battery. I said to myself WTH? So I popped a mag in the second pistol and it would not go into battery either. Another WTH? I popped a mag into my CZ75B and surprisingly it would function. I think a strong spring pushed the bullets into the cases. Then it hit me. I had not adjusted the OAL for the Flat Nose rounds to 1.08.
Just goes to show, you can't get in a hurry when you are reloading. 
Saddle Sore in Plano, Texas
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Dans Club
February 22, 2009
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Headspace for 9mm is .754" to .776" max, so you have some room for the case to stretch before trimming. Actually, I just toss 9mm cases since they're so plentiful. The lands should start (at a minimum) around .9258- some 6 grooves run out to as much as .102". 1.08" seems a bit long but .006" could just be the accuracy of the tool or the difficulty of determining the ogive location. Anyway- I often find the magazine limits the case OAL more so that the barrel dimensions.
A loading technique is to lightly tension a projectile, long, in the brass and then close the breach/ bolt/slide on the dummy round. This will engrave the lands (on soft bullets) and if you haven't jammed it in too far- when you unlock the action and pull the round out; viola! A maximum length cartridge for that firearm.
I write pertinent info on the dummies with a Sharpie:
Technically, the glass is always full; half liquid, half air....
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