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Bobbing a revolver hammer
- Thread starter Dr. Marneaus
- Start date
NYECOGunsmith
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After any hammer bobbing, be sure to do all the safety and function checks, then take it out and shoot it, a full box of whatever you plan on carrying it for self-defense, to ensure that the lightened hammer is NOT going to result in light firing pin strikes. This can happen on any revolver.
You could bob the hammers on 100 guns of the exact same model, with sequential serial numbers, and bob the hammers exactly the same amount, weighing them and they weigh within .1 grains of one another, and a percentage of them will then have light firing pin strikes and not set off a cartridge 100% of the time.
The difference is in the hammers fit within the frame, and the friction that results from that fit.
If the friction is high, the heavier (pre bobbing) hammer (assuming the gun was 100% reliable in ignition prior to the hammer bobbing!) will have enough energy (velocity squared times the weight of the object moving, same equation as for a bullet's muzzle energy or down range energy) to set off the primer.
But if you lighten the weight, while you might think that this will speed up the hammer's flight time (which should affect its energy), it doesn't always. It may not speed it up enough to equal the energy it formerly had.
I've had a few that slowed down, a lot, and didn't set off the primers with 100% reliability.
The spring was delivering the same energy, and with the lighter hammer, it should move faster and still generate enough energy to set off any primer, but if the spring now has too much energy for the light weight hammer, and you have done nothing else to the action, you may find the hammer now slows down because it is being driven forward and slightly sideways, so it now has friction in the frame it didn't have before. So you may need to replace the spring , with a lighter one, or even with a heavier one.
Just like with a firing pin in a bolt action rifle for example where for the greatest reliability, fastest lock time and greatest accuracy, the firing pin should be perfectly centered in its tunnel, and that tunnel perfectly centered with the axis of the bore, well, a revolvers hammer should be perfectly centered in the frame opening.
If it's not, then it's rubbing somewhere, and that slows it down. The cure for this is generally polishing the sides of the hammer and the insides of the frame and fitting an oversized pivot pin to the hammer to eliminate all side slop, along with polished washers on either side of the hammer pivot (sometimes off different thicknesses on each side to get the hammer centered) to get rid of the slop and allow the gun to function properly and maybe gain a tiny bit of accuracy.
You just don't know what's going to happen when you alter any component in a gun's cycling until you test it.
You can make guestimates, but that's about it.
So, if your life is going to depend on it being 100% reliable, after you do anything to a gun, test it with a fairly large amount of the ammo you intend to carry it loaded with.
You could bob the hammers on 100 guns of the exact same model, with sequential serial numbers, and bob the hammers exactly the same amount, weighing them and they weigh within .1 grains of one another, and a percentage of them will then have light firing pin strikes and not set off a cartridge 100% of the time.
The difference is in the hammers fit within the frame, and the friction that results from that fit.
If the friction is high, the heavier (pre bobbing) hammer (assuming the gun was 100% reliable in ignition prior to the hammer bobbing!) will have enough energy (velocity squared times the weight of the object moving, same equation as for a bullet's muzzle energy or down range energy) to set off the primer.
But if you lighten the weight, while you might think that this will speed up the hammer's flight time (which should affect its energy), it doesn't always. It may not speed it up enough to equal the energy it formerly had.
I've had a few that slowed down, a lot, and didn't set off the primers with 100% reliability.
The spring was delivering the same energy, and with the lighter hammer, it should move faster and still generate enough energy to set off any primer, but if the spring now has too much energy for the light weight hammer, and you have done nothing else to the action, you may find the hammer now slows down because it is being driven forward and slightly sideways, so it now has friction in the frame it didn't have before. So you may need to replace the spring , with a lighter one, or even with a heavier one.
Just like with a firing pin in a bolt action rifle for example where for the greatest reliability, fastest lock time and greatest accuracy, the firing pin should be perfectly centered in its tunnel, and that tunnel perfectly centered with the axis of the bore, well, a revolvers hammer should be perfectly centered in the frame opening.
If it's not, then it's rubbing somewhere, and that slows it down. The cure for this is generally polishing the sides of the hammer and the insides of the frame and fitting an oversized pivot pin to the hammer to eliminate all side slop, along with polished washers on either side of the hammer pivot (sometimes off different thicknesses on each side to get the hammer centered) to get rid of the slop and allow the gun to function properly and maybe gain a tiny bit of accuracy.
You just don't know what's going to happen when you alter any component in a gun's cycling until you test it.
You can make guestimates, but that's about it.
So, if your life is going to depend on it being 100% reliable, after you do anything to a gun, test it with a fairly large amount of the ammo you intend to carry it loaded with.
NYECOGunsmith
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NYECOGunsmith
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NYECOGunsmith
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Can affect them a good deal, if the firing pin strike is not flat all the way across the point of impact, it can shift the cartridge in the chamber, more so if it is a standard .22 chamber and not a Bentz (tighter than standard .22 LR chamber, but not as tight as a Match chamber) or Match chamber and if the ammo is plinking stuff and not match grade.
Since the .22 LR head spaces on the rim, and those, at least in non-match grade ammo, are notorious for being all over the place dimensionally, and they are slightly tapered from the case walls to the major diameter of the rim, the specs range for rim diameter and thickness is pretty wide actually.
Ammo that had a perfect 90 degree transition from the case walls to the front head space surface of the rim, and a perfectly flat head space surface on that rim and on the chamber, would be the most accurate combination that you could get in those respects.
That bit of taper can allow the case to crush down a bit when the firing pin strikes the rim, so there will always be some amount of tilting going on.
But if the firing pin, whether square, rectangular or round doesn't impact the rim evenly, it can cause that tilt and magnify it due to leverage.
That tilt, of course, that can throw off accuracy as the projectile is no longer concentric with the bore as it starts down the bore.
Miniscule amounts of offset I admit, but if you are trying for a one-hole group at 25 or 50 yards for a 10-shot group gun, you have to consider a lot of things.
Match grade ammo seeks of course to hold all the cartridge dimensions, as well as bullet weight, velocity, cartridge rim dimensions, cartridge wall dimensions, etc. to a very tight standard with little deviation.
And match grade chambers go hand in hand with match grade ammo, designed to hold the round as precisely concentric with the bore as possible, and to place the projectile as perfectly concentric with the central axis of the bore as it enters the leade and starts to engage the rifling.
Since the .22 LR head spaces on the rim, and those, at least in non-match grade ammo, are notorious for being all over the place dimensionally, and they are slightly tapered from the case walls to the major diameter of the rim, the specs range for rim diameter and thickness is pretty wide actually.
Ammo that had a perfect 90 degree transition from the case walls to the front head space surface of the rim, and a perfectly flat head space surface on that rim and on the chamber, would be the most accurate combination that you could get in those respects.
That bit of taper can allow the case to crush down a bit when the firing pin strikes the rim, so there will always be some amount of tilting going on.
But if the firing pin, whether square, rectangular or round doesn't impact the rim evenly, it can cause that tilt and magnify it due to leverage.
That tilt, of course, that can throw off accuracy as the projectile is no longer concentric with the bore as it starts down the bore.
Miniscule amounts of offset I admit, but if you are trying for a one-hole group at 25 or 50 yards for a 10-shot group gun, you have to consider a lot of things.
Match grade ammo seeks of course to hold all the cartridge dimensions, as well as bullet weight, velocity, cartridge rim dimensions, cartridge wall dimensions, etc. to a very tight standard with little deviation.
And match grade chambers go hand in hand with match grade ammo, designed to hold the round as precisely concentric with the bore as possible, and to place the projectile as perfectly concentric with the central axis of the bore as it enters the leade and starts to engage the rifling.
