Bobbing Hammer Spur


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Onward Allusion
July 11, 2014, 01:34 AM
Does bobbing the hammer negatively impact ignition reliability on centerfire revolvers? I know not to do this with rimfire because more than a few have said that it can lead to light strikes. However, I have seen a good number of centerfire revolvers that had their hammer spurs bobbed. I've also never heard of anyone saying that it would affect ignition on centerfires. Thoughts?

BTW, I only shoot in double-action with my revolvers (semi's too for the most part).

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RustyShackelford
July 11, 2014, 02:10 AM
I've heard & read a few remarks, both + & - about bob/removed spurs.
I heard the ignition speeds increase because there is less weight. I've also heard with some loads there may not be enough push to strike the primer correctly. :uhoh:
FWIW; Most of the DA only revolvers I've owned in the past had no hammer spurs & worked fine with all types of rounds(JHPs, magnum, SWCs, FMJs). I had a SP101 2.25" barrel snub that was DA only & in the 2000s, I owned a NYPD surplus .38spl GPNY. It had a factory 4" stainless steel barrel with a spurless design.
I liked the spurless style because the sharp spur wouldn't jab my side or get strung up on any clothing in a rapid draw.

It's a design that worked well for me. :D
Author & legal use of force expert; Massad Ayoob endorses the DA only revolver format too. He's put out several articles & police industry training guides suggesting the use of DA only/spurless styles.
You can avoid the false claims of "cocking a hammer" or firing single action by a prosecutor or criminal investigator too.

Drail
July 11, 2014, 03:24 AM
Simply bobbing a hammer does not affect the reliability of primer ignition. It actually produces a little more energy than a stock hammer. Only when you start using lighter mainsprings to power the hammer do you start having failures to ignite. The force that sets the hammer into motion is supplied by the mainspring. Using a lighter hammer does not change that force. The biggest advantage to bobbing the hammer is that having less mass striking the frame reduces movement of the gun when the shot breaks and with the hammer moving faster the lock time is reduced.

MrBorland
July 11, 2014, 10:05 AM
All else equal, a lighter hammer actually increases reliability. IOW, you can lighten the action without loss of reliability. To a point, of course.

A lighter hammer travels faster. It's still transferring the same amount of energy, since the energy's supplied by the mainspring; but since it's doing so faster, it's delivering more "power" (energy x velocity) to the primer, and it's power, not energy or momentum, that ignites primers.

All this has limits, of course. A lighter hammer has less resistance to internal friction, so a gun that's out of spec or in need of a good action job may become unreliable upon bobbing. It's best, then, to bob the hammer as part of an overall tuning, IMO.

Haywood
July 11, 2014, 10:26 AM
I have bobbed hammers on a few of my Snubs with no ill effects.

chicharrones
July 11, 2014, 10:34 AM
In my limited experience, the size and weight of a hammer spur on a something like a snub nose DA revolver is insignificant enough that when removed it doesn't affect a proper functioning gun. So, if the gun in question isn't having misfires before having the spur cut off, it highly likely won't have misfires after the spur is cut off.

Of course, testing the gun after a bob job is definitely recommended.

Onward Allusion
July 11, 2014, 12:55 PM
Very interesting. Thanks for the info guys.

Bud0505
July 11, 2014, 01:58 PM
Does bobbing the hammer negatively impact ignition reliability on centerfire revolvers? I know not to do this with rimfire because more than a few have said that it can lead to light strikes. However, I have seen a good number of centerfire revolvers that had their hammer spurs bobbed. I've also never heard of anyone saying that it would affect ignition on centerfires. Thoughts?

BTW, I only shoot in double-action with my revolvers (semi's too for the most part).
Probably goes without saying but I would buy an extra hammer before I bobbed the original.Just in case.

RustyShackelford
July 11, 2014, 04:16 PM
Some gun show booth staffs or sales clerks say a revolver is DA only just by the removal of the spur. :confused:
This is not true. The hammer can still be cocked & the revolver fired SA(single action).
Many CCW license holders & cops "bob" the spur to avoid problems but that doesn't make it DA only.
FWIW; a good custom shop for DA only/action jobs is www.Geminicustoms.com . They offer different packages & services.

Jim K
July 11, 2014, 04:25 PM
Whether lightening the hammer will cause misfires depends on the gun. On a gun with a light hammer like the J frame S&W, it well may do so. But sometimes misfires are not the result of just bobbing the hammer. In all too many cases, that is accompanied by lightening the mainspring (hammer spring) and the combination causes misfires.

I second the idea of having a spare hammer and other parts, or at least making sure they are available, before doing any such work.

Jim

JaxJim
July 12, 2014, 05:06 PM
I have an Iterarms 774a revolver I bobbed the hammer on. It did become less reliable (soft primer strikes) than before the bob. I had removed a couple of coils off the mainspring prior to the hammer bob to lighten the trigger pull.

I replaced the mainspring and this revolver was once again reliable.

This was all done about 20 years ago and I don't bring this revolver out of the safe to play much anymore. I'm quite certain though it is reliable now.

So, if you haven't done any bonehead things like reduce the mainspring, you're probably good to go. I've learned from my past indiscretions and now purchase reduced Wolff springs and save the OEM one for if/when needed.

gun_with_a_view
July 12, 2014, 11:43 PM
The firing mechanism build for Smith 642 and 442 hammerless revolvers is somehow different than the company's hammer models. The trigger pull is said to be lighter and smother with no loss of firing capability. A gunsmith could probably explain the specifics.

Old Fuff
July 12, 2014, 11:55 PM
The firing mechanism build for Smith 642 and 442 hammerless revolvers is somehow different than the company's hammer models. The trigger pull is said to be lighter and smother with no loss of firing capability. A gunsmith could probably explain the specifics.

Not really.

The placement of the hammer and trigger studs (the pins those respective parts rotate on) is the same as those J-frame models that have conventional hammers. All J-frame's use the same trigger. That said, older parts don't necessarily interchange with newer MIM ones.

You do find differences between individual revolvers for various (and often unpredictable) reasons.

gun_with_a_view
August 4, 2014, 10:15 PM
Finally found that great article on bobbing hammer spurs:
http://snubtraining.com/snub-training-2013-removing-the-hammer-spur/

Be sure to enjoy the rest of Mike deBethencourt's refreshing website specializing in snub nose revolver and knife training. There's more good stuff in the blog:
http://snubtraining.com/

NMPOPS
August 5, 2014, 06:33 AM
I have personally bobbed the hammers on several Smith's and have 2 M-64s with factory bobs. I doubt S&W would bob hammers if this was a problem. The only down side is Holsters. Holsters with thumb breaks don't work very well with bobbed hammers.

Geezer Glide
August 5, 2014, 07:06 AM
This one has had a lot of rounds through it since I bobbed it. No problems, at all.

http://i64.photobucket.com/albums/h174/horry_dresser/013_zps9274b8c7.jpg

scbair
August 5, 2014, 10:15 AM
S&W and Ruger DAs have never suffered any reliability issues when their hammer spurs were ground off, in my experience. I have seen some Colt D frames (Cobras, specifically) that did suffer light primer strikes after this "surgery."

Just my own experience.

Kaeto
August 5, 2014, 10:35 AM
Charter Arms sells a spurless replacement hammer for their guns on their website.

http://www.charter2000.site.aplus.net/cgi-bin/mivavm?/mm5/merchant.mvc+Screen=PROD&Store_Code=CFAE&Product_Code=HAMDA&Category_Code=4PRT

OrangePwrx9
August 5, 2014, 11:00 AM
The compressed hammer spring has a fixed amount of energy. Most of that energy is transferred to the hammer when the trigger is pulled. A hammer lightened by bobbing will accordingly move faster. The energy expended on the primer by the firing pin should be approximately the same, disregarding hammer spring inertia losses...which should be vanishingly small.

MrBorland
August 5, 2014, 11:31 AM
A hammer lightened by bobbing will accordingly move faster. The energy expended on the primer by the firing pin should be approximately the same, disregarding hammer spring inertia losses...which should be vanishingly small.

You've got most of it right, except the assumption that energy is what ignites primers.

Power is what ignites primers, and power is energy times velocity, so all else being equal, the faster hammer hits the primer with increased power, which is why you can actually often lighten the action somewhat when bobbing the hammer without loss of reliability.

The loss of inertia is the same as the loss of momentum, which is of no consequence in regards to reliability, since momentum isn't what ignite primers either.

Jim Watson
August 5, 2014, 12:01 PM
I have seen one instance of bobbing the hammer causing misfires.
A friend cut off the hammer spur of his Taurus 85 and ignition got spotty. He crammed in a J Smith mainspring and got it back firing every time, but the DA sure was tough.

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