Hammer Bob

[pantannojack]

If getting a J Frame hammer bob'd is it advisable to up the spring tension for reliable ignition?

 

[ContinentalOp]

I don't think it's necessary as long as you're using the factory mainspring. Even with a lighter mainspring, if you were getting reliable ignition before the bob I don't think it would matter.

Just my layman's opinion.

 

[Hapworth]

Should have no effect on primer ignition. You're fine.

 

[chief38]

If getting a J Frame hammer bob'd is it advisable to up the spring tension for reliable ignition?

Without knowing what the current spring tension (weight in lbs.) is, I really can't give you an honest answer. Most J Frames have more than a heavy enough spring (from the Factory) and so I doubt you would need to put in a stronger one - UNLESS someone has cut a few coils off or already replaced it with a lighter weight one.

The second thing I would like to mention is that you might want to buy another Hammer and bob the new one, not the original. This way if you ever get the hankering or want to sell it, the original is easily and quickly replaced with no fitting required. just saying........

 

[zzclancy]

Bobbed

If getting a J Frame hammer bob'd is it advisable to up the spring tension for reliable ignition?

After I bobbed the hammer on my S&W 21-4, 44 special I had light primer strikes with Winchester ammo. Some say you shouldn't some say you will. I did. All factory springs with the set screw all the way in.

I installed an Apex extended firing pin. No more light primer strikes with Winchester or any other big named ammo.

Personally I like bobbed hammers or internal hammers on revolvers for CCW.

Just make sure you try any ammo you plan to carry after it's done. Plenty of videos to show you how to install an extended firing. Apex extended firing pin is $15.95 plus shipping.

 

[ImprovedModel56Fan]

I've bobbed maybe half a dozen hammers. Never altered my factory mainspring. NO problems.

S&W, on the other hand, UNNECESSARILY increased factory spring strength on a special order (NY-1) of DAO Model 60 revolvers. BIG MISTAKE. Before they could correct this wholly unnecessary move, they upset the Rodman's Neck crowd or their bosses to the point that the contract was cancelled.

You could probably do a search of old threads and find a detailed technical discussion of why increased spring power is unnecessary. Has something to do with the increased speed of the lighter hammer and the kinetic energy imparted on impact. I don't fully understand it, because I don't understand why KE is holy, and momentum isn't.

Anyway, my limited experience tells me what I need to know, and I understand that the NYPD experimented with a few dozen revolvers and observed the same thing.

Bob away!

BTW, do not ignore zzclancy's post. My experience was with older J frames, as was NYPD's. Nothing wrong with applying his test to older guns, but he can tell you that it is particularly necessary with new ones.

 

[chief38]

I've bobbed maybe half a dozen hammers. Never altered my factory mainspring. NO problems.

S&W, on the other hand, UNNECESSARILY increased factory spring strength on a special order (NY-1) of DAO Model 60 revolvers. BIG MISTAKE. Before they could correct this wholly unnecessary move, they upset the Rodman's Neck crowd or their bosses to the point that the contract was cancelled.

You could probably do a search of old threads and find a detailed technical discussion of why increased spring power is unnecessary. Has something to do with the increased speed of the lighter hammer and the kinetic energy imparted on impact. I don't fully understand it, because I don't understand why KE is holy, and momentum isn't.

Anyway, my limited experience tells me what I need to know, and I understand that the NYPD experimented with a few dozen revolvers and observed the same thing.

Bob away!

BTW, do not ignore zzclancy's post. My experience was with older J frames, as was NYPD's. Nothing wrong with applying his test to older guns, but he can tell you that it is particularly necessary with new ones.

As long as it came up..........

The NYPD has just about the worst record I know of in their "dumbing down" guns rather than spending the money, time, trouble and effort to properly train their Officers!! They did the exact same thing with their Glocks by adding the 12 pound trigger after some of their Offices shot themselves with the 5.5lb. standard triggers. Instead of re-training the Officers not to be so careless and teach them better techniques, they more than doubled the trigger pull to the point that many of their Officer's can't hit the broad side of a barn!

I was friendly with one of their training officers and still friends with yet another. I have been to the NYPD shooting facility at Rodman's Island and I have shot their guns and they are ridiculous! If an Officer can not be trained to safely carry a pistol with a 5 1/2lb. trigger then I suggest he should not be on the job until he/she is capable. In many instances there are shootings involving the NYPD and the round count is so outrages in relationship to hits to stop a threat - it's embarrassing!

Off Duty , they still cannot carry anything but a smaller back up gun (approved by NYPD) that has the same ridiculous trigger pull. If they get caught with a gun or are involved in a shooting with a gun that does not conform to their spec's, - immediate dismissal.

 

[SweetMK]

Removing weight from a rotating item such as the hammer will allow it to accelerate faster.
If it accelerates faster, the velocity at primer impact will be higher.

the impact force = 1/2 M(Vsquared)

since the velocity is squared, the force increases much faster than the force being decreased by the weight reduction.

SO,,, in the end, bobbing a hammer should create BETTER ignition,,
(strictly scientifically/mathematically speaking)

In the real world,, as Mr Spock would say,, "It is my best guess,,"

 

[chief38]

Removing weight from a rotating item such as the hammer will allow it to accelerate faster.
If it accelerates faster, the velocity at primer impact will be higher.

the impact force = 1/2 M(Vsquared)

since the velocity is squared, the force increases much faster than the force being decreased by the weight reduction.

SO,,, in the end, bobbing a hammer should create BETTER ignition,,
(strictly scientifically/mathematically speaking)

In the real world,, as Mr Spock would say,, "It is my best guess,,"

Yes, it accelerates faster however since it weighs less, the impact may not have more energy on the primer. A lighter bullet travels faster than a heavy one, but most time hits with less foot pounds of energy unless it is driver much faster (+P velocities). I'm not a Physicist, but that is an interesting thought. I suppose it would have to be tested or weighed before and after bobbing - then do the math. Not saying you are wrong just speculating.....

 

[Hapworth]

Removing weight from a rotating item such as the hammer will allow it to accelerate faster.
If it accelerates faster, the velocity at primer impact will be higher.

the impact force = 1/2 M(Vsquared)

since the velocity is squared, the force increases much faster than the force being decreased by the weight reduction.

SO,,, in the end, bobbing a hammer should create BETTER ignition,,
(strictly scientifically/mathematically speaking)

In the real world,, as Mr Spock would say,, "It is my best guess,,"

This is my understanding. In fact, if you lighten the hammer you can lighten the mainspring tension and still get the same reliable ignition because you don't need as much mainspring drive to run the lighter hammer.

Randy Lee, Carmony and a few others had long talks about this over on the Enos forum back in the day and it's all still there. They acknowledged that common understanding for decades was that reducing the hammer's mass would cause ignition problems, but all their extensive testing proved otherwise. They considered the issue settled, and I'm no one to argue with them.

Lightening the hammer does not contribute to misfires in an otherwise sound revolver.

 

[Muley Gil]

As long as it came up..........

The NYPD has just about the worst record I know of in their "dumbing down" guns rather than spending the money, time, trouble and effort to properly train their Officers!! They did the exact same thing with their Glocks by adding the 12 pound trigger after some of their Offices shot themselves with the 5.5lb. standard triggers. Instead of re-training the Officers not to be so careless and teach them better techniques, they more than doubled the trigger pull to the point that many of their Officer's can't hit the broad side of a barn!

I was friendly with one of their training officers and still friends with yet another. I have been to the NYPD shooting facility at Rodman's Island and I have shot their guns and they are ridiculous! If an Officer can not be trained to safely carry a pistol with a 5 1/2lb. trigger then I suggest he should not be on the job until he/she is capable. In many instances there are shootings involving the NYPD and the round count is so outrages in relationship to hits to stop a threat - it's embarrassing!

Off Duty , they still cannot carry anything but a smaller back up gun (approved by NYPD) that has the same ridiculous trigger pull. If they get caught with a gun or are involved in a shooting with a gun that does not conform to their spec's, - immediate dismissal.

Ain't it funny that military and police around the world carry Glocks with the 5 1/2 pound trigger and they have very few ADs????

 

[ContinentalOp]

As long as it came up..........

The NYPD has just about the worst record I know of in their "dumbing down" guns rather than spending the money, time, trouble and effort to properly train their Officers!!

I don't know if it's still done this way, but last time I read about their firearms training, their in-service training/qualifications, post-academy, amounted to 2 days/year, including legal/policy updates and range time.

 

[Johnnu2]

When I bobbed my J Frame Airweight hammer, I did not change any springs. To be absolutely sure of proper ignition, I test fired a lot AND, I also brought it out to my outdoor range and left it on the bench in below freezing weather for several hours. Then, I test fired it and found no probs with ignition. I DO recommend buying a spare hammer (as I did) just in case you mess up the bobbing operation. Here's mine (the hammer is MIM; trigger is forged... both as from factory):





J.

 

[lefty_jake]

I am quite interested all aspects of tuning revolvers, including the relationship between hammer mass and mainspring tension. I find the discussions about mass vs speed and kinetic energy vs momentum to be useful, but I think there is a key factor which is not always considered, which is the behavior of primers.

For reasons that I don't claim to understand, centerfire primers like to be hit very sharply, and if the hammer is moving very fast, it does not need a huge amount of energy to ignite centerfire primers. Rimfire behaves quite differently. Rimfire rounds need to be crushed with some substantial mass to ignite reliably.

So the rule of thumb, which I mostly learned from this forum, is that centerfire guns generally work just fine with a lightened hammer, and rimfire guns do not. Clearly, the physics of spring force and hammer energy cannot fully explain this phenomenon.

This difference between centerfire and rimfire is well illustrated by the aftermarket hammers made by Apex Technologies for competition revolvers. Their hammers for centerfire double action revolvers are very skeletonized, while their rimfire hammer is called the "mass driver" and has extra mass. I have no connection to them, but I do respect their expertise with competition revolvers.

 

[Hapworth]

I am quite interested all aspects of tuning revolvers, including the relationship between hammer mass and mainspring tension. I find the discussions about mass vs speed and kinetic energy vs momentum to be useful, but I think there is a key factor which is not always considered, which is the behavior of primers.

For reasons that I don't claim to understand, centerfire primers like to be hit very sharply, and if the hammer is moving very fast, it does not need a huge amount of energy to ignite centerfire primers. Rimfire behaves quite differently. Rimfire rounds need to be crushed with some substantial mass to ignite reliably.

So the rule of thumb, which I mostly learned from this forum, is that centerfire guns generally work just fine with a lightened hammer, and rimfire guns do not. Clearly, the physics of spring force and hammer energy cannot fully explain this phenomenon.

This difference between centerfire and rimfire is well illustrated by the aftermarket hammers made by Apex Technologies for competition revolvers. Their hammers for centerfire double action revolvers are very skeletonized, while their rimfire hammer is called the "mass driver" and has extra mass. I have no connection to them, but I do respect their expertise with competition revolvers.

This is an excellent point, as OP only specified J-frame, not caliber. Rimfires are different beasts and not as amenable to this type of tuning, compared to centerfire.

(Apex Technologies, by the way, is the aforementioned Randy Lee's company.)