How does a hammer fired gun ignite a primer?

[SamuelBLong]

BOM if you want / need it milled vs grinding it yourself, I can accommodate.

[JodyH]

Here is another pertinent question-- can I use cutting tools and sanding tools on a new (MIM [I think]) SIG hammer without any special considerations?

I used a Dremel cut off wheel and sanding drum on the spur of my S&W MIM J frame hammer with no ill effects. Just touched it up with cold blue when I was finished.

[JDM]

BOM if you want / need it milled vs grinding it yourself, I can accommodate.

I may take you up on that if it ends up working and my homemade bobbed hammer is too ugly to pass muster.

[JDM]

I used a Dremel cut off wheel and sanding drum on the spur of my S&W MIM J frame hammer with no ill effects. Just touched it up with cold blue when I was finished.

Excellent.

Thanks!

[DanH]

Since it requires a certain amount of force to light a primer, and force is a product of both mass and acceleration, changing the weight of the hammer would probably require more acceleration, or a heavier spring.
I'll be damned. That's some physics, right thar. Whoda thunk it had real world applications ;p

[Rich]

Lets us know how it goes!

[David Armstrong]

It is a function of mass and speed. Back in the days of removing hammers on revolvers, general advice was to leave a bump of the spur on J-frames, but K-frame spurs could be ground completely off without worry if one used the standard springs.

[Rich]

It is a function of mass and speed. Back in the days of removing hammers on revolvers, general advice was to leave a bump of the spur on J-frames, but K-frame spurs could be ground completely off without worry if one used the standard springs.

I heard the same. I removed the spurs on my M13 never any light strikes.
I wont buy another J frame with a exposed hammer.

[BN]

USPSA and IDPA Revolver shooters are removing a lot from their hammers and using lighter hammer spring pressure to get a lighter trigger pull. Most of them are using deep seated Federal primers for reliability. I've also seen some radically lightened 1911 hammers.

[TheTrevor]

Hey, I get to share some of the knowledge gained while I was figuring out how to make 5.45x39 run reliably in an AR...

Simply lightening the hammer isn't going to change the total energy delivered to the firing pin, but it will change the energy impulse and acceleration. Energy delivered is determined by the potential energy stored in the spring, not by how much mass it has to move when released.

The effect of a lighter/faster hammer on ignition is closely related to the profile of the firing pin, and drag on the firing pin within its channel. A relatively large surface area (e.g. like a rimfire firing pin) driven by a lighter hammer depends largely on how soft the primer impact area is, because that faster snap with less mass behind it gives the primer less time to deform during the impact impulse.

On the other hand, a more tapered or pointed firing pin driven at higher speed (but with the same total energy) will displace more primer metal and generate a deeper strike. This is why AR "speed hammers" (or the functional equivalent in a Geissele trigger pack) can reliably ignite hard Berdan-style primers in Russian milsurp ammo. The same gun with a generic AR lower parts kit hammer (with the added mass in the "tail" hanging off the back of the hammer) is likely to have a significant failure rate igniting Russian milsurp ammo.

Case in point, I was getting a ~12% failure-to-fire rate on 7N6 ammo in my 5.45 AR with a generic hammer, but when I installed a 2-stage LPK which included a tail-less "speed" hammer, that dropped to <1% with no other changes. I could pretty much eliminate the remaining failures by relieving a 5.56 firing pin to hit 0.015 deeper, but I've hit the point of "good enough" and haven't bothered.

As Bill alludes to above, lightening both the hammer AND the springs results in less total energy delivered with an impulse profile little changed from stock, necessitating the use of more-sensitive deep-seated Boxer primers.