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Firing Pin Stop Radius - Large vs Small Radius

7209 Views 18 Replies 10 Participants Last post by  roaniecowpony
I'm interest to hear the advantages and disadvantages of small radius and large radius firing pin stop.
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Large has less point of stress on the hammer. Easier to initiate pulling the slide back

Small radius has more stress, holds the slide forward just a tad longer letting the pressure drop. Can be used to handle hotter loads with out having to go to stronger springs. Stronger springs hammer the slide forward causing more disturbance/felt recoil.
 

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I thought the small radius just pushed lower on the hammer than the large radius. Lower on the hammer is closer to the pivot point meaning it needs more force to cock the hammer.
 

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I'm not a 1911 expert, so I'm sure someone can give a better answer than I can.

However, going off of what I know, a reduced radius decreases felt recoil for some shooters and increases lock up time. One of the modifications that's often promoted for .45 Super modifications is an EGW flat bottom FPS.

A greater radius makes it easier to rack the slide.
 

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The above information is correct. When I needed to tune my Kimber Eclipse 10mm for the hotter hunting loads, I tried the stronger springs and got too much force in the slide return and didn't like the standard factory stuff (wouldn't eject it sometimes). I got a flat bottom firing pin stop and put a slight radius on it, went back to the standard springs, and problem solved - everything cycled properly and the hunting loads did not land the empties in the next county upon ejection. They eject fairly close to the factory fodder now.
 

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Discussion Starter · #8 · (Edited)
I took the radius out to about half the factory radius. I'll give it a try at this radius.

 

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If you look at my pic of the hammer base you can see it looks OK, at least as far as I can discern. I have a little more than 300 rounds through that stop on that hammer.

This is a Colt Delta Elite 10mm and they're not puzzy loads. Sierra 165gn Power Jacket HPs. @ 1325 fps.

I've been watching the hammer pin as well and have not noticed any wear or change in dimensions.

I respect your input. If you think I'm missing something please let me know.
 

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Discussion Starter · #14 ·
When I installed the EGW FP stop, i would guess it was .005-.010" R.

It was just too much for my wife to deal with. I would estimate it is now around .060"R. It's much easier to rack. I'll give it a test with this radius. The ejection should be more forceful.
 

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I would guess mine is at about .01-.015. As soon as the slide starts to move back the hammer is starting to ride back, underneath the pin stop. I tried to kind of make the radius longer the farther down under the pin stop I went.
 

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I use stops and the hammer face to get achieve results for different applications. The first pic is of three different firing pin stop profiles. The one on the left is about .035" radius IIRC for heavier loads. The center is a standard A1 radius. The radius on the right is for a steel gun and low power loads, shooting balls loads in this pistol will stand the muzzle straight up in recoil. You can see how far up each radius will contact the hammer face changing the mechanical advantage.
Also, how flat and parallel the hammer face lays against the firing pin stop will also affect unlocking. The second pic uses a hammer cut used with a Ceiner 22LR conversion on a dedicated lower. The way this pistol is setup I get 100% reliability with standard velocity ammo
 

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Discussion Starter · #19 ·
Great information. Glad I asked. Thanks much everyone.
 
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