Light primer strikes?

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11 years 9 months ago #18706 by bollox
Replied by bollox on topic Light primer strikes?
Ordered a new Armalite spring from DSG. In a pinch could I use an ordinary AR15 spring? There are gentle (not severe) dimples in the hammer face but I would find it hard to believe that they altered the geometry from original enough to create this problem.

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11 years 9 months ago #18710 by LebbenB
Replied by LebbenB on topic Light primer strikes?
I'm pretty certain you can use an AR15 hammer spring in an AR10.

A slight marring on the hammer face is okay. I was referring to a deep dimple.

Also, remember that Armalite firing pins are spring loaded and will not come as far forward as an M14/M1A firing pin, resulting in a shallower primer indentation. If you have a friend or shooting partner with an Armalite AR10, ask to see a couple of his spent cases as a comparator for yours.
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11 years 9 months ago #18798 by bollox
Replied by bollox on topic Light primer strikes?
Lebben:

I checked the protrusion of the firing pin and it was .053". I would seem that the protrusion would be set by caliber and not be firearm specific. Do you know what that spec is? It might be handy to know.

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11 years 9 months ago #18849 by mrraley
Replied by mrraley on topic Light primer strikes?
Normal firing pin protrusion is around and not exact…

AR-10 = .050”
M-15 = .030”
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11 years 8 months ago #19089 by bollox
Replied by bollox on topic Light primer strikes?
Headspace is right at .308 no go which appears to be about good for 7.62 NATO. Bolt would not close on .308 field gauge. Tried with different ammo (still milsurp) and the same problem occurred. Next is the hammer spring.

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11 years 8 months ago - 11 years 8 months ago #19488 by bollox
Replied by bollox on topic Light primer strikes?
Installed Wolff heavy hammer spring. Pulled the trigger 6 times and had 6 bangs. Not a real test I know. The primer dimples are still weak to me. I'm going to load it up for the next Appleseed I attend and shoot a couple of AQT's. I intend to buy an AR 15 hammer to install if I get any more light strikes. The slot in the bolt carrier is wide enough. Does anyone know of any cautions against this?
Last edit: 11 years 8 months ago by bollox.

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11 years 8 months ago #19500 by LebbenB
Replied by LebbenB on topic Light primer strikes?
No, an AR15 hammer should work.

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11 years 7 months ago #22828 by bollox
Replied by bollox on topic Light primer strikes?
My travails continue:

AR15 hammer will not function in an AR10 B... at least not my generation. I know they have gone through several revisions. The catch is not in the right place and the whole body of the hammer is too thick. The AR15 hammer will not allow the bolt to be retracted. I've emailed Wolff Gunsprings to see if they have an even stronger spring. Barring that, I am considering finding some fine tubing and seeing if I can crimp it to the legs of the spring to act as a kind of shim giving the hammer spring more preload. If I could find the right size and the crimps were secure... or maybe solder.

Shows the 2 hammers. AR 10 on the left;

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Shows how the low the hammer is supposed to be free to go in an AR10. Notice the low profile;

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Shows how the hammer sits at its lowest point of travel with the AR15 hammer.

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Looking at the 2 hammers it becomes apparent that Armalite had to relieve a bunch of material to get the AR10 hammer to lay down flat enough for the bolt to travel backwards. This causes the hammer spring to have less preload in the "fired" position and may explain why AR10's light strike. The design may make up for this with length of arc the hammer swings through which I did not measure.

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11 years 7 months ago #22833 by 13fcolt
Replied by 13fcolt on topic Light primer strikes?
You've got the NM 2 stage trigger, so a single stage hammer (the one on the right) is not compatible without changing the trigger as well. If it's working with the original set and extra power hammer spring, I'd stop there.

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11 years 7 months ago #22834 by bollox
Replied by bollox on topic Light primer strikes?
I thought mine was the "tactical 2 stage". Are they the same? I appreciate your admonition to stop where I'm at and I do take it under advisement. My rifle is intended as a main battle rifle should the need ever arise. It'll keep me up at night unless I get some more confidence in it. It's the same set of requirements I have for my family's car when we used to live in New Orleans and annually faced the prospect of evacuation. If I'm not confident in it it has to go.

Also. Does anyone know if the spring for the firing pin serves any other purpose other than preventing slamfires brought on by the inertia of the firing pin itself? I just removed mine and cycled 1 commercial round through the action 3 times leading to a very slight indentation on the primer. Nowhere near enough to ignite even a soft primer. May try this out tomorrow and report the results unless y'all have any emergency warnings.

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