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 Notched vs. Round Hammers???
Blain  [Member]
12/17/2010 12:41:05 AM
What are the pros and cons of each? Which do the actual GI rifles have?
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LA_357SIG  [Team Member]
12/17/2010 1:34:39 AM
Rounded hammers are good for 9mm and .22lr AR conversions.

ETA: Notched hammers will not push the hammer back far enough on some AR-22 bolts to catch the disconnector and thus not resetting the trigger. They also supposed to stop continuous firing (without auto sear) by stopping the bolt carrier.

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js308  [Member]
12/17/2010 2:36:24 AM
Originally Posted By Blain:
What are the pros and cons of each? Which do the actual GI rifles have?


A GI version would be a rounded hammer with a hook on the end for the auto sear.
The closest you would be able to get with a semi auto lower is a rounded hammer, minus the auto hook.
The notched hammer is useless. Don't get me wrong, it will run fine. It's just useless!
shadowcop  [Team Member]
12/17/2010 9:04:07 AM
If given a choice, get the rounded hammer.
fook  [Team Member]
12/17/2010 9:29:24 AM
Originally Posted By js308:
Originally Posted By Blain:
What are the pros and cons of each? Which do the actual GI rifles have?


A GI version would be a rounded hammer with a hook on the end for the auto sear.
The closest you would be able to get with a semi auto lower is a rounded hammer, minus the auto hook.
The notched hammer is useless. Don't get me wrong, it will run fine. It's just useless!





Negative.



The notch on a simi-auto hammer is there to catch the the ring on the firing pin to stop foreward movement of the carrier to prevent out of battery ignition of the round in case of disconnector failure. M16 have the benefit of an auto 'safety' sear to prevent this from occuring, therefore the notch is not needed. This is why the ring on an M16 firing pin is smaller than on a AR pin.



It's there for a REASON in a 5.56 simi-auto application.
Krylancelo  [Team Member]
12/17/2010 10:11:09 AM

Originally Posted By fook:
Negative.



The notch on a simi-auto hammer is there to catch the the ring on the firing pin to stop foreward movement of the carrier to prevent out of battery ignition of the round in case of disconnector failure. M16 have the benefit of an auto 'safety' sear to prevent this from occuring, therefore the notch is not needed. This is why the ring on an M16 firing pin is smaller than on a AR pin.



It's there for a REASON in a 5.56 simi-auto application.

This should already not be possible due to the design of the bolt carrier and bolt. When the bolt is NOT fully seated in the carrier (in battery), the firing pin cannot travel far enough to even extend outside of the bolt channel. This is prevented by the body of the bolt carrier itself and is part of the design of the AR15 rifle.

Edited to correct previously posted incorrect information.
Gregory_K  [Team Member]
12/17/2010 10:18:42 AM
Originally Posted By Krylancelo:

Originally Posted By fook:
Negative.



The notch on a simi-auto hammer is there to catch the the ring on the firing pin to stop foreward movement of the carrier to prevent out of battery ignition of the round in case of disconnector failure. M16 have the benefit of an auto 'safety' sear to prevent this from occuring, therefore the notch is not needed. This is why the ring on an M16 firing pin is smaller than on a AR pin.



It's there for a REASON in a 5.56 simi-auto application.

This should already not be possible due to the design of the bolt carrier and bolt. When the bolt is NOT fully seated in the carrier (in battery), the firing pin cannot travel far enough to even extend outside of the bolt channel. The only time it can is if the firing pin retainer is severely bent, broken, or missing.

Out of battery firing is impossible regardless of the hammer type used if the retaining pin is not damaged.


retaining pin sits behinde the firing pin. it does squat to stop what you are talking about. Think about the bolt and bolt carrier and the caming action and how the combo gets shorter when in battery.
CB1  [Team Member]
12/17/2010 10:36:18 AM

Originally Posted By fook:
Originally Posted By js308:
Originally Posted By Blain:
What are the pros and cons of each? Which do the actual GI rifles have?


A GI version would be a rounded hammer with a hook on the end for the auto sear.
The closest you would be able to get with a semi auto lower is a rounded hammer, minus the auto hook.
The notched hammer is useless. Don't get me wrong, it will run fine. It's just useless!

Negative.

The notch on a simi-auto hammer is there to catch the the ring on the firing pin to stop foreward movement of the carrier to prevent out of battery ignition of the round in case of disconnector failure. M16 have the benefit of an auto 'safety' sear to prevent this from occuring, therefore the notch is not needed. This is why the ring on an M16 firing pin is smaller than on a AR pin.

It's there for a REASON in a 5.56 simi-auto application.

all that is good in theory, it does not work in real life. a disconnector failure on a old SP2 caused a 3 round burst. Neither the notch in the hammer or the exposed firing pin collar prevented the burst.




Krylancelo  [Team Member]
12/17/2010 11:00:43 AM

Originally Posted By Gregory_K:
retaining pin sits behinde the firing pin. it does squat to stop what you are talking about. Think about the bolt and bolt carrier and the caming action and how the combo gets shorter when in battery.

You are correct, my mistake. I misquoted some information I read. Here is the correct information, previously posted by Molon.

Originally Posted By Molon @ http://www.ar15.com/forums/topic.html?b=3&f=118&t=518619&page=2:
Here is an excellent picture from Ned Christiansen showing why an OOB firing is next to impossible with an AR-15. In the picture below, the bolt is completely locked in battery, but the bolt carrier has not quite yet fully seated. You can clearly see in the picture that the firing pin is not even close to coming into contact with the primer. In Ned Christiansen's own words, the "firing pin is blocked from contacting the primer by a step in the carrier that stops the firing pin's flange. Again–– bolt is completely locked and FP cannot touch the primer. Misses it by a long shot, by design."




Originally Posted By Molon @ http://www.ar15.com/forums/topic.html?b=3&f=118&t=518619&page=3:
Yet another example of people posting BS in a technical thread without the slightest bit of factual data to support what they are saying. A cartridge in an AR-15 doesn’t fire simply because you can "squeeze the trigger and hear a click.” The cartridge fires when the firing pin strikes the primer with enough force to ignite it. You can "pull the charging handle back 1/2 inch, then squeeze the trigger” all day long and the cartridge is not going to fire BECAUSE THE FIRING PIN CAN NOT PHYSICALLY COME INTO CONTACT WITH THE PRIMER AT THAT POINT.

The picture below shows the bolt in the position it would be in if you had pulled back on the charging handle, not even "1/2 an inch”, but only 1/4 of an inch. The firing pin has been pushed as far forward as it will go and you can clearly see that THE FIRING PIN DOES NOT EVEN PROTRODE FROM THE FIRING PIN HOLE AT THIS POINT, let alone protrude far enough forward that it would be able to effectively strike the primer. The firing pin is blocked from moving any farther forward. As I quoted Ned Christansen previously, the "firing pin is blocked from contacting the primer by a step in the carrier that stops the firing pin's flange. Again–– bolt is completely locked and FP cannot touch the primer. Misses it by a long shot, by design."





.....


The firing pin is stopped by the body of the bolt carrier itself, so that it is impossible for it to fire out of battery. The firing pin cannot physically reach the primer if it is out of battery and the bolt is not locked in completely to the carrier.


Originally Posted By CB1:
all that is good in theory, it does not work in real life. a disconnector failure on a old SP2 caused a 3 round burst. Neither the notch in the hammer or the exposed firing pin collar prevented the burst.

This is a completely different problem than what he was referring to. He was talking about out of battery firing, not multiple firings per trigger pull.
Krylancelo  [Team Member]
12/17/2010 11:28:31 AM

Originally Posted By fook:
Negative.



The notch on a simi-auto hammer is there to catch the the ring on the firing pin to stop foreward movement of the carrier to prevent out of battery ignition of the round in case of disconnector failure. M16 have the benefit of an auto 'safety' sear to prevent this from occuring, therefore the notch is not needed. This is why the ring on an M16 firing pin is smaller than on a AR pin.



It's there for a REASON in a 5.56 simi-auto application.

I did also want to mention that I believe in a quality fully shrouded bolt carrier, the firing pin is not exposed enough for the hammer notch to make contact with enough of the pin to stop it.

I could be wrong but on my shrouded carriers the firing pin just barely sticks out.
fook  [Team Member]
12/17/2010 1:17:00 PM
The info I posted was taken from "The Black Rifle II", pg.310-311.





If you feel it is incorrect, please take it up with the author.
cmeyer001  [Team Member]
12/17/2010 1:26:10 PM
The notched hammers only work with the early design semi auto carriers as produced by Colt. ( possibly some others out there)

If you use a full auto carrier in your AR ( as a lot of folks seem to do ), the notched hammer can not physically work as designed and is therefore unnecessary.



If your carrier looks like the top 2, the notched hammer will function as designed, if your carrier looks like the bottom carrier, the notched hammer can not provide it's designed for function ( other than igniting the primer )
fook  [Team Member]
12/17/2010 2:57:34 PM
Sorry guys, I wrote "out of battery" when I should have said "slam fire"...




halfmoonclip  [Member]
12/17/2010 10:04:05 PM
It is my understanding that the notched hammer/unshrouded firing pin was another 'belt and suspenders' thing that Colt did to avoid full auto fire in a rifle that was not meant to be full auto. (Same school of thought as the 1.70 FCG pins and the nonstandard pivot pin; I like Colt rifles, but they ought to move the factory the hell out of Connecticutistan.)
The notch and firing pin collar were to get tangled with each other if the hammer followed the bolt carrier forward, due to a broken (or more likely) altered sear engagement. I don't know if anyone actually did the 'file the sear if you want a full auto' bullshit, but Colt was determined to keep it from happening.
In actual use, it is still possible for the firing pin collar and the notch to somewhat engage each other in an unshrouded BC; this can lead to mangled firing pin retaining pins.
You want a shrouded BC and a rounded hammer, period.
Moon
js308  [Member]
12/17/2010 10:26:45 PM
Originally Posted By fook:
Originally Posted By js308:
Originally Posted By Blain:
What are the pros and cons of each? Which do the actual GI rifles have?


A GI version would be a rounded hammer with a hook on the end for the auto sear.
The closest you would be able to get with a semi auto lower is a rounded hammer, minus the auto hook.
The notched hammer is useless. Don't get me wrong, it will run fine. It's just useless!





Negative.



The notch on a simi-auto hammer is there to catch the the ring on the firing pin to stop foreward movement of the carrier to prevent out of battery ignition of the round in case of disconnector failure. M16 have the benefit of an auto 'safety' sear to prevent this from occuring, therefore the notch is not needed. This is why the ring on an M16 firing pin is smaller than on a AR pin.



It's there for a REASON in a 5.56 simi-auto application.



Negative.
You must be running the old unshrouded bolt carriers.
Shrouded carriers don't make hammer/firing pin contact.
I will stick with my original "useless" statement.
DBR  [Member]
12/18/2010 1:04:21 AM
The notched hammer in combination with the relieved carrier prevents firing by hammer follow.
Nichonator  [Team Member]
12/18/2010 8:00:30 AM
Good info.
CB1  [Team Member]
12/18/2010 9:13:57 AM

Originally Posted By Krylancelo:

Originally Posted By Gregory_K:
retaining pin sits behinde the firing pin. it does squat to stop what you are talking about. Think about the bolt and bolt carrier and the caming action and how the combo gets shorter when in battery.

You are correct, my mistake. I misquoted some information I read. Here is the correct information, previously posted by Molon.

Originally Posted By Molon @ http://www.ar15.com/forums/topic.html?b=3&f=118&t=518619&page=2:
Here is an excellent picture from Ned Christiansen showing why an OOB firing is next to impossible with an AR-15. In the picture below, the bolt is completely locked in battery, but the bolt carrier has not quite yet fully seated. You can clearly see in the picture that the firing pin is not even close to coming into contact with the primer. In Ned Christiansen's own words, the "firing pin is blocked from contacting the primer by a step in the carrier that stops the firing pin's flange. Again–– bolt is completely locked and FP cannot touch the primer. Misses it by a long shot, by design."


http://www.box.net/shared/static/6epemebg1j.jpg

Originally Posted By Molon @ http://www.ar15.com/forums/topic.html?b=3&f=118&t=518619&page=3:
Yet another example of people posting BS in a technical thread without the slightest bit of factual data to support what they are saying. A cartridge in an AR-15 doesn’t fire simply because you can "squeeze the trigger and hear a click.” The cartridge fires when the firing pin strikes the primer with enough force to ignite it. You can "pull the charging handle back 1/2 inch, then squeeze the trigger” all day long and the cartridge is not going to fire BECAUSE THE FIRING PIN CAN NOT PHYSICALLY COME INTO CONTACT WITH THE PRIMER AT THAT POINT.

The picture below shows the bolt in the position it would be in if you had pulled back on the charging handle, not even "1/2 an inch”, but only 1/4 of an inch. The firing pin has been pushed as far forward as it will go and you can clearly see that THE FIRING PIN DOES NOT EVEN PROTRODE FROM THE FIRING PIN HOLE AT THIS POINT, let alone protrude far enough forward that it would be able to effectively strike the primer. The firing pin is blocked from moving any farther forward. As I quoted Ned Christansen previously, the "firing pin is blocked from contacting the primer by a step in the carrier that stops the firing pin's flange. Again–– bolt is completely locked and FP cannot touch the primer. Misses it by a long shot, by design."


http://www.box.net/shared/static/ier8xqr6bt.jpg


.....


The firing pin is stopped by the body of the bolt carrier itself, so that it is impossible for it to fire out of battery. The firing pin cannot physically reach the primer if it is out of battery and the bolt is not locked in completely to the carrier.


Originally Posted By CB1:
all that is good in theory, it does not work in real life. a disconnector failure on a old SP2 caused a 3 round burst. Neither the notch in the hammer or the exposed firing pin collar prevented the burst.

This is a completely different problem than what he was referring to. He was talking about out of battery firing, not multiple firings per trigger pull.

yes and no. one leads to the other. and it does not work regardless. exposed firing pin carriers and notched hammers are worthless PC garbage
pun  [Member]
12/18/2010 9:31:30 AM
I love rounded hammers,nice and smooth.I got 5 here on the EE a year ago.They were Colt M16 hammers with the FA notch ground off so they were good quality too.I have a couple of DPMS rounded hammers and they work fine too.
iNeXile556  [Team Member]
12/18/2010 9:32:01 AM
So after all this there is still no answer to the original question.

It seems that without the carrier designed to utilize the notch is is simply unnecessary, but not at all detrimental to the operation of the firearm.

On the other hand the rounded hammer would not allow the original design feature to work if used with an unshrouded type carrier.
But would still fire the weapon just fine.

Therefore the only real answer would be if you have an unshouded carrier and would like to utilize the original design intent then use a notched hammer. If not then personal preference is the deciding factor.

With a shrouded firing pin or a FA carrier the notched or rounded hammer is equally suited to perform the function intended.

Does that about sum it up? Can anyone site a real benefit of the rounded hammer?
1saxman  [Member]
12/18/2010 10:38:19 AM
'this can lead to mangled firing pin retaining pins.'

Completely true as is the original Colt reason for the notched hammer on commercial ARs. And, mangled retaining pins can break and allow the FP to fall out, which means the gun blows up on the next shot. If you run the old carrier and a notched hammer, check for bent retainer pin. If it's bent, the notch is grabbing the FP and may eventually cause a catastrophic failure. I don't think you can fix the notched hammer by grinding off the notch, either. Replace it with a non-notched hammer. Seems like I remember when this has been discussed many times over the years that a M16 firing pin with smaller head can prevent notch grab, but that is speculation.
LimaTango01  [Team Member]
12/18/2010 11:22:14 AM

Originally Posted By iNeXile556:
Can anyone site a real benefit of the rounded hammer?


Let's just call this conjecture; to stem the onslaught...


1.The original hammer was rounded, both on the M-16 and the AR-15 ( SP1's). This, apparently, from an engineering stand point, was the correct design.

2. Colt made then change to notched for political reasons.

3. Specialized Armament, when performing reliability packages installs the Type I (rounded) hammer. It also is standard in all of their special production pieces. SAW knows their business.

...I say a steel part has less resistance when moving across a radius surface than when moving across an angular one. Every little reduction in resistance adds up to a more reliable weapon. Plain and simple.
iNeXile556  [Team Member]
12/18/2010 11:23:38 AM

Originally Posted By 1saxman:
'this can lead to mangled firing pin retaining pins.'

.... mangled retaining pins can break and allow the FP to fall out, which means the gun blows up on the next shot.

How does the FP falling out, meaning it cannot strike the primer, lead to the gun blowing up?
iNeXile556  [Team Member]
12/18/2010 11:38:17 AM

Originally Posted By LimaTango01:

Originally Posted By iNeXile556:
Can anyone site a real benefit of the rounded hammer?


Let's just call this conjecture; to stem the onslaught...


1.The original hammer was rounded, both on the M-16 and the AR-15 ( SP1's). This, apparently, from an engineering stand point, was the correct design.

2. Colt made then change to notched for political reasons.

3. Specialized Armament, when performing reliability packages installs the Type I (rounded) hammer. It also is standard in all of their special production pieces. SAW knows their business.

...I say a steel part has less resistance when moving across a radius surface than when moving across an angular one. Every little reduction in resistance adds up to a more reliable weapon. Plain and simple.
I will concede on the resistance point. On the use of rounded hammer by SAW or others using a shrouded carrier, I point out that given the notch is not used it is one less step in the machining of the part. Therefore the use of the a rounded hammer may come from a cost reduction in manufacturing than from any other consideration.


ETA: I use Geissele triggers which use their own hammers. They are neither notched or rounded. They seem to work just dandy. And Geissele too "knows their business".
LimaTango01  [Team Member]
12/18/2010 12:12:26 PM

Originally Posted By iNeXile556:

Originally Posted By LimaTango01:

Originally Posted By iNeXile556:
Can anyone site a real benefit of the rounded hammer?


Let's just call this conjecture; to stem the onslaught...


1.The original hammer was rounded, both on the M-16 and the AR-15 ( SP1's). This, apparently, from an engineering stand point, was the correct design.

2. Colt made then change to notched for political reasons.

3. Specialized Armament, when performing reliability packages installs the Type I (rounded) hammer. It also is standard in all of their special production pieces. SAW knows their business.

...I say a steel part has less resistance when moving across a radius surface than when moving across an angular one. Every little reduction in resistance adds up to a more reliable weapon. Plain and simple.
I will concede on the resistance point. On the use of rounded hammer by SAW or others using a shrouded carrier, I point out that given the notch is not used it is one less step in the machining of the part. Therefore the use of the a rounded hammer may come from a cost reduction in manufacturing than from any other consideration.


ETA: I use Geissele triggers which use their own hammers. They are neither notched or rounded. They seem to work just dandy. And Geissele too "knows their business".

I am not familiar with those FCP but at the point that the carrier contacts the hammer; that point is not radiused?
cmeyer001  [Team Member]
12/18/2010 2:44:55 PM
Geissele DMR Trigger

It is radiused, not as much as the rounded hammer, but much closer to the profile of a "rounded" hammer vs the notched hammer. Also, keep in mind the Geissele has much less mass in the hammer, this has an effect in the design as well.

AR15 "rounded" hammer

Checkout the rounded hammer for comparison.

This may be going off topic.
iNeXile556  [Team Member]
12/18/2010 5:25:45 PM
Hard to say, You make the call.

Comparing my Geissele hammer with a notched hammer from a Armalite LPK, I say the radius of the contact surfaces to be about the same. I could see a problem if the hammer was sharp but I can't think of any hammer that doesn't have at least a slight radius at the bearing surface.

I think the notch is useless however I don't think it is in anyway detrimental to the operation, longevity or reliability of the firearm.






As a disclaimer this is not a Armalite hammer although it looks identical to the one I have in a Armalite LPK.
js308  [Member]
12/21/2010 5:01:24 AM
Just to add

Full Auto Hammer:


Semi Auto Hammer:


Notched, Semi Auto Hammer:


Gregory_K  [Team Member]
12/21/2010 7:07:52 AM
Originally Posted By iNeXile556:

Originally Posted By 1saxman:
'this can lead to mangled firing pin retaining pins.'

.... mangled retaining pins can break and allow the FP to fall out, which means the gun blows up on the next shot.

How does the FP falling out, meaning it cannot strike the primer, lead to the gun blowing up?


+1
halfmoonclip  [Member]
12/21/2010 10:57:11 AM
Originally Posted By Gregory_K:
Originally Posted By iNeXile556:

Originally Posted By 1saxman:
'this can lead to mangled firing pin retaining pins.'

.... mangled retaining pins can break and allow the FP to fall out, which means the gun blows up on the next shot.

How does the FP falling out, meaning it cannot strike the primer, lead to the gun blowing up?


+1

Yeah, I was a little puzzled at that....
When withdrawing the BCG with the charging handle in an unshrouded/notched gun, it is often possible to feel the notch passing over parts inside; no harm, no foul if it is just the ramped secition of the unshrouded BC, but the trouble comes if it is dragging on the FP collar. For the risk of a bent or broken firing pin retaining pin (broken bits down in the action, firing pin actually escaping the carrier) and attendant jams, the notched hammer just isn't worth the hassle.
As I stated before, the whole notched system resulted from Colt erring on the side of extreme caution regarding civilian full auto conversion attempts...even Old Mother Hubbard Colt has stopped worrying about it, (reverting to full circle shrouded carriers and rounded hammers) and so should we.
Moon

dogbutter99  [Member]
12/21/2010 1:29:57 PM
i have a DPMS hammer that seems to be bit longer than others.. so it drags on the bolt more than my other kits.. i also have a notched hammer that seems to drag alot less.. then i have other hammers that drags very little and is a round one.

knowing that i won't be using .22 or 9mm conversion.. and chance of less drag (even though it does not affect operation).. i may choose a notched hammer..

the drag does not affect function.. but when i am practicing charging.. the drag on this particular rifle gets on my nerves.
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