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M4 Hammer/Bolt Wear


jsn124
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Hey All,

 

I'm hoping to see if this "wear" is normal on a new hammer I'm installing. I don't have all my 922r parts yet but wanted to see how the Geissele install would work out. Unfortunately I've had some other fit issues recently so I hope this works out.

 

After carefully installing the hammer (much thanks to StrangerDanger's very detailed thread with pics) I ran the bolt group back and forth maybe a dozen times carefully, well lubed on both the bottom of bolt group and hammer.

 

Its odd because at first it kind of "stuck" as the bolt group ran over the hammer. After doing this a few times it smoothed out.

 

However when I took out the trigger group I could see where the face of the hammer was rubbing the bottom of the bolt group on one side of the hammer only. Here are two detailed pics:

 

1. Hammer wear: hammer_wear

2. Bottom of Bolt group: bolt_bottom_2

 

Is this normal?

 

Now the only thing I can think of is somehow I botched the hammer install but I doubt it. I was very careful and only moved the trigger pin bushing out just enough to slip out the stock hammer and slip in the Giessele. After assembly I noticed when the hammer is released it does wiggle side to side ever so slightly but I believe the stock hammer does this also.

 

Finally the only other culprit I can even begin to imagine is that the Sidearmor top rail I have installed has the screws down too tight putting pressure on the bolt group downwards. But I don't see any unusual wear where the bolt group meets the receiver.

 

You can literally see just the one side of where the hammer is rubbing the bolt group bottom. I doubt it will hurt things but I don't want to run this eventually and cause significant damage.

Edited by jsn124
fix part terminology
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Thanks Unobtanium. I'm holding the trigger group right now. Its definitely not a chip but I see how it would come off that way in the photo. Sorry for the bad angle.

 

That silver spot is perfectly smooth with the face of the hammer and rest of the surrounding area. In fact its polished perfectly smooth. If I run my finger nail over it it doesn't catch in any way.

 

It basically looks like as the bolt runs over the hammer it is rubbing enough to polish away the black finish. I see wear on the stock hammer but not so much one sided which was odd.

 

So I guess I can proceed as normal?

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Thanks Unobtanium. I'm holding the trigger group right now. Its definitely not a chip but I see how it would come off that way in the photo. Sorry for the bad angle.

 

That silver spot is perfectly smooth with the face of the hammer and rest of the surrounding area. In fact its polished perfectly smooth. If I run my finger nail over it it doesn't catch in any way.

 

It basically looks like as the bolt runs over the hammer it is rubbing enough to polish away the black finish. I see wear on the stock hammer but not so much one sided which was odd.

 

So I guess I can proceed as normal?

 

Correct. I don't run an OEM hammer, but I do have my old one. I looked at it and it does show a right-side wear bias similar to yours, as well as the polishing. I am guessing by the look of mine and knowing how few rounds is through it, especially before I swapped hammers, that your M4 is VERY low round-count as of that picture you took.

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Ditto. Looks like normal wear to me.

 

Shiny wear marks crave a little grease. ;)

 

Thanks XTrooper! Yes, I agree with that for sure. I'm not gunsmith by a long shot but I consider myself competent enough to do this replacement (still waiting on other 922 parts). Appreciate the feedback as always!

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Correct. I don't run an OEM hammer, but I do have my old one. I looked at it and it does show a right-side wear bias similar to yours, as well as the polishing. I am guessing by the look of mine and knowing how few rounds is through it, especially before I swapped hammers, that your M4 is VERY low round-count as of that picture you took.

 

Yes, at this point about 25 00 buck shells? :( sad I know! It's been a busy month.

 

What concerned me was the wear on the hammer in the picture is the Giessele I installed late last night and only hand cycled the bolt maybe a dozen or so times. I probably should have lubed much more than I did which is probably a culprit as already pointed out by XTrooper.

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It's called brunishing. The hammer and the bottom of the bolt are steel. Both parts will polish themselves together over time. It's a completely normal and desired effect. Both surfaces will have a polished face perfect for a small amount of grease. After 12000 rounds, no material was removed from either the hammer or the carrier on mine.

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Thanks SD! I agree that the effect is nice and I was only ever concerned since I installed the hammer myself. But in the end it was a very easy procedure. Btw your step by step pictorial thread was amazing and really a great contribution to the Benelli forum community.

 

Again, I appreciate everyone's feedback. If anything I hope this thread serves as a simple reminder:

 

1. Installing aftermarket hammer is straightforward: http://www.benelliusa.com/forum/showthread.php/29526-Benelli-M4-Trigger-Disconnector-and-Hammer-Disassembly

2. Wear on the hammer face / bolt bottom is burnishing and normal / desired.

3. Keep it greased.

4. Enjoy!

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