Notched or Rounded Hammer

[BertBettcher]

What are the differences between the notched and the rounded hammer. I have a notched hammer on my M&P15 and I was thinking of using a CMMG 22 conversion kit. However CMMG says that the conversion kits are not recommended for notched hammers.

Will installing a rounded hammer fix this problem and will the rounded hammer affect my M&P15 when I shoot .223 ammo.

Appreciate your help........

[DialTone301]

I had to change the notched hammer in my RRA for my Spikes kit to work. It now works flawlessly.

[pacrimguru]

rounded hammers are required for many .22LR and most 9mm conversions. they will not affect you shooting .223.

[NCHornet]

I was recently trying to ID the manufacturer of the Hammer in my Colt MT6700 and I was told that Colt is one of the few companies using the notched hammers. But it seems this isn't true. How many manufacturers use a notched hammer that you are aware of? What is the difference? What purpose does the notch provide?
Thanks
NCH

[BertBettcher]

Good question..........what is the purpose of the notched hammer??????

[baffle Stack]

I think they're meant to bind on non-shrouded carriers. Some kind of half baked safety feature, but that's just a guess.

[MarkG]

I think they're meant to bind on non-shrouded carriers. Some kind of half baked safety feature, but that's just a guess.

Non-shrouded carriers with full auto firing pins. The notched hammers (Type II) are slightly shorter than rounded (Type I) hammers to clear the sear block.

Some say the Type I hammer allows the bolt group to cycle smoother.

[BertBettcher]

My M&P15 came with a shrouded carrier and a notched hammer.......so I'm assuming I can switch to a rounded hammer without any problems????

[baffle Stack]

I can't think of any downsides with going to a rounded hammer. You should be good to go.

[BertBettcher]

Thanks to everyone for your advise and input.....appreciate your help......