LMT Hammer for 9mm Upper

[SnoopDoug]

Hey guys, I just ordered a RRA 9mm A4 upper and I was wondering will the hammer in my Defender work? I read a few posts on ARFCOM saying a DPMS or Sporter style hammer, which my LMT appears to have, will function fine but experiences "trigger slap". What is "trigger slap"?

Thanks.

[Azrael2004]

"Hammer slap" is a result of the hammer being reset too quickly, ie slapped down.
An un-ramped 9mm bolt resets the hammer in about 1/2" of bolt travel, whereas a ramped bolt resets in in about 1 1/2" of travel. This eases the hammer to the reset position.

If your hammer has a square notch cut out of the top front face of the hammer it will bind up an un-ramped 9m bolt. (Ask me how I know. )
Look here http://biggerhammer.net/ar15/hammers/ for a good comparison.
If yours does not look like the one in the top row center then you need to get one like that or a 9mm hammer.
DPMS makes one like this or you can get an M16 hammer and cut off the tail in the rear. (Examples are first 2 in 2nd row)
If your bolt is not ramped (does not come from RRA ramped) the 9mm hammer will reduce the slap a bit.
With the un-notched 5.56 hammer it gets slapped down quite fast.
If you have the bolt ramped you will likely need the DPMS style hammer as the 9mm hammers are not reliable with a ramped bolt.

[SnoopDoug]

Cool, looks like my hammer will do. I just need to have my bolt ramped. How does one go about ramping the bolt?

[SnoopDoug]

NM, saw it in another post. Thanks.

[502adamh]

I have a LMT 2-stage trigger group in my Rifle with a RRA bolt (9mm), We had to file down the corner of the hammer to prevent binding when it cycles but works very well. What is the result (symptoms) of "Hammer Slap"? How do you know that it is happening?

[vinesr6]

Send your bolt to ADCO for ramping..$35.

[Azrael2004]

I have a LMT 2-stage trigger group in my Rifle with a RRA bolt (9mm), We had to file down the corner of the hammer to prevent binding when it cycles but works very well. What is the result (symptoms) of "Hammer Slap"? How do you know that it is happening?

You start breaking fire control pins. Or sometimes they just 'springboard' their way out.