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aghauler
03-06-2012, 8:54 AM
I've seen reference to having to change the hammer in the AR 15 lower for use with the 9mm UPPER. Is this really necessary? Seems like it would defeat the "quick interchangablitiy" of different caliber uppers. :confused:

jchen76@gmail.com
03-06-2012, 9:21 AM
If it uses cmmg 9mm upper, no hammer change needed. If you are using rock river arms uppers you need a notched hammer or ramp the RRA 9mm bolt. Either way you'll need a conversion block for your standard ar lower unless you buy a 9mm specific ar lower.

aghauler
03-06-2012, 9:24 AM
If it uses cmmg 9mm upper, no hammer change needed. If you are using rock river arms uppers you need a notched hammer or ramp the RRA 9mm bolt. Either way you'll need a conversion block for your standard ar lower unless you buy a 9mm specific ar lower.

Thanks for the clarification on the hammers. What about the JSE Surplus 9mm uppers? Any idea if a hammer change is needed for them?

jchen76@gmail.com
03-06-2012, 9:29 AM
Appears they sell the RRA system. A 9mm specific hammer is recommended or you can buy/smith a ramped bolt. I've never ramped a bolt when I had a RRA 9mm rifle.

TMC
03-06-2012, 9:41 AM
Olympic (http://olyarms.net/index.php?option=com_virtuemart&page=shop.browse&category_id=12&Itemid=5&vmcchk=1&Itemid=5) uppers do not require any changes to the lower, just put it on the 223 lower and go.

aghauler
03-06-2012, 12:17 PM
Just got a reply from JSE Surplus regarding their 9mm UPPER. Here it is:

"The upper is completely ready to install and use. You will need a mag block for your lower and you will need a non notched hammer to insure the upper will function on your lower."

My Bushmaster LOWER has what I assume is the "notched" hammer, a 90 degree cutout of the top front face. So I have would have to change this to a flat faced hammer? Would this flat faced, no notch hammer work ok with my A1 and A2 5.56 UPPERS? :confused:

fredr1980
03-06-2012, 10:15 PM
Just got a reply from JSE Surplus regarding their 9mm UPPER. Here it is:

"The upper is completely ready to install and use. You will need a mag block for your lower and you will need a non notched hammer to insure the upper will function on your lower."

My Bushmaster LOWER has what I assume is the "notched" hammer, a 90 degree cutout of the top front face. So I have would have to change this to a flat faced hammer? Would this flat faced, no notch hammer work ok with my A1 and A2 5.56 UPPERS? :confused:

Just get a rounded DPMS hammer... it will work on the 9MM JSE upper with their rampped bolt along with any other upper you have.

Fred R.

Sicarius
03-07-2012, 8:33 AM
The 223 rounded hammer is meant for the ramped bolt. CMMG and spikes utilize the ramped bolt. RRA in the past used the original colt design that needed a dedicated 9mm hammer. That might have changed by now though.
Kevin

aghauler
03-07-2012, 9:33 AM
Just get a rounded DPMS hammer... it will work on the 9MM JSE upper with their rampped bolt along with any other upper you have.

Fred R.


Thanks Fred that's an easy fix!

"The 223 rounded hammer is meant for the ramped bolt. CMMG and spikes utilize the ramped bolt. RRA in the past used the original colt design that needed a dedicated 9mm hammer. That might have changed by now though.
Kevin "

Looks like from JSE's earlier reply it seems they no longer require a notched hammer now, so they must have updated their design.

Thanks to all for the replies and suggestions! :)