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Posted: 8/11/2007 5:36:53 PM EDT
In the not too distant future I hope to build a SBR 9mm flattop upper and will naturally need a 9mm bolt assembly.

As far as 9mm bolt assemblies go, could I get a quick education?

It appears that the RRA and the CMMG are both in the $150 range. Are these decent quality? I have read on the forum about people "ramping" their bolts? Is this a modification of some type, and is it necessary or desirable for some reason?

Now on Specialized Armament's website they have two Colt 9mm bolt assemblies. One simply says 9MM SMG (submachine gun no doubt) and the other says 9MM SMG - IMPROVED MODIFIED COCKING ANGLE, TUNGSTEN WEIGHT. They are $329 and $395 respectively. Now What is the difference between these two bolts. Next why would I want to pay more than double for one of these Colts over a RRA or a CMMG bolt? Does the Colt 6450 come with one of these two SMG bolts or is their a different bolt for a semi-auto version? I have a friend with a 6450. Is there a way for me to look at the bolt in his gun and tell what bolt he has?

Are their any other brands of 9mm bolt assemblies to consider?

Answers to any or all of these questions or any additional information would be appreciated.

Thanks!
Link Posted: 8/11/2007 9:05:14 PM EDT

Originally Posted By tacman556:

It appears that the RRA and the CMMG are both in the $150 range. Are these decent quality?

I have a couple of RRA bolt assemblies in use now. They work great.

I have read on the forum about people "ramping" their bolts? Is this a modification of some type, and is it necessary or desirable for some reason?

Ramping is required when you use a standard AR/M16 hammer. If you are using a 9mm hammer, ramping is not necessary.

Link Posted: 8/11/2007 9:20:39 PM EDT
[Last Edit: 8/11/2007 9:23:02 PM EDT by MGP]
Ramping is required when you use a standard AR/M16 hammer. If you are using a 9mm hammer, ramping is not necessary.


If you do a lot of shooting you will want to ramp your bolt if you have safe queen then dont worry about it.. If you dont you will break hammer pins and egg out the holes in your lower receiver. Using a 9mm hammer will have exess force applied to the hammer pin and the lower receiver. Mike
Link Posted: 8/11/2007 9:31:07 PM EDT

Originally Posted By MGP:
Ramping is required when you use a standard AR/M16 hammer. If you are using a 9mm hammer, ramping is not necessary.


If you do a lot of shooting you will want to ramp your bolt if you have safe queen then dont worry about it.. If you dont you will break hammer pins and egg out the holes in your lower receiver. Using a 9mm hammer will have exess force applied to the hammer pin and the lower receiver. Mike


So are you saying that an AR/M16 hammer should be used instead of the 9mm hammer?

Can a 9mm hammer be used with a ramped bolt?

Also, are the KNS anti-rotational pins helpful at all?
Link Posted: 8/11/2007 9:42:37 PM EDT

Originally Posted By Buck50:

Originally Posted By MGP:
Ramping is required when you use a standard AR/M16 hammer. If you are using a 9mm hammer, ramping is not necessary.


If you do a lot of shooting you will want to ramp your bolt if you have safe queen then dont worry about it.. If you dont you will break hammer pins and egg out the holes in your lower receiver. Using a 9mm hammer will have exess force applied to the hammer pin and the lower receiver. Mike


So are you saying that an AR/M16 hammer should be used instead of the 9mm hammer?

Can a 9mm hammer be used with a ramped bolt?

Also, are the KNS anti-rotational pins helpful at all?


You need to use a DPMS no-notch hammer with a ramped bolt and no a 9mm hammer will not work with a ramped bolt.KNS pins will break without the bolt being ramped. Mike
Link Posted: 8/11/2007 9:48:01 PM EDT

Originally Posted By MGP:

Originally Posted By Buck50:

Originally Posted By MGP:
Ramping is required when you use a standard AR/M16 hammer. If you are using a 9mm hammer, ramping is not necessary.


If you do a lot of shooting you will want to ramp your bolt if you have safe queen then dont worry about it.. If you dont you will break hammer pins and egg out the holes in your lower receiver. Using a 9mm hammer will have exess force applied to the hammer pin and the lower receiver. Mike


So are you saying that an AR/M16 hammer should be used instead of the 9mm hammer?

Can a 9mm hammer be used with a ramped bolt?

Also, are the KNS anti-rotational pins helpful at all?


You need to use a DPMS no-notch hammer with a ramped bolt and no a 9mm hammer will not work with a ramped bolt.KNS pins will break without the bolt being ramped. Mike


OK, got it. Thanks for clearing this up.

BTW, who does bolt ramping? Who do you recommend?
Link Posted: 8/11/2007 9:52:19 PM EDT

Originally Posted By Buck50:

Originally Posted By MGP:

Originally Posted By Buck50:

Originally Posted By MGP:
Ramping is required when you use a standard AR/M16 hammer. If you are using a 9mm hammer, ramping is not necessary.


If you do a lot of shooting you will want to ramp your bolt if you have safe queen then dont worry about it.. If you dont you will break hammer pins and egg out the holes in your lower receiver. Using a 9mm hammer will have exess force applied to the hammer pin and the lower receiver. Mike


So are you saying that an AR/M16 hammer should be used instead of the 9mm hammer?

Can a 9mm hammer be used with a ramped bolt?

Also, are the KNS anti-rotational pins helpful at all?


You need to use a DPMS no-notch hammer with a ramped bolt and no a 9mm hammer will not work with a ramped bolt.KNS pins will break without the bolt being ramped. Mike


OK, got it. Thanks for clearing this up.

BTW, who does bolt ramping? Who do you recommend?

IM sent
Link Posted: 8/12/2007 9:49:49 AM EDT
OK so what hammer and bolt come on a factory Colt 6450 and are we saying that it will work fine or that it will wear out prematurely? And what if I put a CMMG or RRA bolt in a CMMG or RRA upper and put it on a factory Colt 6450 lower. Would this cause a problem of pins wearing out and breaking and receiver holes elongating? I am not sure I understand. I thought the 9mm AR was a tested and proven design. I mean the DEA and the Marshalls have used full auto ones for serious work with great success. What's the deal?
Link Posted: 8/12/2007 11:46:34 AM EDT

Originally Posted By tacman556:
OK so what hammer and bolt come on a factory Colt 6450 and are we saying that it will work fine or that it will wear out prematurely? And what if I put a CMMG or RRA bolt in a CMMG or RRA upper and put it on a factory Colt 6450 lower. Would this cause a problem of pins wearing out and breaking and receiver holes elongating? I am not sure I understand. I thought the 9mm AR was a tested and proven design. I mean the DEA and the Marshalls have used full auto ones for serious work with great success. What's the deal?



It will wear out prematurely if you do a lot of shooting. Ramping a bolt does two things takes the exess force off of the pins. Increases the rate of fire if shooting full auto.So ramp the bolt,use a DPMS no-notch hammer and a Q-Buffer from SLash and you will be good to go and will not have to worry about anything braking.One more thing using a Q-Buffer will also stop bolt catchs from breaking. Mike
Link Posted: 8/13/2007 4:32:22 PM EDT
btt

A lot of unanswered questions still in this thread...

Can anyone else chime in and help me out?

Thanks for all the help. I still have a lot to learn.
Link Posted: 8/13/2007 5:03:03 PM EDT
[Last Edit: 8/13/2007 5:06:35 PM EDT by JPN]

Originally Posted By tacman556:
btt

A lot of unanswered questions still in this thread...

Can anyone else chime in and help me out?

Thanks for all the help. I still have a lot to learn.



Almost all (unmodified) 'Colt style' 9mm bolt assemblies are the same ones that are used in the full-auto 9mm M-16's. I've read that there were a few semi-auto 9mm bolt assemblies made, but they are apparently rare.

Ramping changes the angle of the bolt surface that is used to push the hammer back and down to recock the hammer. An unramped(unmodified) bolt has a steeper angle to that surface, so it pushes the hammer down and back in a shorter amount of time (slaps the hammer harder). This puts more stress on the hammer pin, and could result in damage to the hammer pin and/or the hammer pin holes in the lower receiver. If you go through a case or two of ammo a month, you can expect to break something with an unramped bolt. If you go through a box or two of ammo a year, you might never have a problem with an unramped bolt.

Another problem with the unramped 9mm bolt is that it will hang on any hammer that has a notched face. The (semi-auto) 9mm hammer, the (full-auto) M-16 hammer, and the DPMS (semi-auto) AR-15 hammer all have a rounded upper corner on the front face, so they will function with an unramped 9mm bolt. "Match" hammers, such as the RRA 2 stage trigger group, will not work with an unramped bolt (the bolt will hang on the hammer and create a jam that will take some work to undo). Ramping a 9mm bolt may or may not allow it to work with "match" hammers - it all depends on the exact angle and depth of the ramp modification. The safest way to get a light trigger seems to be using a ramped bolt, a DPMS hammer, and a set of light trigger group springs.

RRA, Garrison, and Colt 9mm bolt assemblies are interchangeable. The only 9mm bolt assembly that is not compatible with the others, is the Oly.
Link Posted: 8/13/2007 7:36:17 PM EDT
So is the Colt bolt on Specialized Armament's website that says "9MM SMG - IMPROVED MODIFIED COCKING ANGLE, TUNGSTEN WEIGHT" a ramped bolt? Does "improved modified cocking angle" indicate ramping?

Also, what bolt does a newly manufactured Colt LE 6450 come with? If this is a known problem, does it come with a ramped bolt?

Thanks!
Link Posted: 8/13/2007 8:31:05 PM EDT

Originally Posted By tacman556:
If this is a known problem,



Known?

Probably.

Acknowledged as a problem worth the expense of redesign and retooling?

Well... If the DEA and Marshalls are using them with good results...
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