New upper reciever? > Build It Yourself

Posted: 2/4/2005 6:24:22 AM EDT

I am wanting to change the A2 upper on my Bushmaster 16in M4 Type Rifle, to an A3. Just ordered the tools from Brownells, but I am not sure which upper to use, I just got done reading the thread about the M4 feed ramps, and I want to make sure I get the right upper for my rifle. I guess I could just order from BM but I think I could get the same quality upper from somewhere else, I just want to make sure its going to work. Those with expeirence your input would be greatly appreciated.

Posted: 2/4/2005 7:00:17 AM EDT

[#1]

Your Bushmaster barrel will not have the M4 extension (99.99% chance that it won't). So you want a non-M4 receiver. CMT makes great receivers and you can get them from many of the vendors on this site. I've got one or two from GTS/Denny's Guns.

Posted: 2/4/2005 7:08:09 AM EDT

[#2]

This will answer all your questions....
Clearing up “M4 Feed Ramp” misinformation
You don't want a upper with M4 feedramps without a barrel extension to match.

Quoted:
Almost daily, I get someone asking if RRA uppers have “M4 feed ramps”. I honestly have to answer no. I then get a reply saying, so and so bought one from Brand X, and it had “M4 Feed Ramps”. Or, can you put “M4 Feed Ramps” in it?
NO, the upper your friend bought from Brand X, does not have “M4 Feed ramps”, and NO I cant add them, that would require heavily modifying the barrel extension.
Barrels are built with 2 types of barrel extensions. There are rifle barrel extensions, and there are M4/Carbine barrel extensions. Almost all of the complete commercial uppers sold have rifle barrel extensions. Colt, and LMT are the only I can thing of that use M4/Carbine extensions.
Here is a pic of the 2 extensions next to each other.

You can see the rifle extension, does not have nearly the pronounced feed ramps.

Here’s another pic from the bottom where it is much more obvious.

Here is an M4/Carbine barrel extension installed on a LMT upper receiver.

You can see upper was designed to accept this barrel extension, and there are “feed ramps” leading to the barrel extension.

Here is the common misconception:

This is a picture of a RRA upper receiver with a rifle barrel extension installed, that has been modified. The only thing accomplished in this picture was some of the protective hard coat anodizing was removed. This unfortunately, is what many people consider to be “M4 feed ramps”. They are not.

This is a properly installed rifle barrel extension in a WOA Upper that was built by John Holliger.

You can see the feed ramps in the barrel extension, come down to the receiver and end. There is absolutely no reason to modify anything. A lifetime of use can be had from this upper without a single FTF.

This is a rifle barrel extension installed in a upper with feed ramps. The less steep angle of the rifle extension, extends out past/over the feed ramps. If a cartridge fed into the feedramp, it would definitely get stuck on the extended portion of the rifle extension.

The next time someone tells you about their “M4 Feed Ramps”, or a dealer sells you an upper with “M4 Feed Ramps”, ask what barrel extension was used. I have a feeling 99% of the people out there who think they have “M4 Feed Ramps” have standard rifle extensions, with dremmeled receivers. Buy what you want, but know what you are getting.

Posted: 2/4/2005 8:54:20 AM EDT

[#3]

Thanks Mongo, so if I stay with any quality A3 upper, as long as it is not designated an M4 upper I should be ok? Thanks again

Posted: 2/4/2005 9:15:07 AM EDT

[#4]

txgp17. Very informative post from bigbore. Great, clear photos.

Colt_SBR

Posted: 2/4/2005 2:54:24 PM EDT

[#5]

Check out Del-Ton they have the best price I have seen on upper receivers.

Posted: 2/4/2005 4:50:09 PM EDT

[#6]

I got mine from bravocompanyusa.com ... go there..

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[ARCHIVED THREAD] - New upper reciever?

[ARCHIVED THREAD] - New upper reciever?