Just because you can, doesn't mean you should. Moreover, telling someone that an extension can be modified, while not a lie, is nothing more than mental masturbation when your post contains a caveat for having the knowledge and proper tools.
There is more than a mythological difference between rifle and carbine barrel extensions. Using a rifle barrel in a carbine upper receiver is asking for trouble even if the barrel extension has been "modified" to fit. While you have purportedly seen it done many, many times and claim that it works 100% of the time, your experience is a statistical outlier. Having worked in the industry for many years, the last four at Specialized Armament, I can assure you that most mods that deviate from the original design aren't 100% reliable. There is a reason Colt manufactures two different barrel extensions.
There is no way to modify the ramps on a rifle barrel extension and maintain the feed ramp angle without removing a significant amount of material. The delta is going to change whether you intended it to happen or not. Reliability is going to be sacrificed and the more than likely the structural integrity of the barrel extension.
Socal, how did you get from here:
To here:
Trying to connect the dots...
That is a great sketch showing the difference between rifle and M4 extensions!
Well first off, this is how you connect the dots (a joke) :
I just considered the dremel option after I read this is how a few smiths actually do the modification, and thought it might be a ok way to get it done without a mill setup:
Straight from ADCO's website:
Add M4 cuts to Barrel Ext $15.00
We can modify your rifle extension to match the M4 cuts in an upper receiver. All we do is dremmel it to match - we dont remove it and grind to any specific angle. In short, if you have a Dremmel you can do it yourself.
Second you completely and entirely missed the point of this thread…. see title : Upper Receiver WITHOUT M4 Feed Ramp Cuts?
I DID NOT want to modify the feed ramps and was having a difficult time finding a receiver without M4 cuts since extended M4 cuts are soooo stupidly popular now….
Third, brother, you certainly can successfully modify a rifle extension… reputable companies offer the service, thousands of people have done it themselves…. Also, I never ever claimed to have seen shit, I claimed to have done one such modification on a little Bridgeport mill a few years back for a buddy who was in a similar situation…. It came out perfect, I would guarantee to your professional gunsmith discerning eye that you could not tell the difference between my modified rifle extension and a true m4 extension. I guess if you are used to a coloring book and crayons that this sort of modification would indeed seem mythical, but finding angles, making cuts, and inspecting are all very doable operations.
I can assure you that most mods that deviate from the original design aren't 100% reliable
Original design? What original design???? Eugene Stoner's original design?? M4 feed ramps are not an original design, they were designed for the M4… In fact, the only reason to modify the feed ramps on a rifle extension fitted to a M4 cut upper is to remove the sharp edge of the ramp that ***could*** potentially catch a bullet. Would I want to use a modified weapon on combat? Probably not…. Am I in combat? No. Will any of my rifles ever be use in combat? Nope. For a civilian rec. shooter, like most of us are, this modification is not a big deal, a degree or 2 off on the feed ramp and I would bet dollars to doughnuts that the rifle would function just fine. But what do I know…. this firearm engineering is way over my head…. I'll stick to them metal contraptions that people trust their lives with that fly overhead at 30k feet.
I got my help from this thread, and thank you again to ORD.
-SOCAL out.