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Upper Receiver WITHOUT M4 Feed Ramp Cuts?

EXSOCAL

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Minuteman
Feb 12, 2010
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Idaho
Can someone recommend or point me in the right direction of a good quality upper receiver for an SPR build that does not have M4 feed ramp cuts in it? I have looked and looked and looked. The only one I found is LaRue's upper, but it won't work with the hand guard I'm using (Geissele MKIII).

The reason for my search is I got ahold of a 20" Krieger SPR profile barrel and it has a regular rifle feed ramp barrel extension. I could get the dremel out and match it up to the M4 cuts on the receiver, but this barrel is so beautiful I prefer not to ground on it.

Thanks!!
 
Can someone recommend or point me in the right direction of a good quality upper receiver for an SPR build that does not have M4 feed ramp cuts in it? I have looked and looked and looked. The only one I found is LaRue's upper, but it won't work with the hand guard I'm using (Geissele MKIII).

The reason for my search is I got ahold of a 20" Krieger SPR profile barrel and it has a regular rifle feed ramp barrel extension. I could get the dremel out and match it up to the M4 cuts on the receiver, but this barrel is so beautiful I prefer not to ground on it.

Thanks!!

There is no way to make a carbine barrel extension out of a rifle barrel extension, period, full stop. The ramp angles are different and changing the profile of the extension doesn't make it something it isn't. Finding the proper upper receiver is your best option.
 
You CAN modify a rifle/A2 barrel extension to an M4 style extension, but it isn't always the best way to go unless you just have to do it. I have seen it done many, MANY times and if done right, it works/functions 100% without issue. However, I have seen more than a few basement gunsmith hackjobs using a dremel, some Jack Daniels/liquid courage, and an unsteady hand that have made a total, unrepairable mess of the job. If you aren't 110% comfortable with doing the job, and you do not have all the tools and equipment to do it properly, then have a smith do it for you. There are several, but Steve and the guys at ADCO in OH are one such option (they use the Dremel method, but they do it right as I have seen several first-hand examples of their work and its performance after the fact).

That said, since you are NOT mated to a particular upper that already has the relief cuts for the M4 extension made in it, I would recommend a standard upper. Here are just a few such options that are in stock right now:

Upper Receiver, A4, Flat Top, USGI, Numbered (this one is marked as an "A4" but has standard upper cfg/no feedramps...most ALL of the bbls Fulton sells are non-M4 extension bbls)

AR-Stoner Upper Receiver Stripped AR-15 A3 Flat-Top Matte (depending on your order size, be sure to check out any applicable discount codes that might be available if you go this route)

PK Firearms | Online Store (top RRA upper listed on that page is a flattop WITHOUT M4 feedramp cuts)

Good luck and God speed!
 
There is no way to make a carbine barrel extension out of a rifle barrel extension, period, full stop. The ramp angles are different and changing the profile of the extension doesn't make it something it isn't. Finding the proper upper receiver is your best option.

Um, yeah, that's why he's trying to find an appropriate upper receiver. Period. Full stop.
It helps to read the entire original post, not just quote it. Period. Full stop.
 
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I'm a machinist in the aerospace industry and lucky enough to have unrestricted access to a really nice machine shop so the modification from rifle to M4 feed ramps is no sweat, I've done it once before a few years back with a .250" carbide cutter in the mill for a friend and it came out looking indistinguishable from a true M4 extension. So like ORD says… it is entirely 100% possible and plenty of people do it, but I would rather not do any work to this perfect barrel.

ORD - thanks for the links, I went ahead and just ordered the upper receiver form Fulton Armory. Appreciate the help!
 
I picked up a side charging upper from Sundevil last year. No feed ramps. It is milled out of 6061 T6. Married pretty well with my Seekins machined lower.
 
You CAN modify a rifle/A2 barrel extension to an M4 style extension, but it isn't always the best way to go unless you just have to do it. I have seen it done many, MANY times and if done right, it works/functions 100% without issue. However, I have seen more than a few basement gunsmith hackjobs using a dremel, some Jack Daniels/liquid courage, and an unsteady hand that have made a total, unrepairable mess of the job. If you aren't 110% comfortable with doing the job, and you do not have all the tools and equipment to do it properly, then have a smith do it for you. There are several, but Steve and the guys at ADCO in OH are one such option (they use the Dremel method, but they do it right as I have seen several first-hand examples of their work and its performance after the fact).

That said, since you are NOT mated to a particular upper that already has the relief cuts for the M4 extension made in it, I would recommend a standard upper.

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.

BarrelExtComp-Model1_zpsf2731003.jpg
 
Socal, how did you get from here:

I could get the dremel out and match it up to the M4 cuts on the receiver, but this barrel is so beautiful I prefer not to ground on it.

To here:

I'm a machinist in the aerospace industry and lucky enough to have unrestricted access to a really nice machine shop so the modification from rifle to M4 feed ramps is no sweat, I've done it once before a few years back with a .250" carbide cutter in the mill for a friend and it came out looking indistinguishable from a true M4 extension.

Trying to connect the dots...
 
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.

BarrelExtComp-Model1_zpsf2731003.jpg

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.
 
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I got my help from this thread, and thank you again to ORD.
-SOCAL out.

No problem, SOCAL...glad to help.

@ B. One...I completely understand your position and I agree with you wholeheartedly that the "best practice" if you will...is to properly match the receiver and barrel extension accordingly and to NOT engage in the modification of a barrel extension (and or receiver) to shoehorn a fix to a rather easily avoidable dilemma. That said...whether you want to question the statistical significance of my observations/experience with the mod in question...it is what it is. I have seen and used several dozen examples of the work done by ADCO to mod rifle/A2 extensions to work in Carbine/M4 cut upper receivers (and by others as well) and they DO WORK 100% in the thousands of rounds I have put through examples on my own and what I have observed in rifles belonging to others whom I know and personally trust to evaluation the reliability of their weapon systems. The mod like the ADCO one works and works well "in my experience." YMMV and I strongly encourage anyone considering such a mod to match their uppers and bbl extensions FIRST, but for anyone who is otherwise not in a position to engage in the "best practice"...I don't hesitate to recommend the ADCO mod. PERIOD! ;) No offense or otherwise intended toward you or to your position. I don't doubt your experiences and I think we both agree on what's "best" in this situation. I think we'll just have to agree to disagree as to the efficacy of the bbl extension modification in instances where there may not be another viable option like a receiver (or bbl) swap to ensure proper parts compatibility from the get go. Take care and god bless. I'm out too...off to go drink away my Mounties loss to TX Tech...sigh...what a pathetic display of coaching (once again)! :(
 
There is no way to make a carbine barrel extension out of a rifle barrel extension, period, full stop. The ramp angles are different and changing the profile of the extension doesn't make it something it isn't. Finding the proper upper receiver is your best option.

Ken Elmore, Specialized Armament Best going... Top Shelf 5 Star. My only go to for Colt play forms.