Example of Tolerance Stacking – M4 Feed Ramp Issues

Pardon a 'Newbie' question but, would using Barrel Shims (between the barrel and the barrel nut) help correct the problem of that feed ramp snag you demonstrated with the q tip end? and, what would you recommend for polishing/reducing that overhang? I have quite a few spare parts i would like to experiment with to hone my hobby.

Thank you for the informative videos.

New knowledge in my toolbox. Thank you sir.

I don’t see any quantity components in this video.

I had Core 15 rifle from a few years ago that had this issue as well as multiple others. Easily one of the worst rifles I've bought and I'm thinking due to the Sandy Hook scare. The feed ramps on the barrel extension severely overhanged the m4 feed ramps of the upper, the wall thickness of the lower receiver was thicker on one side, and the rifle was heavily overgassed, it ejected shells at the 1230 o'clock position with shells marring the handguard immediately in from of the ejection port, recoil felt like a light 20 Guage shotgun.

You da man, thanks

My first ar had feeding issues i found the barrel extension had burrs on the feed ramps that were the issue a rat tale file and a dremel buffing wheel fixed it but now I know to check for that before accquiring another.

Damn I’ve been out of it too long, didn’t realize FCD did handguards or uppers.
Love their stuff.

Are those rubber bands mil spec?

have the same problem with a PSA upper I just bought for a build, Geez the one shown on the video is awesome compared to mine!! I put a mag full of ammo in and tested it before I would actuallt shoot it, you name it it did it, FTF, FTE, DOUBLE STACKING, It takes the cartridge right into the barrel upper, the ammo had gouges and one bullet actually went back into the cartridge which put gunpowder everyehere!! gonna have to send it back, from what i've heard thats gonna be a delightful event ! I'm sorry to all the PSA folks out there but this is not a good quality rifle or componets, i've always been leary about PSA but I finally drank the Kool Aid and very sorry for doing so. I have a Bear Creek Arsenal upper that is 10+ better then this PSA upper, better quality all the way around, the charging handle is..well lets just say my wife have better quality cooking utensils, I hope this is not gonna be a big drawn out procedure but probably will, not to mention I destroyed about $15 worh of ammo… well the bright side is I dint just go out and shoot it, I may have gotten Injured or worse

Great video and content. Is is possible to utilize barrel shims to bring the two surfaces of the feed ramp more level versus lightly removing material from the barrel feed ramps?

I've got an A2 upper with no feed ramps? Do you recommend adding them?

Very awesome information 👍 that’s something I’ve never even thought of.

Your videos are gold man, ty.

Is there anything you would do to the receiver to help feeding or is it not necessary?

I had an Armalite factory upper that had the same issue. Armalite took care of the issue immediately and it was a fantastic rifle.

Why would an issue like this not get picked up in quality control inspections at the manufacturer? Clearly, I am missing something in how these things are built.

What is your going rate for doing something like that and how do we make arrangements to send you something? I used a different upper when I encountered this (also all quality components), but wonder if I should just have this process done.

Another example I had is when I combined a G trigger with a Balios Lite lower. G pins are a little fatter than Milspec and balios trigger pin holes are a little tighter. I got the trigger installed using g pins, grease and more hammer than I wanted to.

Thanks for the video. Luckily my Aero M4E1 upper and Larue Stealth Barrel w M4 feed ramp matches perfectly.

Most people don’t know, or understand that M4 ramps are profiled differently than standard ramps. You really shouldn’t mix them, otherwise you end up with this problem….. Now the barrel extension feed ramps will have to be modified to match the feed ramps on the upper….

Carbide bit and a Dremel ? Lol

I always blend then polish those two lower feed ramps after I’ve torqued the barrel onto the upper receiver

There is a lot to be said for purchasing a completed upper from a single source. They have identified any stack up issues with their suppliers and have resolved those issues. Left on your own, its up to you to see what you get. The most important aspect is that you are left to retrofit the components on your own or try different parts.