GUU-5P and M4 feed ramps

[MSW]

Does anyone here have first-hand experience with the lack of M4 feed ramps in the retro AR carbines of yesteryear? My reading about M4 feed ramps was regarding: M855 round being longer than M193 & having a tendency to dive rather than feed in full auto & weak magazine springs.

Did the XM-177, GAU & other carbines have significant feed issues remedied by M4 feed ramps? It seems that these ramps would have been incorporated sooner in carbines if it was a major issue.

My reason: I'm building a 16" GUU-5P carbine ( carbine gas system) on a 604 upper & don't know if it's worthwhile to have M4 ramps cut. I usually shoot XM193 or IMI M193, so it's not likely I'll be shooting M855.

[Circle_10]

I'd be curious to know the answer too. I believe I've heard one anecdotal report of GUU-5/Ps having M4 feed ramps cut into them when rebarreled with the M4 style barrels some can be seen with, but I've never heard anything conclusive on the matter and for all I know if the practice does occur it might not even be universal.
The general consensus seems to be that an M4 barrel and a non-ramped upper works fine (it's an M4 ramped upper and a non-M4 ramped barrel that's a real no-no). From what I gather the M4 ramps mostly come into play, when firing M855, through a carbine gas gun, on full auto, with the old carbine buffer (vs the new "H" buffers). On semi auto, with an H buffer in your gun you *should* be A-OK.

[GRA556]

This is a good question and I hope somebody with some knowledgeable experience let's us know sooner or later.

I will say this; with regards to the USAF GAU models, I would not put anything past the USAF at all to combine new M4 barrels with Vietnam-era A1 receivers or later A2 receivers if they were thought to work, nor would it surprise me to learn the USAF sent the older receivers to a Base machine shop to have the ramps cut in the older receivers if they thought they could get more life and function from those weapons.

I'm sure any firearms-based machine shop can easily cut those ramps and most likely for a decent fee and at the same time polish that area. Can't be that hard.

To that end, I'm sure nobody on here would argue if I made the point that most likely more than once somebody has cut those ramps themselves with a Dremel. Not that I recommend it nor would it be the procedure I would follow but I'm sure it's been done with full success.

[Kain]

Okay, caveat emptor I am not an expert, but I was doing some general reading as well as watching a bunch of the M4 earlier in the week, so maybe I can help. Hopefully.

From my understanding, and what was said, the reason for the M4 feed ramps with the M4, had to do with the shorter gs system causing a faster cyclic rate which caused the carrier to strip rounds before they were fully presented in the mag, or something to that affect. The solution came down to the use of a heavier buffer, or the M4 cut ramps. The argument being that both weren't needed, but Colt put them in anyway as an example of doing something. Personally, in an M4 I think having both is cheap insurance if both aren't needed, but neither here nor there for this thread. So in short, it should work if you are running a heavier buffer, from my understanding, and for the AR you are building no feed ramps would likely be correct. Again, am not an expert persay, and would welcome further clarification on the issue as well.

[GRA556]

Additionally ... FWIW ... I recall reading more than once throughout the course of several years the ramps provide more ease movement when it comes to shooting soft points, hollow points, etc., so I'm guessing that back in the early days these type of rounds were not available. Kind of helps to make sense when we consider the M4 is not exclusively a military weapon as it is used in law enforcement and security also, and of course hunting.

Could be back in the day the older models encountered problems with ammo other than military-issue so the ramps were incorporated. I know before I retired our issued round was the Speer Gold Dot 64 grain soft point and other LE agencies use soft points, hollow points, OTM(s).

It pays to market the weapon as broad as possible, therefore it has always been marketed as a viable hunting weapon also. Very likely the ramps were found to be useful with the sporting ammo often preferred by hunters. Such ammo may not be available or preferred for military/LE use.

[MSW]

I've seen "Bubba ramps" on YouTube & Net--would these home-done ramps be best anodized? I've done anodizing in a prior job, but it seems dissolving Colt factory finish will detract from any value, as Bubba-ramps would.

Does anyone have practical experience with raw aluminum feed ramps?