M*CARBO Brotherhood

S2K SS feed ramp

I did actually search for an answer before creating this post so sorry if I missed it.

Why is the S2K SS feed ramp not polished as a part of the deal? I mean M Carbo is a machine shop and they are producing these parts why not take an extra step and finish the product instead of leaving it up to the end user? I am in no way bashing M Carbo but am extremely curious about this, it kinda is the reason I have been reluctant to order one. I am mechanically inclined enough to do it myself but why should I have to? Would it not take them an extra 10min to do this? As much as I am being charged I expect a finished product.

I dont consider polishing this piece a mod or an improvement, it just seems like unfinished work.

Again I love M Carbo and this is the one and only issue I have.

Thank you


The part comes with a pretty good finish already. The polishing is giving it a mirror finish. It does take more than 10 minutes to polish. I spent 45 minutes to an hour doing mine. If MCARBO did the polishing work, they’d have to pass on the labor charge making the part much more expensive. All that being said, I have 2 9mm S2K’s. One that I did all the MCARBO improvements myself, the other is one of the first MSERIES S2K’s. I polished the feed ramp in the one I built, but the MSERIES was not polished. Both work flawless. There is no difference in the function of the two.


What about longevity?
There is no question about the SS but what about the polymer?
I have only read of one instance of a report about a polymer ramp beat to hell(no pics) so there might be more to it.


The difference between a machine shop and my Dremel is about an hour! :stuck_out_tongue_winking_eye:


My original S2K probably had 1500-2000 rounds through it before I switched the feed ramp. There was wear evident on the polymer feed ramp but it was still in good enough shape that I saved it in my parts box. My concern was the constant heating and cooling from firing. Those temp swings tend to make polymer brittle over time. I carry my S2K daily as a defensive weapon and I wasn’t willing to risk the polymer feed ramp failing in the event I ever needed the S2K for defensive purposes. Murphy always seems to jump up and bite ya when you can least afford for him to.


Several reasons…

The first is about an hour of labor - figure +$75.

Second, I have no use for a mirror polish - mine won’t shine till I’ve rubbed enough lead and copper across it. Polishing removes material and modifies contours - experience with barrels that don’t feed from overpolishing ishard to shake (not my gun or my work fwiw).

Finally, I’m sure they’ll polish it for you if you ask - they have 1. tools, 2. manpower and 3. an hourly rate.


Yep. Everyone should have a machinist teach them how to drill holes in metal. The machinist moves much slower and uses cutting oil to carry away heat. Typical hobbiest drills a ragged triangular hole and destroys bits quickly. Machinist gets perfectly round holes and bits last a very long time. Seems only one is managing the heat his work generates.

Edit to add: Obviously we aren’t drilling holes in feed ramps - we’ll put down the dremel long b4 we wear holes in the part. Point is: a pro takes the time needed to do the job and maintain his tools.


Yes but no one said anything about drilling holes…

We were talking about polishing a steel surface roughly a half inch by half inch. I never finished my thermodynamics class but what do I know…


It’s easy peasy. I got a mirror shine in just a couple of minutes with a felt bob chucked up in my Dremel tool on low speed with some metal polish. Go slow up/down the feed ramp in the direction of travel a round would take and use light pressure. You won’t be changing the contour of anything. That takes actual grinding. 1500+ trouble free rounds after installing the SS feed ramp says I did a good job. :grinning:

Another bonus is the mirror shine makes it super easy to clean. One wipe with a lightly oiled patch and done!


different surfaces function better, with different finishes we used to carry these around,
as a mark to what we machined/ground/polished to

you have 2 metals one sliding at a different angle to the other, repeatedly, on a polished finish there is less drag co-efficient that on a machined piece, this doesn’t mean the machined piece will not feed and wear in, it just means a smoother transition.
add to the fact carbon will not adhere and build up on a polished part as quickly.
there are some diamond impregnated rouges that will cut metal quickly, and you have to take care with, but 90% of them are fully controllable on polishing. .


Damn it, guess I cant use these diamond impregnated rounds


no you cant. but on the flip side the polishing compound is about $800 a 4oz block last time i used it…:+1:


I knew a machinist would bring up a surface finish chart/comparator. I made beryllium copper bushings for years. They required a surface finish of 4 ra or less. Put that in perspective, glass is in the neighborhood of 10ra to 15ra. I have and use a Mitutoya SJ-210 surface tester. When surface finish is super critical such as some seals we manufactured, we would send them out to be tested. They were tested in a helium atmosphere measuring the refraction of light bands. All would be overkill for a feed ramp, especially since carbon serves as a dry lube. Another reason to not over oil your S2K.


@Texprep damn Mike, I still got a Beryllium crescent adjustable wrench, I will have to get pic’s of the old girl, guess what areas it was used in :smiling_imp:
and like they always say brother, for checking alignment or a true surface, light never lies…:+1: