MarColMar and HMG Cetme L a Detailed Comparison

[browningautorifle]

I'm wondering if that's a powder coat finish? That could by it'self cause the mag binding issue... As you say, this is for range...

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[Combloc]

I'm wondering if that's a powder coat finish? That could by it'self cause the mag binding issue... As you say, this is for range...

It's Cerakote .

---------- Post added at 09:50 PM ---------- Previous post was at 09:49 PM ----------

The last piece of furniture we need to look at is the pistol grip. As with the rest of the polymer parts, they did a fantastic job and only real sticklers for detail will notice any differences between the MCM made part and an original.


First up is the left side. MCM part is on the left:

The raised ribs between the grooves are slightly rounded on the original while they are flat on the reproduction. Also notice that the original has a mold ejection pin mark starting in the fourth groove down, running over the fourth rib and into the fifth groove while the MCM has no such mark.


Right side:

The MCM grip has two ejector pin marks, one large one above the grooves and one small one at the bottom front. The original has no such marks.


Looking down into the top of the grips, we see that they are pretty much identical. MCM is still on the left:



Front of grip. MCM is on top:

Both show a mark in approximately the same place where they were removed from the sprue.


Bottom and bottom/rear 3/4 view of grips with MCM on top:



Mold lines differ somewhat between the two but all of the contours are dead on.


Last grip picture showing the manufacturer's mark. The star shaped pattern around the allen head bolt hole is where a star shaped lock washer digs in:


Moving on to some internal parts now. I'm not going to tear the bolt assemblies apart and show you each part because both are original and, as far as I can tell, both have an identical rough phosphate finish which leads me to believe it's the original finish as applied in Spain. There are a couple things of note though.
First up is a picture looking at the bottom of the bolt assemblies with the MCM one on top:

Notice the HMG milled away the right rear corner of the carrier while MCM left it alone. This is the part of the carrier that trips the full auto sear. Interestingly, pretty much every roller lock manufacturer removes this area on semi-auto only firearms whether it be made by HK, MKE, or POF but MCM decided it wasn't necessary and the ATF clearly approved it this way so it's good to go.


In this picture, we again see the MCM unit on top:

The salient thing to notice here is the fact that the finish on the extractor springs differs between the two with the HMG being in the white while the MCM is either blued or nitrided. I assume that both manufacturers have replaced the factory springs with new ones. Although it is not shown, I believe both have replaced the firing pin, recoil and buffer springs as well. The "80" on the nose of the HMG carrier was put there by them and is the serial number of the rifle.

[Combloc]

Next up is the fire control box. HMG used an original box and simply modified it to semi-auto only purposes. Conversely, MCM went full bore and manufactured an entirely new box body while still using original internal parts (except for the springs which are new) which were modified to operate in semi-auto only mode. The intention of both manufacturers was to make sure that an original full automatic box would not fit into the receiver. This was, of course, and ATF requirement. Let's see how they did it.

First up is a left side view with the MCM on top:

Both are aluminum and both look almost identical except that the MCM looks brand new because, well, it IS brand new. Look carefully at the HMG box and you will see a illegible ghost of the original factory serial number starting just behind the hammer pin and running just above the trigger pin. Looking at them from this side, both look in form as the did from the factory.


The right side is where we see just how much both boxes deviate from the original design:

How? We will consider each one separately in a moment. But before we do, notice that, other than the aesthetic condition, there is one obvious difference between the boxes. Notice that the empty hole where the fire selector axle fits is smaller on the MCM box. This was done so that a full auto selector switch will not fit into the box. We'll look at the MCM modified selector lever in a bit. Another thing I want to bring to your attention are the two tabs, one sticking out the front of both boxes and another at the rear, with holes in them. These holes are where retaining pins pass through the receiver to hold the box in place. The rear pin also passes through the front bushing in the butt stock.



First, is the HMG box close up:

If you look at the top edge of the box, you will see that it steps down starting slightly forward of the trigger pin and continues all the way to the front of the box. This was done by HMG to create clearance for a blocker bar that was welded up inside the receiver.

Here is a picture of the blocking bar:

We are looking up into the bottom of the receiver. To the left is the rear of the magazine well. The spring we see to the left provides tension for the magazine release mechanism while the spring seen on the right is the tensioner for the bolt hold open device. The blocking bar is in the middle of the photo. If you were to try and fit a select fire box up into the receiver, it would hit this bar and stop. The step HMG cut into their semi-auto only box allows it to seat without hitting the blocking bar. Got it?? I hope so. While we're looking at this picture, I want to point out a design detail; one that is part of the original rifle as designed by CETME. Notice that the area where the fire control box retaining pin and magazine release bar passes through the receiver is strengthened with additional metal for durability. If additional steel had not been added in this area, it wouldn't hold up to use for very long. In fact, the entire rear of the magazine well is a milled block welded in place and these strengtheners are part of that block. A lot more goes into the design and production of origami firearms than meets the eye. I love little details like these.



MCM did essentially the same thing but went about it a different way. Here is a closeup of the front right side of their fire control box:

Notice that, instead of milling away part of the top edge, they milled away part of the entire front side of the box.


And here is the corresponding area within the receiver:

Instead of a bar, MCM chose extend the milled strengthener block toward the rear of the receiver thus creating what I call a "restrictor plate" because it restricts an unmodified select fire control box rom fitting into the receiver. In addition, it (in theory) does double duty as an aide in reassembly of the rifle. The idea is that there is supposed to be a precision fit between the restrictor plate and the corresponding cutout in the fire control box. When they are fit together, the holes in the receiver and the hole in the box should align perfectly so that the retaining pin pops right through. I say "in theory" above because it doesn't quite work out all the time with my rifle. It's close and sometime the retaining pin presses right through the holes and seats perfectly. But sometimes, it just ain't going for love nor money. Then, you have to remove the pin and wiggle things around a bit before reinserting the pin. With enough fidgeting, it goes together. Whatever you do though, DO NOT beat on the retaining pin if it doesn't easily slide through. It's not designed to be beat on and you WILL screw up your rifle sooner rather than later. You have been warned!
To be fair, my rifle is new and clearly pretty tight. I expect things to loosen up with use and maybe this issue will correct itself as things wear in. Whatever the case, it is far less fidgety to reassemble than the HMG design but some amount of frustration is always going to be there. It's just an artifact of the original CETME design. When you buy an AMG, you just have to embrace the fidget...….no matter who made it!


Here is a detail shot showing the milling marks on the side of the MCM box:

I like it because it reminds me of the purely aesthetic jeweling you see on the inside of many nicer Quality mechanical watches. Whether they did it this way in order to cust production costs or for some other reason I do not know. I only know that I think it looks neat.


Here is a comparison shot of the finish difference on the steel trigger guard between the MCM on the left and the HMG on the right:
I know without question that the grey phosphate finish on the HMG part is original. I do not know if the much darker finish on the MCM is original or whether it has been refinished. What I do know is that it matches the finish on the handguard heat shield.



The last things we are going to look at in this post are the safety selectors.

Here is the HMG:

As far as I can tell, this is exactly as it left the factory.


And the MCM:

Theirs appears to be modified in two ways. First, was the addition of a pin running parallel to the axle shaft. I assume this was done so that it will not interact with full automatic parts should they be fitted to the fire control box. The second modification was turning down the circumference at the end of the axle where it fits into the right side of the box. This precludes fitting of an unmodified full auto selector switch into the box.


This last picture of the night shows the two selector levers side by side for easier comparison. MCM is on the left:



That's it for this post. The last things we will be looking at are all external. This will include receiver details, sights, barrels and a couple o few other things. it will probably take to ro three more posts but we'll get there. As always, thank you for your time!