I love the green @cclj03

here another contribution.
Untitled by j b, on Flickr

Does anyone know if the geissele super gas block will fit under the Mlok CMR? Thanks!

I have not tried it but after installing CMRs and geissele gas blocks on different rifles, I would guess it would not fit.

I would recommend a SLR Sentry gas block. The set screw, adjustable and non-adjustable versions will work perfectly.

Yes it fits no problem.  Only issue I have is can not use the front QD sling mount hole using a 10.5" rail with the mid-length gas system.  If you need photos send me an email or IM with your email and I can send you some.  Vary your gas length or rail length and this will not be a factor.

Post up some pics!

I just emailed some for a request to samcrow. Feel free to post them. I have never posted photos on here.

Let see some more of those CMR builds.

Untitled by j b, on Flickr

Where did those cmrs come from?

My Grendel pistol coming together

Attached File

My main training rifle for the past 2 1/2 years. It’s been dropped, knocked, used in torrential rain, in snow, in 100 degree heat. And it hasn’t missed a beat.

Don't want this thread to archive

My completed build

Looks good @CastorTroy, what barrel length are you running?

12" 6.5 grendel

Are there any users here who have pulled a CMR rail off after firing or extended use to look for contact points between the gas block and the interior of the handguard?

I'm seriously considering one on a planned 14.5 mid gas build, but the sheer amount of comments on this entire thread with gas block being "really close" have me concerned.

My SLR pinned gasblock clears with plenty of room to spare

I have a post and pics in this thread way way back maybe 3 or 4 yrs ago anyhow it was the 1st gen rail and after much deliberating, went with the centurion gas block it didnt touch but was close.  I actually had a smith mill it down on the bottom, let him decide how much to safely remove.  Others back then were filing to the same effect.

It probably wasn't necessary but I like to fix things that probably arent broken.

Does Centurion sell the FSP full length CMRs still?

Colt 6920 cut to 14.5 with some extras from Centurion, Magpul, Trijicon, Geissele, BCM and Surefire

Weapon Werks did the refinishing for me.

This won’t be a safe queen... already have over 1k through it.

Attached File

Are crooked barrel nuts/hand guards a thing with the CMR?  I have one I installed with a 10.5" barrel and it was off center.  Even after lapping the upper it was still off center the exact same amount.

I had a crooked 7.62 rail a couple years back. Contacted Centurion and they replaced it for me

Anyone know if the .625 LP Superlative Arms gas block will fit ok under the new CMR?

Is there any strength or durability differences between the gen1 and gen2 cmr rails

I'm possibly interested in a Centurion CMR for the build I'm working on.  I'm trying to decide between a Centurion CMR, one of the Geissele rails, and one of the SLR rails.  Cosmetically the CMR has the "look" I'm looking for.  I've never used a Centurion so was hoping maybe you guys who have used them could fill me in.  Their website doesn't really offer much in the way of information beyond the very basic product info.

Based on their website and the posts here...it looks like they changed it somewhere along the line and went from a "screw" attachment method to MLOK?  Is that correct?  Is that the difference between the Gen1 and Gen2 rails I'm reading about here?

Which do you like better?

These rails seem somewhat similar to Midwest Industries rails which I am familiar with.  I have a build with an MI rail and am NOT a fan of the attachment method.  They want you to use Loctite.  I'm not a fan of that.  In addition, the MI rail (for me at least) was difficult to get perfectly straight and centered.  It didn't seem as simple to get locked up, straight, and true with the receiver as the other Fortis or Samson rails I'd used.  The MI Rail had two screws at the bottom to clamp the rail on - but some had reported issues with the rail walking so MI includes green loctite to coat the proprietary barrel nut with.  This was a few years ago so they may have improved that by now.

Anyhow, how does the CMR install?  How easy is it to get it straight, true, and centered?  How bullet-proof does it hold?  Any walking or twisting of it?

Thanks!

Well, tell us about your build, but I'm going to tell you already, the CMR is what you seek as it comes in all shapes and sizes, and whatever it is you are looking for, and one of the most solid lockups if that is your only concern. You looking for MLOK, Keymod, or Uniquely Centurion Arms, as those would be the differences between Gen 1 and Gen 2 I believe as I only own a Gen 2, and Gen 2 came with MLOK. Detail your build a little more and I can help you in the direction you seek, but as I said I'm bias as it comes to Centurion Arms though.

Thanks kindly @InfamousAK for hopping in to help.  Its greatly appreciated :)

It will be based on either a SAN TAN billet Ambi upper/lower or an SLR billet Ambi upper/lower.  14.5" lightweight pinned with a VG6 Gamma & CAGE device.  Its kind of a Recce style I suppose (lightweight barrel though) and will wear a 1-6 or 1-8 LPVO.  Its going to have kind of a futuristic, Star Warsy, or blastery type look to it.  Its going to be nice & lightweight (Hopefully to offset some of the weight from the LPVO and mount) but not specifically going for "Ultra" lightweight with titanium or lightweight carriers and such.  I was originally considering a Battle Arms BAD556 Ambi receiver but decided against it due to that "V" shape to the mag well.  I'm also considering an adjustable gas block (As I've never tried an adjustable before) on a .625 gas journal barrel to keep the profile as small as possible.  Or I might still go non-adjustable.   Haven't decided yet.  I know I'd need to keep it small if I went with a Centurion.

It will be a general purpose rifle...range use, carbine classes, up close and shooting fast, and at distance of the bench (well...medium range....longest I can do at my local range is 600 yards).  Most accuracy shooting done 100 or 200 yards.

For the hand guard I'm pretty much narrowed to three manufacturers:  Centurion CMR, a Geissele, or an SLR.  I was dead set on a Geissele when I started but the more I look at the picture threads the more they seem just a bit "square" for this build.  The SLR is tempting because it would probably match up best with an SLR receiver and they have some interesting cosmetic shapes & touches for this build.  I haven't researched the lockup or practicality of the SLR though.  I'm sure the Geissele is GTG.

I was drawn to the Centurion for two reasons:  1)  Appearance and 2) Size.  Its got that small, round, profile with the holes that makes it look kind futuristic and blastery.  I like the MLOK CMR I've seen alright but, cosmetically at least, I seem to like the one with the screw-in accessories slightly better better.  I don't know much about either and the threads I've read about Gen1 & Gen2 and old & new are all very confusing when you're new to the Centurion CMR.  The MLOK seems more practical.  However, the large "flat" area on the sides for the MLOK doesn't look as nice to me as the more narrow flat sides on the ones with the screw-on attachments.  I could go either way.  I have no idea how practical the screw-on style is and I'm not sure how easy it is to attach a Surefire Mini-Scout and Arisaka mount.  I've seen pics of them here but not sure how hard it was to attach.  Or maybe the screw-on ones are just as practical.  I'm guessing that maybe the MLOK version is more practical and the screw-on version, subjectively, is more attractive.

On my other rifles I'm not one of those that swaps accessories much.  Usually a light, sometimes a tape switch and sometimes not, sometimes a Magpul sling mount up on the upper rail halfway down the rail, rail panels to protect my hands, and thats about it.  Once I have it the way I like it, I generally don't change it much.

I'm not glued to any one system.  I've got a keymod rifle, I've got an MLOK rifle.  I don't mind a third system.  Doesn't really matter.  Though I don't think I'd do another keymod.

As far as function goes:  I LOVE the size, feel, & weight of the Midwest Industries G3 SSM rail I have on another 14.5" pinned rifle.  The Centurion size, weight, & feel appear very similar.  However, as previously mentioned, I wasn't confident with the install and lock-up design and even though I got it installed true & centered and its fine now and I DID use their green loctite - I still have my doubts as to how "bomb-proof" it is.  It hasn't walked or moved on me yet though.  I dread if I need to pull that rail off for whatever reason and then having to reinstall it again.

Centurion Arms is what you want, locks up solid, and has many options for mounting accessories, any idea how long in length you want the Rail System, not to mention it would look extremely nice, and smexy bro. I found this option, and this option!

Edit: I would second the SLR as a backup option, or even Parallel Tactical, Geissele, I love, but would be careful, there mounting system has been in question depending on which one you get, up to MK14 I believe would be good to go, but why bother when Centurion Arms, looks, and acts the part, just my opinion though, as Centurion Arms is probably one of the best out there, not too badly priced, and highly underrated.

Gen 1 = Centurion Arms Mounting System, Gen 2 = MLOK.

@InfamousAK - Thank you so much for your help and advice.  That's awesome and I appreciate you taking the time to chime in.  Thanks also for the info on Geissele.  I had remembered briefly reading something about a possible mounting issue but had forgot about that completely.  The Geissele are probably two boxy for this build anyway.  Which is funny because after my last build I told myself I was definitely doing a Geissele rail for the next one.

Looks like its going to be that Centurion CMR or the SLR.

So, when people say "CMR Gen 1" they just mean the NON-MLOK rails that had the screw-in attachments and when they say "CMR Gen 2" they mean MLOK.  Do I have that right?  Did they change the barrel nut/rail attachment method/design between Gen1 & Gen2?  Do the Screw-in accessory styled CMR's (Gen1) have the older Generation barrel nut/rail attachment method or the newer one?  In other words, is there such a thing as a Gen2 with the older screw-on accessories?

Thanks for the links.  The size on those is just about perfect and that is exactly what I'm going for.  I want that VG6 muzzle device as close as possible to the rail on a 14.5" pinned (yet so I still have enough room to work to get the CAGE device on and off and so that none of that rail gets caught in the concussion).

What are your thoughts on the Gen1 CMR's with the screw-on accessories for function and cosmetics versus the newer MLOK CMR's?

Gen 1 did not have the lightning cuts and it is assumed that it is slightly stronger. Gen 2 had lightning cuts to help with venting heat.

Gen 1 and 2 did appear to have a slightly different barrel nut design as I had to swap them out.

Gen 1 look:


Gen 2 look:

You're Very Welcome Bro! Glad I could help!

As far as mounting accessories, I would probably go with the Gen 2, MLOK accessories are available everywhere, as opposed to Centurion Arms Specific accessories, for example, I have a KAC URX 3.1 which I love, but it requires me to find specific accessories, such as Rail Covers specifically from KAC that are getting harder to find in stock these days and since they are not always in stock, and are seemingly harder to find, once they dry up for good will probably become excessively expensive, where as if you get the Gen 2 CMR MLOK, those accessories are more available, as well as a wider variety not exclusively from Centurion Arms, and easier to obtain. Centurion Arms has been pretty good about keeping up with the Gen 1 Accessories, so either way it would probably not matter too much, but personally I would go with the Gen 2, as I did when I purchased the rail, but I would also probably get me a Gen 1 just to say I have one, but that's me.

1Wolf,
You didn't mention length or if you plan to suppress, but just be aware the lengths changed slightly for each gen.  Eg, there are actually 3 different lengths for the 14" CMR:

Gen 1 - 13.65"
Gen 2 - 14.25"
Gen 1 (re-release) - 14.0625 (why may or may not have been a typo)

If just running a FH it's not an issue, but if you wanted to suppress on a 14.5" barrel, Gen 1 14" would work, Gen 2 14" would not - you would need to go with a 14.7" barrel.  That, and the 14" Gen1's have holes offset from gaps on panel guards unlike the other lengths, which some find annoying.  They did correct this with the Gen2.

Gen 1 14" panel mis-alignment:

@cjwwd2 - Thanks for taking the time to post those comparison photos.  I think I'm finally straightened out on the different CMR rails available.  If I'm understanding correctly, they call the original "screw attachment" type rail the "Original Standard Version" and within those there are two generations.  Gen1 & Gen2.  Gen2 has the lightening cuts and has also straightened out the whole "holes don't line up with the panels" thing.  The Centurion CMR product page for the "Original version" has checkboxes that will let me select which generation I want.

Then, they also have the MLOK version which are all Gen2.  There is no checkbox to select a generation on the Centurion CMR MLOK product page.

I'm still on the fence as to whether I'll get the MLOK version or Gen2 of the "Original Standard" Version (Sounds like I'm talking about Kentucky Fried Chicken ;) ).  Gen2 of the "Original Standard" version wins out for me slightly when it comes to cosmetics.  The MLOK version wins out slightly for me when it comes to functionality.

Thanks again @InfamousAK - I'm still on the fence between a Gen2 of the Original Standard Version or an MLOK but the info you posted helps.  I'll just have to weigh a slight edge in cosmetics for this build vs. the practicality of MLOK.  Its good to know they've been pretty good about keeping up with the accessories.

Thanks @78Staff - Length I'm not sure yet on.  I'll just need to decide how much barrel I want to expose for the "look" of this build.  Its good to know that I actually have some additional choices if I'm willing to use either a Gen1 or Gen2 as they have slightly different dimensions.  Thats good info and you just might have saved me some trouble :)  Thank you.

I *think* at this point, with just a rough measurement, that a 13" rail is about as long as I'll be able to go.  Their website says the Original Standard Version is 13.688 and the MLOK version is 13.468.  I think 13.688 or 13.468 should be fine and still give me room to remove/attach the CAGE device alright.  However, I think if I go longer than 14" I might start running into trouble.  I haven't ordered the 14.5" barrel or the VG6 Gamma yet to eyeball it.  Once I get the barrel and the MD then I should be able to be more confident about the rail length.

I probably won't be suppressing it as I don't live in a free state.  However, my wife and I are hoping to move to a free state in the next year so you never know.  One can always hope.  For now, It'll be wearing a VG6 Gamma & CAGE Device.  Its handy to have those exact measurements as I can measure on a current build I have that uses a very similar looking Midwest Industries rail and have a good idea what my future CMR would look like as far as how much barrel is exposed.

Why did they get rid of the gen 1 14 length???!! They fit perfect with the 14.5 barrel.

Do you guys know if a 13.7 barrel would work with the 12 inch rail. Im looking for the same fitment as the gen 1 14 with 14.5 barrel.

Yeah it's why I never upgraded to the Gen 2  Not sure on the 12/13.7, but someone will chime in I suspect.

I'm considering changing to a LAT 13.2" - just looking for something different.

Danm.... That looks so good. I'm gonna be running a surefire brake with warden so that set up would be perfect. Just posted a WTB ad for the Gen 1 14 inch. Crossing my fingers. Otherwise I'll just try and see if the 12 inch will work with the 13.7

What length rail/barrel is this?

Weapon Outfitters has both a 13.5" and 14" Gen 1 CMRs

It's a 14.5 barrel, Original Gen 1 14" (actual length 13.65") CMR

The other "Gen 1 Style" is 14.065 actual length, and the Gen 2 is 14.25" actual length.

Generally:
Original Gen 1 14" (13.65) on 14.5" barrel, Suppressor/mount good to go.
Gen 2 14" (14.25) on 14.5" barrel, Suppressor/mount No Go - requires 14.7" barrel.
Gen 1 'Style' 14" (14.065) on 14.5" barrel - not sure, but likely not.

There is a Gen 1 style 13.5" still. I ordered one recently.

LINK

Looks to be aprox same length as the original Gen 1 14" lol.  That's probably CA realizing the effed up with the Gen2 14" length and fixing it, as lots of folks complained when 14" G2's came out iirc.  Although, realistically it only affects those with 14.5 barrels wanting to run a suppressor.

Still, the ability to switch to a Gen1 Style 13.5" is appealing, keeping the tight gap to a suppressor and keeping all current accessories (if you didn't care to switch to MLok),

and would fix the damn off center panels the OG G1 14" suffers.

Just don't know if I want to spend $230 to fix panel mis-alignment lol.  Hell I ordered two LAT's for that. Still....

Can anyone confirm the CA panels line up correctly on the Gen 1 Style 13.5" please?

ie this...


NOT this...

Answering my own question, I called WO they confirmed the panel gap is fixed, and confirmed the G1 Style 13.5" is the correct model to order if one wanted to replace the OG Gen1 14"...  Nice.  Also will mount up to OG G1 barrel nut.

So one is on the way :).  Damn Arfcom spending my money again!

Any recommendations on a good .750 adjustable gas block that fits well inside the Centurion CMR?

Anyone have any recent experience fitting a .750 SLR adjustable gas block (or other good adjustable gas block) under a Centurion CMR?

I couple pages back I saw an arfcom brother post some pictures of a .750 SLR adjustable gas block underneath a Centurion CMR and it fit, didn't touch, but was really close.  He had mentioned that he wasn't sure if it might contact while firing or with a suppressor on the barrel.  That was back in 2018.  I haven't seen any updates on how it worked out.

Anyone have any recent experience with a .750 adjustable gas block under the Centurion CMR?

According to Centurion the inner diameter of the "Original Standard" Centurion CMR is 1.12" and the inner diamter of the MLOK CMR is 1.230".  The .750 SLR Adjustable gas block is .90 wide.  So 1.12 - .90 = .22.  So thats just .11 inches of space on each side between the gas block & the rail.  Its 1.230 - .90 = .33, or .165" of space on each side between the gas block & rail for the MLOK version.  I know the .750 non-adjustable gas block that Centurion carries is 1.29" tall.  The SLR gas block is 1.40" tall.

You guys think this aim gas block would clear a Gen 1 cmr?
Looks very low profile and a good deal at $6 bucks.

https://www.opticsplanet.com/aim-sports-inc-750-mil-spec-low-profile-gas-black.html

@riptastic5 I’m not sure if you got your question answered but yes a 13.7” will clear a Gen1 CMR.
Found a pic:

Heres a mock up of my build. its coming along slowly but surely. Waiting on a rosco 14.5 purebred barrel to come in.
Still need optic (rmr), light (surefire m300), backup sights (troy irons) and other small upgrades.
I've been buying all my components spread out over time so I havent realized how much I've put in this rifle. Dont think
Im going to do the math or I might freak out...lol