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Posted: 2/6/2026 3:03:18 PM EDT
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I’m looking for thoughts, ideas, recommendations and especially “…don’t use…” for my first upper build. Tax stamps are free, so now’s the time to build a suppressed SBR! I have a Spikes Tactical lower that I had a 6.5 G upper on. I’m looking to build a 5.56mm upper, probably 12.5”. I plan to buy a suppressor dedicated to this rifle. This will be a utility rifle. It needs to be reliable and mid-range accurate, not a showcase piece. I will shoot some local matches, but I’m not a “Presidents Hundred” level shooter. So any recommendations you have on components, suppressor, or assembly, I’d like to hear them! |
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NV, USA
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Make sure your handguard is an absolute bare minimum .5" shorter than whatever barrel length you go with in order to allow for clearance of your suppressor when attached to your muzzle device. Might even be safer to go .75" shorter if you don't want to do any pre measuring. I would highly recommend buying a midwest industries upper receiver rod to use for assembling your upper receiver. |
| I have a BCM 12.5, it has a CAT white bread on it. When I first suppressed it, it wasn't rejecting right. I swapped buffer systems for a VLTOR A5 and it runs perfect. Smooth, soft recoil, little back pressure. I think the 12.5 is a great length, short enough suppressed to be maneuverable but not drop as much as a 10.5 |
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My first sbr was a 12.5 fsb dd barrel with an ops inc can (bhd / mk18 kind of hybrid ?) and it still holds up today. That was in 2006 maybe? Whats your budget and what do you want the rifle to do? |
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I'm looking for a useable mid-range (both price and distance) rifle. My real goal is to build the upper, as opposed to having the upper. I mean to say I am building this to learn how to do it, as opposed to pursing a solution to a requirement. I realize now that I hadn't thought this all the way through. Actually I didn't know as much a few days ago as I do now and the comments and messages from this forum have educated me, for which I am grateful. I have a complete ~18" 6.5 Grendel upper with a free floating handguard that was on the lower. Based on my recent education I started taking that apart. I bought it used, so I have no idea where the parts came from. The handguard for example has no markings on it, at all. No logo or anything. The barrel has the chambering stamped but that seems to be it. Once I get the barrel nut off and have it all apart I'll confirm that I can use the upper receiver (its not marked either), barrel nut, and gas block (set screw, not pinned). If so, as I understand it, I'll need a barrel, handguard, and gas tube. Again, first go at this so I may find I'm unable to use this or that. The adventure continues..... |
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| I put together a 12.5 using a centurion barrel, it was their cheaper non chf barrel. I think this barrel has been discontinued, all centurion has for sale is chf barrels now. I picked the option for them to pin their gas block. Used a blem bcm upper, microbest bcg, centurion quad rail, a2 flash hider. It’s my favorite build so far. |
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thanks for the input! I've been looking at handguards that extend over the suppressor. Products like the Hawk XL at STNGR or the AR-STONER Elite at Midway. Haven't been able to get the barrel nut off the receiver to confirm what I have. Turns out I need a 1 1/4" wrench so I don't bugger the existing barrel nut up. |
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Handgaurds come with barrel nuts, for the most part. Upper receivers are cheap. I don't think it makes sense to part out your Grendel. If I were buying a general use barrel today, I would buy a Geissele. You rarely hear anyone say anything bad about Daniel Defense or FN barrels. Barrels aren't a great place to save money, IMO. I buy Ballistic Advantage barrels for cheap ones. Get an adjustable gas block. |
| A BCM MK2 12.5 complete upper (w/ BCG) is $820 right now on BCM's site. Tough to beat that. My current favorite is a 14.5 that I built with almost all BCM parts and it is great, but I wish I could have gotten a MK2 stripped upper. Apparently, they aren't selling just the MK2 uppers. So, instead, I used one of BCM's blem standard uppers and it works just fine. Check out the prices on Primary Arms before you start piecing it together. I think they have BCM stuff (along with Geissele) right now. |
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Originally Posted By Fir3ball: I’m looking for thoughts, ideas, recommendations and especially “…don’t use…” for my first upper build. Tax stamps are free, so now’s the time to build a suppressed SBR! I have a Spikes Tactical lower that I had a 6.5 G upper on. I’m looking to build a 5.56mm upper, probably 12.5”. I plan to buy a suppressor dedicated to this rifle. This will be a utility rifle. It needs to be reliable and mid-range accurate, not a showcase piece. I will shoot some local matches, but I’m not a “Presidents Hundred” level shooter. So any recommendations you have on components, suppressor, or assembly, I’d like to hear them! Do something retro interesting. My Elisco build nails it as a utility pistol! It was also a cheap build and super lightweight. 
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Joined:
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MN, USA
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I just bought a 13.9 LW Centurion barrel (had them pin it out of the factory), put on their 13" handguard which is actually 13.4" and Rearden came to the rescue with just enough clearance to get my can on. Accidentally put a rifle together with basically zero gap between the suppressor and the rail. Looks great. If I remember when I get home I'll post a picture. I'm quite impressed with the centurion stuff. I haven't shot groups but it's better gassed then my 11.5 criterion and 14.5 BCM. The handguard is also super light. Anyway this is my roundabout rambling way to say that I think Centurion puts together pretty great shit. I just put an LPVO on it and I'm going to try and put together some 100 yd groups and see what it can really do. If you piece it together like I did it's also not much more then a BCM would be. |
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Green Mountain barrel Just ordered this one. If its anything like my other GM barrels im sure ill be happy. |
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Mid length is better , not as good as rifle length but its a 12.5.... With an adjustable gas block I don't think there is any advantage to the low backpressure cans. Griffin Adjustable gas block with a straight gas tube is relatively cheap, simple, and reliable. 2 positions so very little to screw up if your not thinking. Absolutely love mine. Shoot 99% with a can now and easy to switch if I remove it, simple. I like chrome, its easier to clean. Love how handy my 12.5 is and I Shoot it more because of that. Wish my surefire OBC was chrome. Not sure what rail with the Griffin block. My Midwest JUST barely clears, something else would be better. |
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Originally Posted By Fir3ball: Thanks for that info. I really thought that piecing it together would save a bunch of money. That is turning out to not be true. Especially when you figure in the amount of time I have dumped into research, prices, availability, etc. etc. Use the Quote button and we can see who you are replying to 
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16 inches be damned...
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Originally Posted By gurn-blanston: Do something retro interesting. My Elisco build nails it as a utility pistol! It was also a cheap build and super lightweight. https://i.postimg.cc/5yLHkxnZ/PXL-20260215-221548223.jpg Hell yes! It is still my favorite shooter, with a Mini 4 mounted, it is still pretty light.  
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16 inches be damned...
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