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Posted: 12/27/2025 5:45:15 PM EDT
| I am using this thread to track the progress of my 10.3” 5.56 build. Updates will be made by editing the parts list post. |
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Parts List: UPPER -Daniel Defense Mk18 stripped upper off Brownells (upper receiver, forward assist, dust cover, 10.3” barrel w/ .70 gas port, mk18 ris II rail, gas block and gas tube((will replace gas tube))) -Centurian Arms Sandcutter stripped BCG -Centurian Arms Cam Pin, chrome LOWER -LMT MARS-L Stripped Ambi Lower (Includes ambi safety, bolt catch, mag release) -Kratos Deaign Group 8-Position Receiver Extention (A5 Buffer Tube) -several Forward Control Design lower parts (A5 castle nut, 3 way swivel end plate, oversized buffer retaining pin, takedown pins, sling along with extra pins and springs) -Geissele SSAE-X Lightning Bow Trigger (I have several different Geissele models as well as LaRue MBT 2…the lightning bow is my favorite trigger) |
Hello fellow Missourian, welcome aboard!  Sounds like your off to a fine start on a really cool build. Your photos didn't load, typical for new ARFCOM accounts. Try logging out then log right back in, that should fix it. Also check out Missouri hometown forum when you get a chance. Keep us posted on the build. |
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Originally Posted By RollmarksMatter: Crazy right? It’s wild seeing people building things other than what’s currently trendy. I built a 10.3 just last year, OP. And I already had an 11.5. I like them both. Build what you like. Plus, some will say that 12.5 is the new hotness and 11.5 is outdated. 
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Originally Posted By RollmarksMatter: Have some parts arriving today. I update as stuff comes in. Still trying to decide what optic to go with. Leaning towards aimpoint. Either t2 or comp m4s. Battery life is important to me which is why eotech is out. I have been looking at sig Romeo 8t. M4s for the vibes. |
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Originally Posted By bionicmonkey: OP what buffer and spring? I will tweet things as needed once I get my suppressor for this rifle. It will be a dedicated suppressor. I’ll start with a springco green and will be using bcm’s mk2 buffers. I’ll be tuning the rifle so not dead set on any specific weight yet. |
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Originally Posted By RollmarksMatter: Crazy right? It’s wild seeing people building things other than what’s currently trendy. I remember when 10.5" was the shit, until everyone realized about 4 years ago that 11.5" made a better rifle in almost every respect and only cost an inch of barrel. I guess you could try to call it trendy, but I would call it sobering up to the more practical 11.5" solution. If you are going to build a "trendy" 12.5" mid, may I suggest you consider a BRT 12.5" HFCL Optimum which comes with a an extended carbine gas length. Between carbine and mid. Unless you are always going to run it with a suppressor. Most 12.5" mids run like shit without a can. I'm in the process of bulding this BRT barrel into a rifle. Or you could buy a Hodge 12.5" Small Port carbine barrel. it runs well with good 5.56 brass OR a can. I find it to be fairly subdued even with a carbine length buffer, Sprinco blue and H2. Probably the best choice, especially if you get tired of rolling your own, would be a Geissele 12.5" Super Duty upper. I just ordered one for fun. With Geissele's tuning and recommended buffer/spring setup it is supposed to be the a very good shooter, again a carbine gas system. If I want short, I have a Rattler in 300blk for that. Along with three 11.5" guns... LOL, I build a ton of guns. Hope you are having fun with your build. Looks pretty nice. |
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Originally Posted By ScottsBad: I remember when 10.5" was the shit, until everyone realized about 4 years ago that 11.5" made a better rifle in almost every respect and only cost an inch of barrel. I guess you could try to call it trendy, but I would call it sobering up to the more practical 11.5" solution. If you are going to build a "trendy" 12.5" mid, may I suggest you consider a BRT 12.5" HFCL Optimum which comes with a an extended carbine gas length. Between carbine and mid. Unless you are always going to run it with a suppressor. Most 12.5" mids run like shit without a can. I'm in the process of bulding this BRT barrel into a rifle. Or you could buy a Hodge 12.5" Small Port carbine barrel. it runs well with good 5.56 brass OR a can. I find it to be fairly subdued even with a carbine length buffer, Sprinco blue and H2. Probably the best choice, especially if you get tired of rolling your own, would be a Geissele 12.5" Super Duty upper. I just ordered one for fun. With Geissele's tuning and recommended buffer/spring setup it is supposed to be the a very good shooter, again a carbine gas system. If I want short, I have a Rattler in 300blk for that. Along with three 11.5" guns... LOL, I build a ton of guns. Hope you are having fun with your build. Looks pretty nice. Absolutely is trendy or rather “what is currently considered to be the best”. That absolutely will change with time. Short barrels are meant to be suppressed. I could see the entire market following suite behind the KAC KS1 as suppressor technology advances, which it has been on an absolute warpath for the last couple years. The “optimal” barrel will continue to get longer as suppressor technology makes suppressors shorter. Look at the Tisha… We are going to end up with 14” barrels sporting cans that equal the overall length of of a 10.3” barrel with a rc2. And when it goes that route everyone will say 11.5 is a thing of the past. Thats why I say it’s trendy. Not because it’s not the current optimal short barrels, but because it will in fact not always hold that spot as companies innovate. |
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