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Thanks in advance for any of your comments. I built my kids a 6.8 with a 16" ARP a few years ago for deer hunting and love the gun but now I am wanting to build them another one to shoot suppressed with a 12.5" upper for deer hunting. I got crazy lucky yesterday and bought the ARP 12.5" scout, but did not think everything through. I have been reading all of your post and have a few questions. If I am using a suppressor do I need an adjustable gas block? I am thinking about buying the Silencerco Hybrid, any thoughts or suggestions? Last but not least, after reading your post, I am really confused about how to start buying parts for the lower. This will be a SBA not a pistol. Can I buy standard lower parts or being it is a shorter barrel, I need specific parts for the shorter barrel. I have found stripped lowers that have pistol stamped on it. Do I need a pistol lower work or any lower is ok. Again this is for my kids and does not need top of the line lower parts but i do want to make it a good build. Also any suggestions on triggers and stocks will be appreciated. I am looking at the AAO trigger and the Tailhook MOD 2 but not sure if this the right setup for a hunting rig.
 

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Do not assemble the upper to the lower until your stamp is approved for an SBR. The only exception would be if it is classified as a pistol first, then SBR once the stamp is approved. If you go this route, do not install a buttstock until the stamp comes in.
 

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Do not assemble the upper to the lower until your stamp is approved for an SBR. The only exception would be if it is classified as a pistol first, then SBR once the stamp is approved. If you go this route, do not install a buttstock until the stamp comes in.
Thanks leatherneck. I am looking at what I need to do to get the stamp. I am just currently shopping on what lower parts I am going to buy for this upper. Thanks for your response.
 

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I am currently in the process of building a similar rifle for deer and hogs, although I bought an upper with a scout 16" barrel from Blackstone Arms. I bought a Silencerco harvester 300 last year and just got it cleared a couple of months ago. From my research- yes you should get an adjustable gas block if you are going to run suppressed or you may have gas issues. IMO on a build as expensive as one that is going to have a suppressor it's definitely worth the little extra amount to have an Adjustable Gas Block.

For the tax stamp/SBR process I think it'd be in your best interest to consult with a class 3 dealer for verifications on everything you are wanting to do just to make sure. There is some different classifications on SBR versus pistol that are important to note. If the barrel length is under 16" you can not have an adjustable 'stock' and must have a 'brace' (SBA3 is widely regarded as a really good brace if you want to go the pistol route.) You also may not have any type of foregrip on the handguard to be classified as a pistol. My old understanding was that you were not legally allowed to shoulder an AR pistol but my FFL clarified with me last time I asked and said that is not the case anymore(I would ask around to verify this.) When buying your lower, you should mention to your FFL you may build the lower to be a Pistol or Rifle, my FFL said he does this inherently for lower purchases but some may not. From my understanding what leatherneck mentioned on the process of waiting for your tax stamp is correct, either don't assemble the upper to the lower or(if classified as a pistol) leave the buttstock completely off until your stamp is cleared. A couple of legal things to consider with the tax stamp process and it being for your kids- you should likely put the suppressor and/or SBR tax stamps into a trust that you can add your kids to or they can technically never be out of sight from you while using it. One other thing to consider is anytime you leave your state with an SBR you are supposed to notify the ATF where you are going with it. Suppressors don't require this but it's recommended you let them know still. This is my understanding of the legal matters but again- I'd consult with a class 3 dealer and/or lawyer to make sure.

For parts recommendations it's important to have something really sturdy for hunting- I went with a magpul ACS-L which is very snug but A2 stocks are great for hunting as well. I personally prefer single stage triggers for hunting so I went with a Rise Armament Rave RA-140 which are fairly cheap and I really like it.
 

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Any standard complete lower will suffice if you are going the SBR route but buy a quality one (Aero Precision) since you will be spending 200 bucks to make it a SBR. Just whatever your taste is for the stock and grip. My 300 BO SBR has a standard gas block. Brass gets a little sooty but that is it. My son hunts with a 16 inch 6.8 suppressed and it to has a standard gas block and works fine. Not sure how a 12.5 inch would be though with a standard block. I also got the anti roll pins for mine as well. I like two stage triggers but a good single stage is ok too. My 6.8 has a rock river two stage but there are many good trigger now days. Lowers are getting scarce lately for some reason.
 

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Discussion Starter #6
I am currently in the process of building a similar rifle for deer and hogs, although I bought an upper with a scout 16" barrel from Blackstone Arms. I bought a Silencerco harvester 300 last year and just got it cleared a couple of months ago. From my research- yes you should get an adjustable gas block if you are going to run suppressed or you may have gas issues. IMO on a build as expensive as one that is going to have a suppressor it's definitely worth the little extra amount to have an Adjustable Gas Block.

For the tax stamp/SBR process I think it'd be in your best interest to consult with a class 3 dealer for verifications on everything you are wanting to do just to make sure. There is some different classifications on SBR versus pistol that are important to note. If the barrel length is under 16" you can not have an adjustable 'stock' and must have a 'brace' (SBA3 is widely regarded as a really good brace if you want to go the pistol route.) You also may not have any type of foregrip on the handguard to be classified as a pistol. My old understanding was that you were not legally allowed to shoulder an AR pistol but my FFL clarified with me last time I asked and said that is not the case anymore(I would ask around to verify this.) When buying your lower, you should mention to your FFL you may build the lower to be a Pistol or Rifle, my FFL said he does this inherently for lower purchases but some may not. From my understanding what leatherneck mentioned on the process of waiting for your tax stamp is correct, either don't assemble the upper to the lower or(if classified as a pistol) leave the buttstock completely off until your stamp is cleared. A couple of legal things to consider with the tax stamp process and it being for your kids- you should likely put the suppressor and/or SBR tax stamps into a trust that you can add your kids to or they can technically never be out of sight from you while using it. One other thing to consider is anytime you leave your state with an SBR you are supposed to notify the ATF where you are going with it. Suppressors don't require this but it's recommended you let them know still. This is my understanding of the legal matters but again- I'd consult with a class 3 dealer and/or lawyer to make sure.

For parts recommendations it's important to have something really sturdy for hunting- I went with a magpul ACS-L which is very snug but A2 stocks are great for hunting as well. I personally prefer single stage triggers for hunting so I went with a Rise Armament Rave RA-140 which are fairly cheap and I really like it.
Vuruchi great advice. I will definitely call my dealer so I stay legal with my setup. Thanks
 

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A good FFL will list the lower as "other" during transfer. but simply put pistol lowers can be turned into rifle lowers, but NOT the other way around... id go ahead and do a pistol config while you wait for the stamp approval, that way you can work out any kinks, and get a feel for the rifle in general.. SBA3 comes with a milspec carbine buffer tube.. so once the stamp clears ditch the brace and put on your preferred stock. 👍👍👍
 

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I’m not offering legal advise, but I would recommend reading up on constructive intent and make your own decision of owning a barrel shorter than 16” without a tax stamp (regardless if you install it or not). You might want to consider buying a brace until you get the stamp. Sell the brace once you get the stamp.
 

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If building a 6.8 to use suppressed and unsuppressed would put an adjustable gas block and if using a short barrel would consider building a piston drive upper vs a DI upper as receiver gets less blowback. All that said have discovered 6.8s built with standard gas blocks are usually very tolerant to use with 30 caliber quick change cans. Have four 30 caliber quick change cans and have noticed when use them on smaller bore rifles don't seem to have issues would have on my 308s.

Snap 30 caliber cans on 5.56, 6mm and 6.8 ARs often without any gas adjustments and have no issues if shot "lightly" but if intend to burn a lot of rounds will make a gas adjustment. My theory is the bigger can allows some gas "blow by" which reduces the gas pressure at block and blowback through the muzzle.

One way to step around the SBR issues is buy a inexpensive sealed suppressor or build a Form 1 suppressor and pin it to upper. Have 10.5", 11.5" and 12.5" barreled uppers that pinned cans to so they are all over 16" in length from bolt face as tuned to run only with suppressor and the $200 saved on SBR stamp almost pays for an inexpensive sealed suppressor.
 
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Thanks in advance for any of your comments. I built my kids a 6.8 with a 16" ARP a few years ago for deer hunting and love the gun but now I am wanting to build them another one to shoot suppressed with a 12.5" upper for deer hunting. I got crazy lucky yesterday and bought the ARP 12.5" scout, but did not think everything through. I have been reading all of your post and have a few questions. If I am using a suppressor do I need an adjustable gas block? I am thinking about buying the Silencerco Hybrid, any thoughts or suggestions? Last but not least, after reading your post, I am really confused about how to start buying parts for the lower. This will be a SBA not a pistol. Can I buy standard lower parts or being it is a shorter barrel, I need specific parts for the shorter barrel. I have found stripped lowers that have pistol stamped on it. Do I need a pistol lower work or any lower is ok. Again this is for my kids and does not need top of the line lower parts but i do want to make it a good build. Also any suggestions on triggers and stocks will be appreciated. I am looking at the AAO trigger and the Tailhook MOD 2 but not sure if this the right setup for a hunting rig.
You use standard lower parts. The lower does not need any special markings. You can built a pistol and then when the stamp comes in, swap the brace out for a stock. It is not legal to build a pistol with the intent of shooting it from your shoulder so ignore any of that bad advice. You do not need an adjustable gas block but it is not a bad idea. It will make it easier to tune it to your load and your suppressor. If you are building it as a pistol then you have nothing to worry about as far as constructive intent. The only time that would be a concern is if you had a short barreled upper and only had a rifle lower with a butt stock for it and nothing else. That would make it pretty obvious what your intent was. People worry too much about simple things.
 

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I’ll try to address this in order.

I have a 12.5 ARP scout and my friend has a clone of mine, and I want to build another. It’s my favorite hunting rifle.

the Hybrid can will work fine on it, I have two Hybrids. However, I use the 30 cal end cap on it when I ran it on my 6.8.

Stamp approvals are only 30 days when using EForms. You will do an Eform 1, there are plenty of video tutorials online it is super easy, just save along the way because the 1990’s based ATF software likes to crash.

You will need your lower of choice before you do the Eform 1, so get that.

I do recommend an adj gas block, my preference being Odin Works click adjustable followed by SLR. Since all my gun are suppressed, I used adj blocks on everything, it really is the right way to do it.


I also use low mass carriers from Right To Bear. Since you are tuning the gas, there are only advantages to using a low mass. I use standard carbine spring and buffer.

All other parts are standard. I like single stage flat face triggers, preference is POF, but LaRue and others are nice too.

I would suggest using a Plan B and Cherry Bomb for the Hybrid To keep it light yet secure. Focus on making this SBR light weight.., nothing is more annoying to me than a heavy SBR. An Aero non-forward assist upper coupled with a V7 Hiperlight forearm with low mass carrier is my go-to recipe.

Aero Precision scope mount is light weight but I highly suggest lapping the rings on those mounts. I have had slippage on 6.8 and other wildcats using those mounts before I started lapping and using rosin.

Hope that helps.
 

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Discussion Starter #13
Thanks everyone for your knowledge. I am working on getting my stamp but didn't realize I needed the receiver first so I will just have to sit back and wait till some more inventory of stripped lowers come back in stock!
 

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Yes it would but it is not in stock.

It was in stock until yesterday. I sent you a PM 5 days ago.
Now, election is over and cc are maxed out.....prices will start dropping. Good luck
 
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