AR barrel 16" cut down to 11.5"?


May 5, 2011, 03:59 PM
I did a good amount of research on this topic but didn't find anything that totally answered my questions. I have a 16" AR15 carbine that I have been wanting to turn into an SBR very badly for quite some time now. Yes I know all about the tax stamp and registration. So I have a few questions about cutting down a 16" M4 profile barrel right at the end of the M203 cut and putting threads for a standard flash hider on the M203 cut(which would be the muzzle after the cut had been made)

1. Is it a commonly done thing? by this i mean are there many gunsmith's that have experience doing this very thing or am i going to have to search to no end to find someone that I'm confident with letting chop up my gun?

2. If i opted to sell my current barrel and purchase a new short barrel, is there anything that could not line up or anything of that nature? by this I mean are barrels "drop in" like handguards and stocks are?

I am really hoping that this idea works as it will save me the money and hastle of trying to sell my old barrel(which I'm sure i would not make even get a fraction of my money back from) and finding a good quality government profile 11.5" barrel. That is one huge reason for my wanting to cut my barrel down; most 11.5" barrels that I have found are heavy profile and I want a government profile, which my M4 barrel basically is.

Thanks for any information you guys may be able to provide me with, it is greatly appreciated.


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May 5, 2011, 04:26 PM
1. Yes it's very common. You will *probably* need to have the gas port opened up a little bit to insure the gun cycles correctly. The shorter barrel means the lock up time is going to change. Requiring more gas to cycle the gun. If you poke around the AR Forums, you'll see lots of folks who are happy with ADCO FIREARMS. www.adcofirearms.comTheir website ordering is fully automated. It's only $65 to have the barrel cut, crowned, and re-threadded. If you are sending a complete upper, be sure to choose the $50 Dissassembly/Assembly fee as well. Turnaround is typically less than 2 weeks. They will check the gas port to make sure it will cycle with the short barrel, as part of the chop/crown/thread service.

2. No. Swapping a barrel is pretty easy to do with the right tools and a little know how. You'll obviously need to sight in your gun again after swapping a barrel, but it's pretty easy to do. AR's index on the barrel extension. As long as your barrel is coming from a reputable mfg, headspacing isn't a significant issue on these rifles.

***IF you do end up using ADCO, let them know I sent you. Never hurts to build up some "referral points" when it comes to working with a gun shop. ;)

May 5, 2011, 04:43 PM
ah my mistake I found the link. duh! lol. it is not very clear about whether they will cut a 16" barrel to 11.5" or also whether they enlarge the gas hole and test it for function or not.

May 5, 2011, 06:19 PM
You can email them: or

You just need to specify the length of the barrel in the comment box. They'll cut it down to whatever length you want. I'm positive that the gas port check and sizing is part of the cut down/crown/thread cost. I am stopping by there tomorrow so I can ask for you while I'm there.

If you want it function tested prior to return shipping they'll do it. However, they've been doing them for so long, it's not necessary. They just check the specs to make sure the gas port is the right size, and if it's not, they make it so.

May 5, 2011, 06:35 PM
Sounds great! If you could ask them for me it would be greatly appreciated, and I will be absolutely certain to mention to them who sent me :D makes sense what you said about the gas hole testing not being necessary. sounds like this is exactly what i've been looking for so if all of this is included like you believe it is, then I will be sending my barrel off to them within the next couple days!

May 5, 2011, 06:56 PM
No need to wait. I just got off the phone with them. (An un-related matter, but fortuitous none the less.)

While on the phone with Steve, I asked them specifically: The barrel threading service includes cutting down to your specified length, crowning the barrel, threading the barrel. Include in the comment section barrel length. They do automatically check the gas port and will enlarge as necessary, but it is probably a good idea to put in the comments "Gauge and enlarge gas port as necessary for x.x" barrel."

If you want it function tested, they will do that. You just need to include a handful of your preferred rounds in the box and make note of that in the comment section. (You would need to provide your upper, but not necessarily a bolt.)

May 6, 2011, 03:12 AM
Wouldn't just be cheaper and easier to just sell the barrel or whole upper and get the length you want?

May 6, 2011, 03:48 PM
if i thought that there was even a chance of me getting a decent amount out of my barrel, i would sell it in a heartbeat. unfortunately, I don't know of anyone looking for a used barrel thatll pay more than a few bucks for it.

May 6, 2011, 05:32 PM
All you need to swap a barrel is the barrel wrench ($10), punches for gas tube and gas block ($5 maybe, dont recall size), and a torque wrench ($20 at harbor freight). If you have a free float handguard you may need an armorers wrench or other specific wrench depending on make. Getting a pinned gas block off can be hell but there are specific punches out there which make it much easier. The problem is if the pin mushrooms when driving it out. I've had this happen and had to cut off the gas block but that was before i got the cupped punch. An upper receiver vise block makes things easier too but it aint that hard to rig your own. If you decide send the barrel in you can remove it yourself by buying the tools for around the cost of dissasembly.

May 6, 2011, 06:04 PM
i already have all of the tools to remove the barrel, as i have done it a few times to install and un-install a free float handguard, and simply to give the barrel a good cleaning. the problem is that the only government profile 11.5 barrels I have been able to find for under $260 are heavy profile and i want a government profile, which my barrel is.

I have been reconsidering, however. I knew all along that it was simply for the shorter over all length and that i would not be gaining any ballistic advantage over a longer barrel. I am now thinking that it is just foolish to spend $200 on the tax stamp alone, just to LOSE ballistic performance all just to be a little more maneuverable. If i could have an SBR and another AR then this would all be said and done by now but the fact of the matter is that my firearms budget is quite limited, and I would like to make this ONE AR the only one that I need, mainly because i can't afford to have two! so I am now thinking that I would like to stay with the 16", but i want a pinned A2 front sight. Now i either have to spend a total of about $130 for an A2 front sight and the gunsmithing to have it pinned to my barrel. this makes me think that I should simply buy a new 16" barrel that comes with one already installed, but that leaves the question of who would buy a used 16" barrel with yhm flip up bolt on gas block sight and what would be a fair asking price?

May 6, 2011, 06:39 PM
I think you are making a good choice to keep the barrel at 16 as by shortening it you will actually be loosing a ballistic advantage.

Does your barrel not have grooves for a pinned A2 sight? If so they are easy to install yourself and can be had for under $40. However, most people upgrade to a flip up sight from an A2 so personally i would stick with what you have. You could aslo get a screw on gas block with a rail on top and then just attach a bolt on A2 style sight.

May 6, 2011, 06:41 PM
In testing a 5.56 piston pistol a couple weeks back, I found velocity losses of up to 900 feet per second compared to a 16-inch barrel, which was already close to 200 FPS loss from a 20-inch barrel.
I can't personally see much sense in losing so much terminal effectiveness.

May 6, 2011, 07:39 PM
my barrel came with a pinned A2 front sight, but seeing as how I didn't think in the long run about if i might want to reinstall the A2 front sight, I chopped it, rounded it, and re-blued it so I could have a low profile gas block for a YHM rifle length free float handguard(this was my "dissipator phase"). after i found that i didnt like the added weight and metallic sound that the bolt makes when it closes due to the metal handguard, I put the old standard M4 carbine handguards back on. although i was satisfied with how nice of a job I had done at making my shaven front sight look exactly like an aftermarket low-profile gas block, I didn't like the idea of relying on an electronic sight and not having any irons in case it went out; this lead to the purchase of the YHM gas block/flip up sight. there are two things about this sight that put it out of the question for me. One is the fact that I am(as you may be able to tell) an obsessive perfectionist. If something isn't perfect, I drive myself insane until either it is perfect, or I have fooled myself into thinking it is lol. With a clamp on front sight, this means that you must make sure that the front sight is level by can probably see where this could cause a perfectionist a problem..."finally, i got it! wait....ok NOW i got it! oh wait i still dont think that's completely level....". i STILL don't feel like it's completely level lol. the second reason why I cannot use this sight is the fact that it simply doesn't look right to me in the sight picture itself. if you compare an A2 front sight to the YHM, you notice subtle differences about them like the fact that the "stem" of the front sight on the YHM is half the width of the top of the sight, while the A2 is the same width all the way through. the ears on the YHM aren't as curved outwards as an A2. all that really matters to me is that with an A2 front sight, i feel more confident and notice myself shooting more accurately than with the YHM.
as far as installing the A2 front sight myself, I don't believe I have the tools, and with my luck I would get it just a sliver of a hair off center, ruining the whole thing for me. I do feel that ADCO's $90 fee to pin a front sight is a bit steep though. I could be wrong though as I have not done this specific task myself, it just seems to me like it isn't $90 worth of work, but again i have not done it so I do not know

May 7, 2011, 02:43 AM
If you have any decent local gunsmiths or AR guys that would help you, I wouldn't think it would cost you more than $20-30 or a six-pack of beer, if you mean just putting on the FSB and seating the pins. If the pin slots have to be cut in the barrel, I could see it costing in the $90 range for the work. Once again, I'd just sell the barrel in that case and get what I want.

May 7, 2011, 08:09 PM
The sight pins are installed after the barrel is drilled to match the fsb and are not interchangable from one sight to another. Every pinned sight is a match for the barrel it is attached to.

May 8, 2011, 02:14 AM
Are you sure about that? I've never heard that before. I'm still an AR novice, but I do a lot of reading and have done a couple of builds. I'm not disagreeing, just surprised to not see this before.

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