AR Rifle to Carbine "Conversion"

[cosermann]

Quick question - If one takes and upper off an AR that was originally a 20" rifle with the fixed stock, and puts a 16" carbine upper on it, do the stock and buffer need to be changed out to a CAR stock/buffer for proper cycling/reliability?

 

[TangoFoxtrot]

Quick question - If one takes and upper off an AR that was originally a 20" rifle with the fixed stock, and puts a 16" carbine upper on it, do the stock and buffer need to be changed out to a CAR stock/buffer for proper cycling/reliability?

Depends on gas system length

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[TangoFoxtrot]

Quick question - If one takes and upper off an AR that was originally a 20" rifle with the fixed stock, and puts a 16" carbine upper on it, do the stock and buffer need to be changed out to a CAR stock/buffer for proper cycling/reliability?

If its going from a rifle length gas to carbine length you may need a heavier buffer.. odinworks.com makes a very nice AND affordable carbine weight system for easy weight adjustment

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[MCgrease08]

I'm by no means an expert, so I'm sure others will be able to tell you based on their experience, but here's my take on it based on my limited experience slapping different uppers on various lowers.

Assuming it's a carbine length gas system then it's possible you may have to adjust. You might be OK just swapping for a different buffer or spring that's not quite as stiff, or adding a few spacers to the buffer tube so there isn't as far for the buffer to travel.

If it's a mid-length gas system you probably won't need to do much, if anything. The gun should cycle OK but you can fine tune based on personal preference.

[video=youtube_share;DYf-MLMODhA]http://youtu.be/DYf-MLMODhA[/video]

Lots of good buffer videos on the YouTube, but you might get bogged down in paralysis by analysis. I'd say start buy just swapping the carbine upper on the rifle lower and seeing what happens. If you don't like the way it's cycling then fine tune from there.

 

[Tombs]

I doubt you'd have any issues running as is. If the upper has M4 feed ramps then one of the potential problems will be taken care of anyway.

Now if this is a full auto lower, you may encounter problems and need to tune buffer weight to run reliably.
The buffer's primary purpose is to eliminate or limit bolt bounce, which isn't much of a problem on a semi-auto.

 

[ditcherman]

Another option would be for you to add a JP Enterprises spring kit and you won't have to change the tube or stock. Make sure and get the builders kit and you can tune it with different springs. At 189$ it may not be the cheapest option but they run nice IMO. They do come with a spacer for rifle length tube, leave it out for carbine.

ETA I'm also of the opinion that it would run ok, pretty sure I've switched lowers around and things ran but can't remember specifics.

 

[charley59]

Answer: NO. It works just fine. Putting your carbine 16" upper on an A2 stocked lower, you may find it's actually quite nice. Perhaps it's the weight of the A2 stock, but it just shoots softer than the same upper on a carbine stock. That rifle buffer weights about 5.4oz or the same as a H3 carbine buffer. Yes, carbine length uppers work great on AR stocked lower. 20" rifle barrels work great on a carbine stocked lower. Done it many times, never had a problem. Do not change springs or buffers or any other changes. Enjoy!

 

[cosermann]

Thanks for the feedback everyone. Should have mentioned it has mid-length gas.

 

[KokomoDave]

I like the "silent" systems that are tunable.

 

[TangoFoxtrot]

I like the "silent" systems that are tunable.

I've started using armaspec, they have so far been as good as JP but dang near half the cost of JP

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[sgthud]

I have not had any issues with switching from 20 to 16. You should not have to switch the stock style with the changing of uppers, but if you have issues I would work the buffer or spring.

 

[charley59]

I should have mentioned either carbine or mid-length gas, you can run the A2 stock on your gun without problems. Caliber 5.56 NATO or .223 Rem.

 

[Hohn]

Quick question - If one takes and upper off an AR that was originally a 20" rifle with the fixed stock, and puts a 16" carbine upper on it, do the stock and buffer need to be changed out to a CAR stock/buffer for proper cycling/reliability?

Not likely. The Rifle length buffer system has a lot more margin in it than a carbine setup. That's why you have a market full of carbine buffer variants and lots of people running just a basic A2 rifle setup for fixed stocks.

There are heavier buffers offered, but that's because they are wanted (i.e. perception of reduced recoil) not because they are needed.

 

[Hohn]

I like the "silent" systems that are tunable.

I've started using armaspec, they have so far been as good as JP but dang near half the cost of JP

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I dislike the spindly little springs those systems come with. I can get essentially the silence of a SCS with a Tubb flat wound spring in a nice VLTOR tube (smooth ID of tube), and a bit of grease on the spring. Only this spring is way beefier and consistent. A VLTOR A5 gives nothing up in tenability to any SCS setup. The ability to go from 4 steel weights to 4 tungsten is a huge span good enough for almost anything short of a straight blowback application.

 

[TangoFoxtrot]

I dislike the spindly little springs those systems come with. I can get essentially the silence of a SCS with a Tubb flat wound spring in a nice VLTOR tube (smooth ID of tube), and a bit of grease on the spring. Only this spring is way beefier and consistent. A VLTOR A5 gives nothing up in tenability to any SCS setup. The ability to go from 4 steel weights to 4 tungsten is a huge span good enough for almost anything short of a straight blowback application.

I do like the weight system JP uses. You can change the weight on armaspec also but I do think JP is easier to alter having the 4 weights you mentioned. As for the springs, I have no issues with armaspecs.. I bought all of mine as kits.. maybe they come with better springs?

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