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There have been mutliple projects done by different users in cutting barrels and adjusting regulators and such. Would you mind sharing the technical specifics on opening up the regulator and any other information that would assist in properly modifying their system? It would also help to mention the benefits (things like balance, etc.) or issues (cycling with suppressors, etc.) in response to the modification.

14.5"
12.5"
10.5"

(certainly not regulated to these 3, if you have insight on other dimensions please chime in!)
 

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http://acrforum.com/forum/showthread.php/348-10.5-quot-sbr-acr!?p=3639&viewfull=1#post3639

Here is a post bigdog made with reference to a port spec on the 10.5" barrels. I knew it was on here somewhere. The ACR runs very efficiently on gas. While the carbine barrels use more pressure the 12.5" barrels (in mid length gas) should still run fairly tight with just a minot tweak to the factory port.

As for the 14.5" barrels the standard port on the 16" barrels has worked fine for me. Zero issues thus far.
 

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the 10.5 suppressed balances like the 16" acr w/o the can. i'm still tuning mine on unsuppressed mode but suppressed i have over 500 rounds with zero problems

i cant remember the factory gas port size but according to bm they are using a .052 for the mil (5.56) and .058 (.223) for the 10.5" barrel, this is not confirmed yet but hk94dude is running his 10.5" with a .063 and no problems, if i do another sbr my 2nd 10.5" barrel set will not be adjustable, i'm going to send it to adco and have them turn it down and shrink the gas port to around .052 as a test
 

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Sorry to bring up a dead thread. Is .052 the standard size on the 16" barrel? I'm about to have a 14.5 made and am trying to find all the specs to give to the guy that I can find. I don't have a caliper with me or else I would to it myself. Can anyone give me that info to send along to him? I just need an accurate figure that will work with the standard block and regulator so that I don't have any complications since this will be a pin and weld 14.5
Also, does anyone off hand know how far up the op rod needs to be cut and reprofiled for a carbine conversion?
 

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install the gas block and set the barrel on the extension. The piston needs to fit in the gas block with the regulator in it and touch the table along with the extension. Any length you cut off needs thinned out too since it has 2 profiles.
 
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