Wayne B Posted October 16, 2019 Report Share Posted October 16, 2019 How would you explain an A Series which is, by all visual indications actually a B Series? The owner clams his rifle in an AR-10(T) Navy Carbine There is no (T) marking on the receiver, and I do not know what the Navy has to do with it. Could this have been part of a special production run for the Navy? AR-10 A4 US 5XXXX (A series SNs are said to begin with an A, for example A000001) It has an early fiberglass Handguard with the fluted ring at the rear and a SS Barrel and Muzzle Brake (both are magnetic) with three angled slots on each side. Is this an aftermarket Brake? There is no Forward Assist There is no vertical recessed portion on the left side of the magazine well. The angle at the bottom of the Mag well seems to be less than that shown in images of A Series Lowers. It has B Series Mag Well Cuts as shown in an ArmaLite video. The Bolt Stop is wide, as in B Series. The Magazine Catch boss appears square as B Series (Not rounded at end). An ArmaLite agent told the owner that he needed to purchase a special Bolt Stop if he wanted to use their new GEN II Magazines. New GEN II Magazines fit and lock in. Early ArmaLite waffle magazines do not. Nor do SR-25 Magazines. I haven’t been able to test fire the rifle to check function with these new Magazines. This new Bolt Stop is narrower than the existing Bolt Stop which appears to be for a B Series rifle. According to the paperwork it is an AR-10 Bolt Stop Replacement Kit PN: EA6075 $18.75. (This is engraved AR-10A, which doesn’t seem right). The original is wider, and looks like one for the B Series. Quote Link to comment Share on other sites More sharing options...
mrraley Posted October 16, 2019 Report Share Posted October 16, 2019 (edited) Just from what you have described... this is an early "B" version. No forward assist. The bolt stop was shorter due to the converted M14 magazines had a spring loaded plunger in the follower to trip the bolt stop. So it would need a newer one to use the GEN II mags. Tech Note 66 Tech note 71 On that year, the muzzle brakes were pinned on due to the "assault weapon ban" at the time. Most likely it might have two (2) cross pins OR is pinned and welded at the 6 o'clock position. If it is, you will see a small circle that has been blended into the brake itself to hide the pinning. If you have pictures, I might be able to tell you more about it, with the exception of the year made. Edited October 16, 2019 by mrraley Quote Link to comment Share on other sites More sharing options...
Armed Eye Doc Posted October 16, 2019 Report Share Posted October 16, 2019 @Wayne B Listen to this man.^^^^^ He knows what he is talking about. Quote Link to comment Share on other sites More sharing options...
Sisco Posted October 16, 2019 Report Share Posted October 16, 2019 30 minutes ago, Armed Eye Doc said: @Wayne B Listen to this man.^^^^^ He knows what he is talking about. +1 If mrraley says that, then that is what it is. He is the final answer on all things Armalite. Quote Link to comment Share on other sites More sharing options...
mrraley Posted October 16, 2019 Report Share Posted October 16, 2019 Anodized ones are easier to spot, but even the stainless steel you can see at the right angle. Quote Link to comment Share on other sites More sharing options...
mrraley Posted October 16, 2019 Report Share Posted October 16, 2019 Good reading right here... Quote Link to comment Share on other sites More sharing options...
Wayne B Posted October 17, 2019 Author Report Share Posted October 17, 2019 Quote Link to comment Share on other sites More sharing options...
mrraley Posted October 17, 2019 Report Share Posted October 17, 2019 That right there was a brief run where they actually had the muzzle brakes pressed on. As for the bolt stop, that's an easy upgrade and I might even have one. Quote Link to comment Share on other sites More sharing options...
Wayne B Posted October 17, 2019 Author Report Share Posted October 17, 2019 Mrraley, I thank you for taking the time to assist me. So, It really is a B series, in spite of the A in the serial number (AR-10 A4 US). The Bolt Stop is incorrect for the new GEN II Magazines. Please correct me if I am wrong. What about the Magazine Catch? The boss on this one appears square as B Series (Not rounded at end). Quote Link to comment Share on other sites More sharing options...
edgecrusher Posted October 17, 2019 Report Share Posted October 17, 2019 24 minutes ago, Wayne B said: So, It really is a B series, in spite of the A in the serial number (AR-10 A4 US). A-4 is in regards to the configuration not the serial number Quote Link to comment Share on other sites More sharing options...
mrraley Posted October 17, 2019 Report Share Posted October 17, 2019 1 hour ago, Wayne B said: So, It really is a B series, in spite of the A in the serial number (AR-10 A4 US). The Bolt Stop is incorrect for the new GEN II Magazines. Please correct me if I am wrong. What about the Magazine Catch? The boss on this one appears square as B Series (Not rounded at end). Yes it is a "B" series. (AR-10 A4) AR - Armalite 10 - Refers to the size (could have been .308/7.62, .243, .300 RSUM) A4 - usually meant it was a flat top with a collapsible butt stock. The mag catch is perfectly fine for the M14 and the Gen II mags. The current bolt stop might not work properly with the Gen II mags, but it will work fine with the M14 converted mags. I will check when I get home to see if I have another newer AR10 bolt stop you could swap out real easy. Quote Link to comment Share on other sites More sharing options...
Wayne B Posted October 18, 2019 Author Report Share Posted October 18, 2019 Yes, I am interested in your Bolt Stop. What do you want for it Do you have any other treasures you might be willing to part with? Regarding this pressed-on Muzzle Brake, any suggestions on removing it? Could anyone tell me any tips on removing an early ArmaLite AR-10 fiberglass Hand guard? I heard somewhere that there was a left hand thread involved. Quote Link to comment Share on other sites More sharing options...
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