willbird Posted July 31, 2019 Report Share Posted July 31, 2019 I was googling on the Sig 400 and found a picture of the gas block...interesting looking part. https://www.sigsauer.com/store/low-profile-gas-block-m400.html Quote Link to comment Share on other sites More sharing options...
willbird Posted July 31, 2019 Report Share Posted July 31, 2019 (edited) A few more pictures here. https://www.osagecountyguns.com/sig-sauer-gasblock-lowpro-m400.html it is a 1/2 oz part. Edited July 31, 2019 by willbird Quote Link to comment Share on other sites More sharing options...
jtallen83 Posted July 31, 2019 Report Share Posted July 31, 2019 (edited) On 7/30/2019 at 12:22 AM, 98Z5V said: Check your bolt. Insert your bolt, and rotate it. If it doesn't rotate - punch that Lawyer Pin out. Heard from @willbird that used a SIG bolt, that his bolt rotated with it in there. Mine didn't, with a ToolCraft bolt. There's an external dimensional extractor difference between the SIG bolt and the "others" apparently. Just checked my new Toolcraft bolt, like yours it does not rotate fully in the Sig barrel. Like the BRN-10 bolt it does not work in the Wilson Combat 338 barrel, closes on the no go gauge but not the field gauge. The standard Brownells bolt passes the headspace gauges, slipped it in the Toolcraft carrier and that should be good. Now to grab one of the last few Sig bolts for my second shorty build, just have to figure out whos extractor and ejectors to build out that bolt with. Where there is will there is a way Edit; @98Z5VI'm looking at this Toolcraft bolt in the Sig barrel, why would it need to rotate all the way around? It slides in at the correct orientation and will sit correctly in lockup with the bolt closed with no interference from the pin? I checked it with and without the extractor. Edited July 31, 2019 by jtallen83 Quote Link to comment Share on other sites More sharing options...
jtallen83 Posted July 31, 2019 Report Share Posted July 31, 2019 I'm a little slow sometimes so ya'll will have to excuse the confusion I may have caused on the pin issue. I got to thinking when I check headspace I always orient the bolt like it would be during function, just turn it enough to see if the lug passes with the gauge, hence I did not catch the pin hitting on a lug when the bolt is not correctly oriented. Went back and checked the "pistol" I have built with the Sig bolt, it will not spin all the way around but like all the other bolts I have checked works fine when in the correct orientation so there may not be any dimensional differences in the lugs. Also just realized the Sig bolt uses two AR-15 ejectors and springs as well as the pin being a different length than any others I have, CDNN has the pins in stock so I grabbed a few. Quote Link to comment Share on other sites More sharing options...
Albroswift Posted August 1, 2019 Author Report Share Posted August 1, 2019 I'm thinking 49 bucks to practice milling Fishgill and blowhole comps and brakes is cheap schooling. Enough to convince myself to get another. Screw it up and it's a pistol barrel or pin a real comp on it. Quote Link to comment Share on other sites More sharing options...
Albroswift Posted August 1, 2019 Author Report Share Posted August 1, 2019 (edited) Rotation The 3 BCGs I tried starting with the gas key lined up with the alignment pin on the barrel extension, bolt extended. Bolt went in and rotated to locked position. While applying pressure I could rotate the BCG a little bit either direction but not 360. That seems good, no? I assembled the 308 barrel with upper receiver and bolt closes and rotates to locked position. I dont have a 308 headspace gauge but I do have a progressive set of dummies ranging from min to a few thou over max in my case gauge I may try them next but I see no problem with the AM10bolt, or either the 223 bolts. The only issue I can see is maybe dropping the BCG on a already chambered round and the pin prevents the extractor from opening up to clear the rim, further testing needed! Edited August 1, 2019 by Albroswift Quote Link to comment Share on other sites More sharing options...
willbird Posted August 1, 2019 Report Share Posted August 1, 2019 OK so I got my Aero M5E1 upper, test fit the shorty barrel, and indeed the Toolcraft bolt locks up just fine with the pin in place Quote Link to comment Share on other sites More sharing options...
willbird Posted August 1, 2019 Report Share Posted August 1, 2019 OK so I got my Aero M5E1 upper, test fit the shorty barrel, and indeed the Toolcraft bolt locks up just fine with the pin in place. Toolcraft Bolt/Carrier group to be exact. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted August 1, 2019 Report Share Posted August 1, 2019 (edited) 9 hours ago, jtallen83 said: Edit; @98Z5VI'm looking at this Toolcraft bolt in the Sig barrel, why would it need to rotate all the way around? It slides in at the correct orientation and will sit correctly in lockup with the bolt closed with no interference from the pin? I checked it with and without the extractor. It only needs to rotate enough to catch the back of the bolt lugs directly behind the front of the lugs in the extension - that's all the rotation a bolt does, ever. It rotates exactly as much as the cam pin slot makes it rotate. Look at the bolt face, extended - push it into the BCG and watch the rotation - that's all it ever does. It's not much. Edited August 1, 2019 by 98Z5V Quote Link to comment Share on other sites More sharing options...
Albroswift Posted August 1, 2019 Author Report Share Posted August 1, 2019 On 7/30/2019 at 7:10 AM, jtallen83 said: Strange as my 11 incher hits dead center. I am curious if there are two different barrels, Sig made a gas block change at about the same time they were producing the pistol version of the 716, possibly the port location changed. I need to mock up my second barrel and see where it hits. I am also noticing Sig headspaced these barrels tight, a BRN-10 bolt failed a no go gauge on most of my barrels but passes on the Sig barrels. Yes it is. Oak is at the Nationals next couple weeks so no tube till then anyway, gives me a chance to double check. What I'll try is installing the gas block and the midlength tube, and mark it inside the receiver. See what I get that way. Thanks for the input. Quote Link to comment Share on other sites More sharing options...
willbird Posted August 1, 2019 Report Share Posted August 1, 2019 1 hour ago, Albroswift said: Yes it is. Oak is at the Nationals next couple weeks so no tube till then anyway, gives me a chance to double check. What I'll try is installing the gas block and the midlength tube, and mark it inside the receiver. See what I get that way. Thanks for the input. That is exactly what I did with mine to get a rough idea. Need to precisely place the gas block and re do the measurement. I came up with 11-1/8" marking it on the strong side for length. I am going to shorten a gas tube to try and I can take metal off with a lathe but have not mastered putting it back on ;-). Bill Quote Link to comment Share on other sites More sharing options...
willbird Posted August 3, 2019 Report Share Posted August 3, 2019 16" no thread sig 400 showed up, looks like it will shorten up nice, has a larger dia where the muzzle will be than my Faxon Pencil does at the end of the 1/2-28. Bill Quote Link to comment Share on other sites More sharing options...
Albroswift Posted August 7, 2019 Author Report Share Posted August 7, 2019 (edited) First of the $49.00 Sig barrel builds pretty much complete, maybe get on the mill this weekend and fishgill one of the barrels. Aero Precision upper and gen2 lower, Toolcraft BCG, millspec FCG, Danial Defense pistol grip, ebay guard, JBO $9.00 gas block. Have a Sig Romeo 5 coming tomorrow. Also looked at the Holosun, they were on several platforms at triggercon as well, maybe the next budget build. Edited August 7, 2019 by Albroswift photos Quote Link to comment Share on other sites More sharing options...
Albroswift Posted August 7, 2019 Author Report Share Posted August 7, 2019 (edited) I saw they are out of the 16in non threaded. (Don't ask why I was looking) Romeo5 and a 3x. Romeo looks good through the magnafier Edited August 7, 2019 by Albroswift Quote Link to comment Share on other sites More sharing options...
Albroswift Posted August 9, 2019 Author Report Share Posted August 9, 2019 On 8/1/2019 at 5:22 AM, Albroswift said: Yes it is. Oak is at the Nationals next couple weeks so no tube till then anyway, gives me a chance to double check. What I'll try is installing the gas block and the midlength tube, and mark it inside the receiver. See what I get that way. Thanks for the input. dimpled the barrel, tightened down the gas block, installed barrel and 12-1/16 tube. Marked center of cut out. Exactly 7/8". 11-3/16" tube it is. Quote Link to comment Share on other sites More sharing options...
shooterrex Posted August 10, 2019 Report Share Posted August 10, 2019 John @ White Oak should be back Tuesday. I emailed them this week telling them what I needed. They put me in line. Quote Link to comment Share on other sites More sharing options...
Albroswift Posted August 10, 2019 Author Report Share Posted August 10, 2019 guess I'm going to be right behind you. Did you end up with 11-1/8"? Quote Link to comment Share on other sites More sharing options...
shooterrex Posted August 10, 2019 Report Share Posted August 10, 2019 11 1/8 is what I came up with. Quote Link to comment Share on other sites More sharing options...
willbird Posted August 10, 2019 Report Share Posted August 10, 2019 They are a little cheaper buying 3 instead of 1, I'd be in for an 11-1/8". Bill Quote Link to comment Share on other sites More sharing options...
jtallen83 Posted August 10, 2019 Report Share Posted August 10, 2019 5 minutes ago, willbird said: They are a little cheaper buying 3 instead of 1, I'd be in for an 11-1/8". Bill How much cheaper? I have a 7.62 marked barrel that may need the same length, I haven't mocked it up yet. Wishing I would have just gotten two of the 308 marked barrels so I could have all the same length......hindsight and all. Quote Link to comment Share on other sites More sharing options...
willbird Posted August 10, 2019 Report Share Posted August 10, 2019 3 minutes ago, jtallen83 said: How much cheaper? I have a 7.62 marked barrel that may need the same length, I haven't mocked it up yet. Wishing I would have just gotten two of the 308 marked barrels so I could have all the same length......hindsight and all. PM sent.....I'd rather not quote their prices for them :-). Bill Quote Link to comment Share on other sites More sharing options...
Albroswift Posted August 11, 2019 Author Report Share Posted August 11, 2019 (edited) Range report 16in non threaded 5.56 Shot nice groups Romeo5/ VMX 3T great combination but under gas symptoms even using lightest buffer lightest spring bcg would set the disconnect/hammer and ejected 100% nicely but not enough travel to reliably lock back or strip next round. I'll strip it down and take a look maybe the gas block/ gas tube not sealing. On another note, started cutting a comp in one of the barrels, first slot came out nice stuck and broke bit in second slot. Learning curve. New bit ordered. Need a CNC! Edited August 11, 2019 by Albroswift Quote Link to comment Share on other sites More sharing options...
Albroswift Posted August 11, 2019 Author Report Share Posted August 11, 2019 (edited) PS tried a really tight fitting gas block, same short stroke issue. these photos with the PA block. port go .052 no go. 055 Edited August 11, 2019 by Albroswift Quote Link to comment Share on other sites More sharing options...
98Z5V Posted August 11, 2019 Report Share Posted August 11, 2019 (edited) Needs more gas port diameter. 0.052~0.055" is too small. 5.56 stuff: Quote 16" mid 5.56 0.078 16" mid 5.56 0.081 16" car 5.56 0.0625 16" car 5.56 0.065 16" car 5.56 0.07 Edited August 11, 2019 by 98Z5V Quote Link to comment Share on other sites More sharing options...
Albroswift Posted August 12, 2019 Author Report Share Posted August 12, 2019 Yes, saw that, thanks. Have a couple of new cobalt bits in that size range ordered. (I'm pretty sure I would just break off my 1/16 reamer if I tried that) Practice on the barrel with the broken mill bit first I guess. I'm thinking driving a slug into the barrel before drilling, but maybe go slow and easy no need. Worried about that tiny bit grabbing when it breaks through the bore. Maybe we are getting to the reason Sig dumped these barrels! Thanks. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.