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MaineMan2

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  1. Scale and #43 drill bit arrived. Please note - I’m basically keeping notes here at this point. Waiting on Armalite spring and email response from Springco. I am curious though about what potential problems a slightly long buffer might cause. I measured something wrong the other day. The Faxon Big Gunner 16” barrel gas port is between 0.0807” and 0.086”. That should be small, if anything, based on info above. #1 AP M5 enhanced 18” barrel, mid-length gas, rifle receiver extension - works fine BCG 18.5 oz. Buffer 5.3” 5.4 oz. #2 AP M516” barrel, Armalite mid-length gas, rifle receiver extension - ejects 1:30 10-12 feet WW 16” barrel, mid-length gas tube, carbine receiver extension BCG 18.6 oz. Buffer 5.28” 5.4 oz. I do need to put upper #2 on lower #1 to see if the problem is in the lower as we suspect. Finally, I’m not compulsive about where the brass ejects. However, when it’s flying out almost straight ahead and going over 10’ something isn’t right.
  2. If the gas port is the correct diameter, then the problem must be mass of the buffer + BCG -OR- spring. Armalite EA-1095 spring is inbound. So is a scale that should be “good enough”.
  3. Not my Ace Hardware 😜. I called them and #43 was “the only one we don’t have in stock”
  4. Turns out a #43 drill bit is in between the 2 data points I already have so I ordered just that bit.
  5. OK inside of buffer tube is exactly 9-11/16” deep. Buffer measures 5.28” long. 5.6 oz. weight came off Aero Precision site - I don’t have a scale in that range. Checking with every drill bit, etc. I can find, the gas port is between .086” and .093”. Probably close to half way in between. Based on everything I can find here, that is too big for a 16” barrel: I will order a new spring when I order the adjustable gas block. I’m assuming dialing back the gas is in order so correct me if I’m wrong! Need to know if it’s worth it to buy a set of numbered drill bits. May be able to weigh the buffer later. The BCG doesn’t come close to the back of the receiver where the buffer sits at rest (don’t know what that’s called). I know for an AR-15 you need to check and make sure BCG doesn’t hit that bridge before it bottoms out in buffer tube. Clearance for AR-15 should be 2 quarters thick. This was much more.
  6. Took a new 308 AR build for its first range visit today. Ejection is very far forward - about 1:30 - and the cases are flying 10+ feet. Winchester white box M80 ammunition. The bolt is locking back correctly. I only fired single shots as my goal was to sight the rifle in. I’d brought 2 rifles to sight in so I switched to the other one rather than shoot this 308 AR more. My first thought is that I need an adjustable gas block, but let me spell out as many details as I can and get your input. Aero Precision M5 upper and lower receivers, BCG, rifle length buffer tube, and M5 308 Rifle buffer kit. The buffer is 5.3” long and weighs 5.6 ounces. I used the exact same parts with a Fulton Armory 18-1/2” mid-weight barrel. Fulton Armory specs an Armalite carbine AR-10 buffer tube for that barrel, so that is what I used. SLR adjustable gas block in the first build; however, I didn’t need to adjust anything. That rifle ejects about 3:30 and runs like a top with the SLR adjustable gas block wide open. (Using the exact same ammo.) I used a Faxon Big Gunner profile 16” barrel for this new build. Stock Midwest Industries gas block. A normal “mid-length” gas tube didn’t come close to the middle of the cam pin cutout in the upper receiver, so I got the longer Armalite AR-10 “carbine” gas tube. I don’t have the pin gauges I would need to measure the gas port diameter but am guessing that Faxon has over-sized it. So is an adjustable gas port the first step? I’m reluctant to mess with success, but swapping gas blocks between build # 1 and build # 2 might save me a little money.
  7. ETA: a year ago I considered crimping unnecessary for 308 Winchester. However, my recent research indicates that more and more people are recommending crimping for gas operated, semiauto rifles. Including a tech at Hornady I spoke with yesterday. Roll crimp for bullets with cannelures. Taper crimp or no crimp for bullets without a cannelure.
  8. Those videos aren’t available on Brownells/Sinclair anymore. However, they are on YouScrewed.
  9. I’m wrestling with another Aero Precision lower and that takedown spring is driving me nuts again. So I found this video: They say to cut off much more of the spring than I had done. Plus now I know why they don’t give you a shorter spring for the rear takedown pin.
  10. PMags. I like Aero Precision S-One handguards. The way they connect to the upper receiver is solid, if a bit fiddly the first time you install one. Weight is very good and that is important to me. However, if I wanted a beast of a handguard that could really take abuse I might look elsewhere.
  11. Agree on WW customer service and bang for the buck with Windham Weaponry ARs. My 308 AR from them has DPMS pattern receivers. Bought 1 or 2 years ago.
  12. Does anyone use a Flex Hone to polish the chamber on a new barrel or is that only for when you have problems? How about lapping the barrel during break in? Thanks, Chip
  13. The horse has been beaten post mortem; however, sometimes a video is worth a thousand words. I typed up the following to get my own understanding squared away. It may or may not be useful to anyone else. At 4:40 in This video you can see the expanding gas entering the chamber inside the BCG. For a moment, the bolt is pushed forward by gas pressure at the same time the BCG is pushed backward. This reduces pressure on the bolt lugs while the cam pin is rotating the bolt out of battery. When the BCG has moved backward far enough for gas rings on the bolt to be forward of the vent holes in the side of the BCG, the gas pressure inside the BCG is released and the bolt can move backward with the BCG (under inertia now). This reflects the genius of Eugene Stoner IMHO. It also demonstrates the critical timing involved in getting this system to operate correctly. Now look at the carrier key/gas tube connection during that cycle. If the gas tube were a bit too long, it’s OK. More gas will be released through the holes in the side of the BCG from that chamber inside it but the BCG and bolt can still keep moving backward. However, if the gas tube is too short, the gas seal between the carrier key and the gas tube could be lost BEFORE the BCG gains enough momentum to move backward as fast and as far as it needs to. (Please note that the gas tube could be so long that it bottoms out in the carrier key, preventing the bolt from fully locking into battery and that would be “bad”.) Another video at 3:15 shows the gas system and bolt at work. (Turn sound down unless you like really bad heavy metal music) BTW that first video does an excellent job of showing how the trigger, hammer, disconnector and auto-sear operate. The handoff of the hammer from the disconnector to the trigger always gave me the creeps but it makes complete sense for select fire.
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