Jfludd Posted July 21, 2022 Report Share Posted July 21, 2022 I recently completed my first .308 build. Went to the range loaded the first round, fired fine, went to fire the 2nd round and click...nothing. I have an adjustable gas block that I have played with 1/4 at a time to full open and it makes no difference. For some reason it just wont "grab" and chamber the next round. I basically have a bolt action rifle at this point lol. I also noticed that it won't lock back open after firing the last round in the mag. I have read a few different things it could be and was hoping to get some help and ideas before just going out and buying more parts. Below is the list of parts I used: Aero M5E1 Enhanced Upper 20 inch Criterion Barrel (rifle length gas) Aero stainless rifle length gas tube Aero M5 Rifle buffer kit - rifle buffer spring - buffer length is 5.3" -buffer weight is 5.6oz - I can measure the actual tube length, but its fairly long. I would guess something like 11" or so. Seekins low profile adjustable gas block Brownells Nickle boron BCG I'm pretty certain i have aligned the gas block properly as i spent some time to do so when assembling but I will double check that. In some of my research it was recommended that the hole on the barrel might not be large enough to match the hole on the gas block and to drill out the barrel to enlarge the gas port...is that okay to do? I was told that it could be a tension issue on the spring? So i added up to 4-5 quarters (individually) to the back of the spring inside the buffer tube- it made no difference. In reading through some other posts on this forum it sounds as if most common practice is a carbine buffer system, could it be as simple as that? The rifle buffer tube is just to long and the bolt isn't traveling back far enough to allow the next round to up form the mag? Could I get a lighter spring rather than change the entire tube? Any recommendations? Its a lot going on, I know lol! Hence why I'm looking for a bot of guidance to try and narrow down some of the possible solutions. Any help would be greatly appreciated. Quote Link to comment Share on other sites More sharing options...
dpete Posted July 21, 2022 Report Share Posted July 21, 2022 First things to do is get an accurate measurement of the INSIDE of the buffer tube, get the quarters OUT of the buffer tube, and measure the diameter of the gas port in the barrel. Using the base of drill bits will get you close. What one fits, what doesn't. Or pull out the caliper. Quote Link to comment Share on other sites More sharing options...
Armed Eye Doc Posted July 21, 2022 Report Share Posted July 21, 2022 How many rounds did you fire through it? Sometimes these rifles need to break in to function correctly. What type(s) of ammo were you using? Quality ammo is recommended in the beginning. Weaker loads may not function well in a new rifle. How much lube did you use? Most need lots of lube during the break in process. I would doubt if the rifle buffer tube is incorrect. The spring could be an issue but not the first thing I would change. If your buffer is truly 5.3 inches long, It is 0.1 inch too long and you may need to shave off a little. Will your bolt hold open if you manually charge it with an empty mag? The more likely reason is that your gas port is too little and causing it to be undergassed. What is the diameter of the journal at the gas block... .750? @98Z5V can calculate what size the hole should be. I agree with @dpete that you should measure the current gas port to see whether it needs to change. Quote Link to comment Share on other sites More sharing options...
Jfludd Posted July 22, 2022 Author Report Share Posted July 22, 2022 17 hours ago, dpete said: First things to do is get an accurate measurement of the INSIDE of the buffer tube, get the quarters OUT of the buffer tube, and measure the diameter of the gas port in the barrel. Using the base of drill bits will get you close. What one fits, what doesn't. Or pull out the caliper. Thank you! I was able to measure last night and the inner tube measures 9-5/8". I can fit a 5/64 drill bit into the gas port, but not a 3/32 I'm tending to think the gas port may be the problem the more I read Quote Link to comment Share on other sites More sharing options...
Jfludd Posted July 22, 2022 Author Report Share Posted July 22, 2022 16 hours ago, Armed Eye Doc said: How many rounds did you fire through it? Sometimes these rifles need to break in to function correctly. What type(s) of ammo were you using? Quality ammo is recommended in the beginning. Weaker loads may not function well in a new rifle. How much lube did you use? Most need lots of lube during the break in process. I would doubt if the rifle buffer tube is incorrect. The spring could be an issue but not the first thing I would change. If your buffer is truly 5.3 inches long, It is 0.1 inch too long and you may need to shave off a little. Will your bolt hold open if you manually charge it with an empty mag? The more likely reason is that your gas port is too little and causing it to be undergassed. What is the diameter of the journal at the gas block... .750? @98Z5V can calculate what size the hole should be. I agree with @dpete that you should measure the current gas port to see whether it needs to change. I've probably only put around 60 rounds of Winchester .308 147 grain boat tail through it thus far. I'll double check on the empty mag/hold up question. But just so I'm sure I'm following you correctly, by that you mean I should be able to insert an empty mag, pull the charging handle back and the bolt should remain cocked back (as if I had pressed the bolt catch) and I can see right into the ejector port? The gas journal is .750, I could only get a 5/64 drill bit into it, and not a 3/32. Quote Link to comment Share on other sites More sharing options...
Armed Eye Doc Posted July 22, 2022 Report Share Posted July 22, 2022 3 hours ago, Jfludd said: But just so I'm sure I'm following you correctly, by that you mean I should be able to insert an empty mag, pull the charging handle back and the bolt should remain cocked back (as if I had pressed the bolt catch) and I can see right into the ejector port? Exactly like that Quote Link to comment Share on other sites More sharing options...
Jfludd Posted July 23, 2022 Author Report Share Posted July 23, 2022 6 hours ago, Armed Eye Doc said: Exactly like that Just checked and yes. It will manually lock back open on an empty mag. What would the harm be if I drill the gas port on the barrel larger? In theory I could just tune it down with the adjustable gas block, if it then resulted in over gassing? From a few other things I’m finding/seeing the gas port should be something like .093 or .096. I certainly don’t have that right now. Quote Link to comment Share on other sites More sharing options...
DNP Posted July 23, 2022 Report Share Posted July 23, 2022 Having to put an adjustable gas block on would be worst case scenario, and pretty unlikely to occur if you start at the low end of where it should be and work up. It has solved many problems with many guns here on this forum. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted July 23, 2022 Report Share Posted July 23, 2022 Your recoil system hard parts are good. Replace the recoil spring with either the Armalite EA1095 spring, or a Sprinco Red spring. Then, for sure, nothing is questionable in the recoil system. Gas tube protrusion is still in question. Your gas port is way too small. You have a Go at 0.078" (5/64"). You have a No Go somewhere over that. You need between 0.090"~0.096" to run Rifle gas on a 20" .308 barrel with a 0.750" gas block journal. It'll be more to the higher side of that, than the lower side. Always test an adjustable gas block Wide Open. You adjust down after the gun runs. Otherwise, you waste ammo, and never, ever find out that your gas port is too small. Adjustable gas blocks can only choke down the amount of gas going to the BCG - they can never add more gas to the equation. Use numbered drill bits - they have a greater size variance over fractional bits. Click this: https://littlemachineshop.com/reference/numberdrillsize.php Quote Link to comment Share on other sites More sharing options...
Jfludd Posted July 23, 2022 Author Report Share Posted July 23, 2022 Understood! Thanks all for the help. I’ll swap the spring, drill the port and keep you all posted! Thanks again Quote Link to comment Share on other sites More sharing options...
Jfludd Posted September 7, 2022 Author Report Share Posted September 7, 2022 Finally got a chance to go to the range. After swapping the spring to the sprinco red and drilling the gas port larger. All is well! She cycles like a charm! Thank you all for the help! Greatly appreciated. Quote Link to comment Share on other sites More sharing options...
unforgiven Posted September 7, 2022 Report Share Posted September 7, 2022 That's great another satisfied customer 🍻🍻🎉 Quote Link to comment Share on other sites More sharing options...
Armed Eye Doc Posted September 7, 2022 Report Share Posted September 7, 2022 That's great news! Quote Link to comment Share on other sites More sharing options...
shooterrex Posted September 8, 2022 Report Share Posted September 8, 2022 Glad to hear it's running right. Quote Link to comment Share on other sites More sharing options...
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