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Discussion Starter #1
Hello all. Hope all is well. I have another question which I believe is somewhat of a technical question. Last night I did an AR 15 lower build and when I installed the buffer tube Buffer Retaining Pin, I screwed the buffer tube right up to the nipple on the Retaining Pin leaving it a little tighter then my others. And when I went to test it, I put two rounds into a brand new short profile magazines which by the way, the spring action inside was very stiff, loading the rounds was unusually hard. I wanted to see if it would fire normally. When I pulled the trigger, the first round fired off, but the second round failed to chamber. My question is, would that be a result of winding the buffer tube tight on the Buffer Retaining Pin, or does that make a difference? On my other AR's I screwed the buffer tube in just enough to hold the retaining pin down, but on this one, I went another full screw. Please advise, thank you.
 

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Typically you only screw the tube in far enough to hold the retaining pin in place. Going the bit further shortens the distance your buffer/spring have to work in, but if the BCG moves far enough aft to be locked back and to pick up the round off of the mag, I doubt that short distance is going to give enough extra resistance to prevent picking up the next round, but it is pretty easy to back it off a turn anyway and eliminate it as a question.

Maybe the gun is under gassed or that stiff mag gave some problems... Mags are easy to swap...maybe the gas block is not quite positioned correctly. I doubt the buffer tube is the problem.
 

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Discussion Starter #3
Hey AgedWarrior. Thank you much. I've fired the firearm quite a few times with another lower and it functioned well. I've backed off the buffer tube one turn and I plan on trying it again with one of my broke in magazines. I really appreciate you helping me. Thank you much.
 

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Can you even go one full turn more once it grabs the buffer retainer? It's been awhile but i seem to remember if you go too far you only get 1/2 or maybe a little more of turn on the buffer before it hits the retainer pin and then the backing plate won't line up at the back.
 
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Discussion Starter #6
Hello AgedWarrior. I think it just might be that. Can it be because the magazine is new and stiff? If so, can it be worked out without firing it, or do I have to try and put some rounds through it? Thank you.
 

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Hello AgedWarrior. I think it just might be that. Can it be because the magazine is new and stiff? If so, can it be worked out without firing it, or do I have to try and put some rounds through it? Thank you.
Being a bit stiff is not necessarily a problem in itself, but the stiffness could be because the follower is binding...that can cause feeding issues pretty quick.
 

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Discussion Starter #8
Thank you AgedWarrior again. Now I have another question. I'm planning an lr-308 build with an 18 inch barrel. I'd like to know your thoughts on what the inner length of the buffer tube should be? I've read that it should be around 7 Inches. What weight buffer I should use and it's length? I've read it should be a heavy buffer (H1 or H2) weighing around 3.8 to 4.68 ounces designed for 308 carbines and be about 2.5 inches long. The length of the buffer spring and amount of coils it should have? And what type of adjustable stock would be okay? Please advise. I apologize if I'm asking to much. Thank you much.
 

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Discussion Starter #9
Hello square target2. Thank you for your input. I had it turned so much that it was resting on the retainer pin kind of hard. I backed it off a full turn and changed magazines, useing one that was broken in. When I charged it and pulled the trigger, it just clicked and the round jammed inside. I worked on it and released it and reloaded the magazine. I then aggressively recharged it. That time, when I pulled the trigger it fired. I pulled the trigger again and it fired again. The firearm is an SPR that's pretty much new. It only had 10 rounds ran through it on another lower. When I first got it, I had no problems firing it. I think the reason it didn't fire at first has something to do with the buffer tube and spring I'm using on this new lower; it's an 80 per center. What's your thoughts? Thank you.
 

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Thank you AgedWarrior again. Now I have another question. I'm planning an lr-308 build with an 18 inch barrel. I'd like to know your thoughts on what the inner length of the buffer tube should be? I've read that it should be around 7 Inches. What weight buffer I should use and it's length? I've read it should be a heavy buffer (H1 or H2) weighing around 3.8 to 4.68 ounces designed for 308 carbines and be about 2.5 inches long. The length of the buffer spring and amount of coils it should have? And what type of adjustable stock would be okay? Please advise. I apologize if I'm asking to much. Thank you much.
Okay...sounds like your building with a carbine butt stock. To my knowledge, there are only two length buffer tubes, carbine or rifle. This is true of AR15 and AR10. The buffer weight in the carbine I believe starts at 3.8 ounce and is shorter than an AR15 buffer due to length of travel for the longer cartridges (I do not remember actual length offhand). The springs I have used were designated for the AR10, but some appear the same as AR15 springs at first glance, and I have heard of folks using the same springs. Personally I bought springs designated for the AR10. You could find that you need a heavier buffer depending on the gas tube length. With an 18” barrel I would suggest at least a mid-length gas system...but that is just my opinion. You might do some reading on line concerning buffer buffers AR15 vs AR10 to help settle some more info for you.
 
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