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Buster Beaver Cerakote
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A bunch of you very kind and educated folks have been trying to help me with an AR .308. At first it would not cycle and then it would have soft primer strikes. I'm thinking that these events may have happened.: You guys got me into the rifle buffer spring and weight from he carbine. You also got me into an adjustable gas block. The adjustment of the gas block was going fine until soft primer strikes. Then all sorts of help to see what the problems is. This morning I was recalling "Bolt Bounce". I wish I could remember the context. Please feel free to tell me where and why this article was written. Anyway, I was thinking that the bolt when in locked back position and I had placed a cartridge with primer only in batter and I let the bolt go. It went with tremendous force. I had been thinking from advice that there was a going into battery problem from headspace or - fill in the blank. This time I began to let the bolt to forward just until I thought it was in battery. "BANG!" I'm I on track? I think now that there is too much spring of bolt since this happens when you manually let the bolt go. Thanks guys! What now? And, what would I do without all of you!?!?
 
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1. If you cycle manually close the bolt with full spring force, will it go bang when you squeeze the trigger?

2. When it autoloads it will not go bang when triggered?

3. When you have a round in battery it only fires if you reclose the bolt manually with a short stroke?

Just trying to be sure I have it right.
 
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If I followed your writing correctly, are you stating an inserted case with only a primer, detonated when you released the bolt manually?

That’s not supposed to happen.
 
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Sorry. This gun used to run. Sort of. It seemed I had the wrong buffer spring and weight. And an adjustable gas block would help. When these were changed The gun would fire and you could see how it needed more gas to cycle. Then it would not fire. Just soft primer strikes. Issues of head space, FP, bolt, BCG, etc were suggested. Instead of taking the gun out to the range, a 2.5 hour trip. I decided to pull factory rounds apart and just see if the adjustments were setting off the primer. Nothing worked. Then I recalled an article about bolt bounce. With the new rifle buffer spring and weight I was watching that massive .308 BCG slamming into battery. Only having built 15's I was, and am, ignorant as to how much energy this action should take. There is no assist on this upper. So I began to release
1. If you cycle manually close the bolt with full spring force, will it go bang when you squeeze the trigger?

2. When it autoloads it will not go bang when triggered?

3. When you have a round in battery it only fires if you reclose the bolt manually with a short stroke?

Just trying to be sure I have it right.
SO to #1 -No, #2 It does not fire so this is unknown. #3 Yes, or at least the primer goes off.
the BCG, manually, with increasing "draw". When it seemed just enough to close, or be in battery. It went bang. I think the bolt is being thrown into battery with so much energy that is't "bouncing" back. i also think that a forward assist would prove or disprove this theory. I want to try to lessen the spring's energy, or bolt, or ??? Not sure if I'm onto something or how I should go about this discovery. Thanks./
 
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If I followed your writing correctly, are you stating an inserted case with only a primer, detonated when you released the bolt manually?

That’s not supposed to happen.
It has only fired via the trigger. In this case, the primer went off by allowing about 3/4th of the buffer spring and weight to charge the BCG into battery. Locking back the BCG and then releasing it will not fire the primmer. Thanks. Sorry about being muddy with the post. Thanks.
 
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It has only fired via the trigger. In this case, the primer went off by allowing about 3/4th of the buffer spring and weight to charge the BCG into battery. Locking back the BCG and then releasing it will not fire the primmer. Thanks. Sorry about being muddy with the post. Thanks.
Are you saying, you pulled the charging handle to the rear 3/4s of the way, released it, bolt goes forward and a primer detenated?

Sounds like a disconnect issue maybe. Or sear issue. Hammer might be following the bolt forward. This doesn’t always lead to a detenation, but it can.

When you do this is the trigger dead? In other words the trigger never set and is forward?
 
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All auto-loading firearms with reciprocating bolts experience bolt bounce to some degree. When the bolt (or bcg) on a firearm slams forward into the barrel to chamber a new cartridge, the bolt (or bcg) and the barrel rebound off each other, sometimes multiple times, before coming to rest.

An example of extreme bolt bounce...
 
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Are you saying, you pulled the charging handle to the rear 3/4s of the way, released it, bolt goes forward and a primer detenated?

Sounds like a disconnect issue maybe. Or sear issue. Hammer might be following the bolt forward. This doesn’t always lead to a detenation, but it can.

When you do this is the trigger dead? In other words the trigger never set and is forward?
I have to pull the trigger. The problem was getting the gun to fire. initially the problem was soft primer strikes. This seems to be the issue? But that's why I'm here. Asking guys with vastly more experience is always a good idea.
 
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I have to pull the trigger. The problem was getting the gun to fire. initially the problem was soft primer strikes. This seems to be the issue? But that's why I'm here. Asking guys with vastly more experience is always a good idea.
Did you assemble your lower receiver?
 
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Did you assemble your lower receiver?
Yes I did. I also took a working Black Rain .308 and tried the lower on this upper and got the same results.
All auto-loading firearms with reciprocating bolts experience bolt bounce to some degree. When the bolt (or bcg) on a firearm slams forward into the barrel to chamber a new cartridge, the bolt (or bcg) and the barrel rebound off each other, sometimes multiple times, before coming to rest.

An example of extreme bolt bounce...
That's awesome!. Now I need a high speed camera. Kidding. Unless anyone thinks different, I want to either slow the forward speed of the bolt or lessen the force of the bolt. I'm not sure of buffer weights and springs in AR 10's. Do people clip springs? Different weights?
 
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Yes I did. I also took a working Black Rain .308 and tried the lower on this upper and got the same results.

That's awesome!. Now I need a high speed camera. Kidding. Unless anyone thinks different, I want to either slow the forward speed of the bolt or lessen the force of the bolt. I'm not sure of buffer weights and springs in AR 10's. Do people clip springs? Different weights?
Light timer strikes can be caused by assembling the lower with the hammer spring installed backwards.
 
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Yes bolts bounce. Using the other lower narrows the possible causes. If your magazine is out of the picture as a contributor to the condition, I would suspect the buffer or spring at this point. You still have the issue with without the mag, and or a different mags? Nearly empty versus full?

I have a few springs and a set of buffers that are just for tuning a build. I have always built with an adjustable block too BTW, but tune to make sure bullet has exited before BCG rear travel is completed and then for gas volume. The less FHS (Flaming Hot Stuff) going into to the works the better. Your tests have taken the gas volume off the table for the moment as a factor.

AR10s aren't something I have personally built, but the principles of operation are the same. So I would say spring and or buffer can still be part of the issue. Loose weights smacking back and forth, mismatched springs and buffers, as well as resistance on the BCG travel all together or individually can cause the Bolt to come to rest not fully engaged.
 
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Did you ever post pictures as requested in another one of your threads? i.e. hammer/spring, the light primer strike, ect.
Crap, I took them. Lets see if I can do this. Thanks for the reminder.

lAst8.jpg last3.jpg last 5.jpg last 2.jpg inside build.jpg IMG_1332.jpg
 
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That last pic has a rod with a black ring that I was using to compare it to another working build. See that nick to the upper end of where the cam lands? Then just at the bottom right you can see where it's also getting nicked. I tried to tap the BCG after releasing it from a locked mag position. It fired. That's why I thought bolt bounce. Now it wont do that. I'm ordering the go - nogo gauges and a re-loaders sizing block to check ammo. Any idea until they arrive would be most welcomed! Thanks guys!
 

arrowshooter

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Nice build. It does look like your hammer spring is in correctly, so that's out. The marring from the cam pin should tell you something is out of spec, or incompatible causing the issue you are experiencing. Getting the head space gauges is good idea, but won't do you and good until you figure out why the receiver is getting chewed up. Need to consider the BCG, receiver and barrel extension.
 

arrowshooter

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Did you flip the receiver over and run the BCG in and out by hand so that you can feel and see what the bolt is doing?
 
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