My .308 learned a new trick... Bolt catch not catching properly.

[AdamO]

So this is something new that just started happening.   I'm unable to manually lock back my bolt. 

 

Gun cycles and shoots like it should.  It locks back fine on its own with an empty mag but with the mag removed I can't lock it back manually pressing the bottom of the bolt release.

 

It wasn't like that when I first built it and I've only put about 150rds down the tube. 

 

Here's the relevant build info:

Aero M5 forged reciever set, Std. Aero M5 LPK, Rainier chrome lined bolt (no FA serrations), Rainier select barrel. I run her pretty much dripping wet.

 

Any ideas why it worked at first and not now?  Should I order up an AR-10 bolt catch from Armalite?

Thanks fellas,

-Adam

[Robocop1051]

Pull the bolt catch off, then check the spring and detent.

[survivalshop]

 Strange that it locks back on last shot , but not manually . Are you sure its catching the Bolt face when locking back on last shot ?  If its catching anywhere but the Bolt face , you have a problem .

[match308]

Make sure you have 308 buffer and not an AR15 as they're longer and will keep the bcg from coming back far enough.

[98Z5V]

I think Adam either broke the bolt catch, or he broke the pin/screw that secures the bolt catch in the lower.

[AdamO]

It's strange.  It's like a 'hair trigger' bolt catch.  Like I said before, it locks back just fine on an empty mag, but with no mag in the well, it just barely works.  I figured out that, with no mag, if I pull the bolt full rear with the CH then engage the catch button it will hold, but just barely.  Any type of shock will send the bolt into battery (like setting it down on the table too hard, bumping the buttstock, etc.)

 

I've not taken the time to run it full to ground just yet.

[survivalshop]

   Std lower parts group , does it have a 308 specific Bolt catch ? Or an AR 15/16 Catch ? 

   

 

 

 

  I broke the first two DPMS attachment screws before & as 98 said , it will act the same way.

Edited April 2, 2015 by survivalshop

[jonnyjet]

I had an issue like this, the bolt catch was stopped by the upper receiver before it would fully hold the bolt. I had to remove the bolt catch, trim it a little with a dremel and it works fine now. 

[survivalshop]

 Does it lock up the Bolt like this ?

 

[AdamO]

Yes SS. that is how it looks when the bolt is locked back.

[survivalshop]

  The reason for it holding the BCG back with a Mag in is, the mags follower is keeping steady pressure on the Bolt face( of course you knew that ) once the pressure to hold it in position is taken away , some Bolt catches seem not to hold as well . If your Catch is in the same position as the one in my photo, it should hold it, but it has to go far enough up on the Bolt Face to do so , not just barely . Must catch on two of the Lugs on the Bolt face .

  Check to see how much play is in the catch in the Lower Receiver , if it has a chance to cock side ways too much , the Bolt face can slip off of the Catch .

    You can increase travel of the Catch to have it be forced up or higher in the Receiver. Make sure its a 308AR Catch & not a AR15 as in one of the upper photo's , you didn't say if it was or not . 

[98Z5V]

Adam, did you by chance install a disconnector spring in the bolt catch plunger?  The two are identical, with the exception that the disconnector spring has it's last coil flared larger.  A disconnector spring in the bolt catch plunger can jam up, because of that last coil.

 

Easy way to find out is check your disconnector spring in the trigger group - if it doesn't have a larger coil on the end, then you know where that spring is...  <lmao>

 

I'll bet Lazerus already knew that, too...  

Edited April 21, 2015 by 98Z5V

[AdamO]

That's entirely possible!  I'll have to look into it when I get home.

[Gil001]

On 2/9/2015 at 10:54 AM, AdamO said:

So this is something new that just started happening.   I'm unable to manually lock back my bolt. 

 

Gun cycles and shoots like it should.  It locks back fine on its own with an empty mag but with the mag removed I can't lock it back manually pressing the bottom of the bolt release.

 

It wasn't like that when I first built it and I've only put about 150rds down the tube. 

 

Here's the relevant build info:

Aero M5 forged reciever set, Std. Aero M5 LPK, Rainier chrome lined bolt (no FA serrations), Rainier select barrel. I run her pretty much dripping wet.

 

Any ideas why it worked at first and not now?  Should I order up an AR-10 bolt catch from Armalite?

Thanks fellas,

-Adam

 

[Gil001]

Hi I'm new to this blog and I have the same problem with a new project I just finish. Only a question how AdamO solve the issue of the AR in question because I have exactly the same issue. Thanks for any news about. 

[shepp]

7 hours ago, Gil001 said:

Hi I'm new to this blog and I have the same problem with a new project I just finish. Only a question how AdamO solve the issue of the AR in question because I have exactly the same issue. Thanks for any news about. 

Welcome to the forum feel free to tell us about yourself in the intro area

[Waldo]

I have a similar issue that I believe I might have identified but not yet resolved. I'm using an Aero precision upper mated with an 80% Arms lower, a CMMG .308 lower parts build kit. I initially thought that I had a failure to feed issue. Releasing the bolt from the locked back position and the first round was not being stripped correctly from the magazine. Instead it was catching the casing approx. 1/3 down the case, stripping it out of the magazine until it jammed up prior to being properly chambered. If you pull the charging handle full back after clearing up the jam, the feed, fire, cycle evolution is fine. Upon deeper inspection I found that the bolt catch is not catching the face of the bolt but instead is stopping the BCG at the BCG forward shoulder instead hence resulting in the bolt face not being in the proper position rearward to either catch and lock open or strip the initial cartridge from the magazine. Viewing without measuring, I can see that when the charging handle is pulled fully rearward, the face of the bolt is requiring approx another 1/16 - 1/8 of an inch of rearward travel to catch. This is all I get though. Looking at these threads has pointed me towards looking at the buffer and buffer spring. Hope this helps someone and if anyone has a comment for something easier / better to try, I'm open to any suggestions.

[Matt.Cross]

Drive the roll pin out of your buffer, remove the rear plug from the buffer, and dump the guts out. Then reinstall the buffer into the buffer tube sans rear plug, allowing extra rearward travel. If the bolt locks to the rear then, you know your buffer is too long.

[survivalshop]

 Remove the Buffer components & weigh the Buffer , measure the length of the Buffer , measure the length of the Buffer Spring & count the Coils . Carbine or Rifle Stock system ?

[Guofu Chen]

Has this been resolved? I am having the same problem with the newly built...

[Armed Eye Doc]

1 hour ago, Guofu Chen said:

Has this been resolved? I am having the same problem with the newly built...

Welcome to the forum.

You would do better if you started a new thread and included the details of your build.  The details of your rifle may be different than this thread.

https://forum.308ar.com/forum/12-general-discussion/

Also, hit up the intro section and tell us about yourself.  We like to meet new people.

https://forum.308ar.com/forum/22-introductions/

[Marcum]

There are a few ways to diagnose the problem and multiple things could cause the bolt catch problem. First thing to try is take out buffer and spring and bolt carrier. See if bolt catch moves as it should with upper on the lower. If it does then the problem is buffer, buffer spring, or buffer tube. An AR10 /LR308  carbine buffer tube is  longer than an AR15 buffer tube. One that works is mil-spec UTG pro AR308 extension tube. Cheaper than dirt has them. The buffer should be 3.8 oz. and 2-1/2" long. Back to the bolt catch. If the bolt catch doesn't move as it should without bolt carrier in place the bolt catch is hitting the upper. To correct the problem either take it to a gun Smith or use a drimmel tool and carefully take off the material where it is touching. Make sure you put a rag in chamber area to prevent anything intering barrel. Keep checking to see if bolt catch starts moving so you don't take material that doesn't  need removed. Most likely it will be in the areas where the rounded corners are above the bolt catch. I bought 5 buffer tubes that claimed to be for LR308 AR10 before I bought the one that works by UTG.

[Marcum]

[98Z5V]

HOLY SHIIT!  Are you even serious here?

[98Z5V]

35 minutes ago, Marcum said:

 One that works is mil-spec UTG pro AR308 extension tube. Cheaper than dirt has them. The buffer should be 3.8 oz. and 2-1/2" long. 

 

I bought 5 buffer tubes that claimed to be for LR308 AR10 before I bought the one that works by UTG.

#1.  Fuk Cheaper Than Dirt.  In the neck.

#2. The buffer should be 5.4oz, no matter what the length, in order to control the additional weight of a .308AR BCG, and the extra force of the .308 Win round, over that of a 5.56 round.  That was the original design, 5.4 oz buffer.

#3.  There is no such animal as a "LR308 AR10".  Those are two completely different platforms.

Now, with all that said, welcome to the board, and we'd like to see an intro post from you, in the Intro Section.