Gun does not cycle; bolt release does not hold BCG

[Marvin Hullinger]

I recently purchased a 308 with upgraded trigger and BCG. First time shooting out of the box, the gun did not cycle properly. Took the action spring out and pushed the BCG against the held up bolt release and the BCG slipped by it. I noticed on my Sig 308 that the BCG front is cut square across the face that contacts the bolt release catch, the new 308 upgraded BCG has an angle cut at a diagonal where it appears that a straight face would hold. I put the lighter action spring from the Sig into the new gun and it still did not hold. Any suggestions?

 

[Armed Eye Doc]

1 hour ago, Marvin Hullinger said:

I recently purchased a 308 with upgraded trigger and BCG. First time shooting out of the box, the gun did not cycle properly. Took the action spring out and pushed the BCG against the held up bolt release and the BCG slipped by it. I noticed on my Sig 308 that the BCG front is cut square across the face that contacts the bolt release catch, the new 308 upgraded BCG has an angle cut at a diagonal where it appears that a straight face would hold. I put the lighter action spring from the Sig into the new gun and it still did not hold. Any suggestions?

 

Welcome to the forum.

Can you provide some details about the rifle?  Is it a factory rifle with upgraded parts or home built from pieces?  We are also going to need pictures of the problem; both the bolt and the catch, preferably from multiple angles.  With a little more information and some pictures, someone should be able to get you fixed up.

[shooterrex]

The bolt catch is supposed to catch the bolt NOT the BCG.

[Marvin Hullinger]

5 hours ago, Armed Eye Doc said:

Welcome to the forum.

Can you provide some details about the rifle?  Is it a factory rifle with upgraded parts or home built from pieces?  We are also going to need pictures of the problem; both the bolt and the catch, preferably from multiple angles.  With a little more information and some pictures, someone should be able to get you fixed up.

The gun was purchased from a dealer that assembled it, They put in the upgraded Tin adjustable trigger and the Tin BCG. The gun did not properly cycle from the first shot. I checked the bolt release mechanism with the lower unattached to the upper to observe the mag pushing against the bolt catch. It looks ok. 

[jtallen83]

8 hours ago, Marvin Hullinger said:

Any suggestions?

Post up all the info gone over in this thread below.

It will help with your issue now and it pays to know what you have with all the variables in these large frame AR's.

[billymagg]

3 hours ago, Marvin Hullinger said:

The gun was purchased from a dealer that assembled it, They put in the upgraded Tin adjustable trigger and the Tin BCG. The gun did not properly cycle from the first shot. I checked the bolt release mechanism with the lower unattached to the upper to observe the mag pushing against the bolt catch. It looks ok. 

If he's close, take it back and let him fix it, I mean I would give him a call and tell him what's going on, and it may be a simple fix.. check as many of the boxes on AlbroSwifts thread as you can, there are some amazing 308AR mechanics here on the forum, but let him know you're having issues up front...

[Marvin Hullinger]

 Here are pics of the bolt, bolt catch, buffer & action spring. Trigger is ATC Tin adjustable trigger. BCG is Tin.

[Rsquared]

That is one PIMP bolt carrier group. Mikedaddy should have something like that for his gold tone AR.

[shooterrex]

Can you lock the bolt back by hand?

If so how about a picture of where the bolt catch is holding the bolt open.

You might need a different bolt catch.

[98Z5V]

On 2/13/2021 at 9:04 AM, Marvin Hullinger said:

I recently purchased a 308 with upgraded trigger and BCG. First time shooting out of the box, the gun did not cycle properly. Took the action spring out and pushed the BCG against the held up bolt release and the BCG slipped by it. I noticed on my Sig 308 that the BCG front is cut square across the face that contacts the bolt release catch, the new 308 upgraded BCG has an angle cut at a diagonal where it appears that a straight face would hold. I put the lighter action spring from the Sig into the new gun and it still did not hold. Any suggestions?

 

It has the wrong buffer in it  - the buffer that's in there is too long - or the receiver extension is too short, internally.  One of those two. Bet the guy that built it just tossed an AR15 Carbine recoil system in it.  7.000" internal on the extension, and 3.250" carbine buffer.

Edited February 14, 2021 by 98Z5V

[unforgiven]

To bad you didn't stop here first brother. 🍺

[Marvin Hullinger]

Thanks all for your valuable comments. 

1. The gun was purchased from a dealer/assembler on the other side of the US; unlikely they will get it back via shipment for analysis and repair. I have made numerous attempts for feedback from them but get only silence.

2. The bolt is not held back when pulling the charging handle all the way. The chamber is not open after shooting. I have not been able to shoot more than one round through the gun at a time as it does not cycle. I have tried to hold out the bolt release "button" and slowly allow the bolt to catch. It slightly catches but when releasing the charging handle ever so slowly the bolt goes all the way.

3. I have another 308, a Sig and will compare the length of the buffers. If they are the same, then the buffer is not for an AR15 (which is longer).

4. The bolt release mechanism appears to be ok. Can anyone see any issues from the pic? 

5. The Sig 308 has a lighter gauge spring, which has less of a force than this gun. Would a spring replacement be needed with a BCG upgrade, assuming the BCG weights less than the standard one?

Anyone have any other ideas? Thank-you so much for your help. I have tried to find a local gun smith but most are not working due to covid.

[dpete]

The best thing you can do is LISTEN! to what 98 tells you and do what is requested.  He is the 308 AR whisperer.  I would bet dollars to donuts that the buffer in your rifle is 3.250" long and about 3.8 oz.  As 98 said it needs to be shorter, 2.50" long and about 5.4oz, IF you have a 7" internal measurement receiver extension.  If the receiver extension is 7" inside length and whoever built the rifle tossed an AR15 3.250" buffer into it I'de bet they have the wrong spring too.

[98Z5V]

2 hours ago, Marvin Hullinger said:

3. I have another 308, a Sig and will compare the length of the buffers. If they are the same, then the buffer is not for an AR15 (which is longer).

 

I can tell you right now, by looking at that buffer, that's 3.250" long.  I'm just sayin'... 

And, I'm betting your receiver extension is 7.000" internal depth.  AR15 Carbine receiver extension.

[Marvin Hullinger]

The buffer is 3.25" long and the internal measurement of the receiver extension is 7". Thanks to 98Z5V and dpete! Please advise on what I should get for proper operation:

1. 2.5" long buffer weighing 5.4 oz, Please; suggest manufacturer, part number?

2. action spring, what spring weight? Please; suggest manufacturer, part number?

3. I have a 7" internal measurement receiver extension, Should I keep it or get another? Please, suggest manufacturer, part number?

Thank-you SIRS !!!

Thank-you forum.308ar.com !

[Marvin Hullinger]

Any manufacturer, model number for a castle nut wrench?

[edgecrusher]

1 hour ago, Marvin Hullinger said:

The buffer is 3.25" long and the internal measurement of the receiver extension is 7". Thanks to 98Z5V and dpete! Please advise on what I should get for proper operation:

1. 2.5" long buffer weighing 5.4 oz, Please; suggest manufacturer, part number?

2. action spring, what spring weight? Please; suggest manufacturer, part number?

3. I have a 7" internal measurement receiver extension, Should I keep it or get another? Please, suggest manufacturer, part number?

Thank-you SIRS !!!

Thank-you forum.308ar.com !

 

[edgecrusher]

I’ll suggest Heavybuffers.com, great supporter of this site and great guy. USA made. 

[98Z5V]

6 hours ago, Marvin Hullinger said:

The buffer is 3.25" long and the internal measurement of the receiver extension is 7". Thanks to 98Z5V and dpete! Please advise on what I should get for proper operation:

Going with heaevybuffers is SUPER easy to do, and you'll get fast shipment (even on a Sunday, I've found), and a top-notch product.  He can sell you the buffer and the right spring at the same time. 

There's a bunch of different ways you can tackle this, also.  I'd suggest going through this thread to get acquainted with the parts, dimensions, weights, and the WHY - of how it should be this way:

 

 

Edited February 16, 2021 by 98Z5V

[Marvin Hullinger]

Hi Everyone:

I found that the bolt does not come back enough for the bolt catch to work. I took out the buffer and spring, re-attached the lower to the upper, pulled back on the charging lever and got the bolt back behind the catch. As 98 suggested, I need a 2.5" buffer, 4.5 oz. 

I looked at the gas tube and it extends into the chamber just as the one in your picture. 

I do not see any 2.5" buffer in the chart, above. Any suggestion on sourcing a 2.5" buffer, 4.5 oz and the proper spring? Should I keep using the 7" internal depth receiver extension? 

Mr 98, 

You mentioned a sweet set up in your chain of posts. What internal depth receiver extension did you use? You mentioned a 5.2" , 5.4 oz. buffer. I see a spring in the chart, above with a 5.2" buffer. Was that the spring that you used? 

I really appreciate how you guys have helped me out!

Thanks!

[edgecrusher]

1 minute ago, Marvin Hullinger said:

Hi Everyone:

I found that the bolt does not come back enough for the bolt catch to work. I took out the buffer and spring, re-attached the lower to the upper, pulled back on the charging lever and got the bolt back behind the catch. As 98 suggested, I need a 2.5" buffer, 4.5 oz. 

I looked at the gas tube and it extends into the chamber just as the one in your picture. 

I do not see any 2.5" buffer in the chart, above. Any suggestion on sourcing a 2.5" buffer, 4.5 oz and the proper spring? Should I keep using the 7" internal depth receiver extension? 

Mr 98, 

You mentioned a sweet set up in your chain of posts. What internal depth receiver extension did you use? You mentioned a 5.2" , 5.4 oz. buffer. I see a spring in the chart, above with a 5.2" buffer. Was that the spring that you used? 

I really appreciate how you guys have helped me out!

Thanks!

CAR-10 buffer on the chart. And it’s 5.4, not 4.5. The other alternative is the Armalite AR10 recoil system. You can buy it from their site, the whole kit including the tube is needed.

[jtallen83]

1 minute ago, Marvin Hullinger said:

You mentioned a sweet set up in your chain of posts.

Here is one set up that always works;

https://www.armalite.com/SACItem.aspx?Item=AR10REKIT01&ReturnURL=/Armalite/Product-Category/AR10-Parts-Accessories/Lower-Receiver-Parts&Category=ac614400-ff09-4cdf-9d35-419a654e7201

 

[shooterrex]

^^^^^^ What he said. I have this setup in 2    308 pistols. If they show out of stock on the web call them.

[98Z5V]

2 hours ago, Marvin Hullinger said:

Mr 98, 

You mentioned a sweet set up in your chain of posts. What internal depth receiver extension did you use? You mentioned a 5.2" , 5.4 oz. buffer. I see a spring in the chart, above with a 5.2" buffer. Was that the spring that you used? 

I really appreciate how you guys have helped me out!

Thanks!

5.200" buffers in .308ARs are Rifle Buffers, and Rifle Receiver Extensions (9 11/16" internal depth, across the board), and Rifle Recoil Systems.  They are not Carbine Recoil Systems, that will accept collapsible stocks.  Only Fixed Rifle stocks.

5.4oz buffers are what you're looking for, as mentioned by @edgecrusher - or as damn close to that as you can get.