Archived Posts » 59,789,155
Bolt wont lock back after last round fired
1/25/2012 12:58:08 PM
I just finished my second lower. It is a SAA lower, with RRA NM lower parts kit, and a Magpul Moe stock. I only have one upper at this time, a 20" bull flat top. So the first time at the range i noticed that the bolt wouldnt stay back on the last round. Never had a problem with the other lower. Same set up but with an A2 stock. I replaced the bolt catch, didnt help. So today i go out and sight in my new Eotech 512. After i had it sighted in i shot a few round off a bag one handed like a pistol. the bolt stayed back like it should. When i would fire it from the shoulder same old problem bolt wouldnt stay back. So i tried it again one handed the bolt would work as it should every time. So what due i need a new buffer, or spring or both. The buffer kit was milspec off Ebay.
1/25/2012 2:11:05 PM
Is the spring from the new lower the same length as the recoil spring in the old lower?
Did you move the gas block on the upper?
Did you move the gas block on the upper?
1/25/2012 2:34:41 PM
What the recoils spring free length now in play (should be around 10.5").
Pull the charging handle all the way back, and tell me if both the last inch of pull is the same tension as the rest of the pull, and where it the face of the bolt ending up against the back of the ejection port window.
Also, with the upper shotgun opened, install a empty mag into the receiver and confirm that the bolt catch fully raises up. Here, it could be either the catch binding in the receiver slot, the wrong spring installed for the catch, or even crap in the bottom of the spring catch channel that you did not clean out, and the correct spring now is creating too much tension that the mag catch spring can not over ride to get the catch all the way up.
To add: would also help to know what mags you are using as well. If crap clone mags, could be the problem, and if Magpul's, could be that the catch tab is not long enough to engauge the mag follower rear tab.
As for if the rifle is correctly stroking, spent case ejection distance should be around 10 to 15 feet out, and not just dribbling out of the ejection port.
Pull the charging handle all the way back, and tell me if both the last inch of pull is the same tension as the rest of the pull, and where it the face of the bolt ending up against the back of the ejection port window.
Also, with the upper shotgun opened, install a empty mag into the receiver and confirm that the bolt catch fully raises up. Here, it could be either the catch binding in the receiver slot, the wrong spring installed for the catch, or even crap in the bottom of the spring catch channel that you did not clean out, and the correct spring now is creating too much tension that the mag catch spring can not over ride to get the catch all the way up.
To add: would also help to know what mags you are using as well. If crap clone mags, could be the problem, and if Magpul's, could be that the catch tab is not long enough to engauge the mag follower rear tab.
As for if the rifle is correctly stroking, spent case ejection distance should be around 10 to 15 feet out, and not just dribbling out of the ejection port.
1/25/2012 4:54:33 PM
1.When i pull the charging handle back, the tension feels the same.
2.The brass is kicking out 8-10 feet.
3.I didnt move the gas block.
4.I am shooting GI mags with green tops.
5.When i put an empty mag in and pull the charging handle back, bolt locks in place.
6.I looked at the bolt face while i had it installed on each of the lowers, it appears to be the same distance from the rear of the ejection port.
7.I picked up a new mag catch, spring, and roll pin this weekend at the gun show. I changed them out but i didnt think to clean out the spring hole.
So what should i try now.
2.The brass is kicking out 8-10 feet.
3.I didnt move the gas block.
4.I am shooting GI mags with green tops.
5.When i put an empty mag in and pull the charging handle back, bolt locks in place.
6.I looked at the bolt face while i had it installed on each of the lowers, it appears to be the same distance from the rear of the ejection port.
7.I picked up a new mag catch, spring, and roll pin this weekend at the gun show. I changed them out but i didnt think to clean out the spring hole.
So what should i try now.
1/25/2012 5:44:26 PM
One other piece of information. The BT spring on the A2 stocked lower, seems considerably weaker than the lower with Magpul Moe stock. The buffer on the Moe stock has a slight diagonal cant to it. It looks like it sticks out to far at the top. Is this normal ?
1/25/2012 5:48:43 PM
Do you have a magpul BAD on it?
1/25/2012 5:55:34 PM
No nothing like that
1/25/2012 10:02:03 PM
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1/25/2012 11:28:17 PM
Originally Posted By huntandfishguy63:
One other piece of information. The BT spring on the A2 stocked lower, seems considerably weaker than the lower with Magpul Moe stock. The buffer on the Moe stock has a slight diagonal cant to it. It looks like it sticks out to far at the top. Is this normal ?
One other piece of information. The BT spring on the A2 stocked lower, seems considerably weaker than the lower with Magpul Moe stock. The buffer on the Moe stock has a slight diagonal cant to it. It looks like it sticks out to far at the top. Is this normal ?
When the upper is closed, the back of the carrier is going to push the Buffer away from the retaining pin, and back a tad into the tube, So don't worry too much about the buffer, unless you start to get some nasty denting on the outer edge face of it.
Buffer spring free length is?
1/27/2012 8:31:08 PM
The extended spring lenght is 10 3/4 inches
1/27/2012 9:03:58 PM
It sounds like the rifle might be a little under gassed (gas port on the small side) or loosing gas somewhere and when it's not firmly held the buffer loosing enough inertia from your body movement to short stroke, but that's just my SWAG.
Have you checked the gas key on the carrier to make sure it's not loose or leaking?
Have you checked the gas key on the carrier to make sure it's not loose or leaking?
1/28/2012 6:33:18 AM
Something is backwards here,
Shoulder mounted should cause the action to cycle better than pistol type shooting the rifle, while pistol shooting will allow the rifle to free recoil more, and may be the extra whip that the catch needed to get up into position to catch the bolt. When shooting the rifle free hand, does the catch engauge then?
Your ejection distance it about right for correct full stroke, so it got to be coming down to the mag and catch the problem here.
When off the bench, is the mag touching the bench and this the problem at hand?
On the mag catch, is the threaded tip of the shaft flush with the mag release button?
When you installed the bolt catch, did you clean the catch spring channel out to make sure that there was not crap in the bottom of the channel, and you are sure that the catch is not slightly binding in the receiver slot for it?
And like always, what are you using to clean and lube the rifle for break in with?
Shoulder mounted should cause the action to cycle better than pistol type shooting the rifle, while pistol shooting will allow the rifle to free recoil more, and may be the extra whip that the catch needed to get up into position to catch the bolt. When shooting the rifle free hand, does the catch engauge then?
Your ejection distance it about right for correct full stroke, so it got to be coming down to the mag and catch the problem here.
When off the bench, is the mag touching the bench and this the problem at hand?
On the mag catch, is the threaded tip of the shaft flush with the mag release button?
When you installed the bolt catch, did you clean the catch spring channel out to make sure that there was not crap in the bottom of the channel, and you are sure that the catch is not slightly binding in the receiver slot for it?
And like always, what are you using to clean and lube the rifle for break in with?
1/28/2012 9:50:45 AM
Wouldn't a bad off hand shooting/shoulder fire form do the same or worse than bag shooting?
1/28/2012 10:23:04 AM
When i was shooting it off the bag with one hand the bolt will stay back after the last round is fired every time. But when shoulder fired with the magazine off the bench it has never stayed back. I double checked the mag catch and the bolt catch. The bolt catch dosnt bind, and seems to work as it should. I can insert a empty mag with the bolt down pull the charging handle back it will lock in place every time. As for cleaning i use hoppies # 9, and Thompson Center grease. It has me baffled because the only difference in the two lowers that i have is the stock. My first one has an A2 stock i never had a problem with it.
1/28/2012 12:14:17 PM
Isn't the Thompson grease for muzzle loaders?
I'd get rid of the Hoppes and grease and get a big can of CLP and Slip2000.
I'd get rid of the Hoppes and grease and get a big can of CLP and Slip2000.
1/28/2012 12:52:56 PM
Yes it is but it was all i could find. I have been planing on geting something more suitable for an Ar
1/28/2012 9:07:05 PM
Originally Posted By huntandfishguy63:
As for cleaning i use hoppies # 9, and Thompson Center grease.
As for cleaning i use hoppies # 9, and Thompson Center grease.
1/29/2012 10:12:42 PM
I had this problem with a DSA receiver extension that must have been too shallow. The bolt pulled all the way back was only about 1/16" behind the bolt catch. I replaced it with a vltor receiver extension and it worked properly again.
1/29/2012 10:19:16 PM
Originally Posted By huntandfishguy63:
When i was shooting it off the bag with one hand the bolt will stay back after the last round is fired every time. But when shoulder fired with the magazine off the bench it has never stayed back. I double checked the mag catch and the bolt catch. The bolt catch dosnt bind, and seems to work as it should. I can insert a empty mag with the bolt down pull the charging handle back it will lock in place every time. As for cleaning i use hoppies # 9, and Thompson Center grease. It has me baffled because the only difference in the two lowers that i have is the stock. My first one has an A2 stock i never had a problem with it.
When i was shooting it off the bag with one hand the bolt will stay back after the last round is fired every time. But when shoulder fired with the magazine off the bench it has never stayed back. I double checked the mag catch and the bolt catch. The bolt catch dosnt bind, and seems to work as it should. I can insert a empty mag with the bolt down pull the charging handle back it will lock in place every time. As for cleaning i use hoppies # 9, and Thompson Center grease. It has me baffled because the only difference in the two lowers that i have is the stock. My first one has an A2 stock i never had a problem with it.
I think that there may be a clue right there, seems like I had something like this once but I cant remember what it was?
1/30/2012 1:58:55 PM
I added a picture and some new information. I stated that both lower's had RRA Nm LPK, i was wrong the lower on the left has Delton LPK, the one on the right has RRA LPK. Maybe you guys can see something wrong with the lower on the right it is the one giveing me problems.
