Bolt Hold Open Question

[Mooseman]

A friend of mine just built his first AR lower. Yesterday I took him and one of my uppers to the range so he could try it out. His bolt hold open does not hold the bolt open unless manually applied. I know that this is not right, but I don't know what he could have possibly done wrong. Any thoughts or suggestions on what I can tell him to try?

 

[jonnyl]

without the upper on will an empty mag inserted into the lower raise the catch at all?

 

[Mooseman]

without the upper on will an empty mag inserted into the lower raise the catch at all?

I'm not sure, but I will have him check that. Thanks.

 

[BradMacc82]

What type of ammo, and what lower and LPK was used?

 

[67temp]

Did he forget the spring and/or buffer for the hold open?

 

[Mooseman]

What type of ammo, and what lower and LPK was used?

The ammo was factory ammo, PMC .223. The lower parts kit was a Magpul with a telescoping Magpul stock. It is an Anderson lower.

 

[Mooseman]

Did he forget the spring and/or buffer for the hold open?

He told me he didn't have any parts left over.

 

[kstone803]

A friend of mine just built his first AR lower. Yesterday I took him and one of my uppers to the range so he could try it out. His bolt hold open does not hold the bolt open unless manually applied. I know that this is not right, but I don't know what he could have possibly done wrong. Any thoughts or suggestions on what I can tell him to try?

Like it doesn't lock back on the last round or when you pull the charging handle it doesn't lock back? If there is no mag in it, the bolt will not lock back by just pulling the charging handle. If it won't lock back on the last round then try a different mag.

 

[Mooseman]

Like it doesn't lock back on the last round or when you pull the charging handle it doesn't lock back? If there is no mag in it, the bolt will not lock back by just pulling the charging handle. If it won't lock back on the last round then try a different mag.

Both. It will not lock back on the last round and it will not lock back when you pull the charging handle. We tried about half a dozen different magazines with no luck.

 

[iH8DemLibz]

He told me he didn't have any parts left over.

The sign of any good mechanic is to have parts left over for the next project.

 

[Mooseman]

The sign of any good mechanic is to have parts left over for the next project.

That is what I tried to tell him.

 

[Mooseman]

I appreciate all of the help and suggestions. I will pass this along to my friend. Thanks again.

 

[Fox123]

not engaging with the magazine follower? the bolt release either not the correct size, or the slot it rides in was milled too far to the rear?

 

[Sticky]

I have seen issues with the engagement of the bolt catch and the mag follower not properly aligning. Remove the upper or break it open, insert a mag (empty) and see how much engagement there is between the bolt catch and the mag follower. Sometimes the mag follower just doesn't get enough of the bolt catch to engage and raise it.

Some mags can work better than others, but bottom line is that the bolt catch probably needs to have a bit of welding (and then filing to smooth and shape it) done to add a little more to the forward most part so that it engages the mag follower. I have seen this done successfully as well to resolve the issue.

I would probably try a different brand of bolt catch first, since that is easier than modding the existing one...

 

[Mooseman]

Thanks for the help guys.

 

[smdub]

I've had a bolt catch that was tight and rubbed on the pin that held it in. There was casting flash in the hole. So it was "sticky" and had lots of drag. I figured it out before I put it together, but a mag follower spring surely wouldn't have had enough force to lift it up. Used a small needle file to clean up the hole so the pin would pass freely through it. It seemed hardened so I didn't want to break a drill off in it.

 

[DeerPark21550]

Hi Mosseman. Id Say the problem is the bolt catch spring has to much tension. Take half a coil or so. This fixed the problem on a few ARs I fixed for people

 

[j_h_smith]

With the upper removed from the lower, check to make sure the lever moves freely. I had one that the pin was too tight, burred, or something and once I replaced the pin, it worked fine. Could also be the fitment of the lever inside the lower.

Good Luck!
Jim Smith