AR Mag not Locking

vetogunban · Sep 15, 2020

I have a 11.5" Spikes 5.56 upper on a generic lower. With the bolt closed the magazine will not lock in place but if I open the bolt the magazine will lock in. I hand cycled several rounds through it with no problems. I had a .300 BO upper on the lower before and did not have a problem with the magazine locking in. I tested it with a 30 round PMAG that I used before with no problem.

Not sure if this is related but the rear take down pin is very tight to push in, to the point I had to tap it in with the back of a screwdriver.

Is this safe to shoot? If so, would this be a problem that will work its self out by running some rounds through it?

Thank you for your help.

Blaster229 · Sep 15, 2020

Take 1 round out of the mag. See if that helps.

teratos · Sep 15, 2020

vetogunban said:
I have a 11.5" Spikes 5.56 upper on a generic lower. With the bolt closed the magazine will not lock in place but if I open the bolt the magazine will lock in. I hand cycled several rounds through it with no problems. I had a .300 BO upper on the lower before and did not have a problem with the magazine locking in. I tested it with a 30 round PMAG that I used before with no problem.

Not sure if this is related but the rear take down pin is very tight to push in, to the point I had to tap it in with the back of a screwdriver.

Is this safe to shoot? If so, would this be a problem that will work its self out by running some rounds through it?

Thank you for your help.

Does it chamber a round OK? May be an obvious question, but have you tried the mag with just a couple of rounds in it instead of it being loaded with 30?

Blaster229 · Sep 15, 2020

teratos said:
Does it chamber a round OK? May be an obvious question, but have you tried the mag with just a couple of rounds in it instead of it being loaded with 30?

Great advice.... Lol

John from MD · Sep 15, 2020

Sounds like either upper or lower is out of spec. Try sliding a piece of thin paper around the joint of the two receivers and see if it stops anywhere. When you have a takedown pin that is hard to get in and out, that is a good sign that something is not kosher.

teratos · Sep 15, 2020

Blaster229 said:
Great advice.... Lol

Beat me to it.....

Occam · Sep 15, 2020

Had this happen to me at a match the other day. Forgot the "30-round P-mags should only be loaded to 28" rule, and while a bit of friction prevented the mag from dropping right out, it was NOT seated well enough for a feed. This had a non-trivial impact on my time for that stage! But nothing cements that lesson like having yourself reminded of it (again!) on the match clock. For non-windowed mags, just load them 'til they're full, then strip two out. All better.

vetogunban · Sep 15, 2020

Blaster229 said:
Take 1 round out of the mag. See if that helps.

Only had 20 rounds or less in the mag and the rounds pushed down easily.

outrider58 · Sep 15, 2020

A lot of mags, including mp5 mags have problems locking. Don't reduce by two rounds. Usually one fewer puts the round in a double stack mag on the 'easy' side of the bolt bottom.

vetogunban · Sep 15, 2020

John from MD said:
Sounds like either upper or lower is out of spec. Try sliding a piece of thin paper around the joint of the two receivers and see if it stops anywhere. When you have a takedown pin that is hard to get in and out, that is a good sign that something is not kosher.

Thanks I will give this a try. If the upper is out of spec, assuming an upper issue since the lower worked with another upper, is this something for a gunsmith to handle?

outrider58 · Sep 15, 2020

vetogunban said:
I have a 11.5" Spikes 5.56 upper on a generic lower. With the bolt closed the magazine will not lock in place but if I open the bolt the magazine will lock in. I hand cycled several rounds through it with no problems. I had a .300 BO upper on the lower before and did not have a problem with the magazine locking in. I tested it with a 30 round PMAG that I used before with no problem.

Not sure if this is related but the rear take down pin is very tight to push in, to the point I had to tap it in with the back of a screwdriver.

Is this safe to shoot? If so, would this be a problem that will work its self out by running some rounds through it?

Thank you for your help.

What is the "generic" lower?
If you have other uppers and lowers to switch around, it might help you figure out what the source of the problem might be.

vetogunban · Sep 15, 2020

outrider58 said:
What is the "generic" lower?
If you have other uppers and lowers to switch around, it might help you figure out what the source of the problem might be.

Stripped lower from Hanover Armory. I do have one other AR pistol I can try it on to see if that makes a difference. Thanks.

John from MD · Sep 15, 2020

vetogunban said:
Thanks I will give this a try. If the upper is out of spec, assuming an upper issue since the lower worked with another upper, is this something for a gunsmith to handle?

It is an easy fix but the finish would be filed down past the anodizing. It makes it too expensive to do. I would be better to sell it off.

photoracer · Sep 15, 2020

Forget all this fooling around with ideas just take one round out of the mag it should work fine. In my early 3-gun days I found that most of the time a Pmag would seat in my 3-gun AR with all 30 in but not always even when you gave it a healthy wack on the bottom to seat it. But sometimes you had to take on out. On the otherhand Lancer L-5 mags would not seat at all with 30, because they have metal feed lips and no give at the top. Same thing with AR PCC if you jam as many round in a mag as you can get. Or you pull the bolt back when sticking the mag in.

outrider58 · Sep 16, 2020

outrider58 said:
A lot of mags, including mp5 mags have problems locking. Don't reduce by two rounds. Usually one fewer puts the round in a double stack mag on the 'easy' side of the bolt bottom.

photoracer said:
Forget all this fooling around with ideas just take one round out of the mag it should work fine. In my early 3-gun days I found that most of the time a Pmag would seat in my 3-gun AR with all 30 in but not always even when you gave it a healthy wack on the bottom to seat it. But sometimes you had to take on out. On the otherhand Lancer L-5 mags would not seat at all with 30, because they have metal feed lips and no give at the top. Same thing with AR PCC if you jam as many round in a mag as you can get. Or you pull the bolt back when sticking the mag in.

My first thought as well. :thumbsup:

Doctor_M · Sep 16, 2020

You can't slap a female reporter on the backside anymore... but it is still acceptable to smack a magazine bottom with authority.

outrider58 · Sep 16, 2020

Doctor_M said:
You can't slap a female reporter on the backside anymore... but it is still acceptable to smack a magazine bottom with authority.

AR mags are fine. Don't hit an MP5 mag just right, it can be a pain.

Bountied · Sep 16, 2020

I've had this issue with certain mag/lower/upper combos with a full mag. A firm smack would seat it and with an open bolt it would go in easily and lock. Why not just load the mag on an open bolt and call it a day?

Occam · Sep 16, 2020

Bountied said:
I've had this issue with certain mag/lower/upper combos with a full mag. A firm smack would seat it and with an open bolt it would go in easily and lock. Why not just load the mag on an open bolt and call it a day?

Because sometimes you're topping off with another mag while the gun's still hot (say, during a match, on the clock).

Bountied · Sep 16, 2020

I don't think vetogunban is running and gunning but yes if you are in a competition opening the bolt to lock it back takes time, it's a little faster if you have ambi bolt controls though. In that case smack that shit until the mag catches or get a new gun.

AR Mag not Locking

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