AR15 bolt closing issue

[SuedePflow]

I went shooting with a buddy on Sunday and he showed me an issue he recently found on his Ar15. With the bolt locked back, he can lightly bump the back of the buttstock and the bolt will slam closed. It doesn't take much force at all and it slams shut every time.

The rifle is a Spikes lower receiver with an Rguns LPK and a BCM upper. I know Rguns LPKs have a bad reputation and I'm assuming it may have something to do with this issue. I know my way around an AR decently but I've never troubleshooted something like this before.

I've noticed his bolt catch seems a pretty loose compared to mine. Would you guys just recommend replacing the catch and spring and seeing if that solves the issue?

 

[jakk280rem]

Sounds like maybe the catch is catching on the carrier and not the bolt or it's just an out of spec catch. Does it do it during firing or only when the bolt is retracted manually? If it does it during firing on last round then it's the catch, if it only does it when manipulated manually, he may not be retracting the charging handle back far enough. If the CH is at full rearward travel but the catch is only engaging the carrier, then there is another issue at play. But for the cost of a catch and spring, I'd say it's cheap insurance.

 

[taliv]

it's hard to say what "lightly bump" means.

any AR will do this. it's not a defect. it's part of the design and something that I demonstrate in the safety portion of my AR classes. lock the bolt open and bump the butt on the ground. it will close the bolt.

the reason is simple. the bolt catch is spring loaded to the retracted position and stays in place from the friction of the bolt it catches on. the bolt is pushed into the catch by the action spring.

by moving the rifle rearward and having it stop suddenly, the bolt/carrier continue moving backwards slightly before the spring pressure sends it back forward. that 'slack' is enough time for the catch spring to retract the catch.

thus, i highly recommend you do NOT store an AR15 with loaded mag and bolt open.

i suppose it's possible that your action spring is too light. or your bolt catch spring is too strong. but if the rifle is functioning ok otherwise, it's unlikely.

 

[rcmodel]

lock the bolt open and bump the butt on the ground. it will close the bolt.

This is a fact.

As taliv explained it so well.

Bolt carrier inertia will retract the bolt enough for the bolt catch to go back where it is supposed to go when you pull back on the charge handle to close the bolt.

Moral of the story is, don't bump the butt on the ground with the bolt locked open.

It will not happen with an empty mag in the gun.

It will happen every time with no mag, or a loaded mag in the gun.

rc

 

[taliv]

the AR isn't unique in this regard either. observe romero in this video doing essentially the same thing with a glock, one-handed

http://www.youtube.com/watch?v=D7stLQvsDX8

 

[SuedePflow]

Thanks for the posts, guys!

any AR will do this. it's not a defect. it's part of the design and something that I demonstrate in the safety portion of my AR classes. lock the 0bolt open and bump the butt on the ground. it will close the bolt.

the reason is simple. the bolt catch is spring loaded to the retracted position and stays in place from the friction of the bolt it catches on. the bolt is pushed into the catch by the action spring.

by moving the rifle rearward and having it stop suddenly, the bolt/carrier continue moving backwards slightly before the spring pressure sends it back forward. that 'slack' is enough time for the catch spring to retract the catch.

That makes perfect sense. I just went a tried it on my AR and it does the same thing.

Learn something new every day.

it's hard to say what "lightly bump" means.

It's tough to quantify. With his rifle, it take the same amount of force as a gentle pat on the back. With my rifle, I have to deliberately hit the stock hard with the heal of my hand or against the ground. Easily 2 or 3 times the amount of force required on mine. But either way, as long as it's not a defect and it doesn't affect the guns operation, we won't worry about it.

 

[SuedePflow]

the AR isn't unique in this regard either. observe romero in this video doing essentially the same thing with a glock, one-handed

http://www.youtube.com/watch?v=D7stLQvsDX8

Wow, I wouldn't have even thought that was possible. I just tried it on my longslide Glock with 13# spring, and I can get it cocked, but can't get enough movement to chamber a round. Almost threw my shoulder out trying too. I imagine it takes some practice. Pretty cool to see it done though.

 

[taliv]

my guess is his action spring is out of spec. i'm just guessing though. assuming you both have carbines, take your action spring out and put it in his rifle and see if it changes things. if so, replace his. they're like, $5 at bravoco http://www.bravocompanyusa.com/Carbine-Action-Spring-p/spring carbine action.htm

 

[Acera]

If you have ever been 'rodded off the range' in the military the same thing happens.

The person doing the ammo safety check runs a cleaning rod from the muzzle and taps the face of the retracted and locked back bolt. That little tap caused the action to slam shut as he pulls the rod out. Confirming that there is no round in the chamber (as it would have been pushed and fallen out of the empty magazine well).

Perfectly normal.