Hard Closing BCG

[gpr]

I noticed my Ar-10 doesn't like to easily close the BCG all the way. For example if I slowly close the bolt with the charging handle, it will pick up a round but it will stop about 1/2" short of fully closing. However if i slowly close the bcg with out a round i can gently let it close completely.

Why does it not want to close when there is a round in the chamber? Is there something I can do to improve this? I tested on my AR-15 and it will easily close with a round in the chamber, much better then the AR-10. It is concerning as when hunting if i need to rack a round I will have to let it slam shut, not quiet. Also on the AR-10 I can't even push the forward assist to close the bolt. On the AR-15 if it doesn't close all the way, slight pressure on the forward assist and its good.

 

[loveha]

Sounds like a super tight head space. Have you tried it on other brands of ammo?
I would get the head space checked.
Is this a home build, or a prebuilt?

 

[hlee]

The extractor claw needs to snap over the rim of the cartridge before the bcg can go into battery. The spring on this part is stronger than on an ar15. If you want to test this, snap a cartridge run under the extractor claw then let the bcg slowly ride home. You’ll need to help it a little as the ejector will try to kick it out until you get it feeding into the chamber.

 

[gpr]

I will check this and might simply remove the extractor. I'm also going to get a headspace gauge to verify it is good as I've been suspicious of a tight chamber since I got the gun.

This is a Stag AR-10 and anytime I use Federal ammo it acts like the ammo is getting stuck in the chamber. To the point of when I pull the charging handle I can barely get the unfired round out. However, last night I was checking it with resized reloaded ammo. This ammo fits the chamber much better and doesn't have the same really hard pull when removing the round from the chamber. But noticed I couldn't get the BCG closed unless I let it slam really hard.

Do they make weaker extractor springs? Cause when slowly closing the bcg and its hung up the last 1/2" slamming on the forward assist didn't budge the bcg.

 

[knuckleballz]

It could be a tight chamber issue. Is the chamber clean? I had an issue with some 7.62x51 cbc factory ammo that had thick necks. It caused feeding issues and occasionally a fired case would get stuck in the chamber and had to be removed with a cleaning rod. Another thing to check is how easy the bolt rotates in and out of the carrier. I similar issue caused by a tight fitting bolt (aero precision nickelboron)

 

[knuckleballz]

Also, obviously we are assuming your bcg is well lubricated

 

[bfoosh006]

Make sure the chamber is clean, .. ( if there is any packing oil / "anti - rust" preventitive still in there ... it can make for a tighter chamber ) and how many rounds have been fired through it ?

 

[gpr]

The BCG has been cleaned and oiled several times, along with cleaning the chamber and barrel. I'd guess 200-300 rounds down the tube.

tonight I'm gonna pull the ejector and try loading a round. See if this is the cause.

I was wondering if there was anything i could polish to help the bolt close easier?

I'm gonna borrow a go gauge from a buddy to check headspace, but I think it is okay as I can load resized brass easily.

 

[hlee]

Grab one of these in 308win (https://lewilson.com/case-gage/) and drop the cartridges that are hard to chamber into it. If they don't go in easily, it's an ammo issue. As you have some that chamber and others that don't, it's sounding like that could be the case.

 

[MontanaMan]

Grab one of these in 308win (https://lewilson.com/case-gage/) and drop the cartridges that are hard to chamber into it. If they don't go in easily, it's an ammo issue. As you have some that chamber and others that don't, it's sounding like that could be the case.

That's a very good suggestion.

Most likely an ammo related problem; tight neck or maybe OS body or base.
If the BCG is stopping 1/2" out, it's not a headspace problem.

MM

 

[Yondering]

If the BCG is stopping 1/2" out, it's not a headspace problem.

This sounds to me mostly like someone new to ARs just isn't used to the fact that the bcg is supposed to slam closed to jump the extractor over the case rim. They aren't like bolt actions where you can just ease the bolt closed. That's just how ARs are, there may be nothing at all wrong with the gun.

 

[whatsupdoc]

This sounds to me mostly like someone new to ARs just isn't used to the fact that the bcg is supposed to slam closed to jump the extractor over the case rim. They aren't like bolt actions where you can just ease the bolt closed. That's just how ARs are, there may be nothing at all wrong with the gun.

^^^^
Exactly, NO AR I have ever tried would let me slowly lower the bolt carrier group over a round and go into battery.

 

[Rocketvapor]

Pull the extractor, pull the gas rings. Look for wear marks from the cam pin in the upper.

 

[Yondering]

^^^^
Exactly, NO AR I have ever tried would let me slowly lower the bolt carrier group over a round and go into battery.

If that's what the OP is expecting, he'll need to either use the FA if his rifle has it, or go with a non-reciprocating side charge handle. Those side charge handles do work well for easing the bolt closed, I have several hunting ARs set up that way, but they do come with their own minor issues as well.

 

[gpr]

Both of my AR-15s will allow me to slowly close the bolt, and if it doesn't quit close all the way the forward assist will close it the rest of the way.

This AR-10 is much more difficult. I tested it last night by chambering a round, then pulling it back just enough the shell isn't ejected. then slowly closing it. With the shell in the ejector already it does lock the bolt up much easier, and slight pressure on the FA closes it completely.

So the extractor spring must have significantly more pressure then AR-15's.

I'm thinking I will polishing the extractor to help it slide over the case rim easier?

If I put an AR-15 extractor spring in, would it cause issues in the AR-10? Its not a big deal and guess I will need to learn to live with it. I use my guns for hunting, and once in a while you need to rack a round quietly, thus why I was testing it.

 

[PusherX11]

If you change the extractor spring you might get a failure to extract where to extractor will slip off the rim during the cycle.

 

[Yondering]

Both of my AR-15s will allow me to slowly close the bolt, and if it doesn't quit close all the way the forward assist will close it the rest of the way.

This AR-10 is much more difficult. I tested it last night by chambering a round, then pulling it back just enough the shell isn't ejected. then slowly closing it. With the shell in the ejector already it does lock the bolt up much easier, and slight pressure on the FA closes it completely.

Your AR10 is performing normally, your AR15s are not, unless we are just having a failure of communication here. If you're slowly riding the charging handle down to close the bolt quietly, a normal AR15 bolt will not lock up on a loaded chamber unless you manually force the bolt closed. If they do, as you describe, your extractor springs are probably very weak, and or the extractors themselves may be damaged or not functioning right. None of those are good, and those guns are likely right on the edge of having extraction issues, double feeds etc.

I hunt with my ARs too, and I get what you're asking for, but no way would I want to compromise the reliability of my rifle to be able to close the bolt quietly. A side charge handle may be your best option if you really need that feature.

 

[bfoosh006]

Is the AR15 much more used ?

The reason I am asking, is I'd bet the extractor is more polished, on the face that slips past the rim.

I'd bet , you could improve the extractor slipping over the rim of the case, by polishing the "face".

That is the portion that slides over the case rim. NOT THE HOOK portion.