Bolt doesn't lock forward when inserting into piston upper

[BanjoGunner]

First time working on a AR piston upper (Adams Arms, mid-length, .223) and I've noticed the following: When assembling, the bolt doesn't click into place and sit flush with the end of the chamber like it does on my DI carbine. Instead, the last 1/2" or so prutrudes out of the chamber under spring tension and I must push it in before before I can close the lower onto it.

I was about to head out for a test fire, but I want to make sure this is normal/okay first.

Thanks.

BG

[jb octane]

There's a spring which pushes it out. It's normal.

All the AA bolts have that spring in them.

[technique]

During assembly? Or when you charge the weapon?

[technique]

If it does (seat all the way/ into battery) when the rifle is assembled, you're likely GTG

[tal3nt]

Are you using a piston bcg?

[BanjoGunner]

Thanks for the quick responses...

Yes, this is during assembly and it is a piston bcg. Once the lower is attached the bolt seats all the way forward as it should and it cycles dummy rounds just fine. My concern was/is that maybe this means it is not really _locking_ into place once a round is chambered and I have no way to tell visually if this is so.

[jb octane]

Skip to 4 min on this video and then you'll get your confirmation around 6 min mark.

[BanjoGunner]

Skip to 4 min on this video and then you'll get your confirmation around 6 min mark.

That's exactly what I needed to see; thanks jb!

Off to test fire...

[tal3nt]

Please report back your experience! Have funnn

[Arnelcheeze]

the Stag / CMMG piston system also has a bolt spring, not sure why, but it works!

[BanjoGunner]

Well the test firing was uneventful, with everything behaving exactly as it should. Got the sights installed, sighted in, and fired off a few rounds after that. A bit too cold to stay much longer than that, forgetting my jacket and all! ...Doh...

Thanks again for the quick responses yesterday.

[m16]

the Stag / CMMG piston system also has a bolt spring, not sure why, but it works!

It's because there is nothing to hold the bolt in battery as the bullet is exiting the muzzle.

In a Stoner gun, gas expands inside the bolt carrier and this does two things; it pushes the bolt forward and forces the carrier backwards.

A piston gun doesn't do this because gas never enters the carrier.

The only way to keep the bolt locked after the bullet has passed the gas port is to add a spring behind it.

[beastie050]

What piston kit did you use?