I recently got an ACR stock to put on my Bren 2 SBR using the Dan Haga adapter which requires removing the factory end plate.

It came as a surprise to me that there was a spring inside the hinge.

My worry is that there might have been something else in there as well that was ejected by the spring that I didn't notice, some kind of detent or something.

The ACR manual seems to be MIA from the Bushmaster website so I can't check the diagrams.

Can anyone set my mind at ease that I didn't lose any parts?

Pretty sure it is just the spring and the big roll pin.

It's only the spring and roll pin, they never released a diagram for the stocks and handguards.  Those parts were sold as a complete piece.

Just a spring.

One of my recent production, black ACR stocks did not have a spring in the hinge.

Anyone know what size roll pin is used?  Id like a spare as one of my stocks has a rather beat up roll pin after I removed a KDG Scar adapter.

I’d have to check but it’s pretty large.  I’m gonna buy a bag of those pins pretty soon for a couple projects.  It’s something like 2.5 inches long with a 3/16 diameter

Did you ever nail down a size on these things?

Just went and pounded one out I had lying around waiting for an MP5 adapter.

2.25” long. Caliper measured it at .195X inches thick, I assume it was .2” before being compressed the first time.

Thanks bud.