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Steyr AUG 9mm conversion kit question


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My manual that came with the kit shows anti bouncing rods and springs installed.

Do all generations of the  9 mm conversions have them installed ?  Are they all OK to be used in semi or full auto stocks?

Do they require any modifications to run with the registered sear besides cocking piece ?  Thank youi.

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My understanding is that 9mm semi auto bolt carrier assemblies do not have anti-bounce rods and springs installed.  Only full auto bolt carrier assemblies have them installed.  I've only run a factory full auto 9mm bolt carrier assembly in a factory 9mm full auto stock with a factory full auto 3RB hammer assembly.  This setup worked just fine.  I have not tried to install a 9mm semi auto bolt carrier assembly in a factory 9mm full auto stock.

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The 9mm AUG kit I bought direct from Pete Athens maybe 4ish years ago and the carrier came with the  anti-bounce rods and springs installed.

I actually bought a set of anti-bounce rods and springs for the 9mm kit, fully expecting to have to mod them for semi-auto stock use and install them into the 9mm carrier.

However when I pulled the thruster caps off the 9mm carrier...out popped two anti-bounce rods and anti-bounce rod springs, already modified by Steyr for use with a semi-auto stock.  All I had to change out was the semi-auto cocking piece for a full auto cocking piece so I could use my transferable Qualified sear based hammer pack.

On AUGs there is no difference now-a-days between a semi-carrier and a full auto carrier other than the full auto carrier has the anti-bounce rods and the full auto cocking piece installed.  The full auto stocks and carrier used to run a fatter guide rod diameter but everything has transitioned to the narrow diameter guide rod setup.

Keep in mind, it is critical that you do not use any carrier that has unmodified full auto anti-bounce rods installed with a semi-auto stock.   

The full auto stock guide rods are ~140mm vs. ~165mm in a semi-stock.  If you run a carrier (either 9mm or 5.56) with full length anti-bounce rods and springs installed you will damage the stock and/or the spring in the carrier as you will have a stack up tolerance issue.  With unmodded anti-bounce rods and springs in a carrier and installed in the semi stock, the carrier will not be able to come all the way back on the recoil stroke and bottom out on the little ~5mm thick donut shaped buffers at the base of the stock guide rods like its supposed to.  Instead the longer semi-auto stock guide rods will crush the springs inside the carrier thruster tubes in short order or potentially damage the stock guide rods.

If you want to run a carrier with anti-bounce rods installed inside a semi-stock with ~165mm length guide rods you need to trim ~1" off the anti-bounce rods and also trim the semi-auto recoil spring (as they are also longer) to make room for the anti-bounce rods, anti-bounce rod springs, and the longer semi-auto guide rods when the carrier is fully compressed on the recoil stroke.

Its a pretty straight forward modification, but some folks are under the impression can buy a complete full auto carrier and then drop it into a semi-stock which isn't the case.

So to answer your specific questions:

Yes in my experience some of the semi 9mm kits come with the anti-bounce rods installed. 

That said it certainly isn't a bad idea to check to make sure they are actually in there if you plan to run it with a sear.  

Its also not a bad idea to make sure the stack up tolerance is correct and the carrier can come all the way back to the donut buffers are the base of the stock guide rods.   Keep in mind, you can't use the charging handle to check this stack up tolerance as the charging handle cant pull the carrier far enough to the rear to bottom it out like it does when firing.   However, you can remove the receiver, remove the hammer pack, install just the carrier in the stock.  Then push the carrier back manually and make sure it can go all the way back and hits the buffers vs. stopping short while looking through the rear of the stock with the hammer pack removed.

Other than that you just need to add the full auto cocking piece to the carrier.  I actually use the polymer 5.56 cocking piece as the 9MM specific one is steel and I didnt want to beat up my sear with a steel cocking piece.  I have had no issues with using the full auto polymer 5.56 cocking piece with the 9mm kit.

Edited by jbntex
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  • 9 months later...

I started a new thread to answer this question, but I thought I'd ask it here too. Will there be/are there "bare"AUG bbls. for sale, so that gas blocks from destroyed bbls. can be fitted to USA-made replacement bbls.? And is it even possible to pull the gas block off of an AUG bbl.? Thanks.

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