Geissele Reaction Rod OK on KAC SR15?

AR/M4 AR Technical Discussion
1

Wondering if anyone can tell me if the Geissele Reaction Rod is OK to use on the KAC SR-15 with its slightly different lug geometry.

My guess is yes but I learned a long time ago that “educated” guesses can be expensive…

Thanks

2

I believe you cannot use the GRR with KAC uppers. There’s a thread here that describes the exact reasons. Something to do with different dimensions or style of the barrel extension.

I could be totally wrong. But I’m pretty sure search will bring it up. I thought GA made a special rod for use with KAC uppers.

3

The Reaction Rod I have fits inside my KAC extension. I wan;t expecting it to the first time I went to use it, but it slide on fine. It was a much more snug fit than a standard extension, but there was no forcing it at all.

4

My grr does not work with the sr15 e3’s. So I purchased kac’s equivalent.

5

Interesting. Mine does NOT fit into two different rifles. I just use the KAC equivalent.

6

I was not expecting it to, but figured I would try and see what happens. Barrel extension is on a SR15 14.5" Carbine upper. I thought perhaps Geissele had taken the E3 bolt/extension into the design with their rods. Mine has somewhat of a loose fit inside standard extensions.

7

Mine is about a year old. Maybe they tweaked the design or maybe you got lucky with a tolerance variation. :what:

8

Well I emailed KAC today and after some back and forth they confirmed a suspicion that I had. My concern was that, even if the KAC tool fit into a standard barrel extension, or if the Geissele fit into a KAC extension, that the contact pattern would not be right.

What I mean is that when you torque on the barrel you want the tool to bear the torque across the flats of the tool - in other words contact across an area. If the geometry of the tool does not match the geometry of the extension, you will get line contact or even worse, point contact. This sort of minimal contact/engagement of the surfaces is to be avoided as it can damage the part or tool with very high localized forces.

KAC confirmed that this can happen, and has happened.

Bottom line: Use the KAC tool in KAC barrel extensions, and the Geissele tool in standard barrel extensions.

Have a KAC tool headed my way. Thanks to all for their input.

9

I actually had this issue with the KAC tool. When it was originally released, it was advertised as being compatible with both the E3 and standard barrel extension. Unfortunately, somewhere between prototyping and production, the design changed and I found out the hard way. I boogered up one of the KAC tools while trying to use it on a standard extension. I didn’t realize that it had minimal contact and the extension sheared the ends of the lugs off of the tool due to a minimal distribution of force (point contact). KAC tool is for KAC barrels only and Geissele is for standard barrel extensions only.

10

We are discussing going back to the original design to allow for both.

11

That would be nice, but unfortunately I’ve already paid for the current version. When I originally got it, I thought it was going to be the dual use version and was pretty surprised to find out that it didn’t work with the standard extension.

12

I sent Geissele an email a while back asking about KAC compatibility and this is the answer I got.

Hello SteveL

Knights just has rounded corners in their barrel extensions, all you would have to do is take a dremel to the reaction rod for it to work. Thank you for the inquiry.

Thank You
Stan Fanelli
Assistant Assembly Shop Manager
Geissele Automatics
1920 W. Marshall St
Jeffersonville PA 19403
Phone 610-272 2060
Fax 610-272-2069

I thought this sounded crazy so I intentionally left the contact information from the person who wrote the response intact and visible for all to see in case anyone wishes to contact them and verify what I was told.