Need help 590A1 Mesa side saddle

[bd457]

A female friend brought her 590A1 to me with the side saddle and trigger group in one hand, and the receiver in he other. It had come apart while she was shooting. I have it all back together except for the bolt that got lost and caused the problem in the first place. What I need from you is: how is the trigger group and side saddle fastened to the receivers? Was this a through bolt set up? If so, can you give me specifics on the bolt? Pictures would be great if you can show me what yours looks like from both sides of the receiver. I picked up a through bolt and nylock nut which will work, but doesn't look like Mesa would have done it this way. Any help would be great. She'd even be happy putting it back together without the side saddle if anyone has the original pin hardware they don't need anymore.

Thanks in advance for any help you can offer.

Mike

[Shoot'nPlumber]

It's called a Chicago bolt set which is essentially a female bolt and a male bolt that screw into each other. Here's a shot on my 590a1

[Shoot'nPlumber]

Here's on the saddle side

[bd457]

Thank You! The only thing I don't understand then is: why is the sidesaddle bolt hole chamfered?

[Shoot'nPlumber]

Thank You! The only thing I don't understand then is: why is the sidesaddle bolt hole chamfered?

Could be a design change to let the Chicago bolt pan head sit deeper. But the hole on mine is not chamfered. There should only be 2 holes. One for for the ejector nut that is replaced with mesas version, and the one for the trigger pin.

[bd457]

Ahh..... I have a couple Chicago bolts from the Mesa I took off my 870. You mention the front replacement bolt. This 590 has a threaded stud that sticks out about .125". Is this right or is there something that threads onto that stud to fit the keyhole in the side saddle?

[Shoot'nPlumber]

Ahh..... I have a couple Chicago bolts from the Mesa I took off my 870. You mention the front replacement bolt. This 590 has a threaded stud that sticks out about .125". Is this right or is there something that threads onto that stud to fit the keyhole in the side saddle?

Yes' it's a nut that threads onto the little bit of threads that stick out of the receiver. It doesn't fit on tight, it only needs to be centered in the key mod slot. If you don't have this nut, I'm sure you can buy one at the hardware store but this one is parkerized so I may suggest a stainless one.

[bd457]

Thanks for all your help! I now know exactly what's missing and how to fix it for her. Have a great new year!

Mike

[Shoot'nPlumber]

It I were you, I would call mesa tactical on Friday. They are a SoCal company out of Arcadia. They have rediculously awesome customer service. Tell them your scenario and that it came apart and some pieces went missing. Thy will most likely find out what you need and can send out replacement for probably the cost of postage or at least give you the specs on the screw and nut sizes. Also FYI the Chicago screws as well as ejector screw require a dab of blue loctite. This will prevent backing out.

[BigPimping]

The depth of knowledge and helpful folks on here never ceases to amaze. Great resource....