I bought and attached a Mesa Tactical Urbino stock to my Charles Daly 601 DPS. The Urbino was not made to be attached to the 601 DPS, but it hasn't stopped me. This will be a set of steps that I did to make it work, and why I had to. Follow at your own risk!
Differences Between the 601 DPS and M4 Receivers
Before we can start hammering and cutting away at our Mesa stock, we have to discuss why we have to jury rig the stock. The 601 DPS has the outwards look of the Benelli M4, but the receiver extension, mounting hardware, and trigger guard are different. These 3 parts make it so that a standard M4 stock will not just be plug-and-play on the 601.
The 601 DPS receiver extension is a different shape, and different length than a standard Benelli extension. Due to this, the "indexing point" for where the stock attaches to the receiver extension is totally different. We'll have to modify the inside of the stock to accommodate this.
The mounting hardware, specifically the nut that attaches the receiver extension to the receiver, is also proprietary. This requires modifying the shim piece that bridges the receiver to the stock.
The trigger guard has slightly different geometry near the tang, which requires sanding on both the guard, and the pistol grip of the stock for proper fitment.
So the back end of the DPS and the M4 are pretty different, which causes some issues. However, another issue arose when comparing how the two stocks mount.
Differences Between the 601 DPS Stock and the Mesa Urbino Stock
It would be too easy if it was just the above that needed work, but of course, the two stocks mount differently.
The OEM stock uses a really simple method to mount. The stock mounts over the receiver extension, directly butting up to the receiver. A polymer shim fits into the buttstock, and indexes inside of the stock. From there, you attach bolt and washer through the shim, which screws into the back of the receiver extension. Once you tighten it down, the stock is shimmed, and is taut in place. Simple enough!
The Mesa Urbino is even simpler to mount. The stock uses a shim to bridge the receiver and the stock. The stock slides on over a standard M4 receiver extension, where the end of the extension hits an "indexing point" in the stock. From there, you attach a washer and bolt to the receiver extension, squeezing the stock into place.
The issue comes with the "indexing point" on the Mesa stock. Since the receiver extension on the 601 DPS is longer, it doesn't actually index on that point. So, you have to remove the indexing point, which leads to the next section.
Modifying the Mesa Tactical Urbino Stock (The Hard Part)
Well, what's the solution for fitting a square hole onto a round peg?
I took the shim, bolt, and washer from the OEM stock, hacked off the indexing point from the Urbino, and smushed them together.
The indexing point on the Urbino stock is shaped like the letter X, with the crossing point of the letter being where the bolt clamps the stock to the receiver extension. I took a nice, sharp chisel, and a hammer, and cut the indexing point out of the stock. This now made a cavity for the 601's receiver extension to pass through, and created a gap to use the shim too. Since the receiver extension is now bolting on at a point where the stock cheek comb is taller, you'll have to wrap the shim in something to make it wider. So you've got to shim your shim! I used high grade duct tape, as it was easy to find the "sweet spot" for keeping the stock taught.
Modifying the Mesa Tactical Urbino (The Easy Part)
The second part to be modified is the shim that bridges the stock to the receiver. Mesa includes a smattering of shims that can mount a sling, so I took one of them, and ground out spots on them, so that they would fit over the receiver extension nut. This provided a sling mounting point, but also keeps the stock from twisting, or coming as loose.
The last thing to be done was to remove material from the pistol grip area of the Urbino stock. After some sanding with coarse paper and a lot of elbow grease, I was able to get the fit between the stock and the trigger guard to be good.
There is a lot of handfitting to be done here, but it pays off well. My stock has a very minor amount of twisting play (1-3 degrees of movement), but is much more comfortable than the OEM one. It isn't all sunshine and rainbows though...
The Downsides to Hacking Away On an Expensive Stock
It goes without saying, but I'll do it anyway; you'll have to do a lot of work that could ruin a stock that costs about a 1/5 of the rest of the gun. If you are comfortable doing that, it is one hurdle out of the way.
The Urbino stock was made to be able to use a sling mount that goes through the side of the stock, but those cannot be used on a modified M4 clone. The sling mount uses the receiver extension to index, but since the 601 has a longer one, it just doesn't work.
Even with a lot of hand fitting, there will still be a tiny bit of twisting play between the stock and shotgun. Mine is minimal, but if you wrench on the stock, you can twist it a little. It won't effect your shooting negatively, but it might make the OCD people anxious.
Was it Worth Doing?
Hell yeah! I think that while the endeavor was time consuming and expensive, I'm glad that I did it. The shotgun feels much better, with a suitable length of pull, and a better sling point.
Full disclosure, I will not recommend that anyone try this out, as this process required permanent modification of the Mesa stock. If you want to attempt this, do it at your own risk!
If you have any further questions about this process, join our Discord server! I'm always happy to help out with more information about any of the topics I cover in my articles.