Bobro Engineering Sig 320 M17 RMR Mount With Integrated Rear Sight

I got an M17 and wanted to put a dot on it and decided to move one of my Holosun 407C's over and got a Bobro Engineering Sig 320 M17 RMR Mount With Integrated Rear Sight and paired it with a Dawson Precision Sig P Series Black Front Sights @ .375" Tall.

Installation of the mount was straightforward and had no issues, the supplied screws are too long to be used with the Holosun and I opted to use the supplied screws that came with the sight without issue, also for the 407C I did not use the sealing plate, as the battery compartment is already closed off. As best as I can tell the sealing plate and supplied screws work best with a RMR as I used the same Holosun supplied screws to mount it previously in a cut slide. The Bobro mount has a forward radius part the goes in the slot for the loaded chamber indicator and help seal that up, this was a nice add on/feature.

Installation of the Dawson front sight required fitting but it is to be noted that it does come over-sized, I fitted it with a small file and high grit sandpaper. Once installed the sights co-witness fine in the bottom of the red dot and I will put them on paper whenever I get to the range after I zero the dot.

Thumbnails for images:
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Regular Member
Awesome. I used the same mount for my SRO on my Legion. Let me know how the impact is with the irons as I’ve not yet bought a front sight for mine. Actually just sent the gun back to Sig for a new barrel because the LCI throws carbon all over my lens.

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So I had 100 rounds a a few minutes to spare and got to the range with this for the first time. First impressions are very positive, I had no issue transferring from a milled glock to this setup in the short range session I had. Gun zeroed fine but only had enough time for a good 10 yard zero as I wanted to try a few things out including testing the irons. I will zero the 407C and check irons at 25 yards when I have more time.
10 yards, 10 rounds testing the zero on the back up iron sights (Bobro integrated rear with Dawson Precision .375" Tall front)
10 yards, last 3 rounds I had to finish the day


Regular Member

I shot mine Friday. I immediately called Sig for barrel replacement and got it back today. LCI covered the SRO. Surprised me because of the goose neck, I assumed it would vent around it before carboning up the lens.

Got the gun back today.

When I did shoot it, no dot adjustments were required at 25. Shot five rounds touching in the center of an A Zone. Continued to shoot several mags through the gun. Carbon and gas became distracting on the second magazine.

Once I know what front sight works, I’ll order one from Dawson. Plan to shoot again Sunday.

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Odd, in 100 rounds I do not have any build-up on my optic. I plan on another 1-200 on friday so i'll see if its covered by then.

And I cant tell by your comments but are you saying you left the LCI in? I removed mine completely but ended up adding the sealing plate since under the 407C

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Regular Member
I sent the pistol back to Sig to have the barrel replaced. The legion barrel had a rather large notch in the barrel for the LCI and it caused gas and carbon to escape through the hole. The m17 is different.

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Regular Member
If you look at my above picture the cut out seems to be identical as far as I can tell from pictures of the legion barrel
Yes but the legion breech face is smooth. It’s just a hole where carbon flys out.

Sig is replacing barrels. The old X5 lacked the LCI cut in the barrel and it was not a problem. All the legion X5s do it.

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Too Established
Network Support III
The choice to put a lci on these guns is irritating. My Pro has it and I’m no fan. The could have done the same thing glock did and used the extractor as the lci.
They did, the extractor on the standard P320s has a ridge that becomes more prominent when there’s a round in the chamber. The additional redundant LCI started on the M17/M18 as a required feature in the MHS program if I remember correctly


Regular Member
It was a requirement for the trials... and I dont understand why. Last time I checked M4 rifles don’t have LCI and every soldier gets one of those... even the ones who aren’t the brightest crayon in the box...