Found this online.

Apparently the Fuse uses a new optic footprint, without mounting posts? See below *

 

Would like to mount a 507k on both my XMacro and on my Fuse - but a couple of questions:

1. On the Xmacro - the optic fits over the integral threaded posts - still only 2 points of contact, and without placing screws there is quite a bit of slip and movement of the optic sitting on those threaded posts - is this adequate? Anyone know the proper screws to use? Post I copied says M3 threads but no length suggestion.

2. On the fuse - I tried one of the posts sig includes - but it is too tall and makes the optic sit tilted up (see photos). Also - there is no place to use the rear silver post as the Holosun doesn’t have a recessed area in the rear. So even if I dremeled down one of the sig silver posts to allow the optic to sit flush - would that one point plus 2 screws be enough?

Thanks in advance for any insight anyone can offer.

 

I just put 507k on my fuse. Just put red dot on Holosun screws 15” pounds. No inserts that your putting on. Shoots great 150 rounds no problems adjusted sight. Good to go

 

If the coating is too thick inside the optic's holes, that may be why the studs are not fully seating into the optic.


.
.

 

Thanks but the holes in the optic are just much shallower than the post. About half the depth of the part that is inserted into it. Tried to capture that in my pics.

 

This is pretty peculiar. I hope you get to the bottom of this. Why Sig upted to rework the optic mounting with the Fuse is a bit of a mystery to me.

I'll do some research and if I can come up with anything, will post back.

 

So far the only thing that comes to mind is that for Holosun optics, your only option is to omit the little insertable recoil posts and just mount it direct. This removes the mechanical stability they provide, since you'd be relying solely on the two screws to resist the recoil forces, unfortunately.

If this is the case, I'd be very careful about initial alignment of the optic, tightening each side in turn. As far as final torque value, I'd sneak up on it, trying maybe 10 in lbs on each side, in turn, then dial in 15 in lbs for final tightening.

Screw length (as a guess) would be either 8mm or 10mm. Both options can be ordered at McMaster Carr, or you could try the M3's that come with the optic.

I've heard rumblings about a new line of Sig optics coming "soon" that uses this new mounting approach (removable bosses). Perhaps Holosun's k series (which has always had an asterisk by it, in terms of RMSc footprint) may not be compatible with this.

One would expect no issues with the Romeo X line, but of couse Sig would have an interest in making that compatible with their pistols, and probably couldn't care less if Holosun's don't fit.

As a business decision, that would be advantageous for Sig since it would steer customers toward an all-Sig solution. This would not surprise me a bit.

Sorry, all I got.

 

I also found this:

Seems to me the Holosun not being 100% RMSc compatible wrt the front recoil bosses is the issue.

Assuming that’s the case, then it seems like a direct two screw mount is the least worst option for the Fuse, omitting the inserts that Sig supplies.

 

This is why I had my gunsmith mill down the two lugs on my Glock 48 MOS so I could direct mount my Holosun 507k. Without the adapter plate, the stock Glock sights give me a perfect lower 1/3 co-witness.

Lee

 

Here’s the 10mm screw I ordered for my use, as an example.

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

And this is the 8mm I have also.

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

(I wanted a bunch of these on hand in case, so I have both lengths.)

 

One last comment, I've been staring at a picture of my X Macro Frankengun XL slide, during an optic install I did last year.

When I asked over on the other forum, it was pointed out there are no recoil bosses, i.e. the small protrusions fore and aft, that are in the RMSc footprint definition.

So the optic gets mounted with two M3 screws, direct, the only additional locating mechanism being the shoulder of the threaded hole in the slide which protrude slightly above the optic area surface.

The Fuse seems to be a change, since the slide on a Fuse now has the actual RMSc locating bosses, but in the case of the mounting screws, omits any shoulder. This previously didn't matter for optics which weren't 100% to the RMSc standard (like the Holosun K series), since there were no recoil bosses on P365 slides. Well, now there are, which are incorporated into the Fuse slide optic pattern.



The point being by that member's comment was that "all" existing k series to P365 optics are currently mounted this way, i.e. with two direct mount screws and no bosses.

(As well, I think based on comments here and elsewhere the threads on the Fuse slide are M4, not M3. So for the case of the Fuse, even with no bosses provided by the slide/optic/Sig inserts, and the fact the new interface uses just M4 screws, it should be at least as resistant to recoil than mounted with two M3 screws, even without the inserts.)

Install torque is another question. For the R X compact, Sig suggests "M3x0.5-11.75mm (SIG P365 slide): 24 inch-pounds. On the R X Pro, they have "M4x0.7-9.75mm screws to steel slide: 28 inch-pounds." Assuming you'd be using M4 screws on a R X compact to the Fuse slide, I would tend to use 28 in lbs.

Ok, NOW that's all I got.

 

The Fuse comes with two recoil lugs. With the Holosun EPS Carry, at least, only the forward lug fits the sight and even when screwed down it isn't the most stable. But the EPS Carry comes with a Shield RMSc adapter plate. With the plate, both lugs can be used and once screwed in place the sight is securely attached.
I have no idea if the k come with a similar/same adapter plate but finding an RMSc to K plate should do the trick.

 

The Fuse comes with two recoil lugs. With the Holosun EPS Carry, at least, only the forward lug fits the sight and even when screwed down it isn't the most stable. But the EOS Carry comes with a Shield RMSc adapter plate. With the plate, both lugs can be used and once screwed in place the sight is securely attached.
I have no idea if the k come with a similar/same adapter plate but finding an RMSc to K plate should do the trick.

That’s a good idea.

 

The adapter plate is maybe a millimeter thick and on the Fuse, this allows a large degree of co-witness with the optic.

 

Take a look at the adapter plate from C&H.

C&H Precision Steel Optic Adapter Plate - Springfield Hellcat with RMSc Footprint to Holosun EPS / EPS CARRY

This looks very similar to the one that comes with the EPS Carry. I've not measured anything but it might(?) be a solution .

There are two, small post in this plate like I think the HS one had. The posts shipped with the FUSE fit the plate, then the plate fit the sight.

 

I'm a bit surprised how many recent posts I've seen rcommening C&H products considering the number of complaints about C&H QA/QC over the last five years. There was a time not long ago when many of us advised against C&H... But many new members have joined since then, so I suppose it makes sense they aren't aware of the history.


.
.

 

I have no personal experience with their products and am really recommending them. I just noticed a similarity with the plate that works with the EPS carry and the Fuse optic cut. I found a pic of the top of the HS plate that I didn't already post. Maybe it will be helpful so I'll include it.

I hadn't noticed until just a moment ago that the HS plate has two 'full size' recoil lugs and two smaller lugs by the instillation screws. These latter, smaller lugs don't seem to be on the CH version. They might also make this HS plate incompatible with other Holosun micro dots.

 

It's a bit hard to see, does the CH plate have these smaller lugs?

 

SCS CARRY-Holosun

Is this K versus RMSc requiring the including plate for use with the Fuse ?

 

I would really like to have someone in the industry tell me why do they (Sig in particular, but others do it too) keep making changes to optics mounts? Seems like there would be about 2 or 3 standard ones by now, a smaller one for open/small optics, and a larger one, and maybe one more in between. When I bought my P320 I saw the list of optics that were supposedly direct fit, and I had two different ones on that list. Neither one fit perfectly, I ended up getting a DPP adaptor plate and all was well, but there are about 4 versions of P320 slides alone, and I kind of think the $34 adaptor plate got me off cheap.

 

Probably because they only care if their own Romeo optics fit. I for one have had mixed results mounting anything other than Romeo optics.

 

Just call Sig Optics Customer Service and they will give you the low down I’m sure. I’d bet they could tell you what you need to make it right.

 

Are customers having better luck with the phone route? I tried email and got no reply after 2 weeks. Haven't had a block of time where I can sit on hold on my phone in front of my pistol for an hour or more.

 

It's a bit hard to see, does the CH plate have these smaller lugs?

You sho

SCS CARRY-Holosun

Is this K versus RMSc requiring the including plate for use with the Fuse ?

You don’t need adapter plate with K series the Holosun EPS carry will mount direct to that. RMSC footprint is the same.

 

You sho

You don’t need adapter plate with K series the Holosun EPS carry will mount direct to that. RMSC footprint is the same.

Incorrect. See post above. Holosun doesn't use a true "Shield Sights" mounting footprint.

.
.

 

What ever you say. Just mounted 407 k no plate. My other guns went from 407 k to EPS carry. Maybe im missing something.

You are, but it's no big deal. Direct mount will work. The OP was asking why his 507k won't sit flush, with the Fuse optic silver insert posts in place:

Would like to mount a 507k on both my XMacro and on my Fuse - but a couple of questions:
...
2. On the fuse - I tried one of the posts sig includes - but it is too tall and makes the optic sit tilted up (see photos). Also - there is no place to use the rear silver post as the Holosun doesn’t have a recessed area in the rear. So even if I dremeled down one of the sig silver posts to allow the optic to sit flush - would that one point plus 2 screws be enough?

As was pointed out, the Fuse is a new design with M4 screw holes and new inserts:

The Fuse comes with two recoil lugs. With the Holosun EPS Carry, at least, only the forward lug fits the sight and even when screwed down it isn't the most stable...

...But a k series optic won't fit because the 507k is not made 100% compliant with the RMSc standard - it lacks full depth holes that correspond to the new Fuse recoil bosses (and never has.)

..."all" existing k series to P365 optics are currently mounted this way, i.e. with two direct mount screws and no bosses.

(As well, I think based on comments here and elsewhere the threads on the Fuse slide are M4, not M3. So for the case of the Fuse, even with no bosses provided by the slide/optic/Sig inserts, and the fact the new interface uses just M4 screws, it should be at least as resistant to recoil than mounted with two M3 screws, even without the inserts.)

So, yes, I believe direct mount, no inserts is the only way to go with a Fuse, just like in the past with k series optics. If Holosun ever changes the k series footprint to be fully compliant with RMSc, then those optics can fit with the new Sig Fuse slide with the inserts.

Now, if you have a Fuse slide, and mounted a k series, or EPS Carry, direct without a plate, with those little silver posts retaining the optic in place, well then that would be pretty interesting, as it would be some other variation going on.

Hope this all makes sense.

 

It is my hunch or guess, that Sig will change the slides on all P365 variations to be like Fuse red dot interface.

 

Obviously Sig sees this as an improvement.
So it will likely show up on all P365 variants.

Holosun will need to catch up with the changes.

 

Thanks for all of the replies fellas - will try to get caught up and reply to a few suggestions.

I emailed SIG directly from their website on the day that I started this thread - even included a link to this thread.
They say 3 business days for a reply - it's been 2 weeks, so perhaps this is the SIG customer service I have read several complaints about across the internet.

 

As luck would have it - I was moving my Holosun 507k from my Hellcat Pro to my P365 Fuse - checked to see if the adapter plate that was required for mounting on my Hellcat would work - no dice.

Top photo shows how the adapter plate is a bit too long in the front to seat on the Fuse - doesn't look like much, I possibly could have used a Dremel to shorten the plate, but I didn't want to ruin my plate and end up with a chewed up mess.

The bottom photo shows how the plate fits perfectly on my Hellcat.

 

Ended up mounting another optic I had on hand with a true RMSc footprint onto my FUSE, I used both metal pegs that SIG supplied with the pistol, and the optic fit perfectly over them, so it is supported very well and felt very stable even before putting in the two M4 screws that came with the optic.

Optic is a Primary Arms Classic Seriec Micro Reflex Gen 2 - about $140 shipped when on sale. In the photos you can see the posts in place, that the optic fit right over, and fit flush with the slide. Haven't taken it to the range yet, but just in co-witness it appears to already be pretty close to dead on.

Put the 507k onto my XMacro - feels like having the threaded posts design would be more stable.

 

Both pistols ready for a trip to the range:

 

Any chance I can see more pics of your fuse and how does the primary arms sight work? Like good or bad I mean lol thanks in advance