Pistols (and pistol mounted optics) I saw this week

[SoCalDep]

Awesome post.

I am snipping out everything but the above to ask this question. I'm trying to confirm the screw you'd suggest for a Holosun 507c, Dot to MOS plate, mounting screw. Is it a McMaster-Carr, standard steel, part number 90920A274, 60,000psi tensile strength, torx screw, with a 0.262" head and undercut profile, as per below?

Same question, for a Holosun 507k? Same screw?

Attachment 79408

Perfect timing. I had a guy come in today who wanted an optic (509T) mounted on a work gun and a couple optics swapped between some fun guns. One of the optics was a Holosun 507C, so I did a test-fit of the McMaster-Carr screws you have referenced above (standard steel - zinc plated... part number 90920A274). I was pretty confident they would work, but the “undercut” on the angled head (don’t know the technical term) made me want to confirm. They worked perfectly with good thread engagement but still not at all protruding from the bottom of the MOS plate. I took a couple pictures and I’ll probably update the other thread about screws and mounting once I get home to upload the photos.

As for the 507K... The optic is less the issue compared to what it’s being mounted on. I have very little experience at this point with the Glock 43X/48MOS guns, and have only mounted a couple Holosun “K’s” on them. I used the supplied C&H precision screws so I don’t know the dimensions and such. I’ve mounted several “K’s” on Sig P365 and have good McMaster alloy steel M3-0.5 x 10mm screws, but that probably doesn’t matter if you’re running a different platform.

[MistWolf]

I got my hands on a 508T X2 this week and compared it to my 407CO X2. The countersink of both optics is right up next to the side of the optic body. The McMaster screws did appear to at least touch the side when sitting in the countersink. When I removed the 407CO from my pistol, I immediately noticed significant wear marks on the inside of the optic body around the edge of the countersink. It appears that the McMaster alloy steel screws, with their 0.307" head diameter barely touch the body as the optic is installed and are able to move the aluminum enough to seat.

The problem (or at least part of the problem) is, the screw has a radius where the shank meets the bottom of the head



and the countersink doesn't



What happens is the point of the angle of the countersink hits the radius preventing the head of the screw from seating fully in the countersink.

If you look at this photo below, you can see where the radius of the screw started to flatten the hard angle into a radius when the screw was cranked down

The photos of the other screws shows they're threaded all the way to the head where the radius is. Be careful if you use them as that has weakened the shear strength (ie- created a stress riser) of the fastener at that point.

On the surface, it would seem the answer to the problem would be to use screws that fit the hard angle. In reality, the holes are not counter sunk correctly. The answer to relieve the angle so the screw with the radius so the head can fully seat when torqued. The radius on the fastener is to reduce the stress riser at that point and the result is a stronger fastener.

However, I get that it's unlikely you have the right countersink cutter or a hole deburring tool on hand. Maybe you know a machinist that can help you?

[MistWolf]

PS- I think the undercut style head illustrated in the chart posted by RJ will fix the problem

[SoCalDep]

The problem (or at least part of the problem) is, the screw has a radius where the shank meets the bottom of the head



and the countersink doesn't



What happens is the point of the angle of the countersink hits the radius preventing the head of the screw from seating fully in the countersink.

If you look at this photo below, you can see where the radius of the screw started to flatten the hard angle into a radius when the screw was cranked down

The photos of the other screws shows they're threaded all the way to the head where the radius is. Be careful if you use them as that has weakened the shear strength (ie- created a stress riser) of the fastener at that point.

On the surface, it would seem the answer to the problem would be to use screws that fit the hard angle. In reality, the holes are not counter sunk correctly. The answer to relieve the angle so the screw with the radius so the head can fully seat when torqued. The radius on the fastener is to reduce the stress riser at that point and the result is a stronger fastener.

However, I get that it's unlikely you have the right countersink cutter or a hole deburring tool on hand. Maybe you know a machinist that can help you?

That would be the case if the hole diameter in the optic matched the diameter of the shank of the screw. I’m not sure that’s the case and the screws very much seem to show wear at the edge of the head more than the radius. While the 407CO picture does seem to show a more radius edge at the bottom inner portion of the angle, those optics haven’t been the issue. The issue has been the Titanium 508T optics.

I’ll add… if it takes a machinist to make something work… It’s a failure for my purposes. This is not a hobby. Life and very much death can depend on this. My goal is to find the most robust mounting solutions to mitigate the greatest common optic failure, which is mountings coming loose. Cops and not cops aren’t machinists but they need their equipment to perform. I get mounting failures and improper threadlocker but if something sucks then it sucks.

The question is… does it suck?

[Nephrology]

That would be the case if the hole diameter in the optic matched the diameter of the shank of the screw. I’m not sure that’s the case and the screws very much seem to show wear at the edge of the head more than the radius. While the 407CO picture does seem to show a more radius edge at the bottom inner portion of the angle, those optics haven’t been the issue. The issue has been the Titanium 508T optics.

I’ll add… if it takes a machinist to make something work… It’s a failure for my purposes. This is not a hobby. Life and very much death can depend on this. My goal is to find the most robust mounting solutions to mitigate the greatest common optic failure, which is mountings coming loose. Cops and not cops aren’t machinists but they need their equipment to perform. I get mounting failures and improper threadlocker but if something sucks then it sucks.

The question is… does it suck?

FWIW I've been using mounting screws sourced from Maple Leaf Firearms (who did basically all the milling for my pistols with RMRs and 508Ts) and all their screws are beautifully countersunk. Not sure where they are sourcing them but you can either buy from them directly or shoot them an email to see if they have any info re: your question.

[MistWolf]

That would be the case if the hole diameter in the optic matched the diameter of the shank of the screw. I’m not sure that’s the case and the screws very much seem to show wear at the edge of the head more than the radius. While the 407CO picture does seem to show a more radius edge at the bottom inner portion of the angle, those optics haven’t been the issue. The issue has been the Titanium 508T optics.

I’ll add… if it takes a machinist to make something work… It’s a failure for my purposes. This is not a hobby. Life and very much death can depend on this. My goal is to find the most robust mounting solutions to mitigate the greatest common optic failure, which is mountings coming loose. Cops and not cops aren’t machinists but they need their equipment to perform. I get mounting failures and improper threadlocker but if something sucks then it sucks.

The question is… does it suck?

It sucks. The question is, why does it suck, because in this case, there are two categories of suck-
1) It sucks hard and the average cop should avoid it
2) Maybe it sucks hard, maybe it's just frustrating. Maybe the average cop can deal with it.

Looking at the question through your necessarily narrow view, if the parts require any sort of modification to fit, it sucks hard.
-If the alignment pins are too tall or the mounting base is too thin, the fastener will bottom out. Full clamping pressure will not be achieved.
-If there is any play in the fitment- fore, aft, side to side, the optic could move under recoil and the fastener head may fail with use, or the holes in the base wallow out.

Solution- Hard pass until fixed by makers.

If the fasteners are incompatible with the installation, maybe it sucks hard, but definitely frustrating to deal with.
-If the unthreaded portion of the fastener is too long, it will bottom out and full clamping pressure will not be achieved.
-If the head diameter is too large and makes contact in any place but the countersink, this not only will compromise clamping pressure, but will place a side load on the fastener. This can lead to failure.
-If the fastener is too long overall, it can lead to interference with moving parts or, if the hole is blind, bottoming out.

Solution- Get the right fasteners. Once the right fasteners are installed, it should solve the problem.

[Clusterfrack]

… if it takes a machinist to make something work… It’s a failure for my purposes. This is not a hobby. Life and very much death can depend on this.

I was looking for a new sigline, and I've found it.

[Controlledpairs2]

I’m not a fan of the DPP screws. I’ve heard rumor there have been quality issues. I’m not a fan of the Staccato DPP direct mount. I don’t know why they have the bosses on the rear right next to the screws as opposed to forward. That said, I’d ordered a few different screws from McMaster-Carr to see if they would work as replacements and after some experimentation I settled on some hex-drive flat head alloy steel screws. I torqued them to 30 in/lbs going incrementally from about 22in/lbs when re-installing the optic. I just used it for two days of a three-day contract optic instructor development course and it held zero just fine and shot great. I still don’t trust it and the plate is on the way to mount one of my SROs.

I’ll continue to test the McMaster screws on another Staccato and hopefully we can get to the bottom of this issue. The McMaster screws have a larger head that sits proud of the base. It doesn’t affect the view through the window but makes indicator marking more difficult and doesn’t look “factory”. That said, I’m wondering if that additional material helps to lock everything in place without allowing deformation of the screw head. The head of the factory DPP screws are pretty small.

SoCalDep, do you mind sharing which McMaster screws you ordered and are testing? How has that been going? I had Leupold send me a batch of OEM DPP screws as I am approaching an annual maintenance, inspection, and potential remount.
Thanks in advance.

[HCM]

If @Erick doesn't mind I'm going to piggyback here till I can write a real AAR. I just finished my 3rd RDS class with Modern Samurai Project (@Asiajedi). Scott's instruction and student diagnostics were excellent as always but just wanted to provide some gear observations:

There were 20ish shooters (we lost a couple on day 2) with a mix of RMRs, SROs, Holosuns and SIG optics. It's a 2 day course with an official round count of 1,000, I've usually shot 800-ish "mas or menos.

There were no direct optics failures in this class or the two prior classes. Two shooters in this class had optics come loose due to mounting issues: a factory optics ready CZ P-10 with an SRO and a 5' Ported PC S&W M&P Core 9mm with a Holosun. The S&W issue was with the CORE mount but the shooter (a USPSA competitor and high volume shooter) said he has had the same issue with the C&H plate on his identical back up gun.

This class I ran a SIG P320 Carry with a factory mounted Romeo1 PRO instead of my usual Glock for familiarization purposes since 320s and the Romeo1 PRO are issued / authorized equipment at work. I had no mechanical issues with the gun or optic. I did however experience two shooter / grip induced stoppages when the base of my thumb inadvertently activated the slide lock in mid string / with rounds in the mag. These were the 5th and 6th such issues I've experienced with the 320 X grip.

There was one other shooter running a 320/M17 Bravo with an RMR on an adaptor plate and one shooter who ran the whole course with a P365XL with a factory mounted Romeo Zero. No issues.

There were several (5-6?) shooters running 2011's, one Triarc, the rest recent STI/Stacattos, one XC model and the rest P Duos. All were running RMRs or SROs. One of the DUO shooters had both a P DUO and a C DUO (the single stack) and switched between the two. One thing I noticed was a couple of the 2011 shooters had their grip safeties taped or rubber banded down. This is heresy because everybody knows in Texas you may only deactivate your grip safety with a piece of raw hide.... Scott Jedlinski also ran an XC the first day - no issues. The other XC shooter had a few return to battery issues the second day as the gun got dirty but they appeared to be related to running a lighter (8lb ?) recoil spring. No issues with the P DUOS or C DUO.

One shooter ran a 5" PPQ with and SRO and experienced failure to fire towards the end of day one.

Everyone else ran Glocks. The only Glock issue was caused by an aftermarket trigger. Shooter finished the class with a borrowed Glock.

Scott was gracious enough to allow me to shoot his RMR equipped LTT Beretta 92 after class. suffice to say, as a long time 92 fan it's going to cost me money.....

If @Erick Gelhaus doesn't mind I'm going to piggyback here again.

I just finished my 4th RDS class with Modern Samurai Project ( @AsianJedi ), this time Scott's Instructor class. Scott's instruction and student diagnostics were excellent as always and it's interesting seeing how Scott's POI and certain parts of that POI have evolved, particularly his method of teaching float and transitions for multiple targets.

Jedi's classes normally attract talented shooters but this class was "the deep end of the pool." Student's included @Mr Pink and his wife (a top competitor in the Tactical Games), Riley Bowman, host of the Concealed Carry Podcast and World Speed Shooting Champion BJ Norris who earned the 17th MSP Black Belt Patch.

BJ Norris (now a US Border Patrol Agent) and myself were the only LEOs and there were no active duty military which was unusual compared with past MSP classes.

There were 18 shooters with a mix of RMRs, SROs, Holosuns and SIG optics as well as two ACROs. One shooter ran a P1, another (the shooter whose CORE failed in the last class) shot the course with Jedi's P2 equipped Walther PDP. There were at least 3 other PDP shooters in the class. One of them had issues with his Freedom Munitions ammunition's but there were no gun related issues with the PDPs. Glock and SIG P320s predominated, followed by Staccatos and Walther PDPs and a lone P365XL/VP9 shooter.

It's a 2 day course with an official round count of 1,000. I shot 800-ish.

There was only one optics failure I was aware of, a Holosun 507k X2 on a P365XL which ejected it's battery and battery compartment in the midst of a string of fire. The shooter swapped for his VP-9 with RMR and continued without issue.

One Staccato P Duo shooter had ongoing issues with his mag dropping out of the gun on the draw / presentation. It seemed to be a grip related issue and the gun ran 100% when the mag was in the gun.

I ran a SIG P320 Carry with a factory mounted Romeo1 PRO from an ALS holster which is our issued / authorized equipment at work. I had no mechanical issues with the gun or optic.

Ironically I received my LTT Beretta 92 RDO just before class so last years "test drive" did, in fact, cost me money.....

[TC215]

If @Erick Gelhaus doesn't mind I'm going to piggyback here again.

I just finished my 4th RDS class with Modern Samurai Project ( @AsianJedi ), this time Scott's Instructor class. Scott's instruction and student diagnostics were excellent as always and it's interesting seeing how Scott's POI and certain parts of that POI have evolved, particularly his method of teaching float and transitions for multiple targets.

Jedi's classes normally attract talented shooters but this class was "the deep end of the pool." Student's included @Mr Pink and his wife (a top competitor in the Tactical Games), Riley Bowman, host of the Concealed Carry Podcast and World Speed Shooting Champion BJ Norris who earned the 17th MSP Black Belt Patch.

Work is sending me to his instructor class in April. I'm really looking forward to it.