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CZ Open


kneelingatlas

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Guys I'm having issues with my gun breaking mount screws. They are 5-40 screws. It's the RTS II mount from CZ custom. The first time it happened it was the front screw and they all had come loose. Got the broke screw out and replaced but used the same middle and back screws. Lock tited the crap out of them. Marked them and they didn't seem to be moving so I didn't check them. I left it at my cerakoters and he said the rear screw was broke. PF is only 173. 10 pound recoil spring. Rest of gun looks fine.

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On 8/11/2015 at 7:48 AM, kneelingatlas said:

I've got a project in mind using a 6" barrel and the full length of a TS slide, taking inspiration for lightening from this pair built by a friend on the other side of the world:

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Holy crap, those are are a sexy looking pair.

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Hi 1212... I've had exactly the same issues with the Czechmate scope mount. However, I see by your note that you have the CZ Custom mount. With their mount you need to add the pins to help keep the screws from loosening during firing. Tolerance on the pin to frame fit should be a nice gage fit, drilled and reamed holes with a tolerance no greater than .0001/.0002 over size on the holes. If you don't use the pins, the screws will always be loosening or breaking. Taper pins may even be an option if the holes are too big.


On the Czechmate, the screws are 4mm x .7. The description below pertains to fit-up with the CZ factory C-More Mount – but don't see too much of an issue with using the same process with the RTS mount, your mounting hardware will change, however.


Most gun screws are high grade but most are limited to a grade 5 fastner and hex drive. You need stronger screws, number one, and move away from the hex drive.


Here's how I fixed the problem on my pistols:


You'll need grade 8 screws instead of the grade 5's as comes with the pistol. The head of the screws should be the Torx head style. You may find the M4-.7 hard to come by in the Torx head drive. They should slso be plated, this increases the thread form by a few tenths and they fit much better, plus the Loc-Tite becomes more effective when cured because of the closer toleranaces. Plus, post plate bake has been done to eliminate hydrogen embrittlement. Screw lengths should be 10mm and 30 mm so that you can trim the length to exactly what is needed. They should only be ground to length or diamond wheel cut for best results – due to the hardness of the screws. Try not to heat them up too much as the screw temper and heat treat will be gone.


If you can not find them easily, please email me with your address and I'll send some off to you. The only company I found they where available from was BOSSARD, but, the screws had to come from Switzerland, or Norway – don't recall right now. I purchased a ton of them because of their minimum order requirement.


Accurately trim the screws to length and square the ends the best you can. Do not chamfer the screw ends as this will delete at least one of the threads. Make the trim as square as possible. You want as many threads to engage the pistol as possible.


You will also have to decrease the head diameter to the same diameter as the existing allen drive screws so that the Torx drive screw seats in the same manner as the original screws.


Install the screws with RED loctite, industrial grade – not the commercial crap. Apply generously to the threads and making sure the head of the screws at the angle have plenty of adhesive, wipe of excess and let set for at least 24 hours.


Having said this, I have not had a single screw failure in either of two pistols over the last year. Previous to adding the Torx screws, every stage of fire the screws had to be re-tightened, it was awful. After just a few re-tightenings the hex head sockets where wallowed out – all around a big drag.


Let me know if you need the screws – no charge.

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