KrisS

I have Holosun 510c on my Bul SAS II. I use Tevo Sports mount although I believe there are also other companies that make such mount (Limcat ?). The key thing is which holes pattern you have for the mount. I believe the Bul mount pattern (at least those sold in Europe) is 3 holes with metric screws (imho it is not compatible with standard US 5 hole pattern but I am not sure). I believe Tevo had mount blanks without holes drilled so you could get such and ask your gunsmith to drill it.

I have 507c and 510c since roughly 2 years. They were both used on Open Gun, Ar-15, 9mm PCC, and on slide on 9mm pistol. They work great, are durable and never had any issue with them. Mechanically and functionally very reliable Red Dots.

In general as guys said already: wait with changing anything for a moment. As for the red dot - I would change it for something smaller with relatively big window or even Holsoun 510c (tevo sports makes nice mounts for it) IMHO load is one of the key elements . I was Using VV3N38, Vectan SP2, Lovex 37.1 and currently RS24. Vectan leaves hard black residue on the parts slowing down mechanisms after 400-500 shots, 3N38 has availability and pricing problem (at least in my Country), Lovex is cheap available and its only problem is stability and "copper like" remainings inside pistol, RS24 seems to be atm the best working powder for me (at least with CMJ 123gn 0,356 from LOS) The key for dot stability IMHO apart from Red Dot flex could be the load, 164 PF is ok from the perspective of IPSC rules but Comp in my gun works best around 168-170 PF making the gun stay flat. You have to try which combination works for you as apart from the pistol and load your grip may do the difference (thats the reason to wait with the changes until you will familiarise with new platform and will see what gripping method is best for you - thumb position on the safety and on the thumb rest is IMHO crucial)

I have BUL SAS II UR Open and my reloads / ammo depending of bullet type OAL is either 30mm or 30,5 mm. As "regular" 9mm is 29,69 mm then I would say it accepts longer OALs (unless they changed their barrel parameters for US then I'm wrong). A lot in terms of OAL depends of bullet shape anyway. You can ream the barrel throat if you need to. With OAL of 30mm and soft plated LOS 124 gn bullets there is roughly 3mm of bullet that sits in the brass. I see no reason to go longer if there is not signs of overpressure at PF of 170-175.

That was jcv industries mount (with trijicon rmr mount pattern). Currently I have 507c on other gun (cz sp-01 shadow) and bul is equiped with holosun 510c. Overall very satisfied with holosuns

Imho what keeps the bullet is mostly neck tension. Although in major ammo where oal is longer and bullet sits very shallow additionall crimps helps a little (but maybe not much). On cmj bullets I use when I apply more crimp there is a „step” that holds bullet in place and prevents (maybe marginally) the bullet setback. If he changes crimp and there is a change in the 1shot pattern then it is ammo related. Changing ammo to different kind /make would be even better of course. I could be wrong though. That’s just unconfirmed theory

Maybe your ammo has too shallow seting depth or to weak crimp. Maybe while loading first round the bullet is pushed deeper than during all other shots. You get higher speed of the first shot and higher poi ? Just a theory. You could use different ammo or crimp yours stronger ?

In Poland cheapest open version is 3,6k$ (with vat tax). Bulesteros is 6,7 k$ taxed as well.

I also have some ammo (like 2% of batch) that does not fit into the chamber just after it is done (cmj bullets have size variations and rub rifling on the sides with 0,356 bullets or mixed brass I use reacts not so good to format). I fix like 75% out of that with Lee Factory crimp die. After that they usually fit into chamber

I have the BUL SAS II UR OPEN. Concerning the magazines you just need to buy Para version. Overall it is very nice gun. This one is a little bit "corrected" comapred to stock version (different mount, Holosun 510c, thumb rest and AA shielded safety). Shoots great out of the box.

I had similar case on 2011 platform and I've found the potential reason / or set of conditions when it happens. I used slowmotion recording with iphone to find out what was the reason and here are my findings: Hitting the right/bottom corner of the mount (and/or empty brass is pushed back in the port on top of next round) when I use some pickup brass, During the ejection the brass is not properly held by the extractor and it goes up instead of low 4 oclock (as my ejector is cut to hit brass back on top and direct it right and back).Brass either hits the returning top of the slide or bottom right corner. Then the brass goes back into port if the slide return too slow or just bounces away "just" hitting the mount with random ejection pattern. Changed extractor to aftec type extractor which helped a little. I will check the stronger and weaker return spring (with DPM it is quite easy) to see what will be the outcome. Current temporary fix is just some tape on the mount corner.

I have tested also other loads with 124 grain bullets and Lovex 37.1 : DMA Reloading FMJ RN 124 gn (OAL 30,10 mm, 9,85 gr for 165 PF), Frontier RN CMJ 124 gn (OAL29,80 mm, 9,82 grn, PF 164) and Frontier CMJ RN MATCH 124 gn (OAL 30,00 mm 9,82gn 164 PF).Again: test it and use it at your own risk. The only complaint on FMJ vs CMJ is FMJ makes compensator very very dirty compared to CMJ.

This is what works for me but you need to be careful and use it at your own risk. Gun: BUL SAS II UR Open OAL 30,0 mm Lovex 37.1 9,9 grn LOS Bullet CMJ RN 123 grn SP Fiocchi primers Medium crimp It makes 167 PF easily Good amount of gas to run the comp, relatively clean but hard to load. Soft kick, better than Vectan SP2 or VV3n38 I am very happy with it

It still works great. Only the back of the optic is beat up more as sometimes the brass hits it when bouncing from the top of the slide. It happens for some of the brass only but as I am reloading based on picked up brass I am aware of this. As for the photos of the mount itself: it was too low and I had to file the bottom of it so there is a celarance

I mostly shoot 9mm Major and my gun is tuned for it (DPM spring system). at the very begging of my use it was shooting "regular" purchased ammunition with stock 9lbs spring just fine. I tested that with 124gn and 139 gn RN bullets with D032 load as well. Did not have any issues with it but it is temperature and lube dependant as well. With minor loads and temperatures below freezing point the slide became a little lazy and once or twice it felt slow but still was cycling nor had double feed issues. Unless Major ammo is not available at your location what is the sense to use minor ammo in a gun that shoots Major PF? I try to stick to one load to have the gun behave same time on trainings and during the matches. You could tune it for minor loads only of course as well.