doublegunshop.com - home Forums General Discussion DIY Gunsmithing @ doublegunshop.com a little over my head

Hello there,

I'm bunker shooter for about 5years, after using different guns I settled on Perazzi MX8, and last year I bought Beretta SO5 and we really like each other
But the problem from the very beginning was a very light bottom trigger ~1.8lb, that results in premature, you know what.., costing me lost targets every time I go to the range. I stopped shooting the gun as it becomes a hazard.
Eventually I modified the set of gunsmith screwdrivers and opened the side locks to find that the sear is rounded with signs of someone working on it.

I always worked on my guns successfully (most of the time ;)), but this is different, and I'm approaching it very carefully, not to screw it up.
I decided to to tackle it myself, as only gunsmith I would take it to has a shop in the other world, and not going to ship it to US.
I bought a Power Custom Sanding Fixture II in the US with attachments I have to modify to fit the sear with help of a CNC operator friend, project challenging in itself.
Bought a set of diemaker stones grits from 100 to 1200. Have stereo microscope with digital camera that is calibrated, with software enabling me to see it and measure on a computer screen with .001mm accuracy.
Sears engagement with hammer is ~.5mm at 87deg angle (top barrel, trigger pull ~2.3lb), my goal is to have trigger pull ~3lb, as is on my Perazzi.
Given that I'm successful in achieving it, there is a a problem that I have to tackle, but not sure how.
I know I need to harden the sear's tip that I'll stone, I have an access to the nitriding process and other case hardening methods, but I don't think it's a good idea to do it to the whole piece, I'm reading about how to, but would really appreciate a targeted advise.
I'm not sure it would be possible to find what steel/alloy the sear is made of, and I assume it's a proprietary secret, the only thig I could do it to measure HCR =43.7 , of the body, surprisingly soft , comparing to trigger group on other guns I checked before.

TIA,

Kaz

Dear Kaz;

I doubt that your SO5 has exotic or proprietary steel of the sear. Hardening a sear is not difficult, but since it is small it is easy to overheat it. You may want to try hardening a small piece of steel to gain experience.

Heat the sear with a small propane torch until a magnet will no longer stick to it and drop the sear into a container of oil (5W-20 works very well) that has been heated to 100 degree F. After the sear has cooled polish it to remove the oxide from the heating. Of course you do not want to polish the tip too much that you just worked to get the trigger pull the way you want. Now you are going to temper (remove some of the hardness) the sear. An experience gunsmith would just take the propane torch and heat the sear until it reaches a dark straw color, but that way of tempering may be a bit too risky for you. Instead you can heat the 5W-20 oil a metal container until the oil is about 450 degrees F and drop the hardened sear in the oil and that will temper it just fine. Let the sear remain in the oil for about one minute. You can go to Harbor Freight and buy a infra red lazer thermometer for less than 20 bucks to gauge the temperature of the oil.

Stephen Howell

Steve,

Lots of advice and experience in this reply. Many thanks.

J

KazO, it sounds like you are much more equipped and well versed in the very critical nature of doing trigger work compared to the average shooter. You have educated yourself on the proper sear angle and sear engagement to achieve the safe consistent trigger pull you require for your Beretta SO5. You understand that proper tempering of the engagement surfaces is important to getting a smooth pull that lasts a very long time. And you had the brains to stop using it when you determined the present trigger became a hazard.

I notice you said the present sear appears to have signs of someone working on it, and that it is visibly rounded. What none of us here know is how much material has already been removed, and if it is even salvageable.
A metallurgist could fairly easily determine what alloy the sear is made of. That would cost additional money. And then you could learn the correct way to reharden and draw the temper for steel of that particular alloy. I agree that the method recommended above would likely get you in the ballpark. But it is only guessing at this point to know the type of steel used, and whether it is an oil, air, or water hardening alloy. You could possibly do a good enough job to make it last for a long time if it was a hunting gun that sees limited use. But you are apparently a high volume trap shooter, and a trigger that works well for 500 or 1000 shots before wearing out again, or fracturing, could put you right back where you are now in a very short time period. And that's all assuming that the present sear hasn't already had too much material removed to do a good job.

Considering all that, and considering that Beretta SO5 parts are probably still available, it might be wise to try to find a new or good used sear, and fit that to your gun. Then carefully stoning a small amount of material of a through hardened part, if necessary, is unlikely to leave you with a sear tip that is not correctly hardened and tempered. Even a brand new part isn't a guaranteed fix. Years ago when I was in college, I bought a Colt .357 mag revolver, and the hammer notch fractured before it had 100 rounds through it. Every few shots during single action firing, the hammer would drop prematurely before the transfer bar came up, resulting in a misfire. As it was a brand new gun, my FFL sent it back to Colt and they replaced the hammer for free, and covered shipping both ways.