Bergara BMR Easy Trigger Mod

READ THE STICKY

Been getting a lot of chatter about Broken Taps. Finally talked to a particularly peeved fellow on the phone last night. He'd broken a tap off in TWO triggers! After walking me through his process I was just dumbfounded to hear he never drilled the hole......He just went right to winding the tap(s) down!
So For those of you Considering the work:

1. YOU MUST DRILL THE HOLE TO TAP DRILL SIZE AND ALL THE WAY THROUGH!

2. THIS IS A SMALL TAP! If you're new to using a tap: Lots of oil, clean often (that means the hole as well as the tap) go Slow.

"Gon' Tap that? Remember, If you love it....Lube It!" -Cody Franke-

Click to expand...

3. IF you do ham-fist it and break the tap off in the trigger...You're only out a few bucks and an ounce of ego. Plus you've learned a valuable lesson.

When it comes to tapping holes: "no" means NO, and "slow" means SLowwwwwww

Other than that, You have done NO real harm!
The Trigger should function just as it did before.

FYI There's a fellow member giving away screws in the TradingPost (just send him an envelope)

BMR trigger modification?

Lots of good, but different information about this............

4-40 tap.

??? number drill bit....... Not sure which..........

Lots of oil and patience (not one of my strong points)..............

On the gun, or off?

Just want to verify before I get started.

Thanks.

Ric

Again ,thank you Gr8guns,just finished the job as the snow flys outside.first idid not drill the hole deep enough the hole was there but not all the way through or it was smaller down in ,I tapped it part way and the tap stopped,you have to know how to tell if the tap stops or if it’s just tough going,from past experience with small taps(!?) I didn’t break the tap! I made the screws gr8guns sent me into dogheads ,then,I did not have a small enough Allen head nor could I find one after searching the attic,guntools,old scope boxes or the barn so I filed a 1/16” down evenly on all six sides with a file and it was a perfect fit( NOT!)😡😐but it did work after I figured the hole problem out,but screw NO.1 took a beating during development and research and after I used needle nose vise grips a couple times it would not go deep enough because o thread bunkering,but the home fixed tool worked well enough to finally get the screw in and set at about 1 1/2#.

Screw

This is screw NO.1

I'll add my two cents -

I found a spare trigger for $30. Bergara's Owner's Manual says replacement of the firing mechanism voids the warranty so I figured I'd try the mods outlined above on a spare.

Although I haven't had a chance to put it in the gun to test it, here's my experience with the mod:

As noted, the trigger is already pre-drilled both fore & aft for additional screws. If I had to guess, Bergara's insurance company didn't want them to actually provide an adjustable sear engagement and light-weight trigger pull. The additional manufacturing cost would have likely been under a couple of dollars, but the added insurance premium might have been through the roof. If you make these mods you do so at your own risk!

Important tip: some of the people that added to the various mod threads say the hole behind the trigger is already completely drilled out -- but it is probably NOT. If you don't run an appropriately sized drill bit all the way through you're likely to break your tap when it hits the shoulder. All you have to do to prove there’s a shoulder is run a pin punch into the hole and you’ll feel it. I don't recall hitting a similar shoulder with the front hole but ran a drill bit through it before tapping it anyway. If yours happens to be drilled all the way through, no harm, no foul. If not and you try to tap without going all the way through with the drill bit there's a good chance you'll have a piece of your tap in the trigger for life.

If you click on over to Snipers Hide and check out the Bergara B14R Issues & Solutions thread (All Things Rimfire forum) you’ll see where AirGunShawn (see his posts here at #59 or so!) took things beyond what’s here at Rimfire Central. Scroll through to post 76 and several follow-up posts for his trigger discussions.

In VERY short summary - Shawn noted that the rear screw we’re all talking about here adjusts the sear and not the true trigger pull. What the set screw does is take up the slack/slop and make the trigger “crisper”. That seems to be clear from the original sticky here, but it seems to get glossed over in this current thread. To my thinking, if it’s a lighter pull that’s likely because the sear is right at the razor’s edge, and possibly unsafe. If it’s set too light a sudden jolt (drop the butt end on the floor) could cause the gun to fire. Read Shawn’s many posts on the topic in the thread at SH - it’s well worth it.

Shawn’s ultimate approach is to go up to 6-32 so he could use plunger screws, so I just started there. An advantage of the 6-32 screws is they have a nylon thread locker to keep them where you put them - no need to use two 4-40 screws back to back to try to lock them in place. He used these screws front and back - the rear screw takes up much of that sear slack and the front screw counters the spring - thereby making the trigger “lighter” without necessarily compromising safety.

I drilled out the holes with a cordless drill without putting the trigger in any vice (held it in my hand!) - since it's predrilled you're not removing much material. You could probably do it while the trigger is in the action but taking it out is probably more convenient. Just be careful about going too far past the bottom of the existing hole(s) and nicking the inner workings - I flagged the bit for the appropriate depth based on running a punch into the hole.

Then I used plenty of 3in1 oil to lube the tap and took it slow - a turn or two and then back it out to clean the tap and re-lube. Still took less than about ten minutes per hole. Toughest part of the job was waiting for the plunger screws - nobody carries them locally.

I started with a standard plug tap - if the holes are already correctly drilled the plug tap is the best way to make sure you start straight and it cuts really easily. But when I did the front hole, the head of the plug tap apparently hit the inner parts before it threaded the entire hole.

Shootrj2003 above (post 73) notes his first screw hung up and I’d guess that’s because the full threads didn’t run all the way to the bottom of the hole. Odds are brute force with the screw itself cut the final threads. I tried that, but after ruining a screw I just went out and got a bottoming tap.

All in all the job was uneventful. Now I just have to go about swapping it out for the original trigger and doing some testing.

I probably won't swap triggers for a while. Until I've put a few more rounds through the gun I'm going to shoot with it the way I got it. I was too excited just to be shooting it for the first time that I didn't really pay any attention to the trigger on my first outing. I suppose that's a good thing!

Pull weight

I have measured my trigger with a trigger gauge. Before installation of the sear adjustment screw, the trigger pull weight was a little over three pounds. I now have a trigger pull weight set at twelve ounces. I originally had left it at 10 ounces, but raised it a couple of ounces. Metal to metal contact causes friction. If the metal to metal contact is reduced in surface area, then friction is reduced, making a lighter pull weight. The angle of the contact surface also changes. Camming action can greatly influence trigger pull. Lightening the factory spring tension changes trigger pull weight. The combination of these things changes pull weight My trigger pull gauge does not measure crispness, it measures trigger pull weight. It is well noted about checking a trigger for slam firing. This step should be done after any trigger adjustments. I respectfully added my differing comments, not as a challenge, but simply some facts to think about. As always, your mileage may vary. I'm not an engineer, I am a retired maintenance mechanic. Running a two and a half inch drive impact wrench has surely rattled my brain.

Trigger cleaning

I haven't had any trouble or complaints with my trigger, but in anticipation of desiring a more adjustable trigger, I did some modifications to another identical Bergara trigger.

I read somewhere about somebody flushing their new Jewel trigger and getting some production chips and gunk out of it so I flushed my modified trigger (Mineral Spirits) and got a BUNCH of chips out of it - no doubt most from the drilling and taping. Flush it over a white paper towel and you'll see all the junk fall on the paper.

Today I flushed my original trigger (about 250 rounds fired so far) and washed a few metal chips out of it too. Enough that I deem it a worthwhile exercise - certainly worth all of the 25 cents worth of Mineral Spirits. I'm not expecting any improvement (or degradation) in operation, but imagine that clearing out any junk might keep parts from grinding and may preserve if not extend the life of the trigger.

If you do the mods outlined here I recommend flushing it out before installing it.