ShotGunWorld Shotguns

It is currently Sun Feb 23, 2020 8:46 pm

All times are UTC - 6 hours [ DST ]


Image



Post new topic Reply to topic  [ 9 posts ] 
Author Message
 Post subject: Spanish 410 boxlock / sear repair or replacement?
PostPosted: Sat Feb 01, 2020 3:02 pm 
Field Grade

Joined: Mon Mar 20, 2017 2:22 pm
Posts: 27
Updated description of project on 2/8/20 posted below!


I acquired a nice little .410 (Spanish double) as a project gun for a reasonable price. It's a Marixa, that was imported by Blumenfeld Co. out of Memphis Tennessee presumably in the 1970's I knew it had trigger/sear issues upon purchase, hence the low price. I've worked on many other Spanish sxs guns, so I have experience with the innards and how they work (strictly an amateur, but capable! :D ).....This gun's issue is that the nose of the sear for the right barrel has been worked on to increase trigger pull weight to an acceptable level....it was less than 2 lbs when I got it..... (currently it's about 4 1/2 lbs pull). This sear work resulted in a too short of a sear nose so that when it engages the hammer notch, the hammer is only about 1/2 the distance off the firing pin relative to where it should be at full cock, and as you would guess causes misfires about 50% of the time.
The simple fix would be total sear replacement, but finding one would be akin to winning the lottery, so my question is how to attempt a repair to this sear? 1) Could the sear be softened and try to peen/displace metal forward of the pin hole to regain some length to the nose/fit it back in an re-harden? 2) tig weld the nose and re work/fit the sear back to proper length?
3) weld the existing hammer notch and re-file a new notch/re-harden/install
Are any of the above feasible?? Ideas or suggestions would be most welcome!
***I only need about .075" additional length to the sear nose to get the hammer all the way back to full cock. Thanks!




Last edited by Kentuckycook on Sat Feb 08, 2020 8:56 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: Spanish 410 boxlock / sear repair or replacement?
PostPosted: Sat Feb 01, 2020 4:53 pm 
Diamond Grade

Joined: Mon Jan 23, 2017 9:08 am
Posts: 1821
Location: Central NH
I'm an amateur as well, but one thing I've learned is when something doesn't work right don't go ruining more parts to 'fix' it.

Have the sear welded, fit it so you have enough hammer travel, and do your best to re heat treat it.


Top
 Profile  
 
 Post subject: Re: Spanish 410 boxlock / sear repair or replacement?
PostPosted: Sun Feb 02, 2020 1:24 pm 
Field Grade

Joined: Mon Mar 20, 2017 2:22 pm
Posts: 27
Yes, indeed! Good advice! My quandary, I guess, is what are folks opinions on the most effective approach? Perhaps cutting the sear nose apart midway between the sear pin hole and the tip then welding in the gap to give me enough total sear length? (Then work it down to fit and adjust the trigger pull weight) This approach might result in minimal adjustment to the tip of the sear making trigger pull adjustments easier/faster? All this assumes I get the weld job pretty close, so that the angle on the sear nose changes minimally!!!! Opinions welcome!
Nothing like rolling the dice, huh?!!


Top
 Profile  
 
 Post subject: Re: Spanish 410 boxlock / sear repair or replacement?
PostPosted: Sun Feb 02, 2020 1:34 pm 
Diamond Grade

Joined: Mon Jan 23, 2017 9:08 am
Posts: 1821
Location: Central NH
I'd weld the tip. That's where the issue is, not in the middle of the sear.

You have the other side to match the angles. I'm assuming the weight is good on the other barrel?


Top
 Profile  
 
 Post subject: Re: Spanish 410 boxlock / sear repair or replacement?
PostPosted: Sun Feb 02, 2020 5:58 pm 
Field Grade

Joined: Mon Mar 20, 2017 2:22 pm
Posts: 27
Yessir. Back trigger/left barrel is good, right at 5 3/4 lbs.
Appreciate the advice! I'll pursue that course of action, and report back in when I get a chance to tackle it. Thanks much!


Top
 Profile  
 
 Post subject: Re: Spanish 410 boxlock / sear repair or replacement?
PostPosted: Sat Feb 08, 2020 8:48 pm 
Field Grade

Joined: Mon Mar 20, 2017 2:22 pm
Posts: 27
Here is an update for those interested: I could find no gunsmiths in my area that were either willing or capable to look at this project, so I forged ahead on my own. Local welders that would/could TIG weld the end of the sear nose were also nonexistent as well.
Despite my initial reservations, I used my Hobart MIG welder to add metal to the end of the sear nose. Initially I used a sacrificial piece of steel, filed to the approximate dimension of the sear nose, to practice on. I settled on a heat setting of 3 and a wire speed of 35 if anyone is curious. My approach was to weld the tip, then file it back to sort of square things up. I repeated this three times until I was satisfied I had plenty of length to work with on the nose of the sear (total time was about 30 minutes)

I then began the filing process to re-acquire the angle on the sear nose using the sear from the left barrel as a rough guide. Just before the sear engaged the hammer at full cock, I switched to a diamond stone to smooth things out and remove the final few thousandths until the sear JUST engaged the hammer at full cock/maximum barrel breakdown.

Next came the hardening/tempering, of which I know very little about:
After de-greasing the sear, it was heated with a propane torch until orange to red in color and quenched in vegetable oil. After cooling, the sear was then sanded lightly with 320 grit sandpaper to clean, and prepare for tempering. De-greased again and heated to a uniform blue color and again quenched in vegetable oil.
(At this point, feel free to tell me what I did wrong with the hardening/tempering)
The sear seems to have some level of surface hardening, based on a rudimentary file test.

It has been installed and the hammer tripped several times and I detect no rolling or peening of the engagement surface so far.
All that is left is to re-assemble the gun minus the stock, test the poundage, and adjust with the diamond stone. I guess time will tell if I got a good/lasting hardness on the sear!
Just to be on the safe side I've ordered several sears from various Spanish guns from Numerich............may have to start from scratch again, but for now I'm optimistic!

There you have it, just my attempt to repair a firearm with a problem no one else was willing to tackle! I had the confidence on all aspects of this endeavor, except the hardening/tempering process...... the success or failure of which remains to be seen at this point. During the interim, I'll be trying to locate someone to give me some hands on training of the heat treatment processes, so that I'll be prepared if I have a re-do on this project or when I encounter a similar job in the future.
Thanks for any and all suggestions/corrections/comments.


Top
 Profile  
 
 Post subject: Re: Spanish 410 boxlock / sear repair or replacement?
PostPosted: Sun Feb 09, 2020 6:37 am 
Diamond Grade

Joined: Mon Jan 23, 2017 9:08 am
Posts: 1821
Location: Central NH
Kentuckycook wrote:
Here is an update for those interested: I could find no gunsmiths in my area that were either willing or capable to look at this project, so I forged ahead on my own. Local welders that would/could TIG weld the end of the sear nose were also nonexistent as well.
Despite my initial reservations, I used my Hobart MIG welder to add metal to the end of the sear nose. Initially I used a sacrificial piece of steel, filed to the approximate dimension of the sear nose, to practice on. I settled on a heat setting of 3 and a wire speed of 35 if anyone is curious. My approach was to weld the tip, then file it back to sort of square things up. I repeated this three times until I was satisfied I had plenty of length to work with on the nose of the sear (total time was about 30 minutes)

I then began the filing process to re-acquire the angle on the sear nose using the sear from the left barrel as a rough guide. Just before the sear engaged the hammer at full cock, I switched to a diamond stone to smooth things out and remove the final few thousandths until the sear JUST engaged the hammer at full cock/maximum barrel breakdown.

Next came the hardening/tempering, of which I know very little about:
After de-greasing the sear, it was heated with a propane torch until orange to red in color and quenched in vegetable oil. After cooling, the sear was then sanded lightly with 320 grit sandpaper to clean, and prepare for tempering. De-greased again and heated to a uniform blue color and again quenched in vegetable oil.
(At this point, feel free to tell me what I did wrong with the hardening/tempering)
The sear seems to have some level of surface hardening, based on a rudimentary file test.

It has been installed and the hammer tripped several times and I detect no rolling or peening of the engagement surface so far.
All that is left is to re-assemble the gun minus the stock, test the poundage, and adjust with the diamond stone. I guess time will tell if I got a good/lasting hardness on the sear!
Just to be on the safe side I've ordered several sears from various Spanish guns from Numerich............may have to start from scratch again, but for now I'm optimistic!

There you have it, just my attempt to repair a firearm with a problem no one else was willing to tackle! I had the confidence on all aspects of this endeavor, except the hardening/tempering process...... the success or failure of which remains to be seen at this point. During the interim, I'll be trying to locate someone to give me some hands on training of the heat treatment processes, so that I'll be prepared if I have a re-do on this project or when I encounter a similar job in the future.
Thanks for any and all suggestions/corrections/comments.

Nice work.

Just make sure that the safety works, and that the gun won't go off from a bump before you call it good.


Top
 Profile  
 
 Post subject: Re: Spanish 410 boxlock / sear repair or replacement?
PostPosted: Sun Feb 09, 2020 8:06 am 
Field Grade

Joined: Mon Mar 20, 2017 2:22 pm
Posts: 27
Of course! If anyone has fooled with sears or sear engagement, then you know that this will change the distance from the tail of the sear to the trigger blade. In my case the sear tail is now approximately 1/8 inch off the trigger blade, so trigger slop is present. I have had to address this scenario on other guns by brazing in a small spacer and filing to a few thousandths clearance when gun is assembled.

The design of this gun keeps things the same relative to the safety engagement even if sear work is done. My trigger pull adjustment is always to the heavy side initially, and I further test by sharp blows to the gun butt on a rubber mat and /shooting the other barrel first to check that different types of recoil does not set the (worked on) sear off, prematurely.
Safety is always paramount. I refuse to use one of my guns until it is right!
Thanks!


Top
 Profile  
 
 Post subject: Re: Spanish 410 boxlock / sear repair or replacement?
PostPosted: Sun Feb 09, 2020 8:37 am 
Crown Grade

Joined: Thu Dec 05, 2013 7:11 am
Posts: 2869
Location: Western Tampa, FL
Congratulations! This is all well above my capabilities so well done indeed.




Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 9 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Registered users: addecus, albanygun, Anatidae, B.L.E., Barmaleykin, Bing [Bot], Blackdog56, Bobcat Welding, casonet, cbradford, ccL, cheecho1960, Chip1975, Chris Ferres, clarksa614, colnz, cootsluicer, Darkhorse60, DDBach, ded&ded, DEG, delaware_export, Diddle, dirty girdy, dogchaser37, Ezra Smack, floridaford, GD1656, Google [Bot], Google Adsense [Bot], Google Feedfetcher, Hadoken, Hal4son, hehunts, hopper810, ILLINOIS, ithacanut, Jaspo01, jer901, Jet Setter, jml, JNW, John H, johnnyappleseed55, jrb999, Kentuckycook, Keperkey, komatsu, Krieghoff07, KRIEGHOFFK80, labloverva, LawDog324, LG, LotsOfClays, maggs01, Majestic-12 [Bot], MarcL22, MAX & TOBY, maximushuntermus, MSN [Bot], oakisland, oinodam, Oldman1949, oneounceload, Pine Creek/Dave, railroad, Road Rat, ROGER_JOHNSON, Rooster booster, Roseinmt, rpenmanparker, Rudolph31, Ryan Vance, Scardog7, scshuey, shacked, shotgunmanny, SierraCJ5, smr51, southdakbearfan, Stuck-N-Kali, sv10001975, SWPAMike, Tal/IL, TerryS, Tex, The Happy Kaboomer, ThrowAway, Tokamecotom, TwoFourThree, viking, wboonn, Woodson, zxcvbnm


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
© 2017 Carbon Media Group Outdoors    - DMCA Notice