Adjustable trigger weight when using a .22 conversion on your .45 1911

Hello, Just wanted to share a few pictures and a brief description of how I adjust the trigger pull on my Springfield RO when switching between the .45 and Nelson conversion.
 This is my first year of shooting 2700. I have quickly become addicted to the game! I started out shooting a Ruger MKIII, and a Les Baer Premier II 1.5" gun. The Ruger was an outstanding pistol, but I was never able to shoot it well. After just a few matches, my centerfire and .45 scores were catching up and beating my rimfire scores. I recently decided to re-do my complete setup. I knew I wanted to go with a red dot, and found a great deal locally on a gently used Range Officer, sold the Baer and the ruger and never looked back. The R.O. got a Kart bushing and EGW slide stop along with a new sear cut using the true radius sear jig. Its now shooting 1.5" at 50 yards with my reloads from a rest, and has an outstanding roll trigger.

 I know the most common thing to do is build a dedicated receiver for the Nelson/ Marvel conversions, and this was where I was headed when I remembered a picture I saw in a 1911 forum. The picture was of a 1911 mainspring housing with a hole drilled and tapped for a setscrew to fine tune the trigger pull. That picture was, I believe, posted by Jerry Keefer. Being in love with my new roll trigger ( and lefty NM grips) I started wondering if this would work in a Bullseye application. For all I know, there are a bunch of people out there already doing this, but I haven't seen it in my limited Bullseye shooting.

 So, here is what I did. I grabbed an old mainspring housing from the spare parts bin and took some measurements, I found that if I was really careful I could squeeze a 4-40 screw on the left side of the housing (directly across from the spring retaining pin). If you have a tap for a #3 screw, you would have a little more room to work with. Then I figured if I use a screw with a head as opposed to a set screw I could cut the screw so that when fully seated it gave me just over 3.5 lbs. what I wound up with this particular sear spring  was the screw extending .030" beyond the housing exerting additional force on just the sear leg of the spring added 1 lb to the trigger pull! I set the pull to 3 pounds 10 ounces with the screw fully seated, with it removed, the trigger is just over 2.5 lbs. Perfect!! I know I could technically come down another .5 lbs but its close enough for me.

 Ive tested this setup pretty extensively, shot a match with it, and hundreds of practice rounds of both .22 and .45, always checking to see if there is any change, none so far. Its worked perfectly.

 I welcome any and all input from my fellow shooters and from any professional smiths out there, especially if you can see any potential problems with what Ive done. Being able to shoot almost the exact same gun for the full 2700 has made a big improvement in my scores and I shot a personal best of 2299 at my last match!
 
 Thanks for looking, and hopefully this helps someone out there, or maybe someone can fine tune this even further. And again, thanks to Jerry Keefer for posting this idea in another forum.

 Here are the pictures:



Here is the threaded hole with the screw removed for the .22 Nelson conversion



I store the screw in a tapped hole in the grip to keep it safe and sound while shooting the 22




and with the screw fully seated, the slotted screw aligns with the serrations on the MSH.

Hello Mark;
Welcome to a great sport..
That's wonderful.. I am glad it's working out for you, and that I was of some help..
That is an old old old...trick, that might be even older than me..and that's getting up there... I was not the first smith to do that... I don't know who it may have been..
I am hearing good things about the Nelsons...
Jerry

Jimmy Clark used to install an adjustable sear screw on the mainspring at the same location on his wad guns.

Thanks guys. I am glad to hear it is a well proven concept. It has been an excellent way for me to eliminate as many variables as possible and just focus on fundamentals. ( I need all the help I can get!).

Thanks Mark, I made this your post a sticky so it stays at the top so anyone can easily find it!

Pretty cleaver idea.  I thought the purpose of using a 1911 conversion was to make your rimfire pistol the same as your .45 and CF gun.  While it is a cleaver adjustable leaf trigger spring, I set all my trigger the same.  ball gun, .22 and .45 all with 4lb roll.

One of the main reasons this adaption came to be, is the off occassion, when a trigger fails weight inspection on the line.. It's quite easy to tweek a few more ounces immediately, to prevent a DQ.. Not all weights, and or weighing techniques are created equal..

Jerry Keefer wrote:One of the main reasons this adaption came to be, is the off occassion, when a trigger fails weight inspection on the line.. It's quite easy to tweek a few more ounces immediately, to prevent a DQ.. Not all weights, and or weighing techniques are created equal..

Heh, the cynic in me would assume the reverse.

I dreamed up this same device last November when my 1911 hardball gun just barely passed trigger weight. Thought it would be handy if that ever happened in the future, I could just give the set screw a tweak and add a quarter pound to the pull. I thought I was being innovative and original. Nice job though.

One problem you will encounter.. It is not permitted on ball guns.

I bought one from Austin Behlert the NJ pistolsmith on commercial row in 1973.  His method was to obtain a 4-40 set screw and the allen wrench for same.  Drill a hole through from the inside clear through the diameter of the allen wrench.  Then from the inside drill, but leave 1/16 of metal in the hole bottom, the proper diameter hole for the 5-40 set screw and tap it from the inside with a plug tap to the bottom of the hole but not through. Put the allen wrench in from the outside into the set screw and unscrew it until it bottoms on the 1/16 of metal you left. Cut the set screw flush with the inside of the housing.  Then remove it and round the edge and polish it where it will contact the sear spring.  Reinsert, back out with the allen wrench to flush and install the mainspring housing.  Turn the screw in from the outside with the allen wrench to adjust pressure on the spring/sear.  This way the screw is captured and cannot be lost and it appears much like the hole for the mainspring cap pin on the other side.  If pull shifts, may need to disrupt the threads slightly or blue locktite.  I think this method may have been picked up later by Nonte in his book Pistolsmithing or in a Gunsmith Kink from Bob Brownell.  Worked well with my Kart on a Colt receiver and could set and keep a good 2-2 1/4 lb trigger but didn't change it.  Used one on my wad gun to keep the 3.5 dialed in so I can't say I was cranking them in and out for big changes.  Regards, John

My 70s Era Clark long slide also had this mod.  Clark just drilled through the housing  then slightly peened over the outside portion to retain the screw.

Funny how things are lost over time.

I am surprised that in competition that they wouldn't make you tape over the screw after the trigger pull was checked.  I shot paintball for a while and your marker (paintball gun) had to be chrono'ed before shooting anyone.  There is a pressure adjust screw and they taped it after your gun was confirmed to be below max allowed.  Some shooters would readjust their markers during a match but most of the officials on the range could hear the difference and DQ the person and ask them to leave and and never come back if it was the second offence.  Someone could easy readjust their trigger pull screw during a match.  I know none of us would and all BE shooters I have met have been good people but there is always a chance.  Don

Magload wrote:I am surprised that in competition that they wouldn't make you tape over the screw after the trigger pull was checked.  I shot paintball for a while and your marker (paintball gun) had to be chrono'ed before shooting anyone.  There is a pressure adjust screw and they taped it after your gun was confirmed to be below max allowed.  Some shooters would readjust their markers during a match but most of the officials on the range could hear the difference and DQ the person and ask them to leave and and never come back if it was the second offence.  Someone could easy readjust their trigger pull screw during a match.  I know none of us would and all BE shooters I have met have been good people but there is always a chance.  Don

If you fire a new national record your trigger must be weighed on the spot. The only time i've had triggers weighted at an NRA event was during random firing line selection at Perry. Haven't read the CMP rules closely enough... not sure if its a requirement to have triggers weighted before the match or  you can show up on the line.  You could also be randomly selected for trigger weighing. I've seen the CMP line check a few triggers that had the trigger weight pass tape on the gun.

I believe CMP required all guns to be tagged as meeting specs.

SERVICE PISTOL TRIGGER WEIGHING AND PISTOL INSPECTION

The triggers of all Service Pistols used in the EIC, President’s, NTI and NTT Matches must be weighed and certified at an Armorer’s Trailer (Commercial Row Vendors are not authorized to weigh and inspect pistols). When pistol triggers are weighed, the pistol will also be checked for compliance with CMP Service Pistol Rules (Rules 6.2.1 and 6.4.3 in the CMP Competition Rules for Service Rifle and Service Pistol).

One year at Camp Perry during the leg match 3 minute prep the tower had everyone on the line step back and several refs randomly weighed triggers.

I love this thread and the mod works good. I had a friend Karl Benning KGB Customs do on for me for a Marvel I built. 

He is not a BE Smith but he is very competent. Once you are done with your trigger job and its safe at #1.75 bump up the spring to #2.25. I never had any problems with backing out. It might wear out the sear spring faster but You don not need to readjust the spring once it is done.

Markj,thanks for sharing this concept !

Makes alot of sense.

Reminds me of the strain screw notion on S&W revolvers (also can be manipulated to adjust trigger weight).