What Recoil Spring for slide mounted red dot on Mil Spec?

First topic message reminder :

A number of years ago I had a gunsmith put a rail on top of my 1911 Mil Spec so I could mount a red dot.   He told me I might have to cut a few coils off the factory spring.  

I have never gotten to feed reliably.  At FTF jam or two every 100 rounds. Usually the last round in the mag.  I am now down to using a 9lb spring and I put in a buffer.  

It happens with pretty much any load/bullet, but I am currently using 4.8gr 700x and a 185 or 200gr bullet. 




I do see an 8lb spring on Midway and also a variable power recoil spring.

I did a search and found nothing.

Any advice would be appreciated.

I wish I was at a skill level where that would make a difference  

I have been using the plated flat points lately. However, I have also used LSWC from Extreme and Hi tec coated LSWC from MBC.  Per your advice, if I start competing, I will be using them instead of plated.

Thanks for the reply.

I'm thinking that 5.5gr of 700X is a bit much for 185gr lead bullets even if the are copper plated. My loads are a bit hot for others but I find I don't have any sight changer from 25 to 50yards. I do recommend getting those higher weight recoild springs and testing for lock-back to determine what spring is needed.

I generally load at 4.8gr.  I just tried the higher load to see if it would work better.   Others seemed to think the mainspring was the issue and 18lb and 19lb I ordered arrived today.  I have a variety of recoil springs to try it will.

Thanks for the reply

SingleActionAndrew wrote:

Bluesguy wrote: I would be interested to know what loads you use of 185gr and 200gr plated bullets and LSWC.

I believe most around here would advise not to bother with plated bullets for consistency/accuracy

I've read that several times on this forum but I scored a guy who shot with plated SWC bullets that made me rethink it.  This was his timed fire target:

Okay, I just put in a 19lb Wilson combat mainspring and a 12lb Wolff recoil spring.  I will try it out next week.

Ran into an issue dry firing.   I noticed that the hammer required an extra effort to get it into the fully cocked position.  I checked the trigger pull and it went from about a less than 5 lb pull to almost 8lb pull.  I thought a lighter mainspring was supposed to reduce the trigger pull.

Is this normal?  It was really easy to change the mainspring so I am not sure what I could have done wrong.  Any suggestions would be greatly appreciated.

Thanks again.

Changing 2 items shouldn't be done. One at a time! The main spring should be large enough to ignite the primer why use anything more? Yes it does effect opening of the slide but has little to do with closing it and closing is where you have the problem! Plus increasing main spring weight will increase trigger pull weight. In addition the problem may have been the recoil spring was too light and it caused excessive wear on the link and slide stop pin! That wear will cause timing problems! You haven't provided a good photo of the lower lug and link,  should also check the slide stop pin! However increasing just the recoil spring weight is a start.
 I was writing this at the same time you were replying. The fact you put in a known 19pound main spring increased the trigger pull because it was heavier than the one that it replaced! What happened with lock-back? Did the slide lock back? Simply put you increased recoil spring and main spring, that increased the opening pressure, if it did lock back then additional recoil spring weight is required. In addition if you keep the 19lb in the gun you will have to bend the flat sear spring or need a trigger job!
 That all 10's target is the result of skill! Almost any bullet will do that at 25yards! I have shot 100-10X with plain lead bullets! I've also fired 100 with ball ammo that was supplied back when ammo was supplied for the distinguished matches, any other ammo other than what was issued would get you disqualified! Most 1911 will also shoot well at 25 yards! 50yards is what makes the difference!

Thank you for your reply.  There are a lot of issues addressed in your post.  I will try to address them in a concise manner:

1 - I changed those two things based on advice from an earlier post toward the beginning of this discussion.  As an engineer, I debated changing more than one variable at the time but decided to follow that suggestion.

2- Multiple earlier posts suggested the mainspring was more likely the issues than the recoil spring. Unfortunately, this form does not provide post numbers.

3 - The main spring I replaced was the original part, which is supposed to be 23lb. As I said, I replaced it with a lighter spring.  19lbs.  So it seems odd the trigger pull is heavier. I also ordered another 18lb spring and still have the original spring.  I could swap them back and forth, but wanted to get some more feedback before I went through that exercise. As per above, the original recoil spring was 16 lbs.  I have been as low as 9lbs.

4 - I will post a picture of the lug. I am skeptical that is the issue because the problem occurred right after I started using the red dot.  According to my records, the gun had less than a thousand rounds through it at that time.

5- I am not sure exactly what you mean by lock back other than I can say the slide locks back after the last round of every magazine and by hand with any recoil spring that I have tried.  I just changed the mainspring today and have only dry fired the gun.

FYI:  All the loads I use shoot well through my stock Trophy Match.  I am not sure I have ever had a jam with that gun.

6 - As far as the plated bullets go...  Accuracy is not an issue for me to worry about now.  When I shoot 70+ on slow fire I am happy.  An 80+ calls for a bottle of scotch.  But I am surprised you seem to imply lead bullets are not as accurate.  I was led to believe, and been told in person by a Hi Master, that LSWC were the most accurate.  Indeed, when I was looking at Les Baer's their bullseye model is designed specifically for SWC.

I appreciate all the time you have taken to try and help.  And will take apart the gun post a picture of the lug, slide stop, barrel and link in the next day or so.

Lock-Back I speak of is when the slide is locked back after last round is fired. Yes it will lock-back by hand if magazine and lock-back lever are working as they should but means nothing when shooting! Firing a round is a good way to determine recoil spring weight. Too much weight will prevent the slide from traveling enough, too little weight allows the slide to hammer back also may prevent proper closing. Vertical stringing or failure to close completely can result. Remember accuracy is with the slide closed to the same position every time so you want as much spring that will allow the slide to return so as to load another round but not too little to cause the gun to hammer itself into problems. So I increase recoil spring weight until slide will not lock-back after firing one round that was loaded in the magazine then use the spring weight just below the weight of the failed spring that did work. The fact rounds work great in one gun don't mean they will work great in another! Simply because the two guns are never exactly the same! Correction might be as simple as changing recoil spring weight. As to main spring, your problem had to do with closing, main spring has little to do with that! Yes increasing main spring will lower the required weight of the recoil spring but the lower recoil spring weight will effect closing that main spring has little to do with!
 Lower lug shape I use has been posted many times. Simply put the leading edge angle of engagement with slide stop pin will increase pressure on the upper side of the barrel as angle is lessened. The friction increase now puts more forward pressure on the engagement increasing upward pressure and can eventually stop the slide. This is noticed by a bump when the slide is allowed to close slowly by hand while loading a round. In some cases it will stop the slide when allowed to close slowly by hand, that's not good because as the gun is shot the increased pressure on the lower lug and slide stop pin will cause increased wear resulting in lowering the angle! Link effectual length will delay the opening of the slide as it increases.
 A music band will sound great if everyone plays the notes at the correct time if not they will make nothing more than noise! The 1911 is the same each item needs to preform at the time it's required so as to provide trouble free accurate shooting! Being able to do that is what makes some gunsmiths great while others are not!

Photo looks like reloading press not 1911 barrel lower lug.

Here are some pictures. Had to figure out how to upload them on this forum.  Not intuitive, but maybe there is an easier way.

I understand dynamics and kinematics and how parts in a system interact.  However, that does not explain why I replaced a 23lb mainspring with a 19lb mainspring and got a heavier trigger pull unless the recoil spring can impact trigger pull.  But the recoil spring has only a static function in the system until the round if fired, which is after the trigger is pulled and the hammer has fallen.

I guess it is possible the spring I received was not labeled properly.  I also have an 18lb spring I could swap out, and then compare that.

At any rate, here are the pictures you asked for.  Let me know if you see something there.

And thanks again for your time and efforts.

I see you saw that reloading press photo.  I was trying to figure out the process for uploading a photo and using it as a test.  I thought I deleted it, but I guess not.  I will do so now.

Now the delete buttons has vanished on that post.  I give up.

Oh, and as far as lock-back goes... I have never had an issue and as I said I started with the 16lb factory recoil spring and worked my way down to 9lb.  Never had an issue locking back after the last round.

Bluesguy wrote:
I understand dynamics and kinematics and how parts in a system interact.  However, that does not explain why I replaced a 23lb mainspring with a 19lb mainspring and got a heavier trigger pull 

That can happen if the hammer strut is not properly seated on the main spring housing.

But after all, it really has nothing to do with a feeding issue If your slide is locking back.

Post an image of what the FTF looks like.

That makes sense and based on the way the gun cocks it does feel like it's catching on something like the edge of the cap.  However, when I slid out the housing just now the sear spring popped out of position, and I am going to have to take the whole gun apart. I want to do that when I am fresh, so not tonight.  I will keep you posted.

Thanks again.

Looking at the frame I see the lower lug is hitting quite low, it should only hit on the top. Possibly due to hammering because of light recoil spring! You run the risk of shearing off the lower lug!
 I see only rub marks on the very top of the slide stop pin, your probably using the link to lift the barrel, link will increase upward pressure quite a bit. In bullseye gun you don't want link lifting the barrel, is should only be used to pull the barrel down from the above locking lugs!
 You inserted a known 19lb spring from Wolff and removed what you think is a 23lb main spring. If you have a known 18lb spring from Wolff or other known vendor try it! I doubt it will change anything and that the 23lb spring is not 23lbs! In addition I do not know why you would want to increase recoil spring and decrease main spring. I would put the supposedly 23lb main spring back in! You want to test lock back to determine ideal recoil spring weight!
 Radius on the lower lug is quite a bit and why you are probably lifting the barrel with the link! Allowing the slide to close slow by hand with a round in the magazine I'll bet there is a bump, possibly if you allow the slide to close slowly by hand it will stop. (for safety use a dummy round you reloaded with no powder or primer)
 Here is a photo Jon posted a while ago, my lower lug is done the same way! It was fixed by welding, the old shape can still be seen tough some was covered by the weld. Notice there is very little radius.

Froneck,

To be honest, this is starting get a little over my head.  I don't have near the knowledge regarding a 1911 that you do.  So let me ask a question or two:

1.  It sounds like you may be recommending custom work on the barrel lug, correct?  I do see the lack of radius at the shoulder where the angled art of the lug meets the top that is parrallel with the barrel.

2.  When you say you don't want the link lifting the barrel in a bullseye gun.  Is it normal for the link to lift the barrel in a factory 1911?  Is this again a custom job for a gun smith?

3.  Why would a bullseye gun want to have a different action than any other 1911?

I am going to take the gun apart, at least enough to reset the sear spring, and then see how it behaves.

Thanks again for the help.

A bullseye gun is for target and uses different loads than the original 1911 that was designed for 230gr ball ammo. And the link did not lift the barrel the slide stop pin did. Military barrels have dimensions that allow that to happen.
 The barrel in the photo is not as easy to do as it looks. Everything done to a Bullseye gun has to work together, so when putting in a better barrel, tighter bushing, better slide to frame fits and so on it requires they work together similar to the band example.
 One thing you need to understand if you intend to shoot Bullseye now called Precision you need an accurate gun! The ability to shoot a good score depends on the shooters skill. If you don't have an accurate gun you can't learn to shoot! If you shoot and get an 8 you have to understand why, if you actually shoot an X but the gun puts the bullet in the 8 ring, you have no idea what you did wrong when actually you did everything right! When you do shoot an X and the gun is accurate and the bullet it put in the X ring you will have what is known as an Ah Ha moment, simply Ah Ha that how it's done! Then as you compile Ah Ha moments you score will increase! You need a gun that will shoot accurately so you can do what is needed to correct shooting errors!
 So a bullseye gun has a well fit bushing, the barrel hood fits the slot well and slide stop pin pushes the barrel up into the locking lugs tight, target ammo and so on so as to gain accuracy where as a military pistol is loose to insure function when in a combat situation, the needed accuracy is to hit a man size target at close range!

I certainly understand the need for tight tolerances in any component that ensures a consistent lock-up. My brother has a Les Baer with something like a 2 in group guarantee.  It's so tight that it is a pain to field strip. I also understand the development of the 1911, and have even read a biography of John Browning.  But first I want to focus on getting the thing to feed consistently.

I am still confused about the link issue.

Are you saying the link lifting the barrel is normal in a "stock" 1911, and that a bullseye 1911 needs to have the lug modified so that does not happen? 

If that's what I need to do to get the gun to feed consistently, that basically means I need to find a bullseye gunsmith. I don't have the skills to make that sort of modification.  Pulling things apart and putting them back together are one thing.  Fabricating parts is something else.

No the link is not used to lift the barrel into lock-up. Link is intended to pull it down from lock-up. If by doing the math of GI parts dimensions the slide stop pin will hit the lower lug before the link can force it upward. If your familiar with Trigonometry it's easy to determine the upward force by the slide stop pin or the link creates if used. The amount of force the round exerts on the barrel when entering the chamber is amplified by the slide stop pin or the link if it's used to push up the barrel so as to lock-up the lugs. Smaller the angle the greater the upward force. That begins to cascade larger and larger because the friction created by the top of the chamber area of the barrel adds more force. It can eventually stop the slide from closing! That force issue is noticed by the bump I mentioned. The bump or increasing closing force ends when the rounds is released by the magazine lips so it feels like a bump! However if the  force created is greater than the force created by the recoil spring it will stop the slide, if it is close the inertia created by the movement of the slide will over come the bump but it slows the slide. Also the radius of the bullet used in ball enters the chamber with less force therefore upward force is lower. By using the lower lug design I posted upward force is low due to increased angle of engagement with the slide stop pin. My guns have no bump and close very smooth! There is NO noticeable bump! A gun I built for my son Adam would shoot the entire season of matches with out an alibi and when tested by the AMU armorer it shot 50X at 50yards. In addition the flat area on the bottom of the lower lug has no angle on GI issued 1911 barrels but on bullseye 1° angel is usually used. (I use 1°)

Again, a lot to digest here.  But yes, with a degree in Mechanical Engineering I am familiar with trigonometry.  For the record, we actually dealing with what's known as kinematics (the study of motion without considering forces) and dynamics (the study of motion considering forces) which is an upper division engineering course.  So good for you if you can analyze the forces!  But back to the main point.

I reinstalled the original spring and everything feels better, like it did before.  So, either I did not install the 19 lb spring correctly, or the original spring was not factory spec at 23lbs, or the 19 lbs. mainspring was mislabeled.  

I once was replacing the transfer bar safety in my Ruger Vaquero.  I couldn't get to work.  I took it to a gunsmith and he had the same trouble until he noticed they sent me the wrong part.  It looked exactly right, but was for another Ruger gun.

I am still a bit confused about what you are recommending.  Virtually every other poster indicated I should change the main spring for a lighter one.  Are you telling me that is not needed?  Is the only way I can get the gun to feed reliably to modify the lug on the barrel?

Primary function of the main spring is to provide enough speed to the hammer so as to ignite the primer! Yes the shape of the hammer and firing pin stop will add to the effective weight of the recoil spring at opening. But it will add little to the strength of the recoil spring to close the slide! Since as the slide closes the spring pressure is lowered, it is important to have as much pressure as possible. 
 I have never had a mislabeled spring from Wolff but I guess it's possible, installing the 18lb spring should confirm which spring is wrong. Keep in mind the most important location of the slide is completely closed so as much pressure to insure complete closure is important!
 To determine the spring weight that required to cycle the slide yet not allow the slide and barrel to hammer themselves into problems using the greatest amount of weighted recoil spring that will allow the slide to lock back, lower spring pressure will only allow hammering and poor closing!
 At this time you should concern yourself with what spring weight will allow lock back that is about a pound lower than the spring that will not allow lock back! The marks on the frame where the lower lugs makes contact show excessive impact, you will have to have the frame machined or some of the lower part of the lower lug removed. Check the web for 1911 Bow Tie. There is some topics about the "Bow Tie" here in this forum.
 Did you check lock back? Remember it can only be checked by firing the last round in the magazine so only 1 pound needs to be loaded. Hand operation will not indicate anything other than lock back functions. You will also have to check the recoil spring weight needed with each different load used.

It was a Wilson Combat 19lb spring.  I have not tried the Wolff 18lb I bought. My question is:  Should I be changing the main spring at all?   I am still not clear on that.

But I am clear that I should go back to 16 lb factory recoil spring and work my way back down.  I don't remember if that failed to lock back, but it's been long enough that I wouldn't trust my memory.  

BTW: When I put the factory spring back in my trigger pull went back to 5 lbs.  So maybe the factory spring was not 23lbs.