shooting high after changing mainspring.

[dugk]

Hello, I just changed the mainspring to 23#, added new cap and plug on my springfield g.i. in order to disable the ILS. I now shoot 6 inches high at 25 yards shooting from sand bags on bench. Any ideas? Thanks!

[gottripletsNC]

Wow, I can't see how a Mainspring could effect a change in POI. But I've seen weirder. You didn't change anything else in the equation did you?

[John]

Operator error maybe? Hard to believe the main spring would affect point of impact, unless there is something really wrong with the pistol.

[Sniper350]

It would help if you provide as much info as possible when trying to trouble shoot a problem:

Like what did you change the Mainspring from # ??

[... removed statement about bullet being in barrel during recoil... ] 1911Tuner can help me out here with the correct info.

Sooo............... anything that changes the recoil characteristics of the pistol has the potential of changing the POI. Sounds like the pistol's barrel is recoiling upward at a faster rate than before, possibly causing the high hits to the target. A stronger mainspring might be causing more resistance to the hammer, which in turn can make the Slide and barrel flip upward more when they encounter the stiffer hammer.

Ah, I could be all wrong ...........like I said Johnny can better answer this mystery.

JF.

[Joni Lynn]

If the change is what caused the point of impact to climb then it would be due to grip. The stronger spring might cause the gun to move a bit more.

[lincoln county law]

I have seen this situation occur before. Six inches is a more dramatic shift than I have witnessed. The factory supplied mainspring must be quite a bit weaker than your new one.Time for 32 gr. bullets! Or, change the front sight, be on target, and not have the magic locking-key option.

[dugk]

I am going to change everything back and go to the range to see if the poi changes back. i dont think it was user error because my sistema was shooting fine with the same 230 gr fmj loads. will post back when i make it to the range.thanks!
eta. nothing else was changed, and old mainspring was factory ils. i cant imagine this would cause such a change either.

[John]

That's rather strange. In order for the bullet to hit that much higher, the barrel must be unlocking when the bullet is still in the barrel. That's very dangerous. The factory main spring is 28 lbs, so it is stronger not weaker. But the factory spring is stronger because it is also shorter due to the ILS things in the housing. So I suppose that overall the effect of the shorter and stouter spring should be the same with that of the longer but lighter one.

Did you by any chance changed the MSH to an arched one at the same time? Or you are using the same MSH?

[1911Tuner]

By invitation...

Let's look at all the possibilities.

First, it would take about .040 inch of upward movement of the muzzle to throw the shot 6 inches high at 25 yards. Switching from a flat mainspring housing changes the POI for me. Can't say what it does for anyone else.

Figure the sight radius...roughly 6 inches...to the distance in inches to the target...900 inches and divide the change by that number.

While unlocking the barrel while the bullet is still in transit is a possibility, I'll say that it's not possible without damage to the lugs and the link.

To move the POI 6 inches at 25 yards requires .040 inch of lift/tilt at the muzzle...which would mean that with the maximum vertical lug engagement of .050 inch...which is doubtful in a mass-produced gun...only a thin sliver of
steel is holding the barrel into lockup with the slide...and that's only if the #1 lug is the one that's engaged. If it's #2...which is entirely possible...it's even less, and if it's #3...it's hanging on by a thread.

This is assuming that the barrel can tilt while the lugs are engaged under pressure...which if it actually is...the vertical force pulling against a horizontally moving slide would very likely cause short-cycle and a telling effect on reliability.

But...Check the front lug corners for signs of damage anyway. Check the link for signs of stretching and the slidestop pin for accelerated wear which would be acute, and about the same width as the link.

Go to the new mainspring. Rated at 23 pounds, it's a bit lighter than the short, stout spring that comes with the ILS housing...which means that the slide is going to get started earlier, and cause the resistance of the recoil spring to come into play earlier...which causes a felt recoil against the frame...which rotates the gun in the hand due to the grip angle and the location of the bore axis relative to the hand position.

Entirely possible that the lighter spring is the cause, especially if the flat housing was switched in favor of an arched housing. Remember that it only takes a tiny bit more than a 32nd inch to move the POI 6 inches at 25 yards.

If you also switched to a heavier than standard recoil spring...it would magnify the effect. I'd try going to a firing pin stop with a small radius to delay the slide a bit more...and using a standard recoil spring if you did opt for a heavier one. Springfield's OEM recoil springs come in at about 14 pounds, so even using a spring with a 16-pound rating will have some effect.

You can also try gripping the gun a little more aggressively unless you already do that. .040 inch isn't a lot, and a little change in the grip can have a telling effect on the POI.

Light, fast bullets pring lower on the target than slow, heavy ones do at such distances.

Oh, where have all the ringers gone? :)

[Paratus]

Did these changes make any difference in the trigger pull???
Could be you are heeling the grip just a tad.

[Lubaloy]

'Oh, where have all the ringers gone?'

Oh.....still here. I'm going to let you figure this one out!
:D
Then.......I'll say "I knew that!"
:o

[1911Tuner]

I'm going to let you figure this one out!

Nah. I'd rather hoped that they could figger it out with the points made. If they don't...well...there's always more ringers.

[dugk]

This is a great forum and the information provided is incredible! I appreciate all the help!

I cannot make it to the range until early next week, but will be sure to post back. I did not change the housing, it is the factory ILS housing. Is 23# the recommended change for the mainspring housing spring? I just wanted to disable the ILS, and hopefully slightly lighten the trigger pull. If another weight is recommended, I will change it if my local smith has the spring. Thanks again!

[John]

The recommended spring ratings for a 5" barrel pistol are:

- 16 lbs for the recoil spring
- 23 lbs for the main spring

Please let us know if you have replaced the recoil spring with something heavier.

[dugk]

I left the recoil spring as the factory original. Should I replace this? Has about 1k rounds on it. thanks!

[John]

That should be OK.

[dugk]

Switched back to normal ils system. Works just fine now. I am going to leave it as is until I receive a new recoil spring in 16#, new mainspring in 23#, and new firing pin stop. I did not notice any unusual wear or damage on the barrel lugs or the barrel link. Is Brownells selling the firing pin stop with the proper radius now, or do I buy the square one and try to radius it myself? A part # would be appreciated if it is available in the proper radius. Thanks

[Frank]

As far as I know, it's only available square, and you'd need to radius it yourself. Brownell's has them. But you can also order directly from EGW (see their banner at the top of the page).

DVC