Mainspring in my open gun

[RickyH]

What mainspring are you using 19-17 ? Should I go lighter or not? What does a lighter spring do?

[Aircooled6racer]

Hello: I use a 17 LB ISMI mainspring and it goes bang everytime. I have tried a 15 Lb ISMI before and it did not always go bang. Not going bang is bad I also use a 9 LB ISMI recoil spring in one pistol and a 8 LB ISMI recoil spring now in the other 9mm open pistol. The firing pin stop I use is a Ed Brown with a large radius. It will also help to know what hammer you have since a super light one may need a 19 LB mainspring. Hope this helps. Thanks, Eric

[CocoBolo]

+1 on the 17, lights anything up, including CCI Rifle. Have not tried Wolf and don't intend to.

[ParaGunner]

What mainspring are you using 19-17 ? Should I go lighter or not? What does a lighter spring do?

I use a 18lb mainspring and never had a failure to fire. Going to a lighter mainspring will lighten your trigger pull but you run the chance of the hammer not hitting the firing pin hard enough to set off a round.

[G-ManBart]

I'm running 19lb ISMI mainsprings in Open, Limited and SS guns....all have pretty light triggers (2-2.5lbs) and will light anything off just fine. When I had Matt McLearn do a trigger job on my SS gun, he specified a 19lb spring and it worked out to be super crisp and light. R,

[JThompson]

19 in mine too. Trigger is just over 2lbs

JT

[RickyH]

I have a 19lbs in my open 9mm and someone told me the dot would track better if it was lighter. but I go with if it's not broke don't fix it.

[Chris iliff]

Had a 17 ismi and 2.5lbs trigger. Forced to use Wolf primers back in the "can't get primers" past. Anyways, the 17 would not light one or two out of every mag. Bought a 19 ismi and never looked back and it touches everything off. It did increase my trigger about 1/8 of a pound or so, if I remember. Not that big of a deal to me. Gun go bang everytime.

[benos]

Moved to the Springs forum for better exposure.

be

[Tzygä]

15lb mainspring ISMI I have Mclaren Extra Long M2i XL firing pin and Koening Low Mass Hammer 1911.

[Pat Miles]

15lb mainspring ISMI I have Mclaren Extra Long M2i XL firing pin and Koening Low Mass Hammer 1911.

+1 for me. No problems.

Pat

[Aristotle]

I'm running a 15lb ISMI with an XL FP and Brazo trigger kit. I run Magnum and rifle primers and they all go pop, I've not had one not pop.

A lighter mainspring has more affect on dot track and the way a gun will recoil than it does to your actual trigger pull weight, btw.

The lighter the mainspring, the less resistance a slide has when moving out of battery when it engages the hammer.

Edited September 17, 2010 by Aristotle

[ty34984]

have a 15 in now and the gun wont go bang...i went with the 15 to try and speed the slide up a bit by letting the hammer be lighter less pressure ...i assume i need a long firing pin and a lighter firing pin spring? or just go to the 17 and see what happens? i think there as a 19 before i changed anything? Ideas

[fastarget]

went to 17lb springs in both my 9 and 45 (not open guns), trigger was a bit better but started having some light primer strikes, I found that the extended Firing Pins are cheap insurance in a competition gun.

[G-ManBart]

have a 15 in now and the gun wont go bang...i went with the 15 to try and speed the slide up a bit by letting the hammer be lighter less pressure ...i assume i need a long firing pin and a lighter firing pin spring? or just go to the 17 and see what happens? i think there as a 19 before i changed anything? Ideas

Why do you want to increase the slide speed? Have you radiused the firing pin stop? That can make as much, or more, difference than a change in mainspring weight.

I don't want to offend anybody, but for folks thinking they're going to see a difference in how flat the gun is, or how the dot tracks by changing just the mainspring a couple of pounds....well, you're looking in the wrong place. Hey, I'm not the world's greatest, but when I shoot ammo over the chrono, I can't see a difference in the dot tracking between rounds that are 50-75fps different from one another, so I absolutely don't believe taking off a slight bit of reisistance (it's not a direct relationship because there's a pivot point (FPS) involved) is going to make a huge difference. I'm sure there's some minor difference, but I'd bet a paycheck nobody would be able to tell which is which in a blind test. You change something, you're expecting to see results, so you really pay attention and things seem to be different....kind of like how your car seems to run better after an oil change and a wash. At the very least, it's such a small change that you're far better off looking other places for performance gains. R,

[CocoBolo]

have a 15 in now and the gun wont go bang...i went with the 15 to try and speed the slide up a bit by letting the hammer be lighter less pressure ...i assume i need a long firing pin and a lighter firing pin spring? or just go to the 17 and see what happens? i think there as a 19 before i changed anything? Ideas

Why do you want to increase the slide speed? Have you radiused the firing pin stop? That can make as much, or more, difference than a change in mainspring weight.

I don't want to offend anybody, but for folks thinking they're going to see a difference in how flat the gun is, or how the dot tracks by changing just the mainspring a couple of pounds....well, you're looking in the wrong place. Hey, I'm not the world's greatest, but when I shoot ammo over the chrono, I can't see a difference in the dot tracking between rounds that are 50-75fps different from one another, so I absolutely don't believe taking off a slight bit of reisistance (it's not a direct relationship because there's a pivot point (FPS) involved) is going to make a huge difference. I'm sure there's some minor difference, but I'd bet a paycheck nobody would be able to tell which is which in a blind test. You change something, you're expecting to see results, so you really pay attention and things seem to be different....kind of like how your car seems to run better after an oil change and a wash. At the very least, it's such a small change that you're far better off looking other places for performance gains. R,

+1. All of my open guns have a radiused firing pin stop plate. This does not seem to affect the slide speed, it does however make ULSC and Make ready a touch easier. Unless you are out running the gun I sure don't see a need to speed it up. http://www.triangleshootingsports.com/images/Open_fire.wmv The comp slows the slide down, so it don't hit so hard, notice the flip is mostly at the end of the stroke in the video.

[2011BLDR]

# 17 wolf in 2 open and 5 limited guns.

out.

2011BLDR

[Mike21STI]

have a 15 in now and the gun wont go bang...i went with the 15 to try and speed the slide up a bit by letting the hammer be lighter less pressure ...i assume i need a long firing pin and a lighter firing pin spring? or just go to the 17 and see what happens? i think there as a 19 before i changed anything? Ideas

Why do you want to increase the slide speed? Have you radiused the firing pin stop? That can make as much, or more, difference than a change in mainspring weight.

I don't want to offend anybody, but for folks thinking they're going to see a difference in how flat the gun is, or how the dot tracks by changing just the mainspring a couple of pounds....well, you're looking in the wrong place. Hey, I'm not the world's greatest, but when I shoot ammo over the chrono, I can't see a difference in the dot tracking between rounds that are 50-75fps different from one another, so I absolutely don't believe taking off a slight bit of reisistance (it's not a direct relationship because there's a pivot point (FPS) involved) is going to make a huge difference. I'm sure there's some minor difference, but I'd bet a paycheck nobody would be able to tell which is which in a blind test. You change something, you're expecting to see results, so you really pay attention and things seem to be different....kind of like how your car seems to run better after an oil change and a wash. At the very least, it's such a small change that you're far better off looking other places for performance gains. R,

Bart, How would one go about radiusing the firing pin stop? is it difficult to do?

[jid2]

Well I decided to fiddle with this stuff on my gun, which is a Para P18.9 that I've openized. It was running the stock hammer, and firing pin with a 17 lb main spring. I wanted to try the 15 lb concept so I got a M2i XL firing pin and a 15lb ISMI spring. The difference in hammer cocking force between the 17 lb and 15 lb was really noticeable, the 15 lb felt like my airsoft gun. Watching the velocity of the hammer with the 15 lb I was wary of it working because it was moving slow enough that I could track it's movement - although barely.

So, I just got back from a lunch-time trip to the indoor range. First pull of the trigger............ ......... no bang. So the combo I have can't do it. Perhaps the heavy stock hammer and strut are not moving with enough velocity. I did a quick swap of springs back to the 17 lb and was back in the bang-business.

[anilson]

+1 for the 17 LBS

I run 17lbs in all three of my limited guns with 1.5-2.5 triggers and they all work well. I buy the Brazo springs.

Adam

[pjb45]

A McLearn extended firing pin is cheap insurance for any gun but especially when using a lighten mainspring and all kinds of primers.

Some old time trigger jockeys used a really light MS to achieve a lighter trigger but the downside was 'it did not go boom'.

I have the right combinatin of firing pin stop (EGW), pin (extended) and around a 17-18 MS. I have almost every primer that was available over the last three years. They all go BOOM when they are suppose to go boom.