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STI Muzzle Flip


Spike84

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Have a situation that's bugging me. I recently got an STI edge in 9mm and put in 9 pound recoil spring with Dawson tool less guide rods and 15 lb mainspring. I watched a video of me shooting a match and I'm noticing way to much muzzle flip? The reason this is bugging me is because I use to have a Barsto .40 Sti edge and I would shoot major loads and get less muzzle flip with that gun. Wondering if there is something different in the design between the 2 guns or why I'm getting muzzle rise? Thought maybe I'm just not holding tight because I'm not expecting much kick since it's 9mm. Also thought maybe the grip safety was s little different but surely that can't make that much difference. I'm shooting 135 pf loads with 147 grain with ramshot competition soft loads . Any ideas possibly try to go all the way to 7 lb recoil and up to 10 lb recoil spring

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2 hours ago, Pirate said:

You may have too light of a spring allowing the slide to hit the frame harder than it should.  I'd try the 10 or even 11lb spring and see how it feels.

I'm thinking the same thing.  I'd get a 10 and 11 lb recoil spring and a 17 lb mainspring and test them out.  The weight of the mainspring will also affect how the slide cycles.  

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It can get complicated but the Recoil Spring weight, Mainspring weight and the angle of the Firing Pin Stop all have an effect on the cycling speed.  But it usually shows up as the muzzle staying too high or the muzzle dipping on follow up shots.  Have you changed your grip or stance?

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Take some slow motion video of you shooting the gun from a side view. This will tell you what is causing the bulk of the muzzle flip. Without seeing any video and from your description it sounds like you are simply not gripping the gun hard enough because the felt recoil is dramatically less than your Major PF setup. If you grip the gun with the same pressure as your Major PF gun then I bet the muzzle flip issue will vanish.

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Have not changed my stance I did shoot s glock for the past year so maybe not use to gripping the sti again. The recoil itself feels buttery smooth when shooting compared to my glock but video does show glock staying absolutely flat and the sti getting about 1-2 inches of muzzle flip on video. I just put 10# recoil spring in and will take some slow speed videos today 

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Your grip is jacked up. Look at the gap between your strong hand thumb/heel and the back side of the support hand. Your support hand is also below the safety giving you less leverage against the muzzle flip. With a proper "High" support hand grip there should not be a gap between the hands at the back of the gun and the strong hand thumb should be resting on the back side of the support hand thumb.

 

A common misconception is that your strong hand thumb should be resting on or pushing down on the thumb safety. With the proper support hand position it should be high enough that its actually covering the safety. If you can build a grip with your strong hand thumb resting on the safety then your support hand is too low on the side of the gun.

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Awesome thank you yes I notice a huge gap in that video so I went back and watched video of me shooting my old gun with major loads and there was no gap I think the large magwell is causing me to grip differently than my old gun thst has standard Sti magwell  or perhaps this is the way I picked up this grip style while shooting glocks either way I now know what to fix thank you 

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The muzzle dip/bounce after the shot when the slide snaps back foreword it caused by too heavy of a recoil spring. 

 

The bulk of the muzzle flip happens when the slide hits the frame at the end of the rearward movement. This is usually due to a high slide velocity. You can slow the slide velocity down by using a heavier hammer spring. 

 

I would suggest going down 1-2 lbs in recoil spring. Then up 2-4 lbs in hammer spring. See how it does in slow motion.

Edited by CHA-LEE
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  • 2 weeks later...

The thing to consider with spring tuning is the firing pin stop radius and hammer spring weight only affect the rearward movement of the slide where as the recoil spring affects how it moves rearward and how it returns forward. 

 

So I think Charlie's advice is sound. Try heavier hammer spring which will not add any dip during the slide returning forward but will help control movement rear. 

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  • 4 months later...

Great information!  I too am trying to dial in on the correct spring combinations for my 40 edge.  If I read all this correctly then the following is what I am looking for:

Muzzle rise can be tamed by the main spring

Sight dip can be tamed with the recoil spring

 

Is this the correct summary?

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  • 2 weeks later...

Hello: Try a 17lb ISMI mainspring and a 10lb ISMI recoil spring. The Edge has a heavy slide so going too light on the recoil spring may cause some feeding or ejection problems. You may also try a lighter bullet in the 121-125 range. Do some quick splits at 7 yards to see where it is hitting for you. You may have to actually go up in recoil spring weight to get the two shots to be on top of each other. Thanks, Eric

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