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STI Eagle 9mm - how to get slide to move faster?


lksyotas
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So from my previous few posts, I acquired a new STI Eagle 9mm last week to shoot ESP in IDPA. I finally had the opportunity to take it out and get some range time and here are a few observations...

The gun fits my hand like a glove and points very naturally. I come from the Glock world so the grip size is comfortable but the trigger is miles ahead of my best trigger I've had in any of my Glocks. In its stock form, I found that the gun was shooting point of aim at 10 yds and didn't need any adjustment for my style shooting. I haven't shot for accuracy yet and have only taken aim at a plate rack from 10-35 yds. My fastest time on the rack was 2 seconds faster than my best with my Glock 34 that's logged 17,000 rounds so that's a huge plus in my book - can only get better from here!

Another observation is the slide to frame fit is great! Nice solid lock up and no free play yet butter smooth when operating. However the slide seems to move rather slow when firing. Its the first gun I've been able to track the front sight throughout the entire recoil phase. It seems to shoot very flat but a tad slow to cycle.

After my first outing with the gun to check for reliability out of the box, I tore it down completely to take a look at the workings. I did a trigger job on it (stock trigger was setup with a nicely set pre-travel, over-travel, and reset but the creep was gritty and distinct), following the trigger massaging, I installed a 9 lb recoil spring, 17 lb mainspring, and STI magwell.

Second time at the range yielded a slightly better performance on the plate racks, this time I didn't notice the slide as slow as previous but it was still distinctly slower than my Glock 34 that I'm used to. The trigger felt crisper and the magwell that I milled the sides down on to fit the IDPA box didn't effect my weak hand grip like I had wondered if it would. For reference, the loads I have shot so far are carry over from my Glock shooting. 147g CMJ, 130-132 PF loaded with Titegroup.

With all this said, what are your recommendations to get a bit faster slide movement while maintaining the flat shooting that the gun exhibits? Thanks for any advice!

Pic of all the parts prior to the work done above:

IMG_2822_zps322b7b41.jpg

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Heavier recoil spring.

Interesting thought and I understand what you mean, so here is the real question I guess...If a heavier recoil spring aids in the slide returning to battery faster, wouldn't it reduce the velocity that the slide travels rearward in the beginning of the recoil phase? Now on the other hand, a lighter recoil spring would allow the inertia of the slide to travel back faster due to the fired round in theory would also again due to the inertia of the slide, make it travel back into battery slower due to the friction of chambering another round. Which part of the recoil phase is it that I'm discerning I wonder, the "flight rearward, or the return home"?

I could be all backwards on this but that is what makes sense in my finite head. So all the experts out there, whats the correct thinking on this?...

Edited by lksyotas
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I think phsyics says that the compression of the spring and the returning of the slide into battery should be equal... Something about equal and opposite reaction. Could be wrong but that's my thinking. If however you lighten the slide that will get you a faster cycling gun compared to using the same recoil spring since there is less mass reciprocating. Not sure if you reload but you might try a lighter bullet and a hotter load.

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The heavier spring may help, but you'll probably pay for it with excessive muzzle dip in return. Lightening the slide would be a no-go. As stated, this is an IDPA build. The lighter bullet with a hotter charge might be the trade off your looking for.

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Lighter bullet, fast powder, more velocity... Have you timed your splits? When I switched to 9mm 147s I felt like the slide was really sluggish. Tried it on the timer, and found I couldn't outrun the gun. My best splits were around .18 and the slide was in battery every time! Might seem slow, but it's probably not really!

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I've got some 115 FMJs laying around. I'll cook them up to a nominal load and try that. I agree that I could encounter nose diving if I go heavier on the recoil spring. I really like how flat the guns shoots now and I dont want to jeapordize that. Anyone know of a good powder that's hotter than titegroup? That's the only pistol powder I'm using currently. I think I also have some MG 124 bullets laying around too. They would probably be a better trade off between the two mentioned all ready. Thanks everyone for your comments.

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Lighter bullet, fast powder, more velocity... Have you timed your splits? When I switched to 9mm 147s I felt like the slide was really sluggish. Tried it on the timer, and found I couldn't outrun the gun. My best splits were around .18 and the slide was in battery every time! Might seem slow, but it's probably not really!

Great point! I did run my timer while shooting the rack. I'll look through the data from the last run and see what my splits were. I def didn't feel like I was waiting for the gun but just as you pointed out, slide felt very sluggish.

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Lighter bullet will definitely help.

Another thing you can look at is the contact point of the hammer and firing pin stop when the pistol unlocks. Some smiths put a bevel on the bottom ~1/3rd of the stop to move the contact point up (closer to the firing pin hole). This allows the pistol to unlock with less energy. Hope I've made sense.

Edited by al503
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Lighter bullet will definitely help.

Another thing you can look at is the contact point of the hammer and firing pin stop when the pistol unlocks. Some smiths put a bevel on the bottom ~1/3rd of the stop to move the contact point up (closer to the firing pin hole). This allows the pistol to unlock with less energy. Hope I've made sense.

Yep, perfect sense. I'll look at this when I get a chance. Thanks!

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Bob @ Brazos wrote an article for the July 2009 issue of Front Sight about shooting steel and changes to your gun to increase slide velocity and light loads.

Go to:

http://www.brazoscustom.com/Home.htm

Under the left side there is a link for Magazine Articles. Click on it.

Go to 2009 - So you Want to Shoot Steel. Good read.

Edited by warpspeed
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Bob @ Brazos wrote an article for the July 2009 issue of Front Sight about shooting steel and changes to your gun to increase slide velocity and light loads.

Go to:

http://www.brazoscustom.com/Home.htm

Under the left side there is a link for Magazine Articles. Click on it.

Go to 2009 - So you Want to Shoot Steel. Good read.

Awesome article, thanks for the link! I've read most of those articles but somehow misse that one.

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When I was shooting for Springco (not legal in IDPA) I had a lot of good results working with commander length springs in full size guns. I would typically start with the factory rate spring weight for a given caliber and then start to work down. You really need to find a balance of spring that doesn't provide to much resistance as the slide wants to come out of battery (transmits to felt recoil) and you don't want a great deal of captured energy as the slide goes all the way back into battery (excessive muzzle dip as previously noted). Everyone feels and perceives recoil differently, so in my experience there is not a mathmatical formula for the solution, little bit of trail and error creates a good starting point. The commander length spring is still under pressure in a full size gun and offered a much better solution than when I was trimming coils off to get the desired result, and they are as cheap as any other spring.

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What main spring are you running? This probably doesn't effect it as much but it would speed up the opening without an effect on the closing. If the factory is 19# going to a 17# would help and a lot of people use 17# springs.

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I like to shoot heavier bullets in my Trojan 147 plated and 160 lead. Trick for me is a 10lb recoil spring and a 15lb main spring did quite a bit of testing and for my set up it was the quickest splits. I would suggest you look at the 1911 store and purchase a 9lb, 10lb and a 12lb recoil spring along with a 17lb and 15lb mainspring. Spend a little time at the range testing with a friend which spring set up works best for your grip and the load your shooting. The resistance on the main spring also effects slide speed. 15lb mainspring has been in my pistol for three years and no misfires with Wichester small pistol primers.

Place three targets for the test, shoot all three two each record the splits and how close the hits are to each other. Your looking at how close the hits are not where you hit the target. Quickest splits with closest hits are the springs you want to leave in the gun.

This will take a little time and a shooting friend operating the timer and taking notes will speed up the process.

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Wow, lots of great feedback guys. I am very appreciative. I have 8, 9, 10, and stock recoil springs and replaced the mainspring with a 17lb one. I'll report back with range findings next time I get out to shoot. If these combos don't yeild a good result, I'll switch to 124s and see how I fair. It's hard finding bullets right now so I might be stuck eating up the 147s I have left to load. Hopefully the shortages don't last much longer.

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