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What weight mainspring for winchester primers on sti


Craig1981

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7 minutes ago, Craig1981 said:

Just curious what weight mainspring you guys are using to get 100% reliability with winchester primers. I was using a 17lb but was getting light strikes a lot.

Lots of folks run 17's. Check your primer seating first.

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Craig1981, what kind of gun are you using?  

When the slide is off, is there firm hammer pressure against the frame when the hammer is in the forward position or does it "flop" back and forth?  (i.e., is there pressure from the mainspring against the hammer strut, even when the hammer is forward against the frame?)

Does it pass the "pencil test" - put a pencil in the (empty!) barrel, point vertically, pull trigger, pencil should launch enthusiastically and clear the muzzle by about a foot.

Does it have a standard or lightened FP spring?

 

Edited by teros135
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39 minutes ago, Craig1981 said:

I have the extended dawson firing pin the 17lb was giving me lots of light strikes.  On my press I can't adjust primer depth. Don't think it's a primer seating issue because the winchester spp works great for my other guns.

One of my 2011s had that similar problem. What I did was replace the extended fp with a std one. The misfires went from about 10/100 tp 1/300. But I need to make it ultra reliable so I got a19# ms and cut 1-1/2 coils to simulate the 17# and the problem completely went away. 

What teros posted above is good and I went thru them. 

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4 hours ago, teros135 said:

Craig1981, what kind of gun are you using?  

When the slide is off, is there firm hammer pressure against the frame when the hammer is in the forward position or does it "flop" back and forth?  (i.e., is there pressure from the mainspring against the hammer strut, even when the hammer is forward against the frame?)

Does it pass the "pencil test" - put a pencil in the (empty!) barrel, point vertically, pull trigger, pencil should launch enthusiastically and clear the muzzle by about a foot.

Does it have a standard or lightened FP spring?

 

Thanks for the advise. Have 2 of them that don't set off winchester reliably. One is an sti matchmaster. The other is a custom built 2011. Matchmaster doesn't have extended firing pin. Didn't set off winchester with factory Springs. Got the trigger job and still doesnt. Tried the pencil thing. Launches them further than a foot and hammers are tight with slide off with hammer forward.

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I have the extended dawson firing pin the 17lb was giving me lots of light strikes.  On my press I can't adjust primer depth. Don't think it's a primer seating issue because the winchester spp works great for my other guns.



What firing pin spring are you using? That may be your issue.
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I have 2 STI 2011s, both 38super. I load Winchester SRP exclusively in this caliber. The old one I've had for many years and many rounds, 17lb mainspring, NEVER had a misfire.  I bought my new (used) one and got many light strikes. I finally put in a 23lb mainspring and the problem was cured.  

I wasn't happy with this, so after many gunsmithing adventures I got rid of the lightweight  hammer and put in a heavier one with a 19lb mainspring.  Much better. YMMV.

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