STI Trubor help, please .... won't run with major ammo

[mscott]

I was determined to figure this out, but have run out of ideas.

About the gun ..... I bought this as a lightly used Trubor with only a couple hundred rounds on it. It's a Dawson tuned hard chromed gun from 2007. I was having brass jam between slide and mount, so eventually went to a sideways mount. I put a new 17# ISMI mainspring in it and have tried 7,8, and 10# recoil springs. Gun has a solid guide rod. To date I've got about 3k rounds on it. Extended ejector is beveled correctly according to everything I've found.

I have been loading 115 MG JHP with 9.3 of HS6 at 174 pf and 124s with 7 gr of Auto Comp. Both at 1.165 oal. Neither load will run reliably. I get the same malfunction, which is like a horizontal stovepipe pictured below. The gun will run on minor ammo no problem. I've got 115 MG at 130 pf loads that run fine. Also use Bayou 124 and 147 coated bullets with WST and WSF powder. All fine.

I thought the slide was moving too fast and tried the 10# recoil spring. No good.

Put an Aftec in it (and radiused the firing pin stop) and no change. Tried just 1 spring in Aftec both front and back only. No better.

Local shooter suggested I try really short ejector as in .130 long. No better.

Installed Brazos tuned ejector. No better.

So I'm down to looking at mags. I have 6 of them .... 2 - 170mm with Grams guts, one with Dawson base pad and one with Grams. 2 - 140s and 2 - 123s all stock. Seems like no pattern to malfunction and has happened with all mags using major ammo. All mags run fine with minor ammo. It seems that the slide is bringing spent case back and round in the mag below is pushing it up far enough to where ejector doesn't work correctly. Looked and feed lips on mags. Adjusted 2 of them to where the feed lips are about .350 in the rear and slightly more in front. On all of my mags the farthest gap on feed lips is .360. When I went out tonight I made sure my thumb was no rubbing slide and kept it on the outer edge of safety. I did get through 1 mag tonight at the range without a malfunction, but it was only once. Jam happened about 6 times at local match last Sunday.

I'm still thinking mags, but I'm here to listen. Any thoughts?

Edited August 22, 2015 by mscott

[Sarge]

Cmore touching the slide under major PF recoil? The pic may be deceiving but it sure looks close.

Ejector isn't broken?

Spacers in the mags?

[mscott]

C More not touching. I milled top of slide for clearance.

Ejector is fine. Have tried 3 different ones.

Arredondo spacers in a couple, factory plastic in couple, steel in one.

[GrumpyOne]

How can it be mags if it runs minor PF ammo just fine?

[Aircooled6racer]

Hello: Are you using a shock buff by chance? Thanks, Eric

[mscott]

No shock buffs in my guns.

Also worth noting is that ejection with major ammo is all over the place. They go out to the right about 6', some go straight forward, some straight up, and some even come back at me. Minor ammo eject straight out to the right about 4' away.

[Sarge]

No shock buffs in my guns.

Also worth noting is that ejection with major ammo is all over the place. They go out to the right about 6', some go straight forward, some straight up, and some even come back at me. Minor ammo eject straight out to the right about 4' away.

Extractor needs tuned possibly.

[mscott]

Have tried stock STI extractor and Aftec with various configuration of springs. Both give same results.

[Steve RA]

Based on the information so far, and the pic, I lean toward an extractor problem of some sort.

[al503]

Looked and feed lips on mags. Adjusted 2 of them to where the feed lips are about .550 in the rear and slightly more in front. On all of my mags the farthest gap on feed lips is .560.

You mean .350?

[mscott]

yes, .350

fixed my post

[JWard79]

Are the minor loads the same oal or shorter? Might try playing with your major load oal, and see if that makes a difference.

[mscott]

Thought about that a little bit ago. I ran an Open Glock a couple years ago, so might try some of those loads.

Also might try a mag without a spacer.

[MrPostman]

Mixed brass or same headstamp on your major loads? Slight differences in brass can contribute to erratic ejection, especially with over sammi pressures in 9 major. Some brass is stretched more and harder to extract than others, shooting minor loads the brass isn't stressed like they are in major so there would be no difference in mixed brass and same headstamp.

If you are using the same headstamp brass then you may want to buy an extended ejector and profile it yourself. The extended arm will help get the spent brass off the extractor quicker, in theory this should help the next round to slide under the extractor into the correct position for reliable feeding.

Edited August 22, 2015 by MrPostman

[Badkarma]

Just my 2 cents... check your extractor.

[Ming the Merciless]

Have you measured the extractor tension using the Weigand extractor tension gauges and a trigger pull scale? I like mine set to around 18 to 20 ounces with lightly sprung guns. Your symptoms sound exactly like too little extractor tension that lets the case flop around and hit or not hit the ejector in a random manner resulting in random ejection patterns. It may run minor power factor because the recoil isn't as violent and the case isn't coming off the extractor before it hits the ejector.

Edited August 22, 2015 by Ming the Merciless

[mscott]

Extractor holds a case against the breech face pretty well. Don't have any tension gauge, so can't check that. Using the Aftec I was thinking there isn't anything to adjust other than the springs.

Thought about the mixed brass problem a while ago and was ready to sort brass. While at the range one day I saved every piece from a jam and had 8 pieces on the bench. There were 6 different headstamps, so not sure where to go with that.

[MrPostman]

I would try some new same headstamp brass and see. That way you can completely rule out the brass if it doesn't fix the problem.

Edited August 22, 2015 by MrPostman

[Aircooled6racer]

Hello: It is your extractor. Try the Aftec with no front spring, just the back one. Also check the breach face on either side for burrs. Check the disconnector rail radius as well. Make sure your grip screws are tight. Thanks, Eric

[Aircooled6racer]

Hello: I forgot to add check for coil bind on the recoil springs. Thanks, Eric

[stardust tommy]

also check for extractor clocking (loose fit between extractor and firingpin stopplate)

[stardust tommy]

check if the extractor tip does not touch the barrel when in battery

sometimes you can bend the extractor for more tension but when the inside of the extractor touchtes the inside of the extractor tunnel you can bent what you want... remove some of the innerside of the extractor

[RenoShooter]

When I put in an Aftec extractor on my new STI it did the same thing as yours is doing. I did the case to the breech-face test with an empty case by slipping the case under the ejector and seeing how well it held in place. It was far looser than the factory extractor! I called Aftec and they told me that many still need further adjustment. Doesn't matter about how many springs you're using if it's too loose. I adjusted per Aftec's instruction and got it close. Improvement, yay! But, I could not get it close enough so I ended up putting it in the extractor tuning tool and getting it perfect. The steel is much harder so it's more difficult to twist the handle down on the tool, but it worked. I did the same on my backup STI, (same exact model), and it runs perfect as well. Hopefully that's all your issue is as it would be easy to try. On side note, the Aftec's like to run a little looser then a factory extractor. So if you're using the tool and a gauge to set your ounces it doesn't like to be cranked up as much as a factory one. Hope this helps, but it's probably clear as mud, right?

[blacklab]

I think you should sell it to me. Cheap. I'll let you know if I can get it to work.?

Edited August 22, 2015 by blacklab

[mscott]

I appreciate all the input from everyone, but I'm about to declare this gun for minor ammo only and just shoot Alphas.

Took it apart to check everything. No burrs anywhere. Aftec fits fairly tight and don't think it can be clocking much if at all. It is not touching barrel when in battery. Grip screws were a bit loose, so tightened them up. Took front spring out of Aftec (I'm pretty sure I already tried this before, but not positive) and headed to the range to beat up the plate rack. I loaded up some short 1.135 oal near major ammo as well.

Started off with long major ammo. 4th shot was jam. Had another before mag was finished. Loaded that mag with minor ammo and ran perfect. Tried the short major ammo and no good as well. Cycled through several mags and seems to be no specific mag or time for jam. Sometimes at beginning of mag and sometime near the last few. 147 Bayou minor 135 pf ammo cycled nicely with good and consistent ejection pattern in all mags I tried it in. Pic at bottom shows some of the brass I've been getting back with major ammo.