PSA: Glock 20 and Surefire X300-B Fail to Feed

[treillw]

Spent a lot of time monkeying with multiple variables on my Glock 20, trying to figure out why it was failing to feed.

95% certain that I have this solved. Shot a little under 50 rounds today in various configurations with no issues. Added the Surefire back on and it jammed three times in under 10 rounds. I intuitively loosened the screw on the light and that seemed to help for a few rounds. Called Surefire, quizzed them, they agreed it was too tight, and told me the torque spec is only 6 in*lb. Previously I had it as tight as I could make it with my fingers plus an ~1/8 turn with a penny.

Gotta set it to 6in*lb with the torque wrench later and run some more rounds through it, but it definitely seems to be a big component of the issue, if not the entire issue.

Figured I might save somebody else some frustration by making this post. Very happy that I no longer have an expensive paper weight!

Good luck!

EDIT: I think that the "Glock Pig Nose" (ie turned up frame tip contacting the slide) is what is keeping the slide from fully going into battery. You can see that the slide rubs the frame over about a half inch length at the tip of the frame. Without the light, the frame "nose" is free to flex over its entire length, back to essentially the trigger guard. With the light, ~90% of the frame "nose" beyond the trigger guard is effectively rigid aluminum. The recoil spring is capable of pushing the unstiffened frame out of the way when returning into battery, but cannot overcome the extra friction from the stiffened frame. I will report back with more information. I'm debating whether I want to sand down the polymer nose, or go to a stronger recoil spring.

 

[Turkeygetpwnd38]

Spent a lot of time monkeying with multiple variables on my Glock 20, trying to figure out why it was failing to feed.

95% certain that I have this solved. Shot a little under 50 rounds today in various configurations with no issues. Added the Surefire back on and it jammed three times in under 10 rounds. I intuitively loosened the screw on the light and that seemed to help for a few rounds. Called Surefire, quizzed them, they agreed it was too tight, and told me the torque spec is only 6 in*lb. Previously I had it as tight as I could make it with my fingers plus an ~1/8 turn with a penny.

Gotta set it to 6in*lb with the torque wrench later and run some more rounds through it, but it definitely seems to be a big component of the issue, if not the entire issue.

Figured I might save somebody else some frustration by making this post. Very happy that I no longer have an expensive paper weight!

Good luck!

That’s bizarre for sure. I have the exact same setup with thousands of rounds through it, I tighten the same light as tight as it’ll get, never had an issue.

 

[treillw]

That’s bizarre for sure. I have the exact same setup with thousands of rounds through it, I tighten the same light as tight as it’ll get, never had an issue.

 

[cobbc03]

Try a heavier recoil spring/guiderod, doesnt seem like screw tightness would make a difference.

 

[Coopsdaddy]

Good to know,im putting the A version on mine,sounds like your is the B version.

 

[Matt5266]

Just curious, what gen Glock?

 

[treillw]

Try a heavier recoil spring/guiderod, doesnt seem like screw tightness would make a difference.

Well, my first hand experience says that it does and if you search around elsewhere online, you will find similar instances. I have a 20lb tungsten guide rod installed and have swapped it back and forth in various configurations with the stock spring, stock barrel, and kkm barrel. Weapon light installed caused 2 or 3 jams in under 5 shots immediately after installation. No other configuration produced the same result in ~40 rounds.

 

[treillw]

Good to know,im putting the A version on mine,sounds like your is the B version.

B version is nicer in that it fits better on multiple platforms. Surefire salesman said that he prefers it over the A, as the A can be sloppy on different sized rails. Planning on tightening to spec and shooting again today. I can let you know how it goes.

 

[treillw]

Just curious, what gen Glock?

Four

 

[Coopsdaddy]

Thru my research the a version seems preferred but you have to take the time and make sure your adapter and the wedge screw is installed.
Mine fit perfectly on the g20 and good on my g45 but fit perfectly as well as soon as the wedge screw was tightened.
The b does fit more platform but is also more universal from my understanding.
I definitely pay attention to mine and update if any problems.

 

[cobbc03]

Well, my first hand experience says that it does and if you search around elsewhere online, you will find similar instances. I have a 20lb tungsten guide rod installed and have swapped it back and forth in various configurations with the stock spring, stock barrel, and kkm barrel. Weapon light installed caused 2 or 3 jams in under 5 shots immediately after installation. No other configuration produced the same result in ~40 rounds.

Try a 24# spring. If I'm not mistaken my gen 3 came with a 20# or maybe it was 18#, and I upgraded to 24#.

 

[Yoder]

I don't understand why a heavier recoil spring would fix a failure to feed problem. I'm no expert so maybe you guys are right, but the first thing I do with all of my Glocks is install a lighter spring. It makes it less finicky with lighter competition reloads. As a test, grip the gun as hard as you possibly can, lock out your elbows and shoot it. If the spring is a little bit too heavy the problem will get better. If it does, buy a lighter spring.

 

[treillw]

I don't understand why a heavier recoil spring would fix a failure to feed problem. I'm no expert so maybe you guys are right, but the first thing I do with all of my Glocks is install a lighter spring. It makes it less finicky with lighter competition reloads. As a test, grip the gun as hard as you possibly can, lock out your elbows and shoot it. If the spring is a little bit too heavy the problem will get better. If it does, buy a lighter spring.

I would lean towards @cobbc03 's thoughts that the recoil spring is too light - it's shooting 200 grain bullets from 1193 to 1235 fps (9 shot min and max).

 

[RockAndSage]

I would lean towards @cobbc03 's thoughts that the recoil spring is too light - it's shooting 200 grain bullets from 1193 to 1235 fps (9 shot min and max).

OP, the tighter screw torque is changing the geometry of the polymer frame, applying friction to the slide assembly. That will suck energy out of the moving parts. A heavier recoil spring would only make that problem significantly worse. The best options are to stick with surefire's torque specs - if that doesn't work, start by lubing the portions of the slide that are coming into contact with the front of the frame. If you want to double-check, or identify where the rub is occurring specifically, you can use dykem - dab a little on that inside of the front of the frame, reassemble, and cycle a few times. The rub will show clearly.

I've seen a similar problem on longslide Glocks - competition shooters will get them hot enough to where the polymer on the front of the frame starts "pig-nosing" and curling up. That makes contact with the underside of the front of the slide and increases the friction surface area by a couple of orders of magnitude over what the gun's designed to cycle with. It slows the rearward speed of the slide down, causing both ejection problems and failures to feed/chamber. Lubricating those spots usually fixes the problem, simply by getting the slide back up to more appropriate speeds.

 

[treillw]

(Added to original post as well):

I think that the "Glock Pig Nose" (ie turned up frame tip contacting the slide) is what is keeping the slide from fully going into battery. You can see that the slide rubs the frame over about a half inch length at the tip of the frame. Without the light, the frame "nose" is free to flex over its entire length, back to essentially the trigger guard. With the light, ~90% of the frame "nose" beyond the trigger guard is effectively rigid aluminum. The recoil spring is capable of pushing the unstiffened frame out of the way when returning into battery, but cannot overcome the extra friction from the stiffened frame. I will report back with more information. I'm debating whether I want to sand down the polymer nose, or go to a stronger recoil spring.

 

[RockAndSage]

(Added to original post as well):

I think that the "Glock Pig Nose" (ie turned up frame tip contacting the slide) is what is keeping the slide from fully going into battery. You can see that the slide rubs the frame over about a half inch length at the tip of the frame. Without the light, the frame "nose" is free to flex over it's entire length, back to essentially the trigger guard. With the light, ~90% of the frame "nose" beyond the trigger guard is effectively rigid aluminum. The recoil spring is capable of pushing the unstiffened frame out of the way, but cannot overcome the stiffened frame. I will report back with more information. I'm debating whether I want to sand down the polymer nose, or go to a stronger recoil spring.

The way that light is interacting is very interesting. I'd start with sanding that frame though - minimize the friction surface, before adding additional resistance for the energy of the shot to have to overcome with a heavier recoil spring.

 

[treillw]

OP, the tighter screw torque is changing the geometry of the polymer frame, applying friction to the slide assembly. That will suck energy out of the moving parts. A heavier recoil spring would only make that problem significantly worse. The best options are to stick with surefire's torque specs - if that doesn't work, start by lubing the portions of the slide that are coming into contact with the front of the frame. If you want to double-check, or identify where the rub is occurring specifically, you can use dykem - dab a little on that inside of the front of the frame, reassemble, and cycle a few times. The rub will show clearly.

I've seen a similar problem on longslide Glocks - competition shooters will get them hot enough to where the polymer on the front of the frame starts "pig-nosing" and curling up. That makes contact with the underside of the front of the slide and increases the friction surface area by a couple of orders of magnitude over what the gun's designed to cycle with. It slows the rearward speed of the slide down, causing both ejection problems and failures to feed/chamber. Lubricating those spots usually fixes the problem, simply by getting the slide back up to more appropriate speeds.

We must have been typing at the same time. I believe your onto the issue, but I think it is related to stiffness, rather than geometry modification. I measured from the bottom of the light to the top of the pig nose with a caliper having the light barely tight and then at full torque spec - it is not distorting the frame, at least locally, as it measures exactly the same.

I think sanding is a better option than lubrication. Don't want to run out of lube when I really need it. Although, it could be a good way to see if decreasing that slide friction solves the problem though; I suspect it will.

I'm not sure if a heavier recoil spring would help or hurt. It going back into battery that it is having issues with. The recoil of the round can overcome the extra slide friction pretty easily it seams and the friction disappears as soon as the slide moves around three-quarters of an inch and breaks contact with the frame.

The extra friction is added to the closing cycle right before the slide is coming to rest, where it is the most easily effected. Not sure if the extra closing force of the recoil spring would be enough to get it fully back into battery.

I guess the question is, what spring weight should a G20 shooting 200 grain hardcast at 1230 +/- fps have?

Thanks for the input. It confirms what I'm thinking.

 

[Wrench]

I find that 22# is as much as the stock mags can keep up with. If you go beyond that, the slide is so fast it won't feed. I've been running 20# springs with 200's at 1250 with good luck.

 

[Coopsdaddy]

Seems a common denominator in glock problems are people messing with them.
If 200 or under i would run it stock.
These guns see 10 of thousands of rounds with very few issues.
The 200plus grain or the pig nose is another issue.
I think you’re on to the issue.
I was in a class this weekend and the guy had 30 years experience in all kinds of law enforcement and had a documented g19 with over 30000 rounds with only a few stock recoil springs and a couple cleanings.It was just a gun he beat on to see how far it would go.

 

[Yoder]

I have a G17 with over 50k rounds on it. The stock spring was 17lbs. For competition loads this was too heavy and caused failures to feed. I've experimented with springs down to 11lbs. 11 worked for a while, but as it got older the gun wouldn't go back into battery. I settled on a 15lb spring. With the 15lb spring, I've never had a failure of any kind with factory or any of my reloads in tens of thousands of rounds. I've used mostly 115 and 147 gr. I think heavier springs cause more issues. They make the gun more sensitive to limp wristing, lighter loads and shooting in awkward positions. The frame of my gun is pig nosed pretty bad, but it doesn't touch the slide. One other thing to consider when tightening the light is the frame bulging horizontally, not vertically (pig nose)? It could be pushing the frame rails out when the light is tightened down causing the slide to have more drag. Maybe check that with calipers.