Understanding the "45° bump"

[Tedfs]

No I'm not an engineer but understanding why things happen has always interested me.

What I'm wondering is, what parts are working in a pistol to make the slide go forward on it's own
when a mag is inserted with enough force and at the right angle.

When my G 19 was brand new, the slide would go forward fairly consistently on it's own. After about
the 12,000 round mark, the slide wouldn't always go forward on it's own even though the same technique
was being used.

Recently some work was done to the slide that required a refinish and now the slide goes forward
relibly again if enough force and the correct angle is used. Which has me wondering if the finish
thickness plays into this as well.

What I would like to figure out is, what parts are involved in producing the slide going forward
on a Glock when a mag is inserted with enough force and the right angle is used. Yeah other pistols
do it but for the sake of simplicity, Glock will be the focus.

And no, I don't think anyone should rely on using this 100% of the time, it's a tool in the box to
use like anything else. I just want to understand what parts are involved and why it works.

Any thoughts or ideas are welcome, this had been bugging me for a few years.

[John_Wayne777]

There's a big heavy slide under compressed spring tension being held in place by a small engagement surface on a tiny piece of stamped steel pinned to a light, flexible frame. It's really not surprising that the right sort of bump would defeat that.

[Tedfs]

True but then why does it become less reliable over time as parts wear ?

There has to be certain parts involved that wear over time and make this technique less repeatable. Finding out which parts are involved is what I'd like figure out.

[Kevin P]

JW777 told you the parts and how they interact. Also you mentioned the slide got refinished. If you think about it those surfaces that are engaging together probably have reduced friction which is why you can do it again.

[glocktogo]

The slide stop is the part that holds the slide back. Depending on the wear condition of the slide stop and slide stop notch, lubrication and finish, some Glocks will do it repeatably and some never will. I see guys on the range slamming the mag in hard just to make it happen and one time I saw a guy do it so hard that he knocked the baseplate off and all his ammo went flying out the bottom.

If you're applying more force than necessary to reliably seat the magazine just to make it work, stop. All you're doing is upsetting the gun and taking more time than necessary to get back on target.

[Tedfs]

That's what I was thinking as well, however, this works on other autos that have metal frames as well.

But I'm trying to dig a little deeper here and find out exactly which parts are involved with the Glock.

It happens reliably with a fully loaded 15 round mag down to about 5 - 6 rounds then it pretty much stops working.

Taking the slide off and inserting a mag, I can see where the cut for the catch on the mag is almost hitting the catch itself. The round hits the bottom of the ejector and is prevented from going much further.

I guess a call to Glock is in order...

[skyugo]

my 19 only auto forwards on a full mag. my g26 has never done it.
i think it's basically an inertia thing. the frame must get bumped forward, while the inertia of the slide keeps it in place long enough for the slide stop to disengage.

[theblackknight]

I can get it about 85% with my MP9 with 5 snapcaps in a mag. Round count is somewhere around 6500. Not 100% with the snapcaps, but once Im on the timer in a match, I dont have to think about it.

http://www.youtube.com/watch?v=LMsDeV2PCSU

[glocktogo]

That's what I was thinking as well, however, this works on other autos that have metal frames as well.

But I'm trying to dig a little deeper here and find out exactly which parts are involved with the Glock.

It happens reliably with a fully loaded 15 round mag down to about 5 - 6 rounds then it pretty much stops working.

Taking the slide off and inserting a mag, I can see where the cut for the catch on the mag is almost hitting the catch itself. The round hits the bottom of the ejector and is prevented from going much further.

I guess a call to Glock is in order...

We told you which parts are involved. They are the slide stop, slide stop notch in the slide and the magazine you're inserting. What other parts do you think are involved???