Glock 21 Gen 4 Shooting Low - Why?

[speedseeker]

So, just ramping up a Glock 21 Gen 4 to shoot local IDPA matches (CDP for something different and fun) and have found its shooting a bit low. Specifically, I'm seeing a ~5/6 inch dip from point of aim at 12 yards. I'm running Sevigney competitions with .215 height fiber in the front.

When I swap out for a Glock 34 with the same Sevigny sights at the .215 height I'm point of aim/point of impact.

Is it possible it is me? Is there something with the configuration of the gun? Perhaps the reduced slide length/sight radius? Most issues I've encountered with Glocks have related to windage not shooting either low or high?

Any thoughts? Tips for correction?

Thanks, speedseeker

[DRAB81]

What ammo are you shooting? I have Sevigny's on my GEN 4 G21 w/.215 front and it doesn't do that. I've shot factory ammo & some reloads, from 7-15yds with no issues. It's dead on for me at 15yds, so other than it being something you're doing, I'm stumped.

[Blue Jacket]

I had a third gen 21 with a heinie rear and had to use a .195 Dawson fo to get it to hit poa. Maybe you just need a shorter front sight.

[DRAB81]

Using Dawson Precision's calculator (in inches), and my GEN 4 G21 sight radius (Sevigny Sights) and your POA/POI difference:

(Sight Radius x POA/POI Difference) divided by distance, will give you your change in front sight height

7" (sight radius) x 5" (POI difference) = 12 

12 / 432"(12yds) = 0.0277

.215 - 0.027 = .188"

So a .190 or .195 front sight may be the solution. Have a few other solid shooters try it out first. If they all have the same issue as you, the front sight change should fix it.

[JBP55]

The rear sight on a G21 is .016 taller than the rear sight on a G34. If you are running the same height rear sight on both pistols the front sight needs to be .016 lower on the G21.

[DRAB81]

The rear sight on a G21 is .016 taller than the rear sight on a G34. If you are running the same height rear sight on both pistols the front sight needs to be .016 lower on the G21.

Aren't all Sevigny rear sights the same height?

.

Edited May 22, 2012 by MEAT

[Braxton1]

Aren't all Sevigny rear sights are the same height?

Yes, the adjustment is made by different height front sights. I would e-mail Scott Warren to see if he makes a shorter front sight. I have only seen the stock .215 and the optional .245 that most use on the G-34/35 guns.

Scott sometimes takes a minute to e-mail you back (He's a full-time LEO), but he WILL get back to you.

If he doesn't offer one, the other option would be to continue using the Sevigny rear and switch to a shorter Dawson Precision sight.

[speedseeker]

Using Dawson Precision's calculator (in inches), and my GEN 4 G21 sight radius (Sevigny Sights) and your POA/POI difference:

(Sight Radius x POA/POI Difference) divided by distance, will give you your change in front sight height

7" (sight radius) x 5" (POI difference) = 12

12 / 432"(12yds) = 0.0277

.215 - 0.027 = .188"

So a .190 or .195 front sight may be the solution. Have a few other solid shooters try it out first. If they all have the same issue as you, the front sight change should fix it.

Wow, this is great feedback. The shame of it is I love the Sevigny's and I don't think they make a shorter front sight. I'll definatly have a few other shooters give it a go and see what happens before I make any moves.

BTW, to your initial question. I'm shooting Federal Red Box hardball from Wally World.

Edited May 24, 2012 by speedseeker

[speedseeker]

Aren't all Sevigny rear sights are the same height?

Yes, the adjustment is made by different height front sights. I would e-mail Scott Warren to see if he makes a shorter front sight. I have only seen the stock .215 and the optional .245 that most use on the G-34/35 guns.

Scott sometimes takes a minute to e-mail you back (He's a full-time LEO), but he WILL get back to you.

If he doesn't offer one, the other option would be to continue using the Sevigny rear and switch to a shorter Dawson Precision sight.

"The rear sight on a G21 is .016 taller than the rear sight on a G34." Hmm...who woulda thunk it? The fact that the Sevigny's are all the same height in the rear suggests the difference on the Glock isnt the actual sight but the depth of the cutout and/or the hieght of the rear sight. Any idea why Glock would have that kind of a difference between platforms?

I'll definatly take your advice regarding contacting Scott. I believe your right though I havent seen anything other than the .215. and .245 offered. I do really like the Dawson's and would go that route if I had to but one of the major reasons I like the Sevigny's is because of the size of the light bar I get given how thin the front blade is relative to the rear notch. Last I checked you cant get a dawson that thin can you?

Edited May 24, 2012 by speedseeker

[DRAB81]

I'd contact Dawson Precision. You can use a Sevigny rear with just about any front sight specs you can think of. I have seen Dave post that if it's not on his website, call and he'll probably make it for you. I run the .115" wide fronts with my Sevigny rears, but I think he makes them as narrow as .090". Plus if you buy a Dawson front sight, you can exchange it until you find the height you're looking for.

[Braxton1]

The difference is actually in the sight itself on the factory Glock sights; the dovetail is exactly the same size/depth.

On every other Glock, the rear sight is 6.5mm tall. On the G-21 and G-37, the OEM sight is 6.9mm tall.

Glock chooses to make different rear sights to compensate. Warren Tactical does the adjustment in front sight height, which is actually easier to do. Front sights are easier to machine and easier to change the machine set-up to make different heights. They are a whole lot easier for the end user to swap out also.