View Full Version : Finally Getting a Handle on Glock Accuracy
I’ve looked at a lot of things in my quest for better Glock accuracy: training, sights, parts, technique, etc. Yes, modern pistols shoot better than we can hold them, but a new-ish Gen 3 G17 with an RMR02 installed by One Source Tactical has been driving me nuts lately with crappy groups. As I talked with DocGKR and others here trying to solve it, a common theme came out: Glock accuracy is ammo-dependent.
This weekend, I learned just how ammo-dependent it really is. I tested 11 different types of the cheap FMJ ammo that people here have mentioned that they use to train. I shot a total of 68 5-shot groups, more or less evenly distributed across four 115-grain loads, three 124-grain loads, and two 147-grain loads. Everything was factory ammo—no reloads.
Yep, Glock accuracy is definitely ammo-dependent—much more so than I expected.
Averages for the three best loads hovered around 3.5” offhand at 25 yards. One of the cheapest grouped under 1.5” at times.
The worst load (and one of the more expensive ones in my area) averaged over 6” at 25 yards, and turned in some groups over 7”. It strings vertically in the test gun—badly enough to be useless at 50 yards—but it shoots very well at 50 in another new-ish Gen 3 G17. And of course, I've been blaming the gun and beating myself up for being a crappy shot as I've gone through several thousand rounds of that exact load over the last few months.
I’ve got enough of the test ammo left that I’ll probably shoot some 50-yard tests and try it in other Glocks, but for now, I’ve got the RMR-equipped G17 figured out.
But if you were curious, that’s how ammo-dependent Glocks are.
Your mileage will almost definitely vary.
Okie John
TriviaMonster
11-28-11, 13:16
You got any stats as far as bullet weight and its relation to groupings? And no, not all ammo is created equal.
-Chris-
I was hoping for just that sort of insight, especially since I've had superb luck with a couple of 147-grain loads in some other Glocks, but no such luck. One of my favorite 147-grain loads was clearly the best, but the other was among the worst. I'd love to think that bullet weight was the key, but I didn't see that.
Okie John
How about sharing what ammo performed the best...:confused:
The top three were American Eagle 124-grain FMJ, Sellier & Bellot 115-grain FMJ, and Tula 115-grain FMJ.
I deliberately left that out because I'm pretty sure it won't be the same in other guns. I was impressed more by the variation in results than by which load shot the best groups.
Okie John
I read an article in Blue Press by Duanne Thomas. He said the WOLF 9mm was one of the more accurate loads to test 9mm pistols with.
I know people often associate WOLF with crap ammo, but Russian primers and Rimfire ammo are really good stuff.
I dont have a glock, but tula groups better than the federal stuff out of my gun. I was really surprised that I could save $2 a box and group better(.4osw). My bros glock also shoots the federal like crap... Im starting to think its just some of the worst stuff out there. Seems very inconsistent.
Great job Okie. I just thought the economy fmj ammo was all crap. This is very interesting. Thanks much.
Thanks for posting your results. Interesting to hear that the Tula groups well, but I've personally seen squib loads, improperly loaded cartridges and extraction problems with this brand all during one high round count class. I'd still avoid it regardless of the savings.
littlejerry
11-28-11, 19:30
a new-ish Gen 3 G17 with an RMR02 installed by One Source Tactical has been driving me nuts lately with crappy groups.
Okie John
I'd check to make sure everything is screwed down on that slide. I was at the range with a friend a few weeks ago as he was sighting in his new OST slide/barrel combo. The front sight came loose after a few rounds and the RMR just plain fell off the gun after putting ~150 rounds down range. None of the screws had any loctite and they backed out during the range session.
Regarding cheap ammo I've been shooting Brown Bear and WPA 9mm exclusively for over a year and haven't had any issues with accuracy- even at 100 yards.
I did a similar testing awhile ago, and came to a different conclusion. I found no appreciable difference in group size between 6 different loads. Relationship between point of aim and impact were different, even for the same bullet weight and loading pressure, but groups were about the same. In fact, the group size wasn't the reason behind my test, trying to figure a correct front sight height was.
How about sharing what ammo performed the best...:confused:
I'd also be interested.
I wonder what it is about Glocks that makes Brand X perform worse than in other handguns.
warpedcamshaft
11-28-11, 20:43
My Glock 17 experiences reflect those of the OP. I have experienced significant variations in precision with different types of ammunition. Certain loads seem significantly more precise, and will often shoot to different points of aim. The variations in point of aim seem to not only affect vertical point of aim, but also horizontal.
However, I don't generally have issues finding loads that I can keep around at most 3 1/2 inches at 25 yards with 5 shot groups offhand.
Some other pistols I have fired (even Glocks in other calibers) appear to be somewhat less ammo specific. I am not sure if these variations are caused by variations in 9mm ammunition among manufacturers or some other factor.
I may try an aftermarket barrel in one of my Glocks some day just for testing purposes. (Just to satisfy my curiosity)
One of the best FMJ rounds I remember were the PMC 115gr. in the camo box. I don't know if they even make it like they used to any more. You could blow the ten ring out of a B27 at 25 with them.
That is the round I used for quals with my Gen 1 Glock 17. I need to look for some of new PMC for practice ammo to try instead of WWB.
Great job Okie. I just thought the economy fmj ammo was all crap.
That’s I thought—I actually bought it expecting it to be pathetic.
I'd check to make sure everything is screwed down on that slide.
I did that after it rusted when I got stuck in the rain a few weeks ago. I pulled the RMR, hit the cut in the slide with Rustoleum, and screwed it back together with plenty of LocTite. Most loads strung vertically by no more than 30%, which is typical for me with iron-sight Glocks. The worst loads strung by more like 100%--that's gotta be an ammo issue.
I did a similar testing awhile ago, and came to a different conclusion. I found no appreciable difference in group size between 6 different loads.
POI of the best six loads I tested differ by less than an inch. POI of the worst six differ by less than two inches. POI of all 11 loads differs by 2.5". The more ammo I test, the wider I expect the extremes to be.
Relationship between point of aim and impact were different, even for the same bullet weight and loading pressure, but groups were about the same. In fact, the group size wasn't the reason behind my test, trying to figure a correct front sight height was.
Most loads hit very near the same point. POI in the extreme cases differed by 2.5”, which could put shots 6.5” apart if you’re shooting 4” groups with both loads. That’s one thing I REALLY like about the RMR—there’s no screwing around with new front sights at $40 each, and you're not cranking the rear sight back and forth in the dovetail with a sight tool. You just whip out a screwdriver and rezero--it's like suddenly having flush toilets after living with outhouses.
The variations in point of aim seem to not only affect vertical point of aim, but also horizontal.
Yep, ran into that, too.
Okie John
That’s one thing I REALLY like about the RMR—there’s no screwing around with new front sights at $40 each, and you're not cranking the rear sight back and forth in the dovetail with a sight tool. You just whip out a screwdriver and rezero--it's like suddenly having flush toilets after living with outhouses.
Two summers ago, during a night class, I learned a valuable lesson - how my eyes perceived red dot differently depending on lighting conditions. A carbine zeroed perfectly during daylight was one inch off at twilight. I knew that before - due to astigmatism, I see dot in all kinds of shapes depending on distance, indoors/outdoors etc. The new part was that dot didn't change its shape as darkness moved in, but zero shifted - for me and 3-4 other shooters. Since you're using RMR, you may want to exclude that variable too.
Not to steal OPs thread, but here are some tests I did a while back:
http://i839.photobucket.com/albums/zz314/Umbrarian/Guns/9mmAmmoResults.png
Not to steal OPs thread, but here are some tests I did a while back:
No worries.
I only tested two of the loads that you did, the CCI Blazer Brass 115 and Winchester 147 TMTC. Your groups are better across the board than mine were.
Okie John
From my own experiences ammo choice / load is always a variable for any weapon that I have fired. While there are definite differences, especially in weights, I have not personally noticed an unusual amount of difference in the Glock that would make me feel that it is uniquely different from other weapons. But then again I mostly shoot 3 types of quality factory ammunition and have not conducted side by side testing of a wide array of ammo through any of my Glocks and other pistols. However doing something like what Renegade did above with a wide array of ammunition and then doing the same with several other pistols would be interesting. Of course the controls or consistency throughout the test firing process would need to be maintained.
However doing something like what Renegade did above with a wide array of ammunition and then doing the same with several other pistols would be interesting.
Someday, I'll have the time and money for that.
I hope.
Okie John
I would love to see your results if you get the chance. :)
I did a similar testing awhile ago, and came to a different conclusion. I found no appreciable difference in group size between 6 different loads. Relationship between point of aim and impact were different, even for the same bullet weight and loading pressure, but groups were about the same. In fact, the group size wasn't the reason behind my test, trying to figure a correct front sight height was.
I assume you were using irons, right? Are we looking at an optical/iron difference here - for whatever reason?
john
I would love to see your results if you get the chance. :)
Will do. I'm definitely going to continue the tests as time and money permit.
When I test ammo, I fire 4 each 5-shot groups offhand at 25 yards and record the average Extreme Spread (ES). I record all groups fired, not just the good ones. I also repeat this sequence on different days to get a broader idea of how these loads perform and to help reduce the influence of shooter-induced error. The group sizes I mention online include the results of at least two sets of targets, so a minimum of 40 shots on eight targets.
I also determine the group's elevation by averaging the height of each shot above or below a fixed line and averaging that. This varies more than I expected, so I the POI figures I mention are the average of the elevation for all eight groups.
Five-shot groups can be misleading by themselves, so I also plot all 20 shots on a sheet of graph paper to see what patterns emerge. I start by measuring the vertical and horizontal dispersion to see which loads string and how badly.
I also note the percentage of shots that fall into a 3" circle and those that fall into a 3.75" circle. If the centers of these two circles is far apart, it probably means I'm at fault, not the ammo. This is probably more important than ES in finding the most accurate loads in the long run.
So clearly these tests aren't ideal, but I think they're a pretty solid start for a guy who doesn't have access to a Ransom Rest. I'm open to suggestions in methodology if anyone wants to chime in.
Okie John
No worries.
I only tested two of the loads that you did, the CCI Blazer Brass 115 and Winchester 147 TMTC. Your groups are better across the board than mine were.
Okie John
I tested from an bench rest.
I assume you were using irons, right? Are we looking at an optical/iron difference here - for whatever reason?
john
Yep, as I alluded to, I was trying to figure out a correct front sight height, so irons.
I am not particularly looking for rds/irons difference, to me optics always groups better. I was just pointing out that if OP tested his 14 loads under different lighting conditions, then perception of dot could have varied.
Not to steal OPs thread, but here are some tests I did a while back:
http://i839.photobucket.com/albums/zz314/Umbrarian/Guns/9mmAmmoResults.png
Is the 115 gr. Winchester (Q4172) the same as Winchester White Box 115 gr.?
I am not particularly looking for rds/irons difference, to me optics always groups better. I was just pointing out that if OP tested his 14 loads under different lighting conditions, then perception of dot could have varied.
I shot these tests on one weekend. The light was very similar both days--flat and relatively low, which is typical for November in the Pacific Northwest.
I don't have much time on the RDS yet, but so far, I find that the dot does in fact look different at different times. I'm not sure how much of it is my astigmatism and how much is lighting.
Okie John
Is the 115 gr. Winchester (Q4172) the same as Winchester White Box 115 gr.?
Yes, that is what people refer to as "White Box".
Yes, that is what people refer to as "White Box".
Thank you, very useful information.
Unfortunately it means "I" am still the problem when it comes to Glock accuracy.
Thank you, very useful information.
Unfortunately it means "I" am still the problem when it comes to Glock accuracy.
Are you using a rest? I sure do not shoot 1 inch groups at 25 yards offhand. I had an adjustable one that pretty much kept the gun locked down with almost no movement.
Thank you, very useful information.
Unfortunately it means "I" am still the problem when it comes to Glock accuracy.
eh, you need to test it yourself from a rest or at least a bench. No two barrels like the same load. There may be some common likes/dislikes due to the polygonal rifling, but just because someone's gun shoots load x the best does not mean yours will. However, it would seem from that test that it is at least loaded consistent.
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