Glock 20 accuracy issues

Discussion in 'General Glocking' started by Objekt, May 26, 2007.

  1. Objekt

    Objekt

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    Today I tested some 10mm reloads, for both velocity and accuracy. Accuracy has been an issue with my Glock 20 to a greater degree than other pistols I've owned, and I'm trying to find out what it likes, and whether there's something wrong with it.

    So far, the answer is "doesn't like anything." Accuracy is marginal at 10-15 yards, and downright lousy farther out.

    Here's a picture of the target I used today, with different reload groups indicated by color. I fired 15 rounds of each from a Weaver-ish stance at about 10 yards. Hold was with bullseye center resting on top of the front sight, using two hands, taking my time & trying to be as consistent as possible:

    [​IMG]

    Red: 5.4 gr. Titegroup under a 180 grain Rainier plated bullet (0.401" diameter). Cartridge OAL 1.270".

    Yellow: 7.0 gr. Unique, 180 grain Rainier plated bullet (0.401" diameter). Cartridge OAL 1.270".

    Green: 6.0 gr. Titegroup, 180 grain Rainier plated bullet (0.401" diameter). Cartridge OAL 1.270".

    Orange: 6.0 gr. Titegroup, 180 grain Hornady XTP hollowpoint bullet (0.400" diameter). Cartridge OAL 1.270".

    The loads using XTPs were most accurate, and also the most consistent in muzzle velocity: average 1113 ft/s, standard deviation a mere 11.21 ft/s. I'm used to seeing that kind of consistency in quality defense ammo, such as Hornady TAP, but not in my reloads, since I use mixed brands of brass that's been fired any number of times.

    I'm disappointed that this was the best group I could get at only 10 yards. The first three groups are just horrible, and all off to the upper-right for some reason. Though the smallest group, and centered in azimuth, the group of XTP reloads still has more spread than I would have liked. My Springfield XD, 1911s, and Glock 30 can all make one ragged hole at 10 yards, regardless of the ammo.

    So what's wrong with my Glock 20? Or am I expecting too much of it?
     
  2. f4tweet

    f4tweet

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    It looks like your powder amounts are in the .40 cal range, and so velocity is low. I use a recipe of 180 gr plated Rainier, 11.0 gr. of Accurate #7. 1.250 OAL, .420-.421 crimp, with WLP. This recipe is published in a Accurate handout. So far it has worked splendidly for me. The #7 is very clean burning. The velocity is very close to 1200fps. Try something of at least 1200 fps. I'll bet your accuracy improves. I am able to hit man sized steel targets at 125 yards 4 out of 5 times with this load. Try it. LOL
     

  3. Objekt

    Objekt

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    Unfortunately, I'm limited to the 1100 ft/s neighborhood with the powders available to me. Maybe I'll try a lighter bullet so I can push it faster.
     
  4. Chuck TX

    Chuck TX CLM

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    My G20 and G20L seem to prefer Power Pistol and Blue Dot, using Rainier 180gr. I don't go over OAL of 1.255 for average loads and OAL of 1.265 for Nuke loads. Maybe you need to seat it a touch deeper for better results.
     
  5. Objekt

    Objekt

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    The thing that bothers me is, the one time I fired some high-velocity ammo in my G20, it had a malfunction.

    I fired a full 15 rounds of Winchester Silvertips. They are one of the few factory loads that give full 10mm performance, hurling a 175 gr. JHP bullet at about 1300 ft/s. Unfortunately, one of them failed to eject. I had a thread about it here several weeks ago.

    Meanwhile, I've fired just over 500 rounds of my reloads, using from 5.0 grains Titegroup to 7.0 grains Unique, with no malfunctions of any kind. Usually it's my reloads that are somewhat unreliable, and factory ammo *always* works. Go figure. :supergrin:
     
  6. Chuck TX

    Chuck TX CLM

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    Weird. Is that with a completely stock G20?

    The only time I had trouble with mine was with a too stiff of a recoil spring. And that was in my G20 Longslide with a match barrel (before it was broken in).
     
  7. Tito

    Tito

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    I would definitely stick to book loads using light bullets and fast burning powder (Tightgroup and Unique are both relatively fast burning).

    You can generate some scarry high pressure with all that space in the case for the fast burning powder to expand.

    I think 4fteet had it right by recommending Accurate Arms #7 or #9 or something slower burning. You might also try 800x or Blue Dot.
     
  8. NailShooter

    NailShooter

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    ...EXACTLY 16" on center

    I'm with Tito.

    800X seems to work pretty well in my G20 with 180 FMJs. The closer I load to max (from the powder manufacturer's manual) the better my groups get. YMMV


    Nail
     
  9. Glolt20-91

    Glolt20-91

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    In checking the Speer manual, 180grs -- Unique 7.2-8.0grs, 1.250" COAL. With your COAL out so far with a low powder charge you'll get terrible accuracy. Neither Speer nor Sierra list Titegroup for 180grs.

    With 175gr/180gr loads in 10mm, I've had very good results with Blue Dot, Unique, Power Pistol, HS-7, and 800X. My choice for inventory loads is AA #7 and AA #9 that drop in about 1350fps/180gr. One AA #9 loading is at 1375fps/755fpe, ES 23fps, SD 07fps with enough cushion to go a little higher in the fully supported KKM 6" barrel. Very good accuracy at 25 meters. :)

    Slower powders that fill the case more tend to give better accuracy than lower fill faster powders that run the risk of a double charge.

    175gr Silvertips/800X gives 1392fps MV.

    Bob
     
  10. Objekt

    Objekt

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    I used data straight from the powder manufacturer (Alliant). They list 7.0 grains Unique, 1.250 OAL as the max powder charge and min overall length, respectively.

    However, my Lee reloading manual agrees with yours.

    So, who's right?

    The Lee manual also doesn't list Titegroup loads. I got the data from, again, the powder manufacturer's online data.
     
  11. Objekt

    Objekt

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    I'm glad I only bought a 1 lb. can of Blue Dot. Today's chronograph session revealed that even a max charge (10.4 gr.) of Blue Dot, seated to near minimum OAL (1.255" average) could only push a 180 gr. Rainier bullet to an average of 1074 ft/s.

    A 165 grain Sierra JHP went but slightly faster, averaging 1101 ft/s. I suspect it didn't go a whole lot faster because a true jacketed bullet is harder than the plated Rainier bullet, so obturates less, causing higher (but still safe) pressure and lower muzzle velocity. Or maybe it's just a normal variation. 27 ft/s is just a hair over one standard deviation.

    Blue Dot didn't get the Glock 20 any more or less dirty than Titegroup, Unique, or any other powder I've used recently, but there were a lot of unburned flakes all over when I was finished shooting. Quite a few landed on the chronograph.

    Accuracy was much improved. By seating the bullets more deeply, I was able to get one ragged hole at 10 yards. The next thing is to see what load groups best farther out.

    The next powder to try is Accurate #9. Lee lists a muzzle velocity of 1242 ft/s, and Accurate gives 1235 ft/s.