10mm Inaccuracy. Help!

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mousegun380

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Hello,

I'm an experienced reloader and usually a pretty darn good shot with just about any pistol I pick up. However, I just received a new Glock 20 and I sincerely can not hit the side of a barn with it. I worked up some loads for the gun and arrived at the following:

New Starline brass
Federal LPP
Ranier 180gr RNFP
Bullseye 6.6gr
COL 1.260"
Book velocity 1088fps (Hornady book)

They chrono'd not only very close to book velocity, but also extremely consistently:
1092
1077
1088
1061
1092
1100
1093
1069
1106
1081

avg 1086

I went to the range yesterday to have some fun, previously only having had shot the gun when chronographing the rounds. I put 200 rounds through the gun and it just wasn't patterning very well. I was shooting a paper target at 10 yards. I then went to a metallic range and wanted to shoot some gongs. I could not hit a 12" gong at 25 yards to save my life. Some shots were in the dirt and others were over the top.

I returned to the range today with a scientific method. I shot a 10 shot string at 5 yards (center target). On this same paper target, I shot my old trusty 9mm as a control (lower left target). See image 1. Not a great group for that range, but at least in the neighborhood.

Then I shot a 10 shot string at 10 yards. See image 2. Getting worse... Some of the shots look like they might have keyholed, but I think this is actually due to a lack of support on the target stand. They were pretty shot up.

Then I shot a 10 shot string at 15 yards. See image 3. 2 on paper, 8 misses.

The bullets don't seem to be tumbling since the holes all look normal. The gun has a lot of recoil, but it's also huge and heavy so it's manageable. It feels like more than a .45 but less than a .44 mag. I'm at max load with Bullseye, but at a safe velocity, and at a lower velocity than the upper limits of this cartridge. I'm also within spec of the Ranier plated projectiles.

Any insight would be helpful. I'm going to buy a box of factory ammo to test the gun at 15 yards again to eliminate my reloads, but if it doesn't get better I guess I'll need to sell it.
 

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Why in the world are you using a 'Max load' of Bullseye with plated bullets in a 10mm in the first place??

The powder is wrong for best performance in a 10mm.

And plated bullets are for sure wrong at Max pressure in a 10 Mm.


You don't have the Right Stuff.

You got the 'Wrong Stuff'!

rc
 
Try a few factory jacketed bullets and see how it does.
Hi velosity 10mm loads generally don't like lead bullets.
 
Yeah, I wouldn't use Bullseye & 180gr.

#7, Longshot = yes :)

Bullseye for light loads behind coated lead :)
 
KWG, upon inspection the barrel appears to be normal. Thanks for the suggestion.

RC, thanks for the input. This is a terrible excuse, but I chose Bullseye because I had two pounds of it I bought during the shortage, it was listed as an option in the Hornady book, and according to the data it was capable of getting into the velocity range I was looking for. I have actually never used it before wanted to use it up. As for why max load, I was trying to build range loads that would approximate SD recoil and to get there, I started low and worked up to max because the rounds were being very consistent on the chrono and were approximating book velocity. I did not doubt their safety. Accuracy is of course another story.

I have Power Pistol, Unique, Titegroup, and Longshot on hand. Would you suggest any of those?
 
Power Pistol , Unique HP 38, and Longshot. You do not want those fast powders like TH or BE.

I am not a fan of plated bullets in anything,
 
As for why max load, I was trying to build range loads that would approximate SD recoil and to get there,
The old adage I seem to always come up with is:

If you want to move a bowling ball as fast and far as you can? ( Heavy bullet.)

Would you hit it as hard as you can with your clenched fist? ((Fast powder like Bullseye.)

Our would you rather Push it as hard as you can with your palm? (Slower burning powder.)???

rc
 
I have had a 10mm for a long time and run many test loads through it with varied powders and bullets weights. The overall best powder I have for mine is AA-9 for the 180 and 200gr loads.

I wold say that if you could find some #7, Blue Dot, or HS-6 or the other posted above, you would be set up better to get where your looking to be.
 
Huh?

I'm pushing coated lead over 1,500fps with no issues.

:confused:
I know it depends on several factors, but, I have a 16" carbine barrel that simply does not like any lead. It is however super accurate with jacketed bullets. Go figure.
 
Yes, Power Pistol (or another in that burn rate range) with either a good hard cast bullet or jacketed.
I'm not a fan of plated bullets in anything with more pressure than a 38 Spl or 45acp. For those they are fine.
 
Using AA #9, Longshot, 800X, and BE-86 in my Glock 20 with Hornady 180 grain HAPs and it is more accurate than I am. My favorite load is 13.0 grains of AA #9 behind a 180 HAP, nice tight groups, clean burning, and great velocity.
 
Thanks for all of the recipe and powder suggestions. I will get some factory ammo, and make some new loads and report back!
 
Try a strating load at 92% of your max. Increase the charge by 1 percentage point at a time until you find the sweet spot. Most times I find my most accurate load are between 92% and 98% of the max charge.
 
What really struck me as odd was that in maybe 10 years of reloading, I have certainly had more and less accurate loads with the wide variety of calibers I load, but they have all been essentially accurate. This is the first time I have ever had one that was so incredibly inaccurate. I almost can't believe that that bullet could take such a crooked path inside of 15 yards so as not to even hit the paper! I guess there are always lessons to learn.
 
I know others probably have different experiences, but I never could get plated bullets to perform as well as jacketed in 10mm - specially when you start doing real 10mm velocities of 1200 - 1300 FPS. The same plated bullets do fine for me in 40 S&W.
 
I run plated exclusively for everything I load, but I always make sure that I am not exceeding the max velocity spec from the manufacturer. Usually Ranier or Berry's.
 
I run plated exclusively for everything I load, but I always make sure that I am not exceeding the max velocity spec from the manufacturer. Usually Ranier or Berry's.
Yes, sorry about that, I looked at the velocities you posted after hitting submit - my bad!
 
Power Pistol , Unique HP 38, and Longshot. You do not want those fast powders like TH or BE.

Just to pick nits, the burn rate charts I've seen show HP-38/231 to be about the same as Bullseye or Titegroup.

Oddly, Lyman 49th claims that 231 was frequently their "best accuracy" load in 10 mm, and surprisingly they usually indicate that was the max load, even with lead bullets. Since they specify that the accuracy load is based on "ballistic uniformity" (not stated whether that means ES or SD or some function combining them) not shooting at actual targets, I'm skeptical of that rating. Hammering soft bullets like that seems dubious.

Mousegun, that Lyman manual gives 5.5 grains of Bullseye as the starting load for 180 grain JHP. It would be an interesting experiment to make up a few of that load and see if backing off the pressure solved your problem. If so, that would seem to be a convincing sign that you are over-stressing those bullets.

I've not shot them in 10 mm, but in .44 Mag, the plated bullets I've tried that gave closest to the accuracy of good jacketed (XTP or Nosler) in heavyish loads (max of 4227) were RMR's plated HPs. IIRC, they are a little more $ than most plated, but still cheaper than jacketed. You might try a few to see if they group better than the Rainiers for you.
 
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For what its worth, I had similar awful results with 165 grain Xtreme plated bullets with a healthy dose of Longshot in my Glock 20. Literally was having trouble hitting a plate size target at 10 yards! The same bullet and powder shoot extremely well in my Glock 23 at around 1050 fps. I determined the plated bullets really don't do well at higher velocities. But that is really not news because the plated bullets folks all tell us that.
 
So you've absolutely eliminated the shooter?

This level of inaccuracy almost seems impossible.

:)
 
My plinking load is a 165gr JHP and AA#7. While doing my tested all of the loads I had were pretty accurate. I settled on .2 grains over start load. I would try that combo and see if you can get the gun to cooperate.
 
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