So I bought a brand new Glock 20 and set up to reload for it. Within the first five rounds I noticed horrible accuracy, way worse than even I’m capable of. I’m talking 6 inch groups at 7 meters. On the sixth shot I noticed a funny looking hole. I finished shooting two mags and out of 30 rounds 5 of them tumbled. Can anyone help me diagnose my problem here?
New Starline 10mm brass 180 gr Xtreme plated bulletsCCI Large Pistol primers
8.5gr Longshot (Hodgdon calls for 8.5-9.5gr)
I’ve shot thousands of Xtreme’s 9mm plated bullets without issue and inspection of the .40 ones I’m using doesn’t lead me to believe they’re the problem. There is absolutely no bore leading nor would I expect any from plated bullets. My powder charge is the minimum recommended for this caliber/bullet combo. inspection of the pistol shows no deficiencies visible to the naked eye.
My gut instinct is that I need to add powder and see if the higher velocity will stabilize the 180gr projectiles. I don’t have a chronograph to measure velocity but by using the minimum powder charge I’m afraid I’m not getting enough muzzle velocity to stabilize the bullet. The brass is showing a barely perceptible fish belly. I’m not sure if I should interpret that as a pressure sign or if it’s normal for 10mm fired in a Glock.
I had horrible accuracy with some 10mm rounds using Berry’s plated. I switched to Precision Delta 180 FMJ’s and the problem went away. Same primer,powder etc.
I have had accuracy issues with plated bullets as well. Trying to solve the problem I found two seperate issues. The first was substantial differences in the diameter of the individual bullets. Many were out of spec, being smaller than they should have been. The other issue was crimp (obviously, the inconsistant bullet diameters added to this issue). I losened up the crimp I was using and it made a huge improvement in accuracy.
Tumbling can occur when the jacket is not concentric to the core. This puts the center of the axis off center and you will get a tumbling effect. It happens more with plated bullets than with cup and core jacketed bullets due to the differences in manufacturing. With plating, if one area plates up thicker then is sized to dimension, that has the same effect of a jacket not being consistent. You don’t mention copper fouling in the bore, so I’m taking that to mean it’s not stripping the plating off.
That load looks good and LS is a great 10mm powder (9.2gr behind anything 180gr jacketed is a great load). Crimp should only remove the bell and should measure .419-.421.
Xtreme brand bullets have thicker plating than Berry’s, so jacketed data is fine. If your crimp is good, I’d jump up to 9.2gr of LS and try that. Just like riding a motorcycle, speed is a stabilizer. Find the sweet spot and stay away from the extremes which enable instability.
The bulged brass is due to the crappy support of the chamber. Some find it acceptable, but I don’t and use KKM barrels in my Glocks. At 8.5gr you’re right around 30,000psi. You might have soot on the case mouth which will be cleaned up with more pressure (seals the bore and keeps the gas forward of the casing where it should be).
So what are you favorite loads for critters? I bought a case of ammo to break the thing in and get some brass out of the deal. However, I want to push the 10mm to its full potential and load some good rounds for critter detail. I do have a Lone Wolf Barrel so I can shoot the higher pressure stuff.
Still working on it. My starting point was with Power pistol and 180 grain Montana Gold FMJ bullets and 180 grain Gold dots. The Gold dots did not group for crap the Montana Gold shot well. Both were in the 1400 fps range over the chrono.
My buddy has been reloading 10mm for his Dan Wesson. He gave me a box to try out. Load is as follows:
AA#7 11.5gr
Hornday FMJ-FP 180gr
FC Brass
CCI 300 Primer
They are smoking accurate in his Dan Wesson, curious as to how they will do in the G20.
I got pretty good results with a Glock 19 with essentially minnimum loadings. I never tried to push them fast. Everything I’ve read about plated bullets recommended slower speeds.