9mm troubles

Loaded up some 9mm yesterday for testing today. Recently put a new barrel on my PCC gun and decided to lengthen the OAL of my ammo for this gun. Sightened in and shot a group with my previously loaded ammo and everything was fine. Shot (5) 5 round groups with the new loads and everything was satisfactory. Range brass, cci sp primers, 115gr LRN, seated to 1.075, and 4.5gr. of W231.

Decided to shot one more group a few hours later....8” group at 17 yards. Next group was worse....found 3 factory rounds and shot a 1.2” group. Loaded up 3 more reloads and shot a 1.1” group. Then again but this time it was 6” and the next was 9”. This is my steel challenge gun, so I have to get this dialed in.

Checked red dot and it was tight. Don’t understand how it shot fine then sprayed then fine and then sprayed again? No visible leading at all. These are coated lead. Another pcc and pistol shot the reloads fine earlier in the day. I don’t necessarily think I have a reload problem by any means, but want to get opinions to cover all problems.

Thanks.

FROGO207 said:

Did you check the barrel for lead buildup? I would start there.

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Forgot to add that in the post, yes I did. Barrel looked clean throughout the shooting. I almost feel like it has to be an issue with my red dot, but unsure why it would shoot two good groups in the middle of that.

fxvr5 said:

drop the 5-shot groups method. they can be misleading because small groups happen by chance. https://www.ssusa.org/articles/2019/9/25/accuracy-testing-shortcomings-of-the-five-shot-group/

shoot more rounds per group, like 10-15.

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Thanks, very informative. Will try that. Probably will take my old barrel with me and throw it back on to compare. I had shot a bunch of high round count groups with it,...mainly just because didn’t want to change the target.

Skeptic13 said:

Do you have a different 9mm pistol that you can try them in? Or can you put the old barrel back in your PCC? Does the barrel need some breaking in? Did you go back and shoot more of your old load? Or just go back to your previous load.

It would see with this issue you are going to have to eliminate issues to get to the root cause. Is it the barrel, the new COL, just a fluke?

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I believe I’m going to take my old barrel and another red dot, plus make up a few other charges just to see what helps.

TonyAngel said:

What do you mean by "new load?" Different powder or different bullet. Same manufacturer that you've been using. Did you mic to bullet for uniformity of diameter? If it shoots fine with one ammo and not another, it's usually the ammo.

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Powder and bullet is the exact same. I extended the overall length by .025. My previous barrel had a short throat. Still have plenty of the old ammo loaded, but it’s spraying it as well.

Hope to go back Monday and rule some variables out.

UPDATE: Went and did some testing today. Ended up shooting 5 rounds when I showed up just to confirm the bad grouping. They are in the first picture attached....1 round barely caught the top corner. I didn’t shoot a bunch of high round count groups, because after 4 rounds I could tell it was well past acceptable. Ended up shooting another 75 rounds 5-10 at a time checking groups. 30% didn’t hit the box but it seemed point of impact moved around a lot. Nothing consistent. Didn’t see any leading to speak of. I loaded up these 100 rounds last night checking the powder weight and OAL on each to insure it wasn’t something I did. Swapped back to my older barrel and the same ammo and it shot great. Last pic is a 15 round group with the old barrel.

Load was 115gr coated LRN seared to 1.053 with a charge of 4.5gr of W231.

I’m not sure if this barrel just doesn’t like the load/bullet or just won’t shoot in general.

G

ballman6711 said:

Glad to see you found the problem.

May try slugging both barrels to see if the new barrel needs a larger diameter bullet.

chris

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I forgot to add but I did shoot 10 rounds of the same bullet sized to .357 instead of the normal .356. No change on that as well. The other gun will shoot either size find.

If for some reason the bore was really tight would that cause accuracy issues for lead? I’m sure I’ve read about this but can’t remember.

I do need to slug the bore....just need to pick me up a rod, my current ones diameter is too large.

Richard Jay King said:

What happens when you shoot the same load with jacketed bullets????

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Honestly don’t ever load jacketed bullets in 9mm. Just run them for full power 357mag. Might could round some up and try it out though, but I would hate to think I could dial it in with plated or lead.

lordpaxman said:

Do yourself a favor and order some RMR jacketed bullets, you get a THR discount as well! Can you get some factory jacketed and try that?
I wouldn’t think an undersized bore would lead to worse accuracy, perhaps an increase in pressure. It could be way over size so even your .357 wasn’t being spun correctly. Where’d you get the new barrel and can you ask them for any information?

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I got some of my factory jacketed ammo out last night that I stored away a while back. Went to a private range this morning and shot it....definitely better. The barrel is a taccom super feed 16” ULW. It’s a sleeved barrel that only has 5.25” of rifling. It feels great on the gun and I really like it other than i haven’t been able to get it to group on most of what I shoot. I reached out to taccom the other day about another question and didn’t get that great of a response....I don’t believe they would be giving any information on this as well.