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Rough bore on 9mm full size

2935 Views 10 Replies 6 Participants Last post by  FieroCDSP
Has anyone eyeballed the bore on the M&Ps and compared it to other pistols they own? It seems the bore on my 9mm is very "rough" compared to my other pistols. This can be felt when pushing a patch through the bore and easily seen with a bit of magnification. I looked at the bore through my "OptiVisor" head worn magnifier (used for tying flies and a lot of other things the older I get) and can see machining "chatter" marks the full length of the bore. The bores on my 1911s and other handguns I've owned have a mirror polish on them.

Also, the ramp and bore seem to have the same finish on them as the exterior of the barrel.

I think this roughness causes the bore to build up with more debris from my cast bullet handloads and makes the bore harder to get clean than any of my other guns. My 9mm is also not quite as accurate as I'd hoped and wonder if a smoother bore would make a difference.

I've read somewhere about using JB paste to smooth bores. Any experience with this? Will the bore smooth out after a few thousand rounds of cast lead bullets (my gut feeling is, no)? Is it possible this roughness would contribute to inaccuracy?

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I don't how rough the rough you are describing is, so I can't really comment on how it might be affecting leading of the barrel.

However, I do know that a lot of deadicated lead shooters make a point of breaking in their new barrels with jacketed ammo (100-200 rounds depending on who you ask, opinions seem to vary) to reduce leading later on.

So perhaps getting it nice and clean and running a couple boxes of cheap factory ammo through it will cure your problems.
rjs said:
I have run a couple of hundred WWB rounds through the gun right off the bat. (Have to get brass from somewhere to reload
). The WWB will group under an inch, off hand at 7 yards so that's not bad. I imagine the copper coated lead bullets aren't as hard as actual jacketed bullets.

I do think my groups are getting tighter with more rounds through the pipe. I don't think I'll ever be able to shoot as good of groups as I do with my SA 1911 SS Loaded. But, then, that gun cost twice as much and has a better trigger.

I'd just as soon not send the gun back in (and I'm sure they'd want the whole gun) as I did the online trigger job (worked very well). I probably don't have any warranty any more.

Thanks for the ideas, guys.


Your issue is with the barrel, not the trigger job. They can't void your warranty for the trigger job, just refuse to service any modified parts or warrant any problems that they view to be caused by the modified parts. The more realistic problem with manufacturers is them undoing your trigger job. I don't know if S&W do this or not as I made sure I was certain my gun was running fine before modifying it.
rjs said:
I really like this gun. I just need to figure out why I can't hit plates as well as I can with my 1911's. More practice is the answer, I bet.


Well, that's simple. Figure out what you are doing differently with the two guns because of ergonomics or differences in their operation, and practice compensating for them.

For me, transitioning from my 1911 involved gettig used to a hinged trigger again, dealing with the longer takeup, getting rid of the factory sights (mainly the rear), and developing a decent repeatable grip that keeps everything aligned as it should.
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