.354"?

[thx997303]

So, is this a normal groove diameter for 9mm?

I slugged the barrel twice, and got this both times.

This is a Springfield Armory XD9 and it seemed tight right near the chamber.

Thoughts?

[canyon-ghost]

Howdy,
Yes, it's tight for 9mm. The 9mm is supposed to size at .355, and industry has changed it to .356 for some time. Now, with a lot of gun owners complaining about chambers and leed being bad, machinists have been running things a tad tight to stop an educated public from complaining. I guess we either size down or shoot jacketed. Of course a guy can polish it out with valve grinding compound and ease some of the problem, say 600 grit on a patch.

Have a TC barrel from 2006 that is tight, my S&W isn't near as picky and has a better twist rate than the TC.

[Shiloh]

I wasn't aware that the industry standard had changed to .356. It was .355 forever.

Shiloh

[canyon-ghost]

I think I'm quoting Speer #13, which has an extensive section on the 9mm. So, this is possibly a 'Nineties' thing. But, just as his barrel is .354", the human factor shows up.

[lylejb]

it seemed tight right near the chamber

THAT makes me wonder... It is possible to have a constriction in a barrel, but that's more common in revolvers.

I would suggest you slug the barrel, from the muzzle, and stop before you get to the tight spot. Then, from the chamber end, drive the slug back out the front. Measure this slug. If it's any larger you have a constriction.

A constriction could explain the unusual slug measurements (slug being sized down as it passes the tight spot) and could cause accuracy and leading problems.

If it is the same size then your fine. Just the tight side of spec's

[thx997303]

I will have to do that, I wonder, would I be able to have the constriction opened up were that the case?

[thx997303]

Okay, so I slugged the front part of the barrel, and it slugged at .355" so it is .001" tighter right after the chamber.

So, I guess the chamber end needs to be opened up a bit, but how to do this?

Edit: I just reread the above posts, how many passes would you go before measuring if I were to do the polishing compound? And how would I assure it stayed round?

[canyon-ghost]

I usually count to twenty with a patch, assuring that it stays round is harder. That's more or less something you use a reamer for. With compound, I really don't think you'll take off more than half of that, .0005". You could use a round patch pusher or jag and just lay the patch over it. I use compound with oil, suspending the compound in the oil, as it were.

There is also fire-lapping, where you coat the bullet with compound and use a reduced load (to alleviate pressure) but, I've never done that. Veral Smith on his LBT page knows quite a bit about that.

And, as I said before, a reamer can open it up but, you'd have to borrow one or find a machinist that has one. Ed Harris on Cast Bullet Assoc. site is well acquainted with reamers and their application.

I do 20 strokes, clean it out, then do 20 and clean again. A guy could measure every time he cleans it out. This will be labor intensive too.

[thx997303]

Hmm, seems like it wouldn't be horribly critical as far as size and perfect concentricity were concerned, so long as the chamber end were uniformly .355" or even a little larger wouldn't hurt.

So long as the muzzle end of the bore is undamaged, opening up near the chamber would allow improved cast boolit shooting.

[GabbyM]

S&W made 9mm barrels to .3545" for years. Don't know what the new ones are now. all my stuff is old.

I'd still size them to .357" just to fill the millitary size chamber for better bullet alignment to bore.

Have you shot this pistol yet?

[thx997303]

I've shot it quite a lot. It is quite accurate.

The issue I'm running into is the bore is .001" tighter at the chamber than at the muzzle.

[technetium-99m]

I've shot it quite a lot. It is quite accurate.

Then I wouldn't mess with it. JMHO

[GabbyM]

Nothing ten or twenty thousand rounds won't fix.

If you've leading in the last half of the barrel then one may think that .001" may be holding you back. What do you recon that barrel measures when that 32K psi round goes bang?

[geargnasher]

Nothing ten or twenty thousand rounds won't fix.

If you've leading in the last half of the barrel then one may think that .001" may be holding you back. What do you recon that barrel measures when that 32K psi round goes bang?


Now you've got it! If it was a revolter it might lead like crazy due to pressure loss at the cylinder gap and the extra beef of the frame not permitting expansion.

Gear

[Char-Gar]

354-355were typical 9mm groove diameters a few years back. The Euro 9s ran larger. My 1950s P38 ran .357, My 1913 DWM Luger runs .356 and my two Browning HPs run .357. I size my bullet .358 and shoot them in whatever 9mm pistol that is at hand. I have never hand any feeding or pressure problems.

.354-.355 were also Colt 38/357 standard for many years. Again, I sized my bullets .358 and got splended accuracy from the Officers Model, Officer Model Match, Army Special, Official Police, OM Trooper and Phython.

In reloading for the 9mm Luger, what you need to watch is the case length. These cases vary from maker to maker and even from different lots of the same maker. For max accuracy, segregate you cases by length of the same maker. That will do more to boost accuracy than anything else I know.

[thx997303]

Umm, so is the chamber end being .354" and the muzzle end being .355" likely to cause a problem?

Guess I'll size to .357" and try em out.

[Char-Gar]

All of the precise measurments are interesting, but you never can tell what a firearm will do until your fire it. Lots and lots of theory goes down the tube when the trigger is pulled. As long as the load and pistols are safe, then go for it and after that the questions will have answers.

[AZ-Stew]

I'm not sure what all this talk is about reamers. You cant "ream" a rifled barrel to open up the groove diameter (which is what you're measuring when slugging a barrel) without first reaming all the rifling out of it. You'd have to completely ream away the lands to get to the grooves. Be careful who's advice you take.

Size your boolits a couple thousandths larger than your largest slug measurement. If you get good accuracy, you're done. It's far cheaper and easier to vary boolit size than it is to mess with the gun. Remember, you can't put metal back once you've removed it from the gun. Amateur gunsmithing with the wrong tools and wrong techniques can destroy a good gun. Leave it to the experts.

Regards,

Stew

[canyon-ghost]

Don't think I could disagree with Chargar and Stew, if it shoots good, the math doesn't mean much. An extra thousandth might go away from shooting it anyway. A reamer is just used to solve chamber problems for cast in rifles sometimes-yes, it's probably radically drastic, never used one.
All I can personally vouch for is the lapping, it works, and I only use it once on a firearm. I'm as afraid of hurting my firearms as the next guy. Err on the side of caution, it pays.