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9mm Bullet Width


REHChief

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I hate to start a new topic on this because I'm sure it's been covered elsewhere but I've search and search and can't find it.  

 

I was wondering what everyone's thoughts are on running a .357 width 9mm coated bullet.  I know 9mm bullets are .355.  I shot a buddy of mine's 160 gr 9mm ammo and loved how soft it was (made 128 PF).  He said he runs 2 thousandths over and never has any issues.  Before I decide to copy his loads, I like to turn it over to the experts, at least experts compared to me:)  

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With everything else unchanged (OAL, powder type, amount of powder, crimp, etc), I would think the PF would increase as the bullet's width increases, no?  Well, then again there's more friction between the bullet and the barrel as it goes down the rifling.  I'm thinking the speed of the bullet would be the thing that changes but I'm not sure in which way?  🤔  Or is this one of those "I'm over thinking it" things?  

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1 hour ago, REHChief said:

With everything else unchanged (OAL, powder type, amount of powder, crimp, etc), I would think the PF would increase as the bullet's width increases, no?  Well, then again there's more friction between the bullet and the barrel as it goes down the rifling.  I'm thinking the speed of the bullet would be the thing that changes but I'm not sure in which way?  🤔  Or is this one of those "I'm over thinking it" things?  

You are not really overthinking it. You just don't know how it all works yet. IN very general terms the fatter, coated bullet will go faster simply because it will expand and seal up the barrel better after fired, therefore making maximum use of the gas behind it. A harder jacketed bullet at .355 will be slower because it does not expand nearly as much so gas gets passed it when fired, therefore not maximizing the gas. 

 One of the hardest .355 jacketed bullets out there is Montana Gold. It is known to take more powder to get up to desired speed because of all of the above.

 

Hope that all made sense.

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Besides, a lot of factory barrels are substantially larger than the book's .355".

Aftermarket "match grade" barrels tend to run smaller.

And, as P.O. Ackley said, by the time the (oversize) bullet has traveled its own length, it will FIT the barrel.

 

Assuming the round "plunks", the danger is "bullet pinch" with the case neck tight in the chamber.

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If you slugged your bore you may be surprised to learn it is not .355".  Many makes vary between .355" and .358".  I'm told some are larger but I've not seen it.  Even if yours is .355", shooting a .356" cast bullet that was coated to .357" will do no harm.  I'll say the manufacturer is suspect, because most makers size their bullets after coating so the are a consistent .356".  Some even give you a choice between .355, .356 and .357.

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1 hour ago, CZ85Combat said:

I have used .355"-.358' bullets in 9mm. As long as you do not use a Lee Factory crimp Die you should be OK.


CZ85 -  Can you help me understand why it is bad to use a Lee Factory crimp die if you are loading bullets that are in the .357-.358 range….Thanks Mark

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1 minute ago, Sigarmsp226 said:


CZ85 -  Can you help me understand why it is bad to use a Lee Factory crimp die if you are loading bullets that are in the .357-.358 range….Thanks Mark

It will probably resize the bullet down to .355 or smaller

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23 hours ago, Sigarmsp226 said:


CZ85 -  Can you help me understand why it is bad to use a Lee Factory crimp die if you are loading bullets that are in the .357-.358 range….Thanks Mark

Grumpy is on target. The FCD will resize the bullet in side of the case and you will no longer have a .358" bullet.

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I run .358 160 Bayous or BBI RN in my 929 REVO

They shoot just as well, very accurate, out of all my 1911's, Sig 226's and even the 320's shoot them OK. (320's like 124/5 at.358 a whole lot more though)

 

Old school thought was run lead/coated .0002 over bore size.  I find testing 100 packs of .357 and 358. a lot easier than slugging my bbl and measuring it.

Proof is in the puddin, Puddin!  If they shoot accurately and make PF they're good to go.

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On 8/4/2021 at 7:34 PM, CZ85Combat said:

The FCD will resize the bullet in side of the case and you will no longer have a .358" bullet.

 

It doesn't, though, at least not necessarily. I shoot .358" 160gr bullets in my .38 Short Colt, and crimp with a 9mm FCD. Pulled bullets still measure .358".

 

The carbide ring can't size the bullet, because 9mm is tapered. If the case fits all the way into the die, the carbide ring must be substantially wider than .355". Size at the case mouth is determined by the adjustment screw. It can be backed out to the point where it crimps but doesn't swage the bullet down.

Edited by Fishbreath
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20 hours ago, Fishbreath said:

 

It doesn't, though, at least not necessarily. I shoot .358" 160gr bullets in my .38 Short Colt, and crimp with a 9mm FCD. Pulled bullets still measure .358".

 

The carbide ring can't size the bullet, because 9mm is tapered. If the case fits all the way into the die, the carbide ring must be substantially wider than .355". Size at the case mouth is determined by the adjustment screw. It can be backed out to the point where it crimps but doesn't swage the bullet down.

Agree and have checked and verified this many many times!!!

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I found .358" Bayou 160 gr was more accurate in my 929. I had issues with accuracy and was pissed until I went back in my logs from 30 years ago and found that on a revolver you go .001"over the cylinder diameter to get more accuracy no mater the barrel's bore diameter. ( This is old school revolver experts from the past) I found that they shoot great in my CZ's and STI DVC. You have to bell the mouth more as to not shave the coating off while seating and use minimum crimp. Very soft shooting and in my 929 out of my ransom rest I went from a best of 2.75" 10 shot group down to 1.09" at 25yds. Also my reason for going to a heavier bullet is the 929 has a twist rate of 1:10  instead of 1:16 which mean it will shoot a heavier bullet more accurately. ( I found that out when testing my Colt 1:12 twist to my S&W 1:18.75 twist with 125 and 158 gr bullets. the Colt shot the heavy bullet more accurate than the S&W and the S&W shot the lighter bullet more accurate than the Colt. )

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On 8/3/2021 at 3:45 PM, REHChief said:

With everything else unchanged (OAL, powder type, amount of powder, crimp, etc), I would think the PF would increase as the bullet's width increases, no?  Well, then again there's more friction between the bullet and the barrel as it goes down the rifling.  I'm thinking the speed of the bullet would be the thing that changes but I'm not sure in which way?  🤔  Or is this one of those "I'm over thinking it" things?  

 

Just chrono some test loads and remove all the guesswork.

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4 hours ago, superdude said:

 

9mm and 38/357 have the same SAAMI barrel specs; .355" + .004" groove diameter. 

 

https://saami.org/wp-content/uploads/2019/02/ANSI-SAAMI-Z299.3-CFP-and-R-Approved-2015-12-14-Posting-Copy.pdf

 

OK let me ask the same question a different way: hasn't it been shown by many 929 users here that it has a bore that is oversized compared to 9 mm bullet dimensions?

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3 hours ago, SGT_Schultz said:

 

OK let me ask the same question a different way: hasn't it been shown by many 929 users here that it has a bore that is oversized compared to 9 mm bullet dimensions?

 

9mm barrels are oversized for .355 bullets, too.

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