Author Topic: BBI 9mm .357 diameter  (Read 217 times)

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Offline K31Scout

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BBI 9mm .357 diameter
« on: February 04, 2018, 05:29:56 PM »
I've loaded 1000's of Acme .356" and Blue .355" and am happy with both. 

I have an older bag of BBI 147gr flat nose that are supposed to be .356" but all are measuring .357" and plunk at 1.060 so I have to seat them to 1.050 OAL.  I have not loaded any at this time until I consult here.  I like to use WSF powder.

With 147gr coated lead I normally load 3.7gr thru 4.0gr of WSF.  With the shorter seating depth and larger diameter of the BBI would it be wise to reduce the starting load of 3.7gr and by how low can I go? 
CZ 75 SP-01
CZ P-07

Offline IDescribe

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Re: BBI 9mm .357 diameter
« Reply #1 on: February 05, 2018, 07:54:33 PM »
In the same way Blue Bullets are slightly undersized at .355, BBI are slightly over-sized at .357.  This is NOT a bad thing if the pistol will handle them at an acceptable OAL.  I'd much rather have over-sized than under-sized.  In fact, in my ShadowLine, I'd much rather have over-sized than standard size.  Over-sized lead tends to be good lead.  ;)

SO...

The first thing that I would do is some math to determine seating depth.  WHAT is the length of the bullet itself?  case length + bullet length - OAL = seating depth.   Just use a case length of .750 for 9mm Luger -- no need to measure case by case.  So .750 + BL - 1.050 = seating depth at your OAL.  If I had to guess, I'd guess you're seating depth is going to be somewhere around .350, which is deeper than I like to go, NOT because it creates some danger with the powder, but because the interior diameter of the case starts to narrow around .300 below the case mouth, and it may start to bow out the case walls or swage down the bullet base if you seat too much deeper than that.  People do it, and do it successfully.  Personally, when the base of the bullet is beveled, I'll go as deep as .320, but no deeper.

IF my guess of .350 is close, and IF those were my bullets, I'd load them for another pistol.  IF I had no other 9mm pistols, I'd load them at 1.050 and work up from starting load and see what happens.  WSF is a slow-ish, well-behaved powder.  You're not going to blow up a pistol at starting load for being seated .060 deeper than normal for a 147gr bullet.  I have no idea about your "normal" loading for 147gr with WSF.  Sort of meaningless here.  Go back to the drawing board, and by drawing board, I mean a loading manual.  ;)  START with STARTing load.    If you're nervous, knock a couple tenths off starting load, even, but I wouldn't sweat it with that powder, and assuming I had a chrono to use to see where I was in terms of velocity.  Starting load should be fine.

What are your goals for the load?  9mm minor action pistol?

Offline K31Scout

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Re: BBI 9mm .357 diameter
« Reply #2 on: February 06, 2018, 06:58:29 AM »
Good guess ID.  Bullet measures .650" in length.

I have a bag of 250 of these gathering dust and just want to get them around 132pf for practice with no particular goal except to use them up.  Starting load data is 3.7gr WSF with a suggested OAL way above 1.050".  I'll load these for my 1911 that allows a longer OAL.  Thank you. 
CZ 75 SP-01
CZ P-07

Offline IDescribe

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Re: BBI 9mm .357 diameter
« Reply #3 on: February 06, 2018, 02:05:21 PM »
Good guess ID.  Bullet measures .650" in length.
It's almost like I've done this a few times.  ;) 



I'll load these for my 1911 that allows a longer OAL.  Thank you.

That sounds like an excellent plan.  :)





 

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