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Old June 3, 2012, 08:08 AM   #1
TNT
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45acp and 45acp +p brass (9mm differences as well)

I have read conflicting stories on this. Originally I thought the reason for +p brass was for a hotter load thicker webbing to withstand the added pressures. Then I see where some are saying due to the thicker webbing the volume of powder was decreased. In another account I seen a pic of the two cases cut in half length ways and the +p had less material in the head so slightly more powder could be used so can someone put some clarification on the differences and separate fact from fiction.
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Old June 3, 2012, 08:58 AM   #2
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Certain brands offer "+P" cases that differ only in headstamp, while some brands' cases actually differ.

Thicker / thinner / alloying / heat treatment / ???.....

There is no cookie-cutter answer.
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Old June 4, 2012, 12:07 PM   #3
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so if that is the case then why even have different brass if the change is only cosmetic?
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Old June 4, 2012, 12:24 PM   #4
buck460XVR
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Quote:
so if that is the case then why even have different brass if the change is only cosmetic?


To differentiate from standard and +P loads. Some guns are not made to shoot +P ammo, so knowing the difference can be important.
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Old June 4, 2012, 12:28 PM   #5
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You are looking at this from the position of a reloader. Back when it was still factory ammo the +P meant that it was loaded to +P pressures. That way when Joe buys a box of 45acp +P ammo, loads up his magazines, throws away the box, dies and his son, Joe Jr., inherits the gun and the ammo he knows that those are +P rounds.

But yeah, after the ammo is shot the headstamp means decidedly less.
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Old June 4, 2012, 12:56 PM   #6
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Starline Brass-Only

The Starline website- http://www.starlinebrass.com/ -
Quote:
45 Auto +P Brass (Large Pistol primer) .892"-.897" O.A.L.
The 45 Auto+P is a strengthened version of the 45 Auto with the same external dimensions. A thicker web and heavier sidewall at base strengthens the case in potentially unsupported areas. This case has approximately 2 grains less internal water capacity than the standard 45 Auto.
38 Special
Quote:
38 Special+P Brass (Small Pistol primer) 1.140"-1.150"O.A.L. (Backordered expected availability: 06/15/2012 )
38 SPL+P has no difference from the standard 38 SPL, other than headstamp designation for load segregation. This is due to the fact that our standard case design will handle +P pressures with no problems.
9MM
Quote:
9MM+P Brass (Small Pistol primer) .748"-.754" O.A.L. (Backordered expected availability: 06/29/2012 )
9MM+P has no difference from the standard 9mm Luger other than headstamp designation for load segregation. Due to standard case design, it will handle +P pressures with no problems.

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Old June 4, 2012, 02:28 PM   #7
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As I just explained in a parallel thread, SAAMI only specs the exterior dimensions of the case and finished cartridge. What a manufacturer finds he needs to do to the inside ti make the brass handle pressure is up to him. Some make it all the same, some don't. Also you can harden brass and increase its tensile strength by working it more, so the number of forming steps can affect it. Hatcher mentions once having headstamp markings struck extra deep to increase head hardness to get cases that would withstand burst pressures so he could determine what those actually were.

The conundrum for most hand loaders is will my pet powder charge be affected by changing from a standard to a +P case. That depends on the volume inside the case under the bullet. In most instances the domestic brands are close enough in exterior dimensions that you can determine this just by weight difference. If a set of +P cases with the same brand headstamp are heavier than the standard cases you have, then they have less capacity and you should back your load down.
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Old June 4, 2012, 07:14 PM   #8
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Thanks Nick I was hoping someone would define the difference
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Old June 4, 2012, 10:42 PM   #9
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Starline +P 45acp brass [high pressure] has thicker walls than 45 Super [higher pressure] or 460 Rowland [highest pressure].

The man at Starline says that is because the +P brass is capable of working in poor case support barrels, where good case support is expected in 45 Super and 460 Rowland.

9mm, 9mm+P, and 9mm +P+ all look the same to me in cross section.

357 mag has a thicker web than 38 special, but that thicker web is just taking up space. I have never heard of anyone who could get a 38 special case web to fail.
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Old June 5, 2012, 07:13 AM   #10
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My Remington 9x19 cases differ from my Remington 9x19 +P+ cases.
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Old June 5, 2012, 09:49 AM   #11
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On the 45ACP case the "normal" web thickness is 0.175" for 45 ACP, 0.182" for 45 ACP+P and 0.198 for 45ACP Super. That is a significant difference in strength IMHO. Unless you have a ramped barrel in your 1911, I'd recommend the +P and/or Super cases when you decide you want to "experiment" with over the top loads along with the use of heavier springs.
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Old June 7, 2012, 10:10 PM   #12
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Quote:
TNT
45acp and 45acp +p brass (9mm differences as well)
I have read conflicting stories on this.
My post is conflicting with some other posts in this thread.
I don't have any great source data, just a can full of cross sectioned brass.
It would be better if we made drawing of our cross sectioned brass and quantified it where it counts.
It would be best if manufacturers gave source data on the range of internal dimensions and brass hardness or tensile yield stress.
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Old June 8, 2012, 02:52 PM   #13
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I agree. SAAMI leaves all those interior details up to the manufacturer, but the military does not. Their spec drawings show a sectioned case profile with hardness points taken at a number of locations. The military also specifies internal head thickness from the breech and case wall dimensions at specific points for both brass and steel cases (separate drawings). It's a much more thorough specification and is the reason military brass is often more durable in self-loaders.
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Old June 8, 2012, 08:29 PM   #14
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Good idea
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