Bi-metal bullets; barrel wear?


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A strange person
June 25, 2012, 08:26 PM
Are bi-metal bullets any worse for barrels than normal copper-jacketed bullets? I know someone started a thread on this a while ago, but it didn't really get alot of responses.

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Hacker15E
June 25, 2012, 08:28 PM
I haven't seen any actual evidence ever presented that bi-metal is any significantly harsher on a bore than copper jacketed.

Deus Machina
June 25, 2012, 09:22 PM
On a purely technical sense... probably.
Will you notice the difference in your--or your grandchildren's--lifetime? Probably not.

adelbridge
June 26, 2012, 03:05 PM
Technically copper/lead bullets are bi metal. I have been worried about steel jacketed bullets but logically if they have a similar POI as copper jacketed bullets they would approximate copper wear on your barrel.

JohnBT
June 26, 2012, 03:56 PM
The bimetal bullets - advertised as bimetal - I have seen and read about do not have any steel in them. They are lead cores covered with iron and then with thin copper. Iron is an element and is relatively soft.

Someone actually ran some Swiss 9mm bimetal through a lab test. Here are the results. I was looking at this ammo because a P210 shooter from Switzerland highly recommended it and J&G was selling it for $10/box by the case. I bought a few. After shooting the first case, heck the first box, I knew he was right. A little hot, clean and accurate.

______________________

9mm GECO 124Gr FMJ. Swiss RUAG Mfg.

Fe = iron
Cu = copper
Pb = lead
__________________

Results

Jacket wt.-18.32grains
Core wt.-105.422grains

Jacket
4.83% Cu (plating)
94.6% Fe
.63% traces of Zn, Pb, Bi, Ni, Cr, Al

Core
98.65% Pb
1.3% Cu
<.05% Al, Fe, Bi, Zn

Samples run on ICP-OES in aqueous acid solution (digestion), 10% Aqua Regia by volume.

Yes, 95% Iron jacket (not steel) with a 5% copper plating. Core is lead.

______________________

243winxb
June 26, 2012, 05:32 PM
Hornady GMX® (Gilding Metal eXpanding) same as bullet jacket at 95% copper & 5% zinc. No lead. http://www.hornady.com/store/GMX-Gilding-Metal-eXpanding/ The land in the barrel is about .004" tall, this is what gets the most wear. Not the groove, because grooves are the same diameter as the bullet. Fire many rounds of ever a 22 LR lead bullet, this will wear away the lands/rifling. Harder alloy/metal = more wear.

Hacker15E
June 26, 2012, 07:34 PM
Here's a pic of the "sandwich" that makes up the bi-metal jacket on Wolf .223.

https://dl.boxcloud.com/bc/1/f84f5df87ca6710dd00b0b5a0e2b6da0/JolueqOGpciD6dgYhecNBoVpYxkvmYe1ZLheZor6BF4DUBIelMQTkFwYIys3nIibNIIEHUp447tBZLaXDzIbNQ,,/8610355f87a6e7e80e6e9ee9a51a8587/

JohnBT
June 27, 2012, 10:00 AM
"Technically copper/lead bullets are bi metal."

Bimetal refers to two layers of jacket material (like copper covered iron), and not to the core whatever it is. I think we need to define terms here. Two metals mixed in an alloy wouldn't be bimetal either.

The Wolf .223 appears to be jacketed with tombac - an alloy.

"Tombac is an alloy formed from copper (84 - 90%) and zinc (10 - 16%) - The addition of arsenic produces White Tombac. "

243winxb
June 27, 2012, 12:42 PM
I think we need to define terms here Good point. What is Bi-Metal. :uhoh: I see some Wolf bullets are steel, with .005" copper coating.

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