A friend who has a Mini-14 told me the dealer who sold him the rifle warned that heavier bullets would wear the barrel out faster.  I've heard that the velocity of super hot loads in some guns can wear the bore faster, but I this is the first I've heard bullet weight being a factor.

Is this so, or was the dealer full of it?

Theoretically, he may be right.  The heavier bullets ARE longer.  Therefore, each longer/heavier round (let's say 77gr) that passes through the barrel has a larger surface area contacting the barrel than a smaller/lighter round (55gr for instance).  However, 5.56mm barrels tend to wear out faster because of the excessive speed compared to other rounds at which the projectiles are fired.  This heats up the barrel faster than rounds traveling at a lower velocity and wears much more than a slower round would.  So in actuality, firing the heavier bullets, which travel at a much slower speed might actually wear your barrel out slower than the lighter loads.  Either way, the difference (if any) is not substantial and I'd have to agree with Troy's BS meter.  I wouldn't loose sleep or another moment that I could be thinking about something more significant over this issue.

The 1/7 twist seems to cause premature throat erosion. The cause is because the twist is so fast that the bullet actually skids a few thousands of an inch before the rifling takes hold and can stabilize it. This condition gets
exagerated with each shot.

Gov't. M16's can show throat erosion after as little as 2,500 rounds. However, that is with the lighter Gov't. profile barrel and always under full auto conditions. Under semi-auto conditions, those barrels will typically go 5 to 7 thousand rounds before breaking down badly enough to warrant replacement. Many times, a Gov't. barrel with 1 or 2 thousand rounds will be replaced as inaccurate, when what it really needs is to have the copper fouling removed from the bore. This is a tedious job, but the reward is a "like-new" barrel.

I have no idea if this stuff is true, I just copied it off the internet.

None of which "applies" to question about Mini-14 which does not have the faster twist rate.

Troy's response, states what I thought when reading your post, Brohawk.

[red][b]Hot[/b][/red] loads contribute more to throat erosion than bullet weight, face it, burn the throat and re-chambering the barrel gets you a whole "new life" as barrel is rarely bad and accuracy returns, so dealer is full of it, as this can occur no matter the bullet weight.

Mike