XD Talk

deapee · 10-18-2006, 10:53 PM

OK...excuse my ignorance for a few minutes here.

When I first purchased my 9mm service, I asked the guy what some good defensive ammunition would be. He recommended the Speer Gold Dot 147gr hollow tips. So I bought a box of 20. I figure'd I'd get another box and fire them all off just to make sure they feel good and work in my gun. They work fine.

Anyway, I figured I'd pick up another box today to load up my sub compact with also and have a few extras laying around and I noticed that there are 147gr and 115gr.

I realize the 147's weigh more, but which is better for defense ammunition, should the need arise?

Common sense would say that the heavier the projectile, the more it will penetrate and the further it will go (being that the air resistance will have less of an effect in slowing it down). I'm assuming that maybe the 115gr's will expand more upon impact?

Anyway, thanks for your time.

TwoValveKid · 10-18-2006, 11:06 PM

Its mostly about energy. Which one will have the greater energy and expansion?

Yes a heavier bullet will, in theory, the heavier will go further, but it also is not flying as fast as a lighter bullet.

**XDAndMe** · 10-18-2006, 11:12 PM

Quote:

Originally Posted by deapee

Common sense would say that the heavier the projectile, the more it will penetrate and the further it will go (being that the air resistance will have less of an effect in slowing it down).

It may be true, but not necessarily. Yes, a heavier bullet will have more resistance to slowing down, but it will also have less initial energy because it's slower. If the two bullets both left the gun at exactly the same speed, then yes, the heavier one would theoretically always get further.

Look at the ballistics figures for both. The resistance to change in velocity (inertia) is related to momentum. The higher the momentum, the more penetration (assuming bullet size/shape is constant). Momentum is a function of mass and velocity (p = m * v). Whichever has the higher momentum should theoretically be the deeper penetrating round, all other factors ignored. In practice though, there will be other external factors that play into the equation which might throw off the result a bit.

**Old School** · 10-18-2006, 11:18 PM

All I know is, 115gr bullets seems to be much snapier than 147gr bullets, which is why I prefer to shoot heavier bullets in 9mm and 45ACP. Perhaps the 147gr are less snappy because they take less energy to get them up to speed? Hell, I don't know. Now I need a Tylenol.

TwoValveKid · 10-18-2006, 11:20 PM

I may be confused...but that statement contradicted itself OS...lol

deapee · 10-18-2006, 11:24 PM

So in either case, the 147gr and the 115gr are good defense ammo in hollow tip? I mean basically it's personaly belief or opinion that is going to lead one person to buy one over the other?

The Knight Of Light · 10-18-2006, 11:29 PM

The 147 from Speer has shown poor expansion in test media from 4 in barreled guns. The Federal 147HST bullet has shown to be the top in 9mm as far as expansion goes. Through some research and talking with a Firearms instructor from the Seward, AK PD I have changed over to the Federal HST because the Speer Gold dot was originally designed for winshields and shooting through auto glass. The HST bullet has taken the market for defensive ammunition. This is a .45 HST expanded in test media.

Note: this is a .45 but the 9mm is very similar.

http://www.le.atk.com/pdf/HSTPoliceADLO05lr.pdf
http://www.le.atk.com/pdf/San.pdf
http://www.le.atk.com/pdf/PortlandReport.pdf

The Knight Of Light · 10-18-2006, 11:30 PM

Quote:

Originally Posted by deapee

So in either case, the 147gr and the 115gr are good defense ammo in hollow tip? I mean basically it's personaly belief or opinion that is going to lead one person to buy one over the other?

You should always do good research for your defensive ammo choices. Test and retest.

**Old School** · 10-18-2006, 11:33 PM

Quote:

Originally Posted by TwoValveKid

I may be confused...but that statement contradicted itself OS...lol

To clarify...

115gr bullets are snappier, meaning more felt recoil, IMHO. Because the heavier bullet is less snappy, less felt recoil.
Lighter bullets take more to get them up to velocity, hence the snappier feel.

I know, I am confused too. I just know it works and that I am going to bed now.

**XDAndMe** · 10-18-2006, 11:33 PM

Quote:

Originally Posted by Old School

Perhaps the 147gr are less snappy because they take less energy to get them up to speed?

They need more. The only reason lighter bullets are more snappy is because they have a higher energy leaving the muzzle, and so there will be a greater reaction force pushing back at you.

I'll use CCI Blazer FMJ as a reference. The 115 gr. loads have a muzzle velocity of 1,145 fps and an energy of 335 ft-lbs. The 147 gr. loads have a muzzle velocity of 985 fps and an energy of 317 ft-lbs.

335 > 317, so clearly the lighter loads will "kick" more. It makes sense because force is equal to the rate of change in momentum over time (F = dp/dt = d(m*v)/dt = m*d(v)/d(t) = m*a).