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Discussion Starter · #1 ·
This is definitely n00b of me. In the past, I've always just picked up the moderately priced rounds, regardless of brand or quality. I have no idea how grains affect performance. Sad, huh?

Anyone mind posting up information about:

1.) General grain loads. HOW and WHY does different grain loads affect velocity, price, and performance?

2.) How about jackets? How do they affect performance?

3.) Bullet types. Hollowpoint, FMJ, Boat-tail, etc etc. Let's compile some good information.

Also, why is it that most gun manuals suggest using a high-grain load for the first couple hundred rounds? How does this affect the recoil spring, trigger, etc?

What ammo does everyone use for general plinking and/or target shooting?

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196 Posts
Grains listed on a box of ammo is the measurement of the wight of the bullet alone. 1gr = 1/7000th of a pound. The weight of the bullet can effect the speed of the bullet (usually the heavier the bullet the lower the fps) and can have an effect on the energy of the round upon impact on the target (heavier bullets carry more of their original muzzle energy for a longer period of time). Another time you will hear 'grains' used is in reference to the power in the ammunition. The more grains the more powder in most cases. This can have obvious effects on pressure, fps, and muzzle energy. It is very very rare to see the powder grains number listed on commercial ammo. It is usually reloaders that you will see refer to powder grains.


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767 Posts
Jacket is the cooper covering over the lead core
FMJ= full metal jacket, basically the copper jacket is formed then the lead is poured in from behind, leaving an exposed lead base...these are your basic round ball type ammo, feeds well and good for plinking,

JHP is an open tip jacket, the copper jacket is formed and the lead is poured in from the top, no exposed lead base and depending on design it will expand well, good for CCW and home protection

CMJ is similar to FMJ but with a cap on the base to prevent exposed lead

SWC.. semi wad cutter, different profile, good for target shooting because it makes nice clean hole and has a larger bearing surface to grip the rifling
doesn't feed as well as the above

boat tails are tapered at the end to improve aerodynamics

manufactures suggest +P inorder to help break in parts

I shot 230 grain FMJ .45acp over 3.8 grains of Clays powder. with overall length of 1.26" is goes about 690 fps
4.0 grains of clay with shoot 730fps
but if I go with 200 grain swc, I need about 4.2 grain of clay to make 730fps. In IPSC shooting you need to make a power factor, which is bullet grain x fps / 1000, so the lighter the bullet the faster I need o move it

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132 Posts
another thing i learned during the famour 2005/2006 kalifornia AR lower land rush, is that the twist in the barrel corresponds to the weight of the bullet.

for example, on a 1 in 9 twist, the lighter the bullet. sat in the 50-70 grains.

for a 1 in 7 twist, the heavier the bullet like over 70 grains is needed.

read it here:

good stuff there.
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