.223 Rem. bullet weights?

N

NINEX19

New member
This may sound like a bit of an elementary question, but I am just starting to learn about loading .223 Rem. I have lots of experience with many different pistol calibers and a few other rifle calibers, so I am not "new" to reloading.

Why does this round have so many weight differences that are often just 1-5 grains off each other? I can appreciate slightly different weights with different profiles, etc, but when you have FMJ that is only one grain off... whats the point? I am thinking specifically of the 62g vs the 63g that I was trying to work with last night. The few sources I was looking at had different powders for each. Why? I had a bunch of 62 grain, but only had the powders for the 63g. The OAL was .002 difference from each other (if I remember correctly).
 
It's because powder charge does not depend on bullet weight alone. Indeed, M.L. McPherson and another fellow fired a bunch of different make 150 grain bullets in .270 Winchester using the same cases and primers and powder charge and measured almost 33% pressure variation. This is due to differences in bullet construction and length. Harder bullets (thicker jackets, solids, bronze or brass bullets) affecting how high the start pressure gets pushing the bullet through the throat to engrave it with the lands, raise pressure. Also, longer bullets raise pressure because they subtract from the amount of space the powder starts burning in.
 
You don't necessarily need a new powder for a different bullet in a slightly different weight. I use H335 for 40 gr, 55 gr, and 65 gr bullets. And I could probably get excellent results for those bullets with 6 or 8 other powders.

As for why there are so many bullet weights, I think that probably developed over time due to changes in twist rate for military use. Then ya also have the match bullets for slow twist, and match bullets for fast twist, and match bullets for very long range competition. And on and on....

This particular cartridge has seen some really extreme changes over time.
 
I think he was asking why there are so many that are very close to one another, and I didn't really address that. One answer is that 0.224" bullets now fit U.S. military rifles and have been around since near the turn of the 19th century so that everyone who thinks they have an idea for a better bullet in this diameter has tried to design it, and a large number have become popular. The same thing happened with .308" bullets. Look around and you'll find the selection available is much larger than for 7 mm and 6.5 mm. It's just an artifact of calibers adopted by our military coming to be widely adopted by civilians, even if not always in the same style guns. Cheap surplus ammo and components is one reason.

As designs are executed, weight is probably not an exact target for the bullet designer as much as an approximate one, though having a slightly different weight may help marketing differentiate it a little. But I don't think that gets much emphasis, as lots of same-weight designs are out there. I suspect it is more often the details of the bullet design and its purpose that wind up dictating the exact weight it has in the end. For example, Sierra has a 52 grain boattail MatchKing and a 53 grain flat base MatchKing. Well, flat bases are easier to get accuracy out of, especially when muzzle blast is high, as happens with shorter barrels. One of the intended purposes for the 53 grain MatchKing is handguns chambered in .223, which have short barrels and lower muzzle velocities, which explains bothering to design it at all. But flat base bullets don't have equal BC's for longer ranges, so the designer (and these bullets were designed decades apart) probably tried to cut down the BC disadvantage by putting a longer, larger radius ogive on the flat base design. But because it is fractionally longer, adding a grain to the weight helps not only the BC, but helps keep the stability factor good at standard rifling twist rates found in the guns it's meant for.
 
I suspect that in addition to hat listed above some differences are just brand specific i.e. 68 or 69 grain match bullets. Also would be surprised if there wasnt some design on the shape, length profile etc and then it weighed what it weighs. Most of the .224 bullets are made to be able to fit into an AR mag, with the exception of the big long rascals.
 
As mentioned above the shape of the bullet makes a big diffrence as well as the bullet composition. The more bearing surface a bullet has the faster you will see pressure signs vs the same weight bullet but in a profile that has less bearing surface.
 
With a small bore, the amount of weight difference can't be as big as something like a 30 caliber. Consider the differences as percentages rather than grains of bullet weight. A .308 bullet commonly runs from 110 to 220 grains (2X) and .224 bullets run from 35-40 to 75-80 grains (also 2X). Using this idea, 1 grain in a .224 is approximately 3 grains on a .308 bullet.
 
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