6.5 Grendel vs. .243 Winchester - hmmm

The 6mm 95 SST is a flat base, the 6.5 123 is a boattail.

Newtosavage said:

so, can anyone answer why the heavier 129-grain SST has a lower BC than the 123-grain SST?

Click to expand...

The 129 is an older bullet, but a foundation bullet in the SST line, while the 123 is derived from the 120 Amax. So the difference is in the profiles - the design for one started as a controlled expansion, high velocity, hunting bullet design, the other started as a thin jacketed target bullet design which could be beefed up a little to produce a low velocity hunting bullet. It’s only sensical to expect a target bullet to have better aerodynamics than a hunting bullet, and we see it all of the time with different bullet brands, where two bullets of the same weight and dia don’t have the same BC. For example, Berger has 4 30cal 168’s all with different BC’s. Nosler 6.5mm 129 ABLR has a BC of .530, vs. the 130 AB’s BC of .488.

Evidence of a difference in profile for the two SST’s - besides the counterintuitive relationship between weight and BC - is in the lengths and BTO’s. The 129 SST is 1.322” long, with a .712” BTO, meaning the tip is .610”. The 123 SST is 1.248” long with a .660” BTO, meaning the tip is .588”. With a longer tip in favor of the 129, I expect the difference will be in a longer boattail in the 123. So lower weight retention and reduced penetration, traded for a higher BC.

Newtosavage said:

Outstanding explanation. I do appreciate that! I am very tempted to try the 129 SST out of my 6.5 Grendel, just for a little better penetration and possibly less meat damage on deer.

Click to expand...

How fast are you running your 123s?

I shot a few axis with 123amax launching at 2500ish and found 100yd penetration excellent, but lacking the explosive expansion I was hoping for.
The 100gr balistic tips had devestating effect on 40lb-60lb goats, but didn't seem to be blowing up even at shorter range and a launch velocity around 2700.

I’d ask the same question about launch velocity. I had pretty violent expansion with 123 ELD-M’s in the buck pictured above, but my bloodshot meat was less than a baseball size diameter on both sides. Definitely not what I would call “meat damage,” and I certainly wouldn’t want any less expansion than I got with him.

Your running about 50-60fps faster than I was, I think (I'm remembering 2480-2490). I wonder if the old 123amax we're harder than the sst, doesn't seem likely, but I wonder.

Yeah, makes sense
I was running mine from an AR with a 20, 31.5gr of cfe223, and coal of 2.34.
Same load from my 24" clocked just under 2700 (again I THINK, I'd have to check my records), but it was a much better barrel.

8208 has been hands down the best powder I have found for Grendel’s.

I got two slugs back last year which looked just like this, wanna say there’s 80-something grains left there. These are ELD-m’s, which were the same bullet as the A-max in the 123, but with the heat tolerant tip. Short shots and violent expansion, but not much meat damage - about as little damage as I would want to have without risking a long tracking job. Less meat damage than shooting a Rage Chisel Point 125grn.

Newtosavage said:

How was the accuracy on that CFE 223? I'm tempted to try it.

Click to expand...

Bout 1 moa with 123s in the 20. .5-.75 in the 24....again I THINK.

I tried 8208 in the 24 only, and from my limited experience it shot basically the same as cfe, but I only had enough for 30rnds or so. No Chrono, only one middling charge weight.

I'm not knocking any of the new and improved stuff but the .243, IIRC, introduced in 1955, has always been just fine for me. I've started a half dozen of my church kids on it for Missouri deer and none have changed. Wish I could use it here. PR OF IL.

It doesn’t need to be better, if it’s as good as or nearly as good as, that’s a good thing right?

My father in law had a really rough time with me hunting with a 7.62x39 AR15 this year. Just kept saying his 270 has always done him well and shaking his head. I just shrugged and said so have all my other bolt rifles as well but I like to try new things. Funny thing is he shoots the same 125 nosler bullet from his 30 herrett pistol as I load for my 7.62x39, only his contender is softball loaded to 2000 FPS and my AR15 gets them to 2620, but he is confident in the power of his 30 herrett and frowns on mine.

The whole purpose of the 6.5 grendel is to shoot it out of a standard AR lower. You sure cannot do that with a 243 so I don't really see the purpose of comparing the two. If you are looking at bolt actions there isn't much reason to look at 6.5 grendel , 6.8 SPC, 300 BLK or any of the other rounds designed to shoot out of a standard AR lower.

MAKster said:

The whole purpose of the 6.5 grendel is to shoot it out of a standard AR lower. You sure cannot do that with a 243 so I don't really see the purpose of comparing the two.

Click to expand...

Part of the purpose shows getting similar down range ballistic performance from a lighter platform in regard to ARs.

MAKster said:

The whole purpose of the 6.5 grendel is to shoot it out of a standard AR lower. You sure cannot do that with a 243 so I don't really see the purpose of comparing the two. If you are looking at bolt actions there isn't much reason to look at 6.5 grendel , 6.8 SPC, 300 BLK or any of the other rounds designed to shoot out of a standard AR lower.

Click to expand...

The two things that make these intermediate rounds interesting to me is the AR15 and their potential for youth or recoil adverse people, but if they are effective and people like them for other reasons more power to them. A year ago this would have been below my comfort threshold for deer, but after giving it a try I was surprised that there wasn’t that much difference in on game performance than rounds that have 2 or 3 times the recoil.

Newtosavage said:

people really need to look at the data and not just the caliber. The level of "ballistic ignorance" is almost intolerable at times.

Click to expand...

This sparks two thoughts from me:

1) I totally agree, when the data is apt and the comparison isn’t stark. Like @someguy2800 ’s anecdote about his father in law’s bias against a cartridge, ignoring his own experience simply because he didn’t only considered the context of rifles. Similarly, I personally poo-poo threads where anyone holds up the old 500ft.lbs. for deer, 1,000 for elk crap. Are they seriously saying a 357mag with the muzzle held to the body of an elk isn’t effective (less than 1,000ft.lbs.)? Folks forget the things they know when they get tunnel vision in specific contexts. Search any forum for “what rifle for elk?” then “what revolver for elk?” - or deer for that matter. You’ll see folks bashing 223 for deer, 243win for elk, but then upholding 357mag for either... It’s almost a willing ignorance - they often know about both and would recommend something contrary to their own advice without realizing it, in a different context.

2) Certain data can be incredibly misleading when the comparison is stark. When you’re talking about a 243win and a 6.5 grendel, there isn’t THAT much difference in parameters to make KE totally meaningless. But the guys who try too hard to examine data only will get mislead by big KE numbers in many cartridges. For example - the famous comparison of (trapdoor friendly) 45-70’s and 243’s. If you ignore momentum, bullet diameter, and SD, only focusing on KE, they look very similar, but on-game performance for the two are VERY different. Kinetic Energy alone doesn’t reconcile the difference, but it IS the basis of many arguments (and online threads) as guys try to explain performance through data. Context is important here to determine which comparison should be apt. 98 is better than 93 in a heaviest pumpkin contest, but the reverse is true in a round of golf.

3) I know I said only two thoughts, but here’s a bonus which itched the back of my brain as I was typing - factory ammo or reloading manual data may not accurately represent the potential for a given round. This thread is an example - many factory loads in 243win are loaded either with light bullets, or short profile heavy bullets - both with poor BC’s. This is in deference to factory rifles with slow twists. The round itself, however, given an appropriate barrel twist, is capable of much more than the milquetoast Hornady factory loads might suggest, as a 243win can push a 105/108 well over 3,000fps. No idea here why Hornady is loading so slow with some of their bullets in 243win. Factory ammo and SAAMI compliant reloading data for older cartridges do not well represent the capabilities of the rounds in modern actions - for example, the 6.5x55 or 7x57 mausers, or the 45-70. Ruger revolvers can be loaded with the rounds seated long, allowing greater charges to be loaded at below book max pressures, but far exceeding book maximum velocities. Many 454 casull factory loads are only loaded to around 50,000psi, about 25% below the SAAMI ceiling for the round - so then we see well-meaning but under-informed guys point at ammo specs on midway and claim a hot buffalo bore load in 44mag almost matches low pressure Hornady 454casull rounds, so buying a 454 is pointless... Equally, you might see guys look at data for a 24” 223rem then drastically over-estimate the capabilities of their 16” carbine.

As a data hound myself, I prefer all shooters/hunters/reloaders understand the data behind their rounds, but I also caution, “garbage in, garbage out.” Sometimes, applying the wrong calculus is the garbage.

Varminterror said:

Factory ammo and SAAMI compliant reloading data for older cartridges do not well represent the capabilities of the rounds in modern actions - for example, the 6.5x55 or 7x57 mausers, or the 45-70. Ruger revolvers can be loaded with the rounds seated long, allowing greater charges to be loaded at below book max pressures, but far exceeding book maximum velocities.

Click to expand...

This.

I really think ft lbs of energy is a pretty meaningless number. The important factory for me in a hunting round is how big of a perminant wound cavity the bullet makes. To get that you need to have a decently large projectile destroying tissue all the way through and get a large exit wound to provide a blood trail.

Big bore rifles and revolver rounds accomplish this by having a big bullet diameter to start with and a lot of momentum to get penetration.

A small diameter rifle does it by having an expanding bullet to gain diameter after impact so that it can destroy tissue rather than just push it out of the way. So for a small bore rifle you need to have a bullet than expands properly and will hold up, enough velocity to get the bullet to work, and enough weight behind it to get tissue destruction all the way out the other side.

The bullets we have now work great over a very wide velocity range and retain there velocity through BC, so you can get very good terminal effect with less initial energy at the muzzle.

Newtosavage said:

I’ve always liked slower, heavier bullets for hunting. Better chance of two holes and less meat damage ime

Click to expand...

I agree, I will typically chose weight over speed.