Do all the comparisons of the 6mm arc vs the grendel seem a little odd?

[greyling22]

I was out at the gun range today and was picking up brass and excitedly picked up a 6.5 Grendel, saw what I thought was another that turned out to be a 6 mm Arc. And it got me thinking about every review or thread I have read comparing these two cartridges. They talk about velocity and ballistic coefficient, but every single one compares a 123grn grendel to a 100-108 grain ARC, then talks about how much faster and better the arc is.

Does anybody know why they don't do a more apples to apples comparison and talk about a Grendel loaded with a lighter weight bullet? For example, the 90grn tnt? I mean I get why magazine riders are promoting a new product and they would for sure want to skew the results, but on a more basic forum level, seems like you get a better discussion. Instead folks regurgitate the same talking points from the biased magazines, or get defensive about "their" caliber.

 

[Varminterror]

I was out at the gun range today and was picking up brass and excitedly picked up a 6.5 Grendel, saw what I thought was another that turned out to be a 6 mm Arc. And it got me thinking about every review or thread I have read comparing these two cartridges. They talk about velocity and ballistic coefficient, but every single one compares a 123grn grendel to a 100-108 grain ARC, then talks about how much faster and better the arc is.

Does anybody know why they don't do a more apples to apples comparison and talk about a Grendel loaded with a lighter weight bullet? For example, the 90grn tnt? I mean I get why magazine riders are promoting a new product and they would for sure want to skew the results, but on a more basic forum level, seems like you get a better discussion. Instead folks regurgitate the same talking points from the biased magazines, or get defensive about "their" caliber.

Because “fast” doesn’t mean squat if you fly like a wiffleball…

The 6mm 110 A-Tip has a higher G7 BC than the 90grn TNT’s G1!!! Comparing just G1’s, the 110 is a .604, compared to the 90 TNT’s .281G1. One is a legitimate long range bullet, one is a short range varmint bullet.

So sure… you can increase your speed in a 6.5 Grendel by reducing bullet weight, but doing so is shooting yourself in the foot… Life at long range only gets worse when you swap a high BC bullet for a lighter, low BC bullet.

 

[David Hoback]

https://www.youtube.com/watch?v=GBchX_b8bTM
The comparison doesn’t seem odd at all.

Oh, and a lighter 6.5mm bullet isn’t used to compare, because it’s about bullet BC and SD; which has to die with weight & LENGTH being equally important.

 

[CapnMac]

Not really that strange. People compare all manner of dissimilar rounds all the time. Like .243 versus 7-08 or 270 or some such. Some of that is because more head-to-head comparisons, like .243 vs 25-06 vs 6.5x55 wind up going off the rails.
Part of it is in that there are so many choices in ammo out there. There's literally a caliber for everyone, and no one of those is better or worse except to the proponents and opponents of a given ammunition.

How many 6 to 7 mm rounds are out there right now? And we now have the .277fury to add to that mix?

 

[Varminterror]

Ask, and ye shall receive…

Here’s some insight as to why nobody talks about fast and light bullets in 6.5 Grendel vs. 6 ARC… because fast and light bullets suck for long range shooting…





There’s only 20-25% more drop for the 123grn 6.5 Grendel than the 6 ARC at 800 and 1000yrds, but the lightweight 90grn 6.5 Grendel load drops twice as much as 123grn 6.5, and around 2.5 times more than 6 ARC…

Fast and light only works until around 300 yards, but like I said originally - they fly like wiffleballs; high speed at first, but low efficiency in poor aerodynamics means they slow down really quickly, and that speed “advantage” at the muzzle evaporates and becomes speed loss…

Speed cannot outrun aerodynamics.

 

[troy fairweather]

I wonder what the 6 arc with a higher bc 85-95 grain would do compared to the 90is 6.5 think the 90 Berger 6mm target is like .409 g1 the heavier 6mms should win farther out but I'd think the 90 6mm would do ok. I'd bet a 85 6mm gets close to 3000fps with the 6arc.

 

[LoonWulf]

I wonder what the 6 arc with a higher bc 85-95 grain would do compared to the 90is 6.5 think the 90 Berger 6mm target is like .409 g1 the heavier 6mms should win farther out but I'd think the 90 6mm would do ok. I'd bet a 85 6mm gets close to 3000fps with the 6arc.

I used to shoot the 87gr Vmax at 2900ish 24" from my 6x47rem, 6arc should beat that by a bit.

 

[greyling22]

hey, thanks for the helpful charts! it's not going to pry the grendel from me, because I use it for hunting pigs and antelope at 1-300 yds, but the energy drop off on the 90grn tnt's is eye opening.

 

[troy fairweather]

I used to shoot the 87gr Vmax at 2900ish 24" from my 6x47rem, 6arc should beat that by a bit.

Can do a lot with that load.

 

[Varminterror]

I wonder what the 6 arc with a higher bc 85-95 grain would do compared to the 90is 6.5 think the 90 Berger 6mm target is like .409 g1 the heavier 6mms should win farther out but I'd think the 90 6mm would do ok. I'd bet a 85 6mm gets close to 3000fps with the 6arc.

It’ll get close enough in a long barreled gas gun to call it 3000, but probably not actually start with a “3.” Hodgdon data puts the 88’s at 2990 from a 24” at 51kpsi. Bolt gun data from Hornady clears 3000 with 85-90’s - using 24” barrel…

But for sake of discussion - a .400G1 at 3000fps yields:

800yrds 5.9 drop 2.0 drift in 10mph 1448fps
1000yrds 9.3 drop 2.7 drift in 10mph 1201fps

So a 85-90grn class 6mm bullet in the ARC case at 3000fps is almost identical on trajectory at 800, but still has more drop and more drift than the 108 load, and gives up almost 40% of the impact energy at 1000yrds… and we’re talking about 24” Hodgdon velocity data with the 85-90’s versus 18” Hornady velocity for the 108’s now, so the gap would be a little wider… not much, only around 125-150fps difference, but a wider gap all the same…

Speed cannot outrun aerodynamics…