Merits of 7mm Rem Mag Vs 338 Win Mag for long range Elk/Moose/Bear cartridge?
- Thread starter Northern Shooter
- Start date
So .338 210’s at .263 sd vs 7mm 160-165’s .283-292 sd. I don’t know initial velocity or the bc to calculate at 200-400 yard impact velocities to compare further but if similar bullet constructions and impact velocities the 7mm is going deeper. It’s a subjective trial and error on which bullets in which cartridges give us that short recovery love for game intended. The examples are all over the cartridge spectrum and the pattern of formula is the same on all the best ones if you reduce it to the numbers. The amount of powder burned can vary wildly to hit that formula with the better proven bullet choices. Too tough a billet with very high sd needs warp speed to try and get the front end to open up wildly and do that quick knock down internal work we like...you can mimic it with slower less tough bullets with less sd. It’s a 16-30” window of penetration you’re typically trying to have the bullet do the most work possible. What bullets were these 210 and 160-165’s? The 210 with less sd and lighter construction slowed down could be the winner despite thinking it may have been the higher insurance deeper penetrating bear medicine? Hitting your faster recovery goals accidentally? Happens a lot in this mostly subjective subject.
Math I did on that was 2000 fps impact. He was nearing the end of the barnes window, bullet exited...from a .270 win 130 gr on a big bull elk at 560. Marinate on that for a second. It had majority of its sd for sure (started with .242) and guessing just baby pedals at the tip. Perfect example to know in terminal ballistics discussion. That set up was perfectly matched to what was left in formula and the last hold on the reticle, no fat. Also the nut behind the wheel knew how to drive.
The .270 win is a 600 yard cartridge with most decent bullets in 130-150 range, my fav 20th century cartridge. The 6.5 cm with 140’s is also a 600 yard cartridge just burns a dozen less grains of powder and fits in a short action, what the 21st century brought us, to me it’s the 21st century equivalent to the 270 win. I’ve decided 400 is far enough for me now so I basically shoot 0-400 what the 270 does from 200-600.
It’s such a great example to show the sd, impact velocity and construction formula for game intended.
Yes they sure will, on this we agree. Mpbrz = Wisest. Everything else...less wise lol. Will start calling it Rman Logic.
We shoot variable sd bullets. We don’t measure it yet but we could.
Let’s look at your elk.
Had you recovered that barnes under offside hide it would have looked like typical barnes around that impact threshold. Like 99.8% weight retention just the tip gone. So let’s say 129 grains and let’s say the tip pedals opened up to .284 diameter. Sd being frontal area x mass = penetration. So you started with .242 sd, then ended with .228 sd. Nearly a solid as it barely changed and that we now know from your example is enough to go through a bull elk. You started with under the typical rule of thumb .25 for elk size game but because you kept nearly all of it with that 2000 fps impact you were able to clear the whole beast, you probably could have caught it with your bare hand on the other side as you were pushing it right to the edge in your example.
Inversely had that been a 130 gr ballistic tip hitting at same velocity and it lost 40% of its weight and expanded its front area at same time to .5”....finished sd somewhere around .045. You would have hypothetically found that bullet going half the distance through the elk in this example. Your placement was perfect so it could have worked but the lighter the sd you go for game intended the more attention needs to be paid to construction and impact velocities to ensure you keep as much of it as possible to get the penetration you need for that critter class.
Because we’re not measuring these things yet and have the charts on the box or built into the ballistics calculators but one day we will standardize measuring the final bullets, their sd reduction rates and will be able to choose bullets all over the spectrum of calibers and cartridges to do the work we like to see done. In the meantime we have to visualize the relationship of starting sd, construction type(how much sd it will retain) and velocity, for game intended.
I wouldn't wanna try it on any lighter game, any slower I sure admit that lol. Thats definitely a big stout animal that offers a lot of resistance to a bullet that is as you said, at the point its becoming unpredictable.
The LRX in said caliber looks sweet.
What you're saying about SD of a fired bullet makes sense to me. Bigger expansion/more weight lost, great deer bullet, or for kills on broadside big game, will be quick. Big wound profile. Makes for a low SD bullet (low remaining weight, wide frontal area) and thus penetration suffers.
Wanna shoot through more animal to count on reaching the vitals, you're gonna need one of tougher construction, thus opening less and losing more weight (to some combination thereof) offering a smaller surface area multiplied by higher remaining weight and squared.
Or, for the last several decades get you one that does both...A Partition lol. Many more options these days
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Got any recovered bullets? Grab your grains scale and your callipers and you can measure yourself.
https://www.vcalc.com/wiki/sectional-density
No, it’s just the most accurate guideline we currently have to start our selection process of what will work for our goals intended as hunters. We’re just late to the party on this as compared to in-flight ballistics and all the objective info we have there.
So grab a collection of recovered bullets, weigh them and calliper them and and you can really math things out if you remember impact velocity etc and can come up with how many inches of critter you went through, how much SD per inch was lost, equally to that how much energy transferred per inch into beast.
Just because we’re not measuring this stuff yet doesn’t mean we’re not going to or that the data isn’t there. It is. Just measure a recovered bullet and you’ll see it’s different than the starting bullet. Discussions will go so much easier once we start looking at the right data. ��
The problem is, none of them end up the same. Case in point. I have a fairly large collection of recovered bullets actually. Here are just the TSX/TTSX/LRX portion of that collection. Again, gathering this data is anecdotal. You can use it but let’s make sure we understand that we don’t have anything that is definitive on this.
Pick an appropriate bullet for the job… and put it in the right place. Good things will happen. It really shouldn’t take a bunch of nearding out on useless math to figure it out. What bullet is the right one? Pick one… they all work… put in the right place.
More practise shooting, will accomplish far more than math practice, to ensure the end result desired.
Just sayin’
R.
More practise shooting, will accomplish far more than math practice, to ensure the end result desired.
Just sayin’
R.
Yeah, thoroughly understanding stuff sucks. But, that IS true 
BTW, Rman, sorry I never got back to you on the McM stock. Ended up not building on a long action Rem 700 after all...but man I can't believe that hasn't sold yet. Its a smoking deal.
BTW, Rman, sorry I never got back to you on the McM stock. Ended up not building on a long action Rem 700 after all...but man I can't believe that hasn't sold yet. Its a smoking deal.
Data is the exact opposite of "anecdotal".
Trends may well emerge...Like that the ones which opened less went deeper than those of similar weight that opened more?
You are overthinking it. As is blakeyboy.
Over understanding stuff, is useless...
Do you really think, at the distances you shoot at, knowing the SD of bullet pulled from a dead critter is useful information? Or at any distance, for that matter?
R.
