A question of sectional density and conventional norms

[EastTNHunter]

So I’m getting antsy for season to start, and I’m beginning to muse on things that aren’t very important but occupy corners of my mind that get stored at this time of year.

I’ve gotten into several conversations over the years dealing with cup and core vs premium bonded vs monolithic bullets. Many were rational and levelheaded, while others were… goofy. But I have tended to believe that the differences in on-game performance was a matter of degrees, ie use a 308 150gr mono vs a 165gr premium bullet vs a 180gr cup and core. But I guess the question with monos is how light should you really go before it becomes detrimental to on-game performance?

This question came from reading threads about people using monos (TTSX, Hammer, etc) at blistering speeds that maintain 100% weight retention and require high velocity to open reliably. If conventional 270win bullet weight is 130-150gr, then monos should be able to go to 110-130gr. Well, could I also go lighter than that on elk-sized game and actually get better performance due to higher speed? If they maintain 100% then they will also main good penetration. How about using 110gr 308 at higher speed on elk?

I guess to sum up the questions for the mono advocates: Is SD even relevant with monos? Would you use a 110gr 308 mono bullet at 3200fps, or a 110 270 mono at 3200fps on an elk? How about a 95gr mono at 3400fps?

Come on hunting season

 

[VikingsGuy]

Lots of questions in there. I can't speak to the 110gr 308 but I can tell you my 130gn .270 has taken elk, and my 150gn .308 has taken elk, zebra, kudu, and onyx. None ran far, most didn't run at all. 130gn is the sweet spot for .270, and 150gn is the sweet spot for .308 caliber cartridges. Keep it simple.

 

[88man]

The biggest factor is shot placement> not bullet construction. Even though people tend to have different aim points with different bullets etc.

 

[EastTNHunter]

Main reason that I asked about 110gr 308 TTSX is because I use that for some youth loads out of the Savage 10 that my daughter hunts deer with. That lightish load (3050fps +\-) has accounted for a few deer with full pass throughs, and I was wondering how much I could lean into it on the speed. Usually use 125 NABs at around 2900fps for the youth loads. I’m WAY too much of a tinkerer

 

[noharleyyet]

You getting any sleep?

 

[Deleted member 28227]

Is SD even relevant with monos?

It is but copper and lead are different materials with different properties so assumptions about SD are going to change.

From a physics standpoint, I believe your thinking is correct. Higher speed will open up the bullet more, and therefore a lighter load may be better for expansion at range.

 

[rwc101]

lighter load may be better

Commie.

 

[BackofBeyond]

If you do much digging around on Hammer Bullets forum, there’s plenty of guys exploring the same hypothesis. Light bullets going very very fast.

Like 110 gr in a .300 RUM fast.

Not sure I’m ready to switch my elk load to it, but it is interesting.

 

[mtmuley]

If you do much digging around on Hammer Bullets forum, there’s plenty of guys exploring the same hypothesis. Light bullets going very very fast.

Like 110 gr in a .300 RUM fast.

Not sure I’m ready to switch my elk load to it, but it is interesting.

They are headed to Africa with a really diverse bunch of rifles and bullets. The light bullet fast thing is hard to wrap your head around at first. Can't argue with the results though. mtmuley

 

[brockel]

They are headed to Africa with a really diverse bunch of rifles and bullets. The light bullet fast thing is hard to wrap your head around at first. Can't argue with the results though. mtmuley

I’m debating on a 109 or 110 from the shorty 6.5 prc.

 

[mtmuley]

I’m debating on a 109 or 110 from the shorty 6.5 prc.

If I have time I'm gonna whip up a load for the 166 in my RUM to take antelope hunting. mtmuley

 

[shannerdrake]

If you do much digging around on Hammer Bullets forum, there’s plenty of guys exploring the same hypothesis. Light bullets going very very fast.

Like 110 gr in a .300 RUM fast.

Not sure I’m ready to switch my elk load to it, but it is interesting.

It’s like we have come full circle. When I was in college we were experimenting with pushing light for caliber bullets as fast as possible. Then the heavy for caliber craze hit and it was about ballistic advantage after X amount of yards.

To the original poster’s question, there are adherent sectional density advantages built into mono bullets as they are long for their weight. So you are correct, they do somewhat defy conventional wisdom. The pic below is worth a thousand words.

 

[std7mag]

Also, a Hammer isn't going to be 100% weight retention.

They are designed to shed their petals.

 

[Gunner46]

Yeah, I get 'cha. Most handloaders go through it. I wasted too much money and time going through the 'What If's". Finally got down to the realization the most every shot I took ended in a tag being punched, regardless of whether I was using what ever bullet design.

Bullet design only helps after you can make a practiced, properly placed shot, at whatever distance you're competent to shoot.

Me? I've settled on a moderate 140gr AB load out of my 7/08, because I Know I'll make a good hit.

Nothing has walked away from it.......

 

[mtmuley]

Also, a Hammer isn't going to be 100% weight retention.

They are designed to shed their petals.

There is a good conversation going on over at the Hammer site regarding twist, rotating speed of a bullet related to twist and stability factor and it's effect on terminal ballistics. Kinda geeky but pretty interesting. mtmuley

 

[std7mag]

Yeah, I get 'cha. Most handloaders go through it. I wasted too much money and time going through the 'What If's". Finally got down to the realization the most every shot I took ended in a tag being punched, regardless of whether I was using what ever bullet design.

Bullet design only helps after you can make a practiced, properly placed shot, at whatever distance you're competent to shoot.

Me? I've settled on a moderate 140gr AB load out of my 7/08, because I Know I'll make a good hit.

Nothing has walked away from it.......

Nutt'n wrong with that!

 

[antelopedundee]

For 6.5mm I like the 129-130 grain bullets so for monos I tend to stick with bullets in that weight class as long as they're compatible with the twist rate in my rifle barrel. Just because an 8 twist is preferred, it doesn't mean that the bullet will never work in a 9 twist barrel.

 

[std7mag]

For 6.5mm I like the 129-130 grain bullets so for monos I tend to stick with bullets in that weight class as long as they're compatible with the twist rate in my rifle barrel. Just because an 8 twist is preferred, it doesn't mean that the bullet will never work in a 9 twist barrel.

If you bring that up with Cutting Edge, they will flat out tell you if THEIR bullet says 1:8, then 1:9 won't stabilize it!

 

[antelopedundee]

If you bring that up with Cutting Edge, they will flat out tell you if THEIR bullet says 1:8, then 1:9 won't stabilize it!

I'm not claiming that to be universally true, but I have seen one bullet shoot as well [group-wise] from a 9 twist barrel as it does from an 8 twist barrel at 100 yards.

 

[buffybr]

Standard cup and core or partition type bullets lose a good portion of their weight (and energy) when they hit an animal, so the remaining bullet has that much less mass and energy driving deep into the animal. Mono copper bullets, like the Barnes, will retain all or almost all of their mass traveling through the animal.

For example, the 180 grain Partition bullets that I have recovered from elk that I shot have a recovered weight of around 110 grains. The recovered 168 grain TTSX bullet that I recovered from a bull elk had lost one petal (probably from when it shattered his upper front leg bone) and still weightd 157 Grains. Most of my recovered TSX/TTSX bullets maintained their origonal weight.

So my take on this is that if a traditional bullet that, will lose almost 40% of it's original weight, has enough retained weight and energy to kill an animal, a mono copper bullet which won't lose much of its original weight, can drop down a weight class or two, to the retained weight of the traditional bullet, and still have the same killing power of the heavier traditional bullet. Plus because the mono weighs less it can be shot faster and flatter.