When considering monometals the 150gr has proved itself to be totally adequate in 30-06 and 308W. My son used 150gr GS Custom in a 308W for a clean pass through shot on a wildebeest. I used 150gr GMX on a large boar with my 30-06. Yet, the Barnes folks recommended 180gr for my 308 Norma Mag. I thought this odd. Especially as Cutting Edge Bullets recommended their 145gr ESP (149gr w/ the tip) for moose, bear and deer in that caliber.
I am thinking the same must hold true for modern lead core bullets. With close to 100% weight retention typical with some, me thinks any 30cal can drop to a lower weight.
Maybe the way the bullets expand contributes to the need for a higher weight? The Barnes folks certainly know their stuff, so who m I to question the recommendation. Perhaps the way lead/Barnes expands has a higher drag effect? The GS Customs and CEB both form that blunt wadcutter shape which they claim creates a larger permanent wound channel. But, even considering this, I just dont think 180gr is needed for any application that a 30 cal is useful for. So, why do we still use it when loading modern bullets? It would seem 150gr is the way to go, maybe 165gr for a higher BC?
I think we may have already undergone a weight reduction with the bonded and or structurally enhanced bullet designs. Hang with me...
Regular cup & core bullets work well in the heavier weights. Why? I believe the heavy for weight cup & core bullets keep the velocity in a region where a standard bullets performs best, say 2200 -2700 fps. These bullets tend to hold together at these velocities, drive deep due to the high sectional density, even if they lose a portion of the bullet. Let’s say a 200 gr bullet out of an 30-06. But out of a 300 xyz Magnum, these heavy bullets can be driven above 2800 fps and out of the working velocity range, especially if a shot is taken at close range. John Nosler brought out the Partition bullet to ensure enough penetration on tough higher impact velocity shots and the trend in lighter bullets began.
The newer bonded and or structurally enhanced lead core bullets hold together much better and tend not to lose as much weight as a standard cup & core. Hunters recognized these tougher bullets hold together at higher velocities and can extend the field range. Probably the most popular weight for larger game in 30 cal is the 180gr. There are some who still prefer the heavier 200gr bullets but you don’t see too many of these in hunting reports. The newer design bullets tend to shoot flatter, drive deep, mushroom in a smooth wide frontal area and do a great bit of damage. Many times the hide catches the bullet on the far side even on very heavy bullets like a Swift or Northfork due to the wide mushroom. With these new bullets we have dropped weight from the old cup and core. I really like a 165gr Partition in the 30-06! The lighter bonded bullets can be driven fast but even the designers would say they have an upper limit and I would guess a 150 gr Accubond out of the 308 Norma at 3200fps would severely stress the bullet at close impact ranges and limit penetration.
The monometals bring in a new dynamic in a couple of ways. They are long for their length, a 165 gr Barnes/Peregrine/GMX is a very long bullet, These are as long as a 200gr cup and core (spritzers, round or flat nose tend to be shorter). The monometals like velocity to open quickly, it’s difficult to drive the very long monometals at high velocities in the standard cup and core weights and have enough velocity to initiate expansion at longer ranges where the velocity is around 2000 fps. Of course, bullet designers can adjust velocity performance by nose design, hollow point width and depth etc. As with your positive experience with 150gr GMX, I used 165gr Peregrine bullets extensively in Africa last year. Drove them completely through a Zebra and Waterbuck and every other animal I shot. I did catch one in a Zebra that was shot at a tad over 200 yards and a large Kudu angling away and through the shoulder. Fantastic performance as they expanded even on a slab sided Civet at close range without a gigantic hole.
So we have gone from 200gr cup and cores to 165 & 180 gr bonded / structurally enhanced bullets to the relatively lightweight 150/165gr monometals.
Can we shoot lower weight bonded bullets, say in the 150 gr range for heavier plains game? Probably, but you may end up giving away penetration on angling shots where you want to reach the vitals. If I was going to shoot lighter bullets, I would stay with the monometals and not risk the chance.
Why did Barnes recommend the 180 gr, good question. What velocity can you drive the 180 vs the 165gr? I’m only guessing here, but would think the 180 gr Barnes couldn’t be driven any faster than 2850 where the 165 gr should get you well over 3000 fps. Do they think the petals may come off at higher velocity during penetration, which may not be a bad thing! I would use the 165gr and drive them fast.
Could they have confused the 308 Norma Mag with the relatively new 300 Norma Mag? I would definitely use the 180gr in the big cased 300 Norma!
Just some ramblings on a Sunday morning,
Edge
