What's Wrong With .30 Caliber? By Bryan Litz

[LR3]

Bryan, one comment and one question: one of the arguements for 6mmBR is that the amount of powder and size of chamber allows for more consistent velocities and therefore more precision since the SD for velocity is tighter hence greater accuracy with repeated shots. While this maybe more of a factor for 338 and 375 magnums, this may not be as important in the comparison with 30 based cases. Hence the importance of hand loading consistency - any comment?

With your military background, how does the ballistic performance of large shell such as 105mm etc or even larger rounds compare with 30 cal and since the research is possibly more advanced, how do the exteme calibers inform our understanding? Do the large military rounds follow the exact same ballistic laws as our 30 cal rounds, since this may add to our understanding of the differences between the calibers.

Great article and very informative.

 

[BryanLitz]

LR3,
I'm not sure what you're asking re: 6mm br and larger cases, but I'll comment anyway!
What you may have been getting at is how much vertical dispersion a small caliber will have from a given muzzle velocity variation compared to a larger caliber.

Consider the 6mmBR shooting 105VLD's at 2800 fps. At 1000 yards, a 20 fps variation in muzzle velocity will cause the vertical impact to shift by 5.5".

A .300 Win Mag shooting 210's at 2800 fps will have 5.0" shift in vertical POI from a 20 fps variation in muzzle velocity.

The comparison favors the higher BC round, but only slightly. In order to achieve the 5.0" of vertical spread, the 6mmBR would have to cut the muzzle velocity variation from 20 fps to 18.7 fps. In real life the 6mmBR would probably be capable of much lower velocity ES than a larger magnum, so the actual results would probably favor the 6mmBR.

In general, higher BC bullets will be less sensitive to all variables (including muzzle velocity variation) than lower BC bullets. This isn't a caliber specific statement, but is a general trend.

As for military munitions, they certainly obey the same physics as our small arms stuff, but they push against different corners of the envelope. An artillery shell is mechanised with moving parts, fuses, threads, etc. It's a nightmare to make something like that balanced. One of the biggest challenges in artillery shell design is making sure the round will trace when fired at high angles of elevation. Depending on the stability characteristics, the round may not be able to trace. If it doesn't, it will fall short of the target and fail to fuse (probably a good thing for the friendlies that sometimes occupy the ground short of the target)
Modern systems are being outfitted with GPS guidance which changes everything.

It may be a surprise that many large scale cannons (20-30mm) have a certain level of dispersion built in to them intentionally to give a shotgun effect. If you're trying to gun someone down in an air-to-air engagement, you don't necessarily want to be shooting small groups. The dispersion is controlled with the bore diameter. The rounds are generally steel body with bronze or plastic rotating bands. The rotating bands are quite narrow, and they engage the riflings while the body of the round augers down the tube. The specific clearance between the projectile body and the bore controls the dispersion quite predictably.

 

[Mysticplayer]

Small cal MG's also have that dispersion built either into the rifle or ammo.

Read an article on Mr. Browning back in the day. His MG's were too accurate for area surpression so they built in some wiggle to disperse the rds.

I tried some surplus powder a few years back and it shot really well at 100yds. I was getting 1/2 min accuracy in my hunting rifles.

However, at 500yds, 3 rds wouldn't all hit a piece of paper. Stunned, I switched powders (H4350) and voila, 1/2 min accuracy retained at LR.

I later found out that this surplus powder was a pull down for 308 machine gun ammo. Maybe the powder was designed to give very irratic SD's which would lead to a whole lot of dispersion the further you got.

When is Berger going to make GPS bullets? Or at least fly by wire?

Jerry

 

[Kevin Thomas]

Jerry,
Not to intrude on Bryan's thread here, but I'll hazard a guess that there was some other issue (perhaps improper storage at some point, etc.) with that powder that lead to the inaccuracy problems you noted or more likely, that it just wasn't a suitable propellant. You didn't mention the cartridge, but the surplus powder would have been something in the burning range of 4895, WC846, etc.. Considering that 4350 is significantly slower, it was probably just an issue of one powder being better suited to this application than the other. There's never been a powder designed to give large SDs, at least that I've ever heard about. The military does deliberately increase dispersion for some types of weapon systems, but there are other (better) ways of doing this as he so aptly described. Seems counter intuitive for a bunch of guys on a long range precision forum, but picture using a "Turkey Extra Full" choke tube on a covey of fast-rising quail at close range, and you'll get the picture.

Excellent thread, terrific article and some very good questions!

Kevin Thomas (the new guy)
Berger Bullets

 

[yobuck]

ww2 surplus military powder is what started the hodgden company in business.
purchased in huge quanities, stored in rail cars in dry locations, then packaged and sold to consumers.
i have been using h 570 powder for decades. im of the opinion this was a machine gun powder.
remember there were very few suitable powders for the large wildcat cartridges some were using. surplus machine gun powder was and still is in use.
ive found none of the problems mentioned here.

 

[Kevin Thomas]

Yobuck,
just a suggestion here on my part based on limited info. The suitability issue stands, though. Bruce Hodgdon did indeed play a significant role in launching the handloading industry we enjoy today, but powders still need to be selected carefully and matched to the task at hand.

As far as the storage issue goes, I've known several guys who were still using huge drums of powder in the early '80s, that they'd purchased from Bruce shortly after the war. I believe Jim Huill still had some of this on hand when he retired and it was still perfectly good. I've seen powders stored under all sorts of conditions with nary a problem, but I've also seen some deteriorate. Always worth mentioning and checking.

Kevin Thomas
Berger Bullets

 

[yobuck]

kevin.
certainly would agree on the proper suitability of powder for a given cartridge. fact is though the powder i referred to was and still is suitable for the 30x378 i use it in.
25 or 30 years ago there were only 2 powders that were suitable to my knowledge. those being h570 and h870.
it goes without saying all powder should be properly stored, and even then its possible for it to go bad.
my point was however that myself or no one i know has experienced the accuracy problem cited as existing with machine gun powder.

 

[Kevin Thomas]

Hey guys,

Actually, the use of the G1 drag model IS an attempt to standardize BCs within the industry. As Bryan has so aptly described, it's far from the ideal for most of the bullets we use. It is, however, something that everyone can relate to; you can check a Hornady against a Speer against a Sierra against a Berger, and they're all speaking the same language. This became normal practice way back in the late 40s early 50s when ED Lowery developed the G series of drag models. At that time, about the only folks discussing BCs were ballisticians. Stop and think back about the blank stare you'd have gotten even 10-15 years ago trying to discuss it with fellow shooters. Since they went "mainstream" the adherence to the G1 is merely an attempt to keep it simple, if you will.

As far as determining BCs, there's another kettle of fish. Problem is, many manufacturers don't have the facilities for determining an accurate BC. Over the years, you'd be flabbergasted to learn how someof those BCs were derived. Ever heard of the Coxe/Beuglass tables? They're listed in Hatcher's Notebook, if you want to see them and read about how they're used. Essentially, it involves visually holding a bullet up against an increasing series of ogival outlines and figuring out which "matched." From there, you had the values for a series of equations for the ogive, the meplat diameter, the boat tail, etc., that would give you a "BC" as gthe end result. Needless to say, the results could be off substantially. Hate to tell you how recently that method wasused by even some big industry names. Doing actual Time of Flight firing, or Doppler Radar testing are the only real way to determine the values, and that takes time, effort and money. The industry is getting there, more by the increasing sophistication of today's shooters than anything else. It's still a long road, but we've come a long way.

Hope this clears up a question or two?

Kevin Thomas
Berger Bullets

 

[yobuck]

kevin thomas.
i dont agree with your blank stare comment regarding bullet bc 10 or 15 years ago. many of us understood the significence of bc long before that.
at least in pa. where im from, that was certainly the case among the long range shooting/hunting community.
i think it would be more accurate to say that due to the rather recent snowballing of those activities, more people are becoming aware of those terms.
certainly more interest is being shown due to increased numbers of participents.
frankly most hunters i know never hung their hat on any advertised statistics. those might cause the sale of a box for testing on the range and mountainside. finally on actual performance on game.
i could be wrong, but it appears to me the newer generation is more statisticly oriented. decisions seem to be made, based on computer generated facts.
now were finding not all those facts were facts at all?
weve all heard the expression sex sells.
could it be bc sells also?

 

[RemingtonMagnum]

i like .30 cal

 

[rossi]

This is a thread for discussion of the article, What's Wrong With .30 Caliber? By Bryan Litz. Here you can ask questions or make comments about the article.

30 cal is good when wind is blowing I have I 308 3006 and 300wm
I favor 185gr lapua for longrange with 300wm my 3006 is my only rifle
shooting 3 168 match king making 1 hole at 100 yards but nowdays
with cost goin up it is good to have 6mmbr low recoil and low cost reloding
ultra accurate best so far is half inch at 300 yards trued rem action 1/8 tvist
kriger 27 inch barrel jevell trigger nightforce 8x32 br scope

 

[Eaglet]

Bryan Litz,

Great article, excellent writeup! Thank you!

 

[BountyHunter]

Brian

My question is why compare a 7mm VLD against two 30 cal non VLDs? That is not apples to apples, kind of indy car to mac truck. Big inherent advantage to the 7mm right off the bat.

Plus I have not heard of anyone getting any better barrel life out of the 7mms especially compared against the mag 30s. Throw the 300 WSM in the mix with 210 VLDs and whole new game especially on barrel life. 28-30" barrel and 2850 is the low end and 3000+ is the upper depending on your chamber and barrel and well over 2000 rds is the norm and 4000 rds with IBS winning gun in 2008, which as you know is 2-3x over many of the 7mms.

Recoil, OK, more mass on the bullet the higher the recoil. However, that is only a factor if shooting if shooting NRA LR or Fclass with high number of shots in short period. Non factor in LR hunting.

How does the 7mm VLD compare against say the JLK 210 LBT with its much higher BC (.680/690 BC?), especially at the higher MV of the big 30s?

BH

 

[BryanLitz]

BH,
Part of what I'm illustrating is that there are few very efficient designs in .30 cal (similar to the smaller caliber VLD's). The heavy .30 cal bullets (Sierra and Berger) are made with the same length ogive as the 155's, which is relatively short for a 200+ grain bullet.
One exception is the 208 Amax, which is has a much different (longer) ogive and boat tail than the lighter weight Amax's.

You have a good point about barrel life. It's usually better with the larger calibers, even the magnums when compared to smaller calibers. My point was that to achieve the velocity required to match ballistic performance of the heavy 7mm's, you need to load the .30's real hot (because the bullets aren't as good in .30 cal). Loading anything real hot will reduce barrel life, but it's being reduced from very long, to just acceptably long.

To be self-critical...
The biggest problem with my article being on this site is that kinetic energy, momentum, or any measure of lethality is not mentioned. The article was originally written for Precision Shooting Magazine, an audience primarily composed of target shooters. I didn't really give any thought to hunting applications where bullet weight and energy are important. This IS where the .30 caliber shines. Despite having less-than-optimal bullets, the big .30 caliber magnums carry a lot of energy and momentum due to their mass. It takes a very long distance for the external ballistic efficiency of something like a 7mm 180 VLD to 'catch up' to the energy of a .30 cal 210 VLD.

-Bryan