BC. How important is it?

P

Pond James Pond

New member
I ask this with mainly longer range shooting in mind.

I am not yet at a level where BC makes much difference, but as I develop loads I am trying to select the bullet-powder combinations now that will meet these needs later.

If I have a good long range load, even if I only use it to shoot 100-300m now, every shot will serve to make me more used to its performance and characteristics.

So that means making smart bullet choices now.

As some know I have been developing a load for my 155gr Amax.

However, as I understand it, longer range shooting would mean somewhat heavier bullets. So I am looking at 167-180gr bullets.

I also understand that Ballistic Coefficient will affect how well the bullet works further away. But how big a deal is it?

My Amax bullets are listed as .435 BC.
By contrast I can get a Hornady 168gr HPBT with a BC of .450 or a 180gr SST with a BC of .480.
Then there is the Lapua offering: the 167gr and 180gr Scenars at .446 and .482 BC respectively and then the impressive .498 of the 170gr Lockbase bullet! :eek:

So the Lockbase is most attractive: an impressive BC in .30 cal, and a lower weight meaning a smidge less recoil.

Here is the issue: comparing the Lockbase with the 180gr SST the Lapua is €10 per 100 more expensive. That adds up.

I know this is mostly down to me, but I want to put the BC difference in perspective. If the BC difference will make next to no discernible change in performance, it makes the choice easier. If it means a noticeable improvement in consistency/accuracy and a flatter flight that also carries a lot of value to me.

So, is the lower weight and .018 greater BC worth an extra €100 per 1000 rounds?
 
If I have a good long range load, even if I only use it to shoot 100-300m now, every shot will serve to make me more used to its performance and characteristics.
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At 300 meters, you're not going to see much of a difference between a 155 amx and a 175smk / 178 amax (bullets I have exp with), assuming all are loaded to a decent velocity for their weight. IMHO, the 155 amax is a great bullet at 300yds. Double that distance and any bullet fired from a 308 can be frustrating with even a mild wind (for me). For me, the benefit of higher bc is in less wind drift. I've spent enough time gathering data for my rifle to pretty accurately put a .308 bullet where it's supposed to be as far as drop is concerned. I could probably use another 10 years or so of practice on wind calls. If you stretch the distance beyond 400 or 500, give the 178 amax a try (if available in your area).
 
While it may all look good on paper/numbers, before you commit remember that each rifle sample may have it's own "preference" for certain loads/weights/lengths. This last moose season we had four different new 30-06s in our hunting group. Pre-season setting up scope/load development was eye opening in this department.

If your interest is in longer range accuracy, start playing with various bullets and loads at shorter ranges. The differences seen at 100 yards/meters will only magnify at the longer ranges; as a general rule. (Not taking wind into consideration.) Obviously if you goal is further out there you want to experiment with loads with that in mind.

Looking at bullet choices with higher BC can only help, except when it degrades accuracy. Also whether or not you are planning on hunting or just making holes in paper makes a difference in bullet selection.

Personally I enjoy loading and shooting 110 -220 grain bullets out of my 30-06. I load the different weights for different intended purposes. 110 lightly loaded is great for "recoil shy" folks, a longer range session, or introducing new shooters to a 30 caliber rifle. While my current moose load is with 200 grain loaded fairly warm but darned accurate. I have been loading 125 and 150 for predator. And recently I have loaded a few other weights just for fun. I am still looking for the "sweet spot" with all of my different weights, types of bullets, and loads; always trying to make it just a bit tighter.

I like shooting, and my interest is in accuracy. I shot 12 rounds yesterday out of one hunting rifle at the range, and 10 the time before. I make up relatively small batches to test, and I record the results so that I can compare in the future. I want my equipment to be as spot on as possible, so that I can work better on the biggest variable, myself.

To me it would be worth the extra expense of buying a number of different weights/brands/types, only if you are getting the results that you want to see for your money; and if that is worth it to you. However, first I would need to see the results for myself; and that is why I enjoy playing with many different bullets, powders, and loads. And why I have more boxes of bullets sitting on my shelves than I "need". And the ones that are "sub-par" still manage to go downrange and make a hole, or happily sit on the shelf in their boxes.

Once you have started to narrow it down, then start stretching out your distance. Slowly. When you are hitting at X yards/meters, then go to X+50 or 100. I like to have multiple targets at multiple ranges. Adjust/finetune your scope and load as you go. Always better to walk before you run. Much less frustration, much more enjoyment! Have fun! And be aware that this can be a never ending pursuit; however, you will notice that your results will improve. And if that is what you are looking for, welcome to the chase!

Feel free to take this advice as you see fit, I am but a humble amateur reloader, shooter, and hunter sharing his experiences. And true long range shooting is something that I am still working on and by no means am I an expert or even close. Still working on what many would consider "mid-range". Enjoy!
 
Thanks for the suggestions.

In an ideal world, I'd like to do something similar.

Realistically I won't have the funds to undertake a comprehensive comparison because bullets and powder are so expensive. I can buy a box of 100 for $50, sure, but I wouldn't want to then consign them to a shelf after the first 25. I want to choose the most likely to work

Same with powder. It costs about $115 for 2 pounds of powder (€86), so if I find a load, as with my Amax using N135, I would feel a bit reticent about then trying N140: I'd worry that I'm going to be stuck with worse results. The devil you know and all that!! This is compounded by the fact that I can only store 10lbs of powder at any given time. 5 are already allocated to my .44 and .38 loads. Must use the remaining quota carefully!

So what I may do is first buy the Lapua bullets as they can be bought individually so I may see what some of them can do. I may even go with the Scenar over the Amax.

All that is why I am trying to make the best choice on paper before buying rather than a whole lot of expensive, and restrictive trial and error!!

The alternative is finding someone/where that is willing to sell me a few cupfuls of N140: enough to do a few OCW spreads.

The final obstacle is places to see what they can do: I have a choice between 100m, 300m and .... no, wait, that's it...:o

There is room to manoeuvre, I just have to tread carefully!!
All a bit of a pain in the rear, to be honest....
 
How far out do you want to shoot? Unless you're trying to go 1000+ yards with a short barreled 308 the 155 A-Max would be good.
BTW the 155gr Lapua Scener is .508 BC
 
BTW the 155gr Lapua Scener is .508 BC
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You sure?!

That would be great, but the Lapua website quotes .460. Still better than the Amax, mind...

As for range. Right now I'd stuck at 300m. However, I've heard of some places for military training that are up to 1000m ans I think there is a private quarry whose owner is a shooter who lets people shoot there: that is about 600-700m.

So there is room to improve, I just don't see myself being good enough for some time, hence why I have not looked into it in more detail yet...
 
You'll have to shoot 30 caliber 155's with BC's around .500 out the muzzle at least 2900 fps to remain supersonic and stable for decent accuracy at 1000 yards.

So, with max safe pressure at about 52,000 cup (61,000 psi), how short of a barrel will do that? It typically takes at least 29 inches of barrel to do that.
 
You'll have to shoot 30 caliber 155's with BC's around .500 out the muzzle at least 2900 fps to remain supersonic and stable for decent accuracy at 1000 yards.

So, with max safe pressure at about 52,000 cup (61,000 psi), how short of a barrel will do that? It typically takes at least 29 inches of barrel to do that.
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My barrel is 26", my 155s can reach .460 and I expect my muzzle velocity is probably around 2650 fps.

So in other words, my 1Km goal is unachievable with my present set up.... :(

Should I be saving for a .338? :o

Won't stop me chasing 600m in the meantime though...
 
US military folks proved recently that more first shot hits on a target at 1400 meters happened with a .300 Win. Mag. than the .338 Lap Mag. 30 caliber rifles are a lot easier to shoot accurately than 33 caliber ones.
 
You can still get out to 1k but accuracy might not be the best.
If people can shoot Lee Enfield and Mosin Nagants at 1k, then you sure as hell can. You might not win any bench rest competitions, but you will get there.

Just re barrel your 308 to 260rem if you wanting better ballistics for not a huge expense.
 
Hmmm... thinks...

Well, in the 2 years since I took up shooting, I have scoured and devoured every gun store and used gun webpage to see what is around and I don't remember ever seeing either a .338 or a 300 Win mag on offer...

The only larger calibres I've seen regular have been .308, 30.06 and 7.62x54 in Mosins. I did see a .270 Zastava on sale once.

I'm going to have to stick to my little .308 for now...

If people can shoot Lee Enfield and Mosin Nagants at 1k, then you sure as hell can.
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I like your can-do attitude!! :D
Of course, I am still cutting my teeth at the 100m range right now, so I think there is some time before my 1000m accuracy needs any critical reviews.

All the same, I'm hoping to pin-point loads that have that potential even if I don't yet.
 
You'll have to shoot 30 caliber 155's with BC's around .500 out the muzzle at least 2900 fps to remain supersonic and stable for decent accuracy at 1000 yards.
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According to most of what I've seen you only need 2600 fps with a .500 bc to stay supersonic and stable to 1000
 
Twist rate is important as the heay bullet may not stabilize. Even if the twist is correct the bullet may not stabilize until 200m.That's where you should do accuracy testing. There's a word for that stabilizing that I never can remember .:(
 
If you have a smartphone, download a free ballistic app and type in same info, just change the BC and look at the drop/fps/energy differences out to 1k. But, your gun has to like that bullet in the first place for it to really matter. The load matters too. I have some factory ammo that is phenomenal but when I load to the same COAL (barring primer and powder) it's completely unacceptable for target.
 
There's a word for that stabilizing that I never can remember
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The bullet goes to "sleep". It stops wobbling and yawing and takes on a concentric spin meaning it has stabilized. Generally in the 80 to 150 yard range depending on weight and design of the bullet. It is recommended that boat tail bullets should be used for long range shooting as where flat based bullets should be used for 100 yard accuracy. Depending on your twist rate and the weight (length) of the bullet it will have a dramatic effect on your accuracy.

Pond, you are getting into a very expensive sport when talking about long range shooting, expensive rifles (barrels & chambers as well as expensive stocks), expensive scopes, expensive ammo, and expensive finding a place to shoot those distances.

I would try to improve on your current 308 maybe with a match trigger and maybe a bedded new stock, and shoot your best at 200 meters right now.

Good luck on your quest.
Jim
 
mete, are you saying that unstabilized bullets at 100 yards that are at the outside edges of an imaginary groups at that range will start to curve towards the center of the group at 200 yards?

If so, how does a bullet in flight know where it is in that imaginary group at 100 yards so it'll know which direction to go back towards the center of the 200 yard one? For example, if it's low and right, how does it know how to go up and left a little bit?

I think the word you're looking for is "asleep." Bullets that are asleep are spining on their long axis that's parallel to their trajectory path. Their ends don't nutate or spiral around the trajectory axis. These bullets are perfectly balanced and spun at the right rpm rate to keep them this way. They look like a perfectly passed football in flight.

Unstabilized bullets that are not asleep have more drag than those that are asleep. They slow down faster than the ones that are asleep.
 
Pond, you are getting into a very expensive sport when talking about long range shooting, expensive rifles (barrels & chambers as well as expensive stocks), expensive scopes, expensive ammo, and expensive finding a place to shoot those distances.

I would try to improve on your current 308 maybe with a match trigger and maybe a bedded new stock, and shoot your best at 200 meters right now.
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My point about bigger calibres was somewhat tongue-in-cheek. Yes, I'd be happy to move up in calibre at some stage, but I do recognise that there is little point at this stage in my development. Aside from that I really do like my existing rifle in many ways other than just its accuracy...

As for my existing set up, I think the only think I would consider is bedding, but I've no idea who wold do this. On the plus side the CZ550 has a set trigger feature. I don't use it at the moment, but I could: that is a very crisp break. I don't see myself needing a new scope. From what I've read my 3-12x should suffice.
 
All that is why I am trying to make the best choice on paper before buying rather than a whole lot of expensive, and restrictive trial and error!!
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Which reloading manuals are you using? Most will have an indication as to the "most accurate" load within a given bullet type/weight range per cartridge with the "best powder" noted.

Just note that your rifle may, or may not, have the same barrel length, twist rate, etc... as the test rifle/barrel used. However, it still is a really good starting point.

A chronograph can also serve you well. Generally more consistent loads equal more accurate loads, and a chrono helps to let you know just how consistent your loads are, or aren't. Another thought that has not been brought up, single loading of cartridges vs loading the magazine. Recoil can sometimes change COAL of remaining cartridges in magazine resulting in changing pressures. (Now we are getting picky, but simple and usually free or inexpensive "fix".)
 
I have a Lyman's manual (49th), I have a VV manual (3rd), I have another VV/Lapua manual, but that is older and when there is a difference I err towards the newer version. Finally, I have the Lapua loading data online.

So there is a heavy VV bias to my data choice, but then all I have are VV powders, so I suppose it doesn't hurt...

I have a chrono, but I have not used it yet. I had planned to find my OCW load, and then chrono that so that I would have the velocity readings needed for trajectory calculators. I hadn't thought to use it in the initial stages of examining charge behaviours on paper. It is also because getting the chrono set up at my range so that I can also see/shoot the targets whilst in a prone position is quite tricky.

For chrono readings, I just planned to shoot half a dozen over the chrono into the backstop, and not necessarily at the target for the sake of ease....
 
I strongly disagree with the premise that you are getting into a very expensive sport when talking about long range shooting, expensive rifles (barrels & chambers as well as expensive stocks), expensive scopes and expensive ammo.

The only expensive items are the barrel and the bullets. All else can be moderately priced and produce the same results as the most expensive stuff out there. For example, an old, well used Winchester 70 action can be had in a rifle for a few hundred dollars plus another few dozen dollars to square it up. It'll equal what a $1500 Stiller or BAT action will do on the range.
 
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