Range Report Wind, BC, muzzle velocity, and barrel length...?

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#1
Ok, I know I am probably over-thinking this one.

I know that high ballistic coefficient bullets like the 6.5mm and 6mm are able to be so effective is due to the reduction in drag and higher velocities than that of say 7.62 (in standard weights).

What I want to know is: If one were to shorten a barrel(to a handy 18-20") on a 6.5mm or 6mm caliber rifle (granted maximum range will suffer due to loss of some velocity), but will it still be effective against the wind in shorter ranges due to the better ballistic coefficients?

I would assume that slower bullets = more exposure to wind during flight time = more effect on bullet by wind. But I would also have to assume that a bullet with superior ballistics to 7.62 would be less effected by wind due to the profile and drag reduction.

Help me out here
 
#2
Re: Wind, BC, muzzle velocity, and barrel length...?

Go to JBM and put in your variables and you can see first hand the differences, which will be there but not as great as you think.

I believe when looking at the differences between a 260 going 2840fps and the one out of my 18" rifle the wind changes were only about 3/10th a mil at 1000, but I don't recall offhand.

The difference between the guys running the 28" barrels and my 18" rifle was only 3 MOA at 1000 yards, and that was without tuning a load to the rifle. If you figure 100fps at the worst in JBM you can see the wind changes.
 
#4
Re: Wind, BC, muzzle velocity, and barrel length...?

Remembering that 3 MOA at 1000 yards is 30 inches, I would say the difference is more than substantial.

But it really depends on the kind of precision that you require out of your rifle system. For example, a difference of 3MOAs of wind in F-class, HP or benchrest competition is enormous, but if it's "tactical" then it does become less daunting.

The wind deflection is not so much a function of the velocity of the bullet but is more related to the difference between the time of flight in a vaccum and the actual time of flight for the bullet. This is where the higher BC bullet comes into its own as the differential in times of flight is reduced.

The ultimate goal is to push the highest BC bullet at the highest possible velocity. This helps minimize the effects of improper wind calls, and again, that really depends on what level of precision you aspire to.
 
#5
Re: Wind, BC, muzzle velocity, and barrel length..

It's not a function of precision, because if you learn what you have you can be just as precise... and again, the wind deflection is not 30 inches, the elevation was 30 inches, which with the scope is just a matter of dialing.

You can't say a person who uses 30 MOA to reach 1000 yards and a person who uses 27 MOA will be less precise... it doesn't work that way accuracy is not handed out by default.

Knowing your dope is a function of precision... blowing a call is blowing a call, and can happen to anyone. I can hit sub MOA targets at 1000 yards, consistently, it doesn't make me less precise it only forces me to be more consistent and less likely to hope the bullet will make up for my mistakes.

Again, picking the right rifle and bullet combination is important, but this is also SH, not F Class Central... if you want to cheat the wind use a better bullet... but pushing any given bullet faster by trying to go longer and longer isn't always the right answer... moving to a better bullet is.

Who is going to be better a guy with a 32" Barrel pushing a 155gr 308 or me with an 18.5" 260...

 
#6
Re: Wind, BC, muzzle velocity, and barrel length...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">

... but pushing any given bullet faster by trying to go longer and longer isn't always the right answer... moving to a better bullet is.


</div></div>

Frank, this is exactly what I needed to hear to make my decision.
 
#8
Re: Wind, BC, muzzle velocity, and barrel length...?

How does one loose or gain precision simply by changing a bullet... is precision something you gain through practice, or is precision given out like a BC, the higher the BC the more precision you get.

Because I feel precision is earned, not achieved simply by adding a few fps or a few extra inches to your barrel. The 308 was originally designed as an 800m cartridge, we shoot it farther because we are arrogant and we can, not because it was meant to do so... just because someone can push it faster and farther, does mean you can't go shorter better or easier.

answering a question with a question is easy, and what is even easier is avoiding the question altogether.

You're arguing it is the arrow not the indian, which I don't agree with.
 
#9
Re: Wind, BC, muzzle velocity, and barrel length...?

Gosh, Sig

It sounds like you are starved for validation....from a complete stranger for that matter. Not good.

It's no mystery that pushing a projectile with the highest BC as fast as possible is what makes longer shots easier.

However, I have little use for a barrel burning monster that must be transported in no less than a Suburban or flat bed truck. I don't (and can't due to safety and facility limitations) 1000 yards. I have no interest in F Class. However, I have much use for light, handy accurate rifles that can make a hit at 600 and not be a burden on my back all day. This should have been obvious in my first thread where I mention rifles with 20" barrels or less. And given that the wind in central IL (especially in Spring) is a bitch to read, any advantage I can get is a plus. Plus I will admit to having a little lust for the 6.5mm.

Mainly, I'm just looking for a little encouragement to get out of my 7.62x51 safe zone and try something new. Frank just put it into words better.
 
#10
Re: Wind, BC, muzzle velocity, and barrel length...?

It is interesting to note that nowhere did I mention .308 caliber and yet LL keeps refering to it. LL is also the one that started talking about shooting to 1000 yards, not me.

I asked what kind of precision you were looking for, mentionning that different disciplines have varying requirements to be successful. It is only in your last post that you inform us what you goal is; plinking at 600 yards with a light handy rifle. That's fine.

So, the original question was in essence "will I do well with a short barreled 6mm or 6.5mm as opposed to a longer barreled 7.62?" The sub-text of that question was "will the higher BC of the 6mm or 6.5mm make up for the velocity loss due to the short barrel?"

The answer to the main question is a resounding YES, especially given your stated goals. No question there and let us know how it works out.

The answer to the second question is also a yes, as I explained earlier.
 
#11
Re: Wind, BC, muzzle velocity, and barrel length...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">How does one loose or gain precision simply by changing a bullet... is precision something you gain through practice, or is precision given out like a BC, the higher the BC the more precision you get.

Because I feel precision is earned, not achieved simply by adding a few fps or a few extra inches to your barrel. The 308 was originally designed as an 800m cartridge, we shoot it farther because we are arrogant and we can, not because it was meant to do so... just because someone can push it faster and farther, does mean you can't go shorter better or easier.

answering a question with a question is easy, and what is even easier is avoiding the question altogether.

You're arguing it is the arrow not the indian, which I don't agree with. </div></div>

Then we shall have to agree to disagree, because it believe it is both the arrow and the indian.

One gains precision with proper tools and that includes proper bullets. It is difficult to be precise with lousy tools or arrows, if you will. On the other hand, accuracy is something that is earned and gained by experience and shooting and learning to read the wind and building your position and so on.

When you marry the precision of the rifle and bullets (the arrows) with the accuracy of the consumate rifleman (the indian,) then you have something worthwhile. A rifleman can be accurate with a less precise rifle setup, for example Carlos Hathcock was very effective with a 2MOA rifle, but the precision is not there to extract tiny groups from such a setup, which is why I asked what kind of precision the OP was looking for and gave some examples.

In this forum, we talk a lot about how to make the rifles and bullets more precise, and at long ranges the BC value of a GOOD bullet will come into play. I'm sure you know, but just for others who may read this thread and not know, the BC value of a bullet has nothing to do with how precise it can be. There are wonderfully precise bullets who have a BC that says they stop after 300 yards. But bullets must be matched to the rifle, or to continue your analogy, you must match the arrows to the bow. There are some threads here that talk about accuracy from the point of view of the rifleman but the vast majority of discussions are about precision enhancements to the rifle, ammo, bipod, etc.

As for your question about whether a 32 inch barrel .308 rifle shooting 155gr SMK will do better than your 18.5 inch .260, I have no clue. I do not use the 155gr SMK and you did not specify what the object of the game is. On the other hand, if you ask whether I could outshoot you at 1000 yards using my .308 with my regular bullets against your .260 in an 18.5 inch barrel, I would say "why don't we find out?"

Finally, even the best indian will not be able to do well with arrows that are unable to reach the target or that do not fly true, which is what makes the whole thing very interesting. I have yet to see a top competitor come to the 1000 yard line with surplus ammo and a lever or pump action rifle, however, every year this combination will kill a lot of deer.
 
#12
Re: Wind, BC, muzzle velocity, and barrel length..

I have seen some excellent marksman do some excellent shooting with less than precise weapons... in most circles the well trained Indian is highly valued, even over a shiny fast arrow.

I brought up the 308, because the "Original" question asked about the differences between a 6.5 and a 308... so rather than dancing around some bullshit, I gave the OP some of my real world experience with the very thing he was asking about.

<span style="font-style: italic">Can a short barreled 6.5 work better than a longer 308... the answer is a resounding yes. </span>

So you admit you don't know -- something easy to find as I gave the tools above, so I will tell you that while the 155gr bullet will use less elevation to reach 1000 yards, about 28MOA, the 6.5 will in fact use less drift even though it requires more elevation, this I believe is a key point to the discussion.

Unfortunately you failed to read the thread properly, including my response, because where 30 inches maybe significant that was in the elevation department and not in the wind drift department which I stated was about 3 /10th of a mil or what would be 3/4 MOA. That difference is in comparing equal 260s of different lengths. 10" to be exact... so what you gain by going long you lose in portability and the benefits of a short rifle cannot be over stated when comparing a cross over rifle.

If I was so incline to shoot F Class, and honestly have no problem with the sport at all... I would be smart enough to have a purpose built rifle made. It would be the 22lbs belly bench rest monster, I would invest in the right front rest &, rear bag combination and would do the same as most other F Class shooters... remove as much of the shooter as possible and use the best bullet I could... probably
something 7mm. Pretending I don't understand your sport is not the same thing as coming here and preaching speed to those who you consider the ignorant.

Don't get your nose bent because you stepped into something trying to use the old standby "Longer and Faster" is better... well a 155gr 308 going 2950 is not better than a 139gr going 2750... the difference between long and short. Not only do I consistently shoot this stuff, I actually take the time to explore the differences and where I can exploit advantages in places other people fail to go.
 
#16
Re: Wind, BC, muzzle velocity, and barrel length..

Great, so you're already changing the rules. I offered my .308 with my regular F-class bullets in my 32 inch barrel against your 260 in an 18.5 inch barrel at 1000 yards. I explained that I do not run 155gr SMKs. Now you want to change that? I'm getting confused here and at my age, that's not good.
 
#17
Re: Wind, BC, muzzle velocity, and barrel length..

Okay, I misunderstood... your 32" 308 against an 18.5" 260... that is fine with me.

Byers Field, CO... let me know ahead of time because I travel for work, but will set a date for the shoot.

Can we make it a two parter... one at 1000 yards F Class style and one where we actually have to walk from the road to the firing line under time ? Seeing how you want to shoot a dedicated F Class belly rest rifle against a tactical rifle we should at least go 50/50 on the mission requirements. I would understand you not wanting too, which is fine with me, but I figured I would ask.
 
#18
Re: Wind, BC, muzzle velocity, and barrel length..

So, you want me to give you home range advantage, at an insane elevation when I live in the Houston area practically at sea level and now you want me to run with my rifle before I shoot? At my age? Why don't you just shoot me and be done with it?

I thought this was a shooting contest, not an ironman contest.

At any rate, I work for a living, so I won't be able to get away and lose billable time for several months or more. On the other hand, if you come to southeast Texas in the meantime, let me know and we can get together then. I think you would enjoy shooting in July or August in south Texas. I do it every summer. Bring a hat.

So, I appreciate the invite and will see about getting up to Buyers Field, CO.
 
#19
Re: Wind, BC, muzzle velocity, and barrel length..

Dude, I work at Rifles Only, in Kingsville, TX. I love the heat... no manicured range there, but we have a 1000 yards...

South Texas, Ha, you ain't south, come to Kingsville... you have to turn right and then drive... for a couple of hours.

As far as the running, this is SH, this is about tactical shooting and running is part of it... I'm not 20 any more either but I run alongside everyone there.
 
#20
Re: Wind, BC, muzzle velocity, and barrel length..

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">but we have a 1000 yards... </div></div>

And lots more, if needed or desired.

And the highest point on Rifles Only is 72 feet AMSL.
 
#21
Re: Wind, BC, muzzle velocity, and barrel length..

Oh, the insanity. I knew I never should have been born at 7200'. I would actually fear going to Houston in the summer (once was enough) and having to shoot in such dense air, although the humidity (when it wasn't blinding me) would slightly offset the low altitude. Running at altitude keeps you young. I almost regret only living at 4100 these days.
 
#22
Re: Wind, BC, muzzle velocity, and barrel length..

I want to see this.

Sig, if you are arguing that your rifle is a better wind cheater, you should have a huge advantage at Rifles Only. The wind there is crazy...15-18 constant with gusts up to 30+, should be perfect for a long barrel, wind cheating 308.


Although I understand your reluctance to run, but I like the idea of letting each rifle get a shot at performing in its element. How about in and out of the buss too?
 
#23
Re: Wind, BC, muzzle velocity, and barrel length..

"How about in and out of the buss too?"

I hate that bus and it's damn broken glass. It is the reason that I will be buying "tactical" knee pads.

 
#24
Re: Wind, BC, muzzle velocity, and barrel length..

Sig is way out of his element no way would he conform to the type of shooting we talk about here. He wants to lay down and "take it easy". Please, this is tactical shooting. You cant get off work cause you don't want Frank to slaughter you at the range which is exactly what would happen.
 
#26
Re: Wind, BC, muzzle velocity, and barrel length..

Great, a question turns into a pi$$ing match.

I saw the original inquiry as something like:

"Can a 6 or 6.5mm caliber still get enough speed out of a 18-20-inch barrel to have decently small wind drift...say, compared to typical .308 Win loads?"

This is an inquiry I've wrestled with, but in the realm of 155s and less elevation (good for unknown-distance ranging and dialing in the come-ups), versus shooting slow and heavy and not getting blown all over the place. 155 Scenars are not a realistic answer for me because a) they just don't group worth crap out of my barrel, and b) I have multiple objections to paying almost as much per bullet as for some factory loaded rounds, and to a foreign country no less!!!

My best answer for that question is it depends on which you're better at doing--calling distance to the target or reading the wind. Reading wind includes how many directions it's blowing between you and the target, too! If you're in a placed where a laser rangefinder may never make you a target for enemy artillery or air strike, then less wind drift will most likely win out. Passive ranging tools make it more a matter of the "Indian's" skills.
 
#27
Re: Wind, BC, muzzle velocity, and barrel length..

Sig685 profile -
Shooting, handoading, competing. I am a competitive F-T/R shooter and I am currently rated an NRA Master in F-class. I compete at 300-1000 yards in F-TR.

Hell he might give the Boss a kick in the arse lyin prone with that Higher BC and velocity -dont right him off to quick
 
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