How much does COL effect accuracy?

[5RWill]

I've loaded another batch of 175gr BT LRs. Some are right at 2.800 like i want and then most differ. I realize the meplats are going to vary a thousandth or so, but i have some that are at 2.795, and some that are around 2.803. Are the ones that are a little below 2.800 going to effect accuracy and velocity of the load due to a bigger jump to the lands? Using a comparator most of them were pretty consistent, overall i think i might have set the seating depth a thousandths or two too low.

Load Data:
Nosler .308 brass
Fed 210m primers
44gr Varget
Berger 175gr BT LR
2.800

 

[YAOG]

Re: How much does COL effect accuracy?


I think COAL is less important than the ogive to lands measurement. The only important things to keep in mind about COAL value is how long is too long to feed reliably in your weapon and does changing COAL adversely affect your load in terms of powder capacity and pressure.

Make sure your COAL is less than what ever COAL gives you 100% reliable feeding. COAL makes no difference as long as you keep enough bullet in the case neck to hold the bullet well without too much neck pressure and chamber reliably. The ogive to cartridge base is the important thing to control as best you can.

 

[jwoolf]

Re: How much does COL effect accuracy?

I find that accuracy "can" be affected by a long jump but, the long jump will usually help you to get a higher velocity out of the load.

All that said, I've been working up a load for a friend's rifle and, he's kissing the lands at 3.002 in his 308 win round with the 175 amax.

So, you're going to get as many opinions as we have folks here on this one.

You have to ask yourself what's important to you. Are you worried about feeding in a magazine? If so, you already have a completely different outlook that another whole set of folks here.

I'd say that in "most" situations, not all, going out close to the lands will get you better accuracy. There are stories that are valid where some folks find their rifles shoot better way away from the lands but, as a general rule, especially with some bullets, close to the lands works best.

You can lose some velocity doing this because the bullet doesn't get a running start before it hits the rifling.

FWIW: I've seen meplats vary over .005 all the time.

The best way to measure is to get a tool to measure of the ogive and measure how far you are away from the lands and forget the COAL. ( unless you are only worried about magazine feeding ) In that case, I'd see how close I can get to max length in the magazine.

When you re-barrel, you can see about reducing your freebore when the smith chambers your new barrel so you can reach the lands before you run out of magazine.

 

[5RWill]

Re: How much does COL effect accuracy?

I'm just hoping my ES and SD remain constant. I've shot 5 shots of the first batch i made and had a ES of 11 and SD of 4.5, avg fps was 2618. So i'm going to shoot 5 more and see what the velocity is hopefully it's still pretty consistent

 

[Fuzzball]

Re: How much does COL effect accuracy?

"How much does COL effect accuracy?"

Ahhh...would you believe it's variable, no one has calibrated that kind of thing.

Actually, as stated above, OAL is virtually meaningless; no rifle cares where a bullet meplat hangs in empty space, it's the jump to the rifling that matters and that's not as critical as some presume.

"i think i might have set the seating depth a thousandths or two too low"? That small a difference is irrelivant to anything.

 

[varmint slayer]

Re: How much does COL effect accuracy?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jwoolf</div><div class="ubbcode-body"> All that said, I've been working up a load for
a friend's rifle and, he's kissing the lands at
3.002 in his 308 win round with the 175
amax.</div></div>

Did you shave the ass end off a 178 Amax? lol just bustin your balls, I know what you meant.

 

[5RWill]

Re: How much does COL effect accuracy?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fuzzball</div><div class="ubbcode-body"> "How much does COL effect accuracy?"

Ahhh...would you believe it's variable, no one has calibrated that kind of thing.

Actually, as stated above, OAL is virtually meaningless; no rifle cares where a bullet meplat hangs in empty space, it's the jump to the rifling that matters and that's not as critical as some presume.

"i think i might have set the seating depth a thousandths or two too low"? That small a difference is irrelivant to anything.</div></div>

Good to hear. I'm really hoping my loads stay as consistent as they were.

 

[Wannashootit]

Re: How much does COL effect accuracy?

Good topic.

Meplat, and bullet comparator were mentioned above. Not trying to hijack- but since it's related...

I watched an episode of Long Range Pursuit- sponsored by Gunwerks(?)Now, I don't know anything about the company, or the quality of their work. But they had a short section on reloading- for precision rounds, presumably- since they're a precision shop- and he measured the bullet's OAL simply by placing the completed bullet/case in a set of calipers and stating it was GTG.

I've only been reloading for less than a year, but a bullet comparator was part of my initial setup. I thought measuring OAL from the ogive was <span style="font-style: italic">critical</span>- isn't it?

 

[BOLTRIPPER]

Re: How much does COL effect accuracy?

remember....in this game we play, most bullets made will not be very consistent....load them up so they feed through the magazine,and don't worry about them jumping around,,,,you most likely will not be able to shoot the difference in accuracy variance

what will show as an inconsistency down range is powder charge differences.....generally up and down or vertical movement

seating depth/ and tension will show as a left or right shifting

....this is an over simplification of a general rule of thumb.

 

[YAOG]

Re: How much does COL effect accuracy?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Wannashootit</div><div class="ubbcode-body">Good topic.

Meplat, and bullet comparator were mentioned above. Not trying to hijack- but since it's related...

I watched an episode of Long Range Pursuit- sponsored by Gunwerks(?)Now, I don't know anything about the company, or the quality of their work. But they had a short section on reloading- for precision rounds, presumably- since they're a precision shop- and he measured the bullet's OAL simply by placing the completed bullet/case in a set of calipers and stating it was GTG.

I've only been reloading for less than a year, but a bullet comparator was part of my initial setup. I thought measuring OAL from the ogive was <span style="font-style: italic">critical</span>- isn't it? </div></div>


Hey Wannashootit,

I bought a Hornady comparator and the appropriate bits to measure the distance to the lands in my .308Win Remington 700 rifle and allow setting up the dies and seaters optimally for the various .308Win rifles my reloading bench is used for. It worked pretty well but I had the itch to try a Redding Instant Comparator so I bought one and the difference is pretty significant in terms of repeatability and speed.

The only trick is that you will need to have a dedicated stand or a spare press mounted on your bench to put the Redding Instant Comparator in so you can go back and forth as you zero in on shoulder or bullet seating depth.

Anywho... Yes the bullet seating measurement is critical for precision handloading but most folks don't take the time or spend the money needed to really understand and optimize their handloads. The important measurement is from the cartridge base to bullet ogive which controls the distance to the barrel lands.

HTH!

 

[Stick Around]

Re: How much does COL effect accuracy?

Control and understanding of seating depth,is easily one of the greatest attributes of Reloading.

Most botch it,just like headspace.

 

[aqualung]

Re: How much does COL effect accuracy?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Wannashootit</div><div class="ubbcode-body">Good topic.

Meplat, and bullet comparator were mentioned above. Not trying to hijack- but since it's related...

I watched an episode of Long Range Pursuit- sponsored by Gunwerks(?)Now, I don't know anything about the company, or the quality of their work. But they had a short section on reloading- for precision rounds, presumably- since they're a precision shop- and he measured the bullet's OAL simply by placing the completed bullet/case in a set of calipers and stating it was GTG.

I've only been reloading for less than a year, but a bullet comparator was part of my initial setup. I thought measuring OAL from the ogive was <span style="font-style: italic">critical</span>- isn't it? </div></div>

Yes. IMHO.

<span style="color: #3333FF"><span style="font-style: italic">edited to say;</span></span>

Remember, anything that goes out to the mass media caters to the lowest common denominator. Most 'everyday' shooters out there don't care about the stuff we on the Hide sweat over.
How many hunters do you know who bought a box of 20 .270 softpoints still have most of them left 6 seasons later? They're not interested in the same level of accuracy as we are.
Just my $0.02, no intention to offend.

N

N

 

[Guest]

Re: How much does COL effect accuracy?

If your stick won't shoot a factory spec COAL, you should change sticks or ammo because one of the two suck.