Correlating seating force with... anything?

[Bart B.]

None of these directly contribute to MV, as none of these directly indicate neck tension.

Bullet extraction force does contribute to muzzle velocity. Compare the same load's muzzle velocity with 3 pounds then 70 pounds with a .100" bullet jump to the rifling.

 

[dmoran]

@Bart B.
As I see it, 3-lbs verses 70-lbs, would be an extreme scenario (especially with a .100" jump) that no doubt could influence a velocity variation.

How about 10-lbs variation, and from hardly any jump (like say 0.010") scenario. How much velocity variation would you predict for it?
Donovan

 

[LHSmith]

I disagree. Tried that long ago. Nothing beats a polished layer of carbon so far that I can find.

Agreed. IMO the key is to wipe the neck ID with a nylon brush soon after firing ....before the carbon hardens. However, for new unfired cases, Imperial dry lube (graphite), or even a pass through with a swab coated with a very light amount of Royal Case Lube (must give a few minutes to allow to dry) will closely mimic a prepped carbon neck.

 

[Bart B.]

How about 10-lbs variation, and from hardly any jump (like say 0.010") scenario. How much velocity variation would you predict for it?

Less than 10 to 15 fps if average bullet pull force is less than 30 pounds. Perhaps 5 fps if average pull is 60 to 70 pounds.

I think it's dependent on the percentage of the average bullet extraction force. And that is going to change with different bullet clearance to rifling, rifling angle plus bore cross section area and diameters.

No data from tests comparing all the variables' contribution to muzzle velocity has ever been published nor ever done as far as I know. Just limited tests without the same conditions and standards. Therefore, data for a given situation across several will vary. We only see trends on our limited experiences.

 

[fguffey]

Try coating the inside of your necks with liquid graphite. It pretty much eliminates friction readings from showing on the force gauge and any seen differences are tension related.

'The force gage'; How many forces does it take to equal 2 tensions? I have tension gages, all of them are calibrated to pounds and then one day I made a seater, it was a seater because it did not have a die body. When it came to seating a bullet it was almost effortless because of the alignment and it had shoulder and neck support.

F. Guffey

 

[dmoran]

@Bart B.
Some experience of mine on very light neck tension:
For two IBS-1000 matches (same day) back in 2009, I took a load that basically had little to no neck tension to speak of, where to say the bullets could be slipped and/or pulled with out much grip. Would estimate all would have taken between 1 to 15-lbs of pull to un-seat them. In testing of that load, the ES was exceptionally low, consistently less then 5-fps, and is what intrigued me the most about it.
At the matches, under match conditions, it shot these groups in the relays:
LtGun (5-shots)
5.095"
8.546"
HvGun (10-shots)
7.431"
9.636"

Never used that load or that light of neck tension ever again, because 1st felt that light of seating could to easily get knocked off. And 2nd didn't feel the low ES matched the actual targets, that appeared wind sensitive in the matches compared to the testing in more optimal conditions, where it produced sub 5" groups.
Donovan

 

[davecb]

No, that's pretty much what I understood you were saying.

And I'm saying that for 2 thou neck tension, that doesn't sound even remotely right.

The necks on my loaded rounds measure .290. I'm using a .288 bushing. I originally tried a .289 bushing but I could move the bullet by hand. I have a .287 bushing but I haven't tried it. All my brass was cleaned with the stainless steel pins so I'm lubing the inside of the necks with the Nico moly/shot. I may have to try putting a scale beneath the ram to see what kind of reading I get.

Dave

 

[davecb]

If the gauge indicates 2 pounds seating force while the bullet goes into the case, that's exactly a 2 pound force.

A 2 pound weight on a bullet would do the same thing. It's a constant force that indicated uniform neck walls thickness and surfaces.

I understand. I do feel a little tension when the bullet first enters the case but then it feels like the tension releases and the bullet seats easily. All the while the needle stays on zero.

I may call 21st Century and get their input.

Dave

 

[Bart B.]

the bullets could be slipped and/or pulled with out much grip. Would estimate all would have taken between 1 to 15-lbs of pull to un-seat them.

I think a lot of grip difference would be needed. A 15X spread.

 

[Bart B.]

I understand. I do feel a little tension when the bullet first enters the case

That's typically caused by the case mouth edge sliding over the bullet heel.

Standard deburring tools leave a sharp inside edge in the case mouth that acts like a chisel peeling wood off a stick. After deburrung my cases with one, I twist an Easy Out in the mouth flattening that sharp edge. Then run case neck over a bronze bore brush to round that edge and clean some carbon out.

No more bullet jacket peeling and consistent seating forces.

 

[Bart B.]

experience of mine on very light neck tension

What was the vertical spread in those groups?

Different atmospheric conditions can cause a 1/10th MOA spread

 

[dmoran]

What was the vertical spread in those groups?

Sorry... to long ago for memory or targets. But in my testing notes to that load, have 3" wrote down, which would have meant to me in general to be in the 3 to 4" range for vertical.
Donovan

 

[Bart B.]

the 3 to 4" range for vertical

A small spread in bullet BC can cause over half that vertical spread with the same muzzle velocity. They all ain't exactly the same.

 

[dmoran]

A small spread in bullet BC can cause half that spread. They all ain't exactly the same.

Without a doubt that is an effect worth noting, and some what common knowledge (especially to LR folks).
In my circumstance back then, those bullets were segregated and qualified. Likely to have been more consistent in BC then common, and that particular lot of bullets were some of the best I ever had, that in BC tests (my own at 100/500) were 1.7% max (after segregation, before qualifying).

On a note; testing BC consistency over chronographs was a common practice to me back in those years. In years since, I let the targets answer those questions pretty much solely instead. We shoot smaller and much more consistent these days, and can more readily see such effects on the targets.
Donovan

 

[Bart B.]

On a note; testing BC consistency over chronographs was a common practice to me back in those years

Did you use two of the same model spaced 25 or 50 yards apart to see the velocity loss percentage for each shot through both?

Sierra's data from such tests they did some years ago are interesting. A 1% spread in BC was normal.

 

[dmoran]

Did you use two of the same model spaced 25 or 50 yards apart to see the velocity loss percentage for each shot through both?

Back then I used two CED-M1 w/ Infrared sky screens. Did initial BC testing of bullet lots at Muzzle + 100yds, then fallowed up tests with segregated bullets from established loads at Muzzle + 500yds.
Computed the BC for the two captured velocity's between the distances (in inches) using RSI software, and later in my own spreadsheets.
Donovan

 

[Bart B.]

Back then I used two CED-M1 w/ Infrared sky screens. Did initial BC testing of bullet lots at Muzzle + 100yds, then fallowed up tests with segregated bullets from established loads at Muzzle + 500yds.
Computed the BC from the two captured velocity distances using RSI software, later in my own spreadsheets.
Donovan

That happens when one does all the right stuff!!!

 

[dmoran]

Sierra's data from such tests they did some years ago are interesting. A 1% spread in BC was normal.

From my own testing of course; I have never tested bullets that "out of the box" would hold a 1% max spread, with a 3% or so being a more likely variance to good lots. The best "out of the box" bullets I ever tested was a lot of Hornady 105-Amax (under 2%), and chalked them up to the polymer tips to being why.
Donovan

 

[davecb]

That's typically caused by the case mouth edge sliding over the bullet heel.

Standard deburring tools leave a sharp inside edge in the case mouth that acts like a chisel peeling wood off a stick. After deburrung my cases with one, I twist an Easy Out in the mouth flattening that sharp edge. Then run case neck over a bronze bore brush to round that edge and clean some carbon out.

No more bullet jacket peeling and consistent seating forces.

I'm sure in this case it's not the case mouth. I have had that happen in the past though. I deburred these and checked them to be sure there was no lip. I bent the end of a paper clip to check the inside of the neck after reaming. Could it be because I am not resizing the full length of the neck? More like 3/16" only. It feels like it's tight until the bullet gets past this sized portion. I was sizing the entire neck before but it seems like my runout is better when I partially size them. I'm using a Whidden full length die with neck bushings.

I did email 21st Century. John suggested trying the .287 bushing. He said it sounds like I'm not actually getting the .002 tension like I think I am. I'll give that a try.

Thanks
Dave

 

[fguffey]

I think a lot of grip difference would be needed. A 15X spread.

Reloaders do not use grip, reloaders do not use bullet hold, they do not know what it is called but they know it is not bullet hold and they know it is not bullet grip. I am the fan of bullet hold, all of my gages are calibrated in pounds.

F. Guffey