OAL Measurement discrepancies - Slotted Case vs Cleaning Rod Method (.010")

[loudandproud]

Hello Guys,

So, I am loading my first "precision" hunting loads for my 10 FCP-M 308. I have my new Lapua brass neck sized, BR2 primers, 8 pounds of Varget and 300 Sierra 180 grain Gamekings (#2160). I am going to try the OCW method for the first time on this rifle.

Today I am trying to find the lands on my rifle for the first time. I just ordered comparators and should have them next week in order to set up the dies off of these "test bullets".

I decided I was going to use both the Slotted Case method and the Cleaning Rod Method (I use two precision ground clamps) to ensure I was getting similar results. I ran each measurement 5 times with two different bullets.
The results are below.

As you can see.. one of these is off. One of the following thing is happening:

1. The bullet is being jammed into the lands .010" when using slotted case
2. The bullet is being pulled out of the slotted case .010" while ejecting because of the friction of the rifling and the ogive (unlikely because of the consistency).
3. I am not getting consistent enough contact with the cleaning rod method.
4. Umpteen other issues...

When I load the same two bullets to 2.786" and paint them with Dykem, they don't show any deep land marks... but I think...think I can see 6 little blemishes in the bluing around the ogive.

Anyone know whats going on here? Suggestions?

 

[Raythemanroe]

Start your loads just touching and work your way out, the easiest way without buying tools (which you should invest in) would be to remove your firing pin assembly and cocking piece. Start with the bullet loaded slightly long and try to close the bolt, then a thousandths at a time bump it with the die until you get lite pressure to close bolt and bump one more thousandth..Measure with your comparator or keep for a dummy bullet..I like to adjust my Forster micrometer die to zero at just touching, that way I can just dial to the setting I want..

 

[BoydAllen]

A couple of observations:
Looking at your table, for you, the cleaning rod method seems to show the smallest variation, and the amount that you show is as good as I would expect from any method. Go with it. The other thing that I would mention is that showing a fourth decimal place, for something like this, and considering the methods and tool that was likely used for the measurement, is a bit silly. Good luck with your load workup.
Boyd

 

[loudandproud]

The height were taken on a surface plate and a Browne and Sharp Height gauge. The measurements of the "test rounds" and most certainly accurate to a tenth. Im fully aware that the rod would be off.. but I'm not going to stack errors that I don't need to stack for the sake of sig figs. What you see here is raw measurements right off the gauge.

 

[finnaddict]

Start your loads just touching and work your way out, the easiest way without buying tools (which you should invest in) would be to remove your firing pin assembly and cocking piece. Start with the bullet loaded slightly long and try to close the bolt, then a thousandths at a time bump it with the die until you get lite pressure to close bolt and bump one more thousandth..Measure with your comparator or keep for a dummy bullet..I like to adjust my Forster micrometer die to zero at just touching, that way I can just dial to the setting I want..

I am guessing the bullet is seated under normal neck tension as if it were a loaded cartridge. Of course in this case no primer or charge.

 

[BoydAllen]

Well... you are certainly not the typical handloader, so I will retract the part about the tool used to measure, but will stick to my point about the fourth place, since you are working down a hole, either dependent on consistency in friction in the case neck, or feel with the rod. (Yes, I do record raw data the same way as you do, even though its indicated degree of precision exceeds that of the least accurate part of the procedure.)As long as whatever method you use it reproducible at the level that you are getting, IMO you are good to go. I do not expect that any tool or technique will give more consistent results, given the nature of bullets and rifle throats. Have you looked at the ogive to case head consistency of your loaded rounds?

 

[loudandproud]

Well... you are certainly not the typical handloader, so I will retract the part about the tool used to measure, but will stick to my point about the fourth place, since you are working down a hole, either dependent on consistency in friction in the case neck, or feel with the rod. (Yes, I do record raw data the same way as you do, even though its indicated degree of precision exceeds that of the least accurate part of the procedure.)As long as whatever method you use it reproducible at the level that you are getting, IMO you are good to go. I do not expect that any tool or technique will give more consistent results, given the nature of bullets and rifle throats. Have you looked at the ogive to case head consistency of your loaded rounds?

I build sprint car motors on the side so I have a tendancy to be alittle anal haha.

 

[gotcha]

Another way to verify your bullet is actually touching the lands is to buff the bullet with steel wool to remove the shine. When the cartridge is inserted into the chamber the lands will appear as easy to read shiney spots on the bullet. On subsequent rounds you can increase or decrease OAL by a few thou. to get the perfect "kiss". Works better than Dykem for me. BTW being OCD is a plus on this forum

 

[mikecr]

What do you have for an end-piece on your cleaning rod?
Could there be 10thou difference to the bolt face contact?

 

[loudandproud]

What do you have for an end-piece on your cleaning rod?
Could there be 10thou difference to the bolt face contact?

I wouldnt think. The rod is an aluminum dowel that is turned the ends clean on. The ends are perpendicular to .0007 according to an indicator.

 

[loudandproud]

Another way to verify your bullet is actually touching the lands is to buff the bullet with steel wool to remove the shine. When the cartridge is inserted into the chamber the lands will appear as easy to read shiney spots on the bullet. On subsequent rounds you can increase or decrease OAL by a few thou. to get the perfect "kiss". Works better than Dykem for me. BTW being OCD is a plus on this forum

Ill give that a shot. The dykem just isnt showing the marks very well.

 

[savagedasher]

With the slotted case how much bullet do you have in the case including the boat tail. That will tell you how much the bullet is deducting from useable case capacity. Then someone with Q L can give you a starting point. Larry

 

[BoydAllen]

I take the loaded round, and grab the whole bullet and end of the neck in a wad of 0000 steel wool, holding it tightly between thumb and index finger with one hand and turning it with the other, which leaves little tiny grooves around the entire bullet (that do not hurt a thing). They make seeing rifling contact very easy to see. For short range rounds, since virtually all of my seating depths are some distance into the rifling, a lot of times I will seat to a mark that I know that a given ogive shape has been known to work well with, or for some of the pointier shapes, do an old fashioned full neck tension, seat long determination of what jam is, and then back it off about .003 to make sure I don't stick a bullet while shooting. I can do all of this when I am loading at the range, and go through a number of two shot trials in a very short time. If two have paper between them, I don't need a third.

 

[queen_stick]

I build sprint car motors on the side so I have a tendancy to be alittle anal haha.

Full size or micro?

 

[loudandproud]

I build sprint car motors on the side so I have a tendancy to be alittle anal haha.

Full size or micro?

Full size 358's amd 360s. Mainly doing street/strip motors now

 

[loudandproud]

I take the loaded round, and grab the whole bullet and end of the neck in a wad of 0000 steel wool, holding it tightly between thumb and index finger with one hand and turning it with the other, which leaves little tiny grooves around the entire bullet (that do not hurt a thing). They make seeing rifling contact very easy to see. For short range rounds, since virtually all of my seating depths are some distance into the rifling, a lot of times I will seat to a mark that I know that a given ogive shape has been known to work well with, or for some of the pointier shapes, do an old fashioned full neck tension, seat long determination of what jam is, and then back it off about .003 to make sure I don't stick a bullet while shooting. I can do all of this when I am loading at the range, and go through a number of two shot trials in a very short time. If two have paper between them, I don't need a third.

I gave that a try on the test bullet mounted at 2.786". Worked perfect... 6 nice little polished blemishes. The little polished bits are no more than 1/64" long... so it must be just touching.

Thanks for your help...that little tip pretty much solved my problem. I now know the cleaning rod method was off, and that the slit case method produced good data.

 

[queen_stick]

I build sprint car motors on the side so I have a tendancy to be alittle anal haha.

Full size or micro?

Full size 358's amd 360s. Mainly doing street/strip motors now

awesome. I used to be on the 'pit crew' for a my best friend who ran a couple different micro's.
Sprint cars are insane! I drove a micro sprint with a 250 air-cooled and another one with a 600 (yamaha r6 motor). All custom built motors running on alc (as I'm sure you know)... ridiculous weight-to-HP ratio in those cars.

Never drove a full size... But I know I would shat myslef if I did! lol

Do you know Doug or AJ Micheal? The only people I kow personally that ran full size sprints (358's and 410's)

 

[audredger]

Hunting loads should be no longer than magazine length unless, you are shooting a single shot.

 

[loudandproud]

Hunting loads should be no longer than magazine length unless, you are shooting a single shot.

Savage's come with plenty of room...

 

[Erik Cortina]

Are you measuring rounds base to tip?