Help with load dev, Where's my node?

[sheshotme]

as far as the inter webs has taken me, I have only read on the "chamber a dummy round" method and the hornady oal gauge method. Enlighten me Gunny!

[ar15barrels]

I was trying to find my maximum OAL to lands of my action. I created 6 dummy cartridges (no powder) with a mild neck resize. Just enough for the bullet to be able to slide in and out of the neck with force. I inserted/removed the 6 cartridges into my rifle's action carefully. then measured with a caliper and comparator. I wasn't expecting such variance in length (ogive to base). i fear I may have to plunk down for those $40 hornady OAL gauges.

You are getting variation in how much the bullets are engraving into the lands from the inconsistency in neck tension holding the bullets.

Try it a different way which will give you a better feel:
Take the empty gun and drop a bullet (no cartridge case) into the chamber.
Using a piece of dowel close to bullet size (or even a pencil), press the bullet into the chamber until you feel it seat against the lands in the barrel.
Now, hold that bullet in place and put a wooden dowel (with a flat end) down the barrel until you feel it touch the bullet tip.
Now mark the dowel at the muzzle.
Now knock the bullet out of the barrel.
Now place the bolt in the rifle and close it on an empty chamber.
Now re-insert the dowel into the barrel until it stops against the bolt face.
Now mark the dowel at the muzzle again.
Withdraw the dowel from the barrel and measure the distance between the two marks on the dowel.
That distance will be the OVERALL length that your bullet was placed at when it was nicely touching the lands.

[mskochinski]

What he said[emoji867]


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[sheshotme]

wouldn't that then be base to tip? and each bullet isn't uniform.

[SixPointEight]

Correct. Once you know the length go to your press and load a case with the SAME BULLET used to make the measurement.

Load a case to the same overall length. Then measure with a comparator to get the ogive length, which will be consistent

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[sheshotme]

now i'm getting 2.98 base to tip. btw how much do i subtract to eliminate the comparator?

[bsumoba]

this is by far the best way to measure your touch to the lands, assuming you can pull the ejector and firing pin assembly out yourself and put it back.

I've learned through trying multiple methods that they all give me different measurements or they don't exactly mimic how the cartridge truly sits in the chamber.

This one mimics the way the cartridge chambers the best and you can fine tune it to get exactly when the bullet touches the lands and then turns into a "jump" within a few thousandths.

if you don't have a comparator to measure your CBTO, then do multiple bullets and measure OAL and I guess you can take the average

[SixPointEight]

I've always left the bolt intact. Size a case with a few thousand the just like I always would. Then slit the neck so a bullet can slide with light tension. Clip into the extractor and seat the bolt

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[sheshotme]

what was he using in the background? seating the bullet with a press? since he's doing it with such confidence to the 1/1000th, I assume he's using a die with a micrometer? this I do not have.

[ar15barrels]

wouldn't that then be base to tip? and each bullet isn't uniform.

That's why you use the exact same bullet to determine the length.
THEN, seat the bullet to THAT LENGTH and measure it with a comparator.
Now you have a COMPARATOR reading for your barrel which you can use with the rest of the bullets in the box that the MASTER bullet came out of.

[ar15barrels]

how much do i subtract to eliminate the comparator?

You don't.
You just USE the comparator number.
After you seat some bullets to the length you want, you can measure the OVERALL length and determine of they will fit into your gun's magazine.

[bsumoba]

what was he using in the background? seating the bullet with a press? since he's doing it with such confidence to the 1/1000th, I assume he's using a die with a micrometer? this I do not have.

if you want to really know your true touch, then this is the best way to go. nothing wrong with the other methods. just know that when you say 10K, 20K, or 30K off the lands that you may not truly be off the lands by that much. so, if you used say the hornady OAL gauge method and got your CBTO from this method, chances are good that you jammed the bullet in 15-20K. Think about it, if you have to "knock" the bullet out with a cleaning rod, then it is most likely jammed pretty good. So, when you seat that bullet "10K off the lands," you might still be 5-10K jammed.

To answer your question, he is most likely using a seating die with a micrometer top, and that is what most of us have. If you do not have one then do trial and error and back out/screw in the die a little at a time until you get the desired outcome.

[ar15barrels]

what was he using in the background? seating the bullet with a press? since he's doing it with such confidence to the 1/1000th, I assume he's using a die with a micrometer? this I do not have.

If you don't have a die that's adjustable to the 1/1000th, why are you concerned with getting bullet seating length measurements to the 1/1000th?

[ar15barrels]

This one mimics the way the cartridge chambers the best and you can fine tune it to get exactly when the bullet touches the lands and then turns into a "jump" within a few thousandths.

The method depicted in the video is faulty.
The SAME bullet is getting jammed into the lands over and over.
How can an accurate measurement be made when the part getting measured is getting re-formed during each measurement?

A new bullet should be seated for each step, or at least at the end, a new bullet should be seated to verify that the earlier measurement was actually correct.

[ar15barrels]

I've always left the bolt intact.
Size a case with a few thousand the just like I always would.
Then slit the neck so a bullet can slide with light tension.
Clip into the extractor and seat the bolt

If your ejector is left in the bolt, your measurement is tainted by the amount of headspace your test case has.