Headspace How to determine

[TXSTDU]

So many times I hear of a new load being .XXX off the lands. How to I measure correctly to determine what my new loads need to be to properly seat my bullet to be the most accurate.

FWIW I have looked and found the go/no go gauges and all that seems to show is if there is too much head space.

 

[Powder_Burns]

Re: Headspace How to determine

Bullet Comparator tool, or use the cleaning rod method to determine distance to the lands. The idea is that your cartridge, when loaded into the chamber, has a gap in front of the bullet up until where the rifling starts, called the leade or throat. Certain bullets are longer than others, and this variance determines how much room ahead of the case the bullet has before it makes contact with the rifling.
Headspace gauges show your headspace, what you are trying to measure is the length of your throat--not the headspace.

 

[Powder_Burns]

Re: Headspace How to determine

I seem to be posting this a lot lately..

how to determine OAL via cleaning rod method:

Take a cleaning rod, insert it into your barrel from crown to breach until it rests against the bolt face. (You do this with an empty chamber)

Use a pencil or piece of tape to mark the position of the cleaning rod at the crown.

Remove the cleaning rod.

Take a once fired case, lightly crimp or size the beginning of the case mouth so it has enough tension to hold a bullet but is still loose enough that you can push or pull the bullet out of the neck.

Take the bullet you are going to be loading, and insert it into the case mouth so that the majority of the bullet is sticking out.

Carefully insert the cartridge into the chamber, taking care not to bump or jolt the bullet so that it sets itself back into the case.

Carefully close the bolt, the bullet will make contact with the rifling and will slide into the case as the bolt closes.

Carefully reinsert the cleaning rod until it makes contact with the bullet tip.

Mark the position of the cleaning rod again, with your tape or pencil. Remove the cleaning rod and measure the distance from the first line to the second line you made. <span style="font-style: italic">This is going to be the cartridge overall length from case head to bullet tip, in full contact with the lands.</span> Anything longer would be considered 'land-jammed', anything shorter is 'jumping to the lands.' So when someone says their load has a .03 jump to the lands, you know their bullet is .03" away from making full contact. If they say they are land-jamming .002, you know the bullet is .002" longer than the maximum OAL.

Do this procedure a few times to get comfortable with what you are doing and take an average reading as your OAL.

Bear in mind that bullets can vary in length!
The ogive is the portion of the bullet which tapers from the bullet tip (meplat) to the shank where the full diameter of the bullet is. Ogive position can vary in relation to bullet length, this is why using a comparator tool is the preferred method.

 

[427Cobra]

Re: Headspace How to determine

Headspace, and how far to-in-off the lands are different measurements, which one are you asking about?