bullet seating depth

[Eagle Eye]

I had some time today and measured bullet seating depth on my M1 Garand and Rem700
I used precision mic's

reading for the 700 was .200, and .203 for the M1.

For each, I seated a bullet in an unprimed uncharged case that had been trimmed to recommended length.

I seated bullet to -.001 max COAL then used the bullet seating tool to see where i was. (btw no cycling issues encountered)

700 I was at .164
M1 I was at .124

In my head this is as close as I can get to the readings obtained by the tool. Is this right?

I haven't tried different bullet shapes yet, but i suspect that will affect things.

thanks for reading

oh and are there any pitfalls I am getting ready to step into?

 

[JCW355]

You need to make sure you start with a low powder charge and work up always to be safe. Your OAL will be different with different bullet types but the distance where your bullet engages the lands on the rifling should be only 1 measurment. That could change over time depending how much a gun is shot. When I reload, I measure to the lands/rifling, subtract a specified amount, I forget that number without looking, start low and work up the powder charge. I also check to make sure the OAL isnt too long to work in a magazine. If it is then you have to make the distance from the lands/rifling greater so the bullet will function. Im talking about 2 different measurement

 

[Larry Morgan]

I have measured seating depth this way on my rifle. There are a few issues I ran into though.. First, in my rifle, a VLD style bullet has just the right taper to form a mechanical lock very easily in the the leade and throat, so it gets more difficult. I had to slowly drop the COAL until it stopped grabbing the bullet. The problem is that I had to full lock the bolt to ensure the round was fully chambered, but if the bullet grabbed, it would have to be knocked out.. Shorter HPBT bullets didn't have this issue. The second is, if you don't have much neck tension, accidentally bumping the bullet can knock it back and give a false reading.

And yes, different bullets and different rifles will each give different readings.

 

[Eagle Eye]

You need to make sure you start with a low powder charge and work up always to be safe. Your OAL will be different with different bullet types but the distance where your bullet engages the lands on the rifling should be only 1 measurement. That could change over time depending how much a gun is shot. When I reload, I measure to the lands/rifling, subtract a specified amount, I forget that number without looking, start low and work up the powder charge. I also check to make sure the OAL isnt too long to work in a magazine. If it is then you have to make the distance from the lands/rifling greater so the bullet will function. Im talking about 2 different measurement

I with ya. I think I am just asking if my thinking about this topic is correct.
The brass i am using is sized to 0.002 from headspace. Case neck was then trimmed to recommended case length. The measure at which the bullet contacts the lands is 0.200 (for the 700). This should not change like you said. I want to get the bullet as close to the lands as possible.

The smallest depth that I can seat the bullet is when COAL is just under maximum. There is a warning that the bullet should be seated at least as deep as it is wide. no problem there. when done, I want to know how close this bullet is to the lands. It turns out the bullet is behind the lands (measurements listed in OP). I figure that this is the smallest distance between bullet and lands I can achieve with this bullet, because the cartridge is at max COAL.
Q1: Is this correct?

Could I achieve a smaller distance between bullet and lands IF I trimmed case neck to just over recommended case length (so lengthening the case overall length)?
I am thinking not, since I am seating to max COAL (just under max).
Q2: Is this correct?

If I tired a different bullet, lets say a round nose, and seated to max COAL, I may find that distance between bullet and lands, relative to the distance in first example, is smaller, larger, or the same. Theoretically I might need to seat bullet deeper (reducing COAL).
Q3: is this line of thinking correct?

 

[Eagle Eye]

I have measured seating depth this way on my rifle. There are a few issues I ran into though.. First, in my rifle, a VLD style bullet has just the right taper to form a mechanical lock very easily in the the leade and throat, so it gets more difficult. I had to slowly drop the COAL until it stopped grabbing the bullet. The problem is that I had to full lock the bolt to ensure the round was fully chambered, but if the bullet grabbed, it would have to be knocked out.. Shorter HPBT bullets didn't have this issue. The second is, if you don't have much neck tension, accidentally bumping the bullet can knock it back and give a false reading.

And yes, different bullets and different rifles will each give different readings.

I had to knock a bullet out several times for the same reason.

Do you determine neck tension by measuring diameter of neck?

 

[swampratt]

A lot of my guns have the bullets seated longer than max OAL that books state.
Do you determine neck tension by measuring diameter of neck?
Yes.. measure neck ID and bullet od..if there is .002" less ID in the case then you have what is refereed to as .002" neck tension.

There are many bullets that do not have the "bullet diameter" into the neck when seated

I seat a bullet in a dummy round like you did. I seat it long, Then color the bullet from the tip to the bearing surface with a sharpie.
I measure the OAL.
I then insert this into the chamber and close the bolt. The oal will change as the bullet is seated deeper into the case.
I open the bolt and remove the round and measure again.

NOTICE the marks on the bullet where you colored it with the sharpie.
I continue to seat the bullet deeper and deeper until it no longer has any marks on the sharpie colored area.


There is a point where you will have marks but the bullet is not stuck..The guns i have usually have .020-.030" area where you can seat the bullet into the lands making marks on the colored round.. but no stiff bolt lift .

Some bullets i have liked to be jammed into the lands for best accuracy..so Basically touching the lands for .030" and then another .010" more.

Not a good practice. especially if you need to extract the unfired round..the bullet may stay in the tube and a case of spilling powder comes out.

Handloaders will try many depths and wizardry to get that accurate round.

mark a bullet with a sharpie and chamber it and see if you get marks on it..if you are chasing the lands.

 

[swampratt]

Then you start measuring the bullet ogive to the base of the bullet and find more than one measurement in the box of bullets.

more tools.
http://www.sinclairintl.com/reloadi...r-hex-style-bullet-comparators-prod34262.aspx

 

[JCW355]

I reload a 7mm mag so the amount of bullet in the case is always greater than 7mm. Now my .243 is different especially when I load it with 55 grain bullets. They are short and to get enough bullet in the case, getting close to the lands is out the window. Like swampratt said you can have a cartridge longer than OAL as long as it functions fitting in a mag or cycling in a semi auto. Cut your cases like your suppose to do otherwise it might not chamber. Bullet length and throat play a role in your bullet seating depth. Yes to question 1, sounds like you're loading a short bullet or have a longer throat so you can't get closer to the lands. No to question 2. Question 3, different bullet profile will have their own max OAL You will have to get that from the bullet manufacturer for that specific bullet. I just remembered I use a stoney point over all case lenth gauge to get my measurements. I hope I answered your questions

 

[Eagle Eye]

You all have been a great help, THANK YOU!

i'll be posting my dope soon enough.