How do I choose the optimum bullet seating depth?

L

Lavid2002

New member
Im using hornady 110 grain FMJ bullets. I put one barely into a casing and gently set it into into the rifle. I closed the action and measured the casing. It was 2.532 This is the "toutching the lands" Measurement correct? So I should subtract .01 or .02 off of this? The book reccomends 2.6 something...wich is obviously too much for this style bullet. The action wont close on it!
It is a 110 grain though. different design. How far should I seat the bullets. P.S. This is NOT a maximum load. Im using minimums to be safe. First .308 load! Thanks fellas! P.S. Ill be loading some HPBTs later so I will follow the same principle. Thanks!
Dave
Be right back...im going to go seat another bullet using my rifle and double check my "touching the lands" measurement
-Dave
 
New measurements

Ok guys. I just BARELY seated one this time, It made me smash it to close the action. 2.559" Is the new TTL measurement.
I cycled the same round 3 tymes so it would be nice and in there, no crazy measurement. Hope this is right. Whats the story?
Thanks guys!
Dave
 
Read to stay .02 off the lands. I did so last night....why? Because I read so...and also it seemd close to me...If I need to seat deeper...No problem back into the die they go! So 2.500? Why so short?
Can you give me the law of OAL. I will obiously seat more than this. And Asking you guys every time would be rediculous.
Thanks!
-Dave
 
P.S. these are for a bolt action savage 12. I also loaded some 168 grain Nosler HP BT bullets. These I also seated .02 off the lands measurement I aquired by seating a bullet into a casing via closing the action on the cartridge ( A tip from a buddy of mine).
What should I do to aquire my optimum OAL for this rifle? And once I get that I read to change it by .005 up and down until I get the best groups.
Yay, Nay?
Any and all advice is appreciated!
 
Lavid: You are confusing me with terminology and perhaps you are confused with the terms.

case length - is the length of your case with out a bullet. There is a minimum case length and a maximum case length (there is no bullet in the case)

OAL/COL - Overall Length ( OAL ) or Cartridge Overall Length (COL) - The total length of a cartridge, measured from bullet tip to base of case.

The COL can be anywhere from 0.005 to 0.040 (and longer or shorter) off the lands for ideal shooting.

Recommended COL for a 110 gr bullet is 2.800

Now with those terms in common, please try to explain your problem again.
 
Recommended COL for a 110 gr bullet is 2.800

Now with those terms in common, please try to explain your problem again.
Click to expand...
OAL-Over all langth. Case length-Is the distance from the headstamp to the top of the neck of the casing. Where Was I confusing?
110 grain bullets can have different ogives and thus the reccomended Over all length varies per design.


Im wondering where I should start with my rifle. How can I figure out my optimum OAL. There are different methods I hard (Using tools bough, or manually seating a bullet Via closing the action and backing off X distance. I am wondering how far I should back off my loads after finding out my toutching the lands OAL measurement.
 
I usually do like you've been doing. Put a bullet in an empty case and close the bolt and measure. Every gun/powder/bullet combination is going to like a different distance off of the lands. It might make a huge difference in accuracy or it may not. I usually start out at .025 off of the lands. I'll load 10 or so like that. Then I'll load another 10 a little closer and maybe another 10 a little further out. Shoot and see if it groups better closer or further from the lands and go from there.
 
The optimum distance off the lands, which should give you the best accuracy, will vary with the bullet and the load. Before you can set the optimum off the lands distance, you must have an accuracy load to compare it to.

Using the COL listed in your literature, work up a load that gives the best accuracy. Once that is developed, start experimenting with with off the lands distances. The tool that will best give you accurate COL readings from the ogive of the bullet, not the tip which varies, is called a comparator.
 
Well. I loaded them .02 off the lands. So well shoot them then go from there...sound good? Again, I am using minimum loads so there are no pressure problems here. Correct?
 
If your too close to the lands it can cause pressure build up especially with a slower burning powder. First rule of thumb is to make sure they fit into the magazine. Dont be so torn up on how much free travel you are going to have. In a varmit rifle like my .222 i have the bullet just kissing the lands, sometimes 1mm off the lands. It makes no difference to accuracy. In the bigger calibers with slower burning powder and those long projectiles they have to drive out, a little free travel is ok. Look at Roy weatherby rifles they free bore with beautiful accuracy. Even the 6.5x55 they travel a mile befor they engrave the lands. The only problem you might have if you seat too deeply is the bullet can hit the lands off center and cause unbalance when it leaves your barrel. In saying that roys rifles have heaps of travel. In my .300 i work to fit the bullet in the magazine first then take things from there. Good luck the .308 is a fine rifle.
 
Make sure the case isn't long, then seat the bullet so that it is just off the lands. Make sure it will cycle reliably; that's why you don't want it touching the lands.
 
yes the last thing you want is for the bullet to wedge in the barrel when you go to eject and powder too spill out through the action. I only kiss on the lands in my .222, all larger calibers i allow about 2mm, or fitting into the magazine which ever comes first.
 
I use the Hornady OAL measuring device and then typically set my rifle loads .02" off the lands. Works great and gives the best accuracy. YMMV, depending on your chamber. I like using the gage better than the old "sharpie" or "blackening" method, it's more accurate.
 
How do I choose the optimum bullet seating depth?

Im using hornady 110 grain FMJ bullets. I put one barely into a casing and gently set it into into the rifle. I closed the action and measured the casing. It was 2.532 This is the "toutching the lands" Measurement correct? So I should subtract .01 or .02 off of this? The book reccomends 2.6 something...wich is obviously too much for this style bullet. The action wont close on it!
It is a 110 grain though. different design. How far should I seat the bullets. P.S. This is NOT a maximum load. Im using minimums to be safe. First .308 load! Thanks fellas! P.S. Ill be loading some HPBTs later so I will follow the same principle. Thanks!
Dave
Click to expand...

Since this is your first 308 load I’d recommend going by the Hornady data (COL) for your Hornady bullet. My older Hornady manual 4th edition lists the COL at 2.515 for the 110gr FMJ bullet. If I were you I would try varying the powder charge before trying to change seating depth. I find I get better results (groups) by varying the powder charge or trying different powders than by changing seating depths.
 
Lavid2002
Ill be loading some HPBTs later so I will follow the same principle. Thanks!
Click to expand...

In my 308 shooting 175gr Moly SMK’s loaded at mag length ( COL 2.800 ) I get under ½ inch groups at 100 yards. If your going to shoot custom bullets then loading into the lands probably would be better, but for factory rifles using 165gr to 175gr depending on your rifles twist rate a COL of 2.800 will probably give the best results.
 
It seemed tow ork just fine. Me and my ar15 shot these today!
We couldnt go to the 100 or 200 yard range, however we did make it to the 50 yard range!
Heres my groups, 1" and 1 1/4". The other loads yeilded 2" groups max.....Not bad for my first few reloads.
DSCF1842.jpg

and
DSCF1843.jpg
 
MIght want to re-look your seating depth.

Here is another two cents on the subject. I also have a .308 Savage Model 12 and just started shooting the NRA mid-range F class at 600 yards. To date, my groups are all under .6 MOA at that range. I use the Hornady OAL gauge and comparators, bullet and case, to determine the max to-the-lands seating depth at the ogive, for each DIFFERENT bullet I reload. I then back off from there, starting at .02 off the lands. I measure every bullet to ensure I am at the correct depth off the ogive. Some like to go to the lands, but I would rather not chance an overpressure. THEN I back off at .01 increments to see where the "sweet spot" is for my rifle - the best accuracy. What is interesting, my rifle gets me the best accuracy with standard commercial Hornady Black 168gr A-Max off-the-shelf ammo! So, I duplicate it. It has a COAL of 2.81. When using Hornady 168gr ELD, it is different, still working on the finding sweet spot for it, and I am going to try Sierra 168gr TMK's. Savage says their testing show the Sierra Match King is getting the best accuracy in their testing. It is is important to understand the terminology: OAL, COAL, ogive difference (secant vs tangent) and so on. Both for communicating with others ensuring you don't use the wrong measurements.
 

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