Bullet seating depth
- Thread starter Silverado
- Start date
One way to do it is to full length resize a case then cut small slits down the neck of the case so that it will hold a bullet inserted into it with a bit of tension. Then you put a bullet just into the mouth of the case then chamber the split dummy round into the chamber of your rifle. The bullet will hit the rifling and be pushed back into the case. Then you carefully remove the case without disturbing the bullet and measure the overall length, I usually do this 5 times to get an average but if you are carefull all the measurements will be really close. This will give you the OAL to the lands so now all that you have to do is subtract how much back you want to be to get the OAL for you loaded ammo.
There is another way where you seat a bullet long in an empty case then smoke the bullet with a candle to get some soot on it then chamber the round. Once you remove the dummy round you measure the length of the rifling marks on the bullet and subtract it from the OAL of the dummy round which will give you the length to the rifling.
Or you can buy a Stoney Point OAL guage, see link below.
http://www.stoneypoint.com/oal_index.html
There is another way where you seat a bullet long in an empty case then smoke the bullet with a candle to get some soot on it then chamber the round. Once you remove the dummy round you measure the length of the rifling marks on the bullet and subtract it from the OAL of the dummy round which will give you the length to the rifling.
Or you can buy a Stoney Point OAL guage, see link below.
http://www.stoneypoint.com/oal_index.html
Without a Stoney point gauge,
1.Resize a case,
2. Seat the bullet long and measure with vernier
3.Mark the bullet with a black magic marker
4. Chamber the round and close the bolt easy
5. Open the bolt, extract the dummy round.
6. the marker will rub off where the bullet is jammed into the rifleing
7. If the bullet gets jammed, tap it out with a cleaning rod
8. Turn seating die down and re-seat the bullet
9. Blacken the bullet again and repeat process until there in no rub marks on the bullet
10. you are now just off the lands, depending on how much you crank the seating die down
Some rifles/ bullets like the bullet touching, some don't.
If the bullet is touching there will be increased pressure.
Some rifles like the bullet touching, some shoot better .005 off the lands some like .020 off some like .040 off.
After you find the load that works, seating depths fine tune the load.
This method is for single loading. If you plan to load from a mag they may be too long.
1.Resize a case,
2. Seat the bullet long and measure with vernier
3.Mark the bullet with a black magic marker
4. Chamber the round and close the bolt easy
5. Open the bolt, extract the dummy round.
6. the marker will rub off where the bullet is jammed into the rifleing
7. If the bullet gets jammed, tap it out with a cleaning rod
8. Turn seating die down and re-seat the bullet
9. Blacken the bullet again and repeat process until there in no rub marks on the bullet
10. you are now just off the lands, depending on how much you crank the seating die down
Some rifles/ bullets like the bullet touching, some don't.
If the bullet is touching there will be increased pressure.
Some rifles like the bullet touching, some shoot better .005 off the lands some like .020 off some like .040 off.
After you find the load that works, seating depths fine tune the load.
This method is for single loading. If you plan to load from a mag they may be too long.
257Roberts
CGN frequent flyer
- Location
- Peterborough ON
I have made my own measuring tools.
I use cut off cleaning rods and locking two collars on the rod.
Close the action cocked safety on.
Insert the rod with the collars into the muzzel. (coated cleaning rod and be gentle)
Lock the second collar against the first collar against the muzzel.
Open the action and easily pull out the rod part way.
Insert your bullet of choice through the chamber and hold it against the rifling. I use a piece of dowel.
Slide the rod back down against the tip of the bullet and slide down the first collar against the muzzel ( sometimes takes 3 hands) and lock it there. Measure the distance between the two collars and you have your Max overall length.
Be gentle and compare three bullets for an average.
It has worked for me. Just make sure that the old cleaning rod is close to the bore size so it will contact the tip of the bullet. Also make sure that the action is cocked or you may measure firing pin protrusion.
I use cut off cleaning rods and locking two collars on the rod.
Close the action cocked safety on.
Insert the rod with the collars into the muzzel. (coated cleaning rod and be gentle)
Lock the second collar against the first collar against the muzzel.
Open the action and easily pull out the rod part way.
Insert your bullet of choice through the chamber and hold it against the rifling. I use a piece of dowel.
Slide the rod back down against the tip of the bullet and slide down the first collar against the muzzel ( sometimes takes 3 hands) and lock it there. Measure the distance between the two collars and you have your Max overall length.
Be gentle and compare three bullets for an average.
It has worked for me. Just make sure that the old cleaning rod is close to the bore size so it will contact the tip of the bullet. Also make sure that the action is cocked or you may measure firing pin protrusion.
Something to consider with any system - and all the ones above work - is that bullet ogives and thus the contact point with the leade can vary. IF one were loading on the hot side, with the bullet in firm contact with the rifling, a change in bullet contour could affect the amount of "jam", and raise pressures.
257Roberts
CGN frequent flyer
- Location
- Peterborough ON
This is very true tiriag. With my method if you wanted each round to touch the rifling you would have to measure each bullet and load accordingly. I also use a sinclair tool that measure the ogive transition at the bore dia. and I am finding that the max length varies .008" depending on the bullet manufacturer.
Its all fun and games untill a primer gets pierced or a case gets stuck.
Its all fun and games untill a primer gets pierced or a case gets stuck.
the way i was shown and have used for years is too find your rifles actual overall chamber length. to do this i close the bolt with and empty chamber. i slide a one piece cleaning rod down the barrel till i touch the bolt face, then i mark the rod at the muzzle. then i open the bolt and insert a bullet to the chamber and lightly tap it onto the lands(just touching). then i re-insert the rod until it just touches the bullet and then mark the rod. put your calipers on the marks and there is you overall chamber length. then i just measure my overall cartridege lentgh and adjust the seating depth till i find what works. i personally don't like the bullet on the land and usually average .oo5 to .010.
Play it safe and take your time starting from factory recommended loads/lengths etc. Many guns/loads etc. benefit from reduced bullet jump. My 602 in 375hh likes the standard oal with a 260gr accubond but likes 300gr hornady rn .020" off the lands, go figure.
No one measurement of over all cartridge length will work, since each bullet shape and weight will contact the lands at a differnt oal. Most of the systems described will work, but remember, if you change bullet shape, weight brand, or if the manufacturer changes style, you need to re-measure. Else you risk ramming a bullet intot he lands, going over-pressure, and at the least, being embarassed as you search for a tool to smack the bolt open. Best possible result. Worst is picking brass gas and wood out of face, eyes and hands.
