Reloading Step 4: Seating the Bullet
Updated: Dec 9, 2022
This is the fifth installment of the multipart Blog all about rifle reloading. In this blog, we will discuss the fourth and final step: Seating the Bullet. Organizing it this way will make for shorter reads and easier to find answers to questions you may have.
Top two rules while reloading:
# 1 Rule = Safety
# 2 Rule = Everything should be repeatable
1. Resize Case 2. Seat Primer 3. Add Powder 4. Seat Bullet
The last step in the reloading process is seating the bullet. The depth at which the bullet is seated is an important piece in the tuning puzzle. The most common way of talking about seating depth is in relation to the .000” mark . The .000” mark is when the ogive of the bullet just touches the lands of the rifling. Many shooters call this the “just touching” or “touch point” mark.
Once you find the “just touching” point, record the B.O.L. (see below) This is the measurement from which all other bullet seating depths will be based. For example; when the bullet is “jammed” into the rifling .010" (.010" farther than the .000" mark), we would call that +.010. If the bullet was off of the rifling (jumping) by .010, it would be called -.010.
Another term that should be defined is sticking point. This is the jam length that causes the bullet to stick in the lands when not fired and ejected. Stuck bullets can cause the powder to spill out in the chamber, possibly getting into the workings of the trigger. It is important to understand that the sticking point is based on how much neck tension is being used. In other words, the sticking point for one person might be different than another.
C.O.L vs B.O.L
C.O.L (Cartridge Overall Length). This measurement is taken from the base of the case to the tip of the bullet using a caliper. I use this measurement when finding the maximum length due to magazine size. Caution: C.O.L. can change based on each individual bullet length. In other words, this is NOT a very reliable measurement when discussing seating depth.
B.O.L (Base to Ogive Length). This measurement is taken from the base (of the bullet or case) to the ogive of the bullet. I use the Hornady Lock-N-Load Bullet Comparator attached to a caliper to get accurate measurements. This is the measurement that should be used when keeping track of bullet seating depth.
Finding the .000” Mark
There are numerous ways of finding the “just touching” mark. Many techniques can be accurate and repeatable. Others...not so much.
It is important to find a method that you can perform and obtain consistent results. Some of these procedures are based on feel. If you choose one of those methods, make sure you can "feel" the same way each time. Unreliable data is, oftentimes, worse than no data at all.
A Few Methods for finding the .000” Mark
Hornady’s Lock-N-Load Overall Length Gauge
Specific directions come with this tool. Below is a quick example of how it works.
This is a rod type device where you screw a purchased, threaded, case onto a rod. A bullet is then placed into the neck of the case. The cartridge is inserted into the chamber and an inner rod is pushed forward through the outer rod. This inner rod travels through the case and will push the bullet into the barrel until the bullet’s ogive hits the lands. Lock the inner rod to the outer rod with a set screw. Withdraw the cartridge and bullet. Place the bullet back into the case until it contacts the inner rod. Record B.O.L
Sinclair’s Bullet Seating Depth Tool
Specific directions come with this tool. Below is a quick example of how it works.
A measured bullet is loosely inserted into the barrel. A supplied seating depth guide is inserted into the action. A rod is inserted through the depth guide and pushes the bullet forward until the bullet’s ogive hits the lands. The rod is then marked against the depth guide with a set screw. The rod and bullet are both removed. A resized case is inserted into the chamber. The same rod is reinserted through the depth gauge until it stops against the base of the case. The rod is again marked against the depth guide with a second set screw. The distance between the two set screws is measured and added with the length of the bullet. This is the C.O.L. The same bullet is seated in the case until the same C.O.L. is reached. Record B.O.L.
Steel Wool the Bullet
Resize the case with a decent amount of neck tension. Seat a bullet long. Use steel wool and shine the bullet. Insert the cartridge and close the bolt. Eject the cartridge. Look for “scratches” where the lands of the rifling touched the bullet. If you find marks, seat the bullet farther in the case. Repeat the process until there are no marks on the bullet. Record B.O.L.
Seat the Bullet Long
Resize the case but use very little neck tension. Seat the bullet long. Measure the C.O.L. Insert the cartridge and close the bolt. Since the bullet was seated long, the lands will push the bullet back into the case. Eject the cartridge. Remeasure the C.O.L. Subtract those two measurements. Change the seating depth by that amount. Repeat the process until the two measurements are the same. Record B.O.L.
Seating Custom vs Mass Produced Bullets
Regardless if the bullet is custom or mass produced, there is a key piece of equipment to remember when discussing seating depths; the point up die. This die is the final step in the bullet forming process.
Custom bullet makers will use a single point up die for a particular bullet. One positive outcome is; the same (caliber, weight, and ogive) bullet will be seated at the same depth regardless of total bullet length. (Assuming no adjustments were made to the reloader’s seating die). In other words, as long as the custom bullet maker does not change the point up die, a bullet seated today would seat at the same B.O.L. as a bullet from ten years ago.
This may not be the case with mass produced bullets (Sierra, Hornady, Nosler, etc). Many brand bullet manufacturers may use multiple point up dies for the same type of bullet. The negative outcome is; even though the reloader’s seating die did not change, there may be different seating depths.
It is not uncommon for a handloader to seat mass produced bullets out of the same box and have several different B.O.L. readings. The reloader is not doing anything wrong, the bullets are simply different. You will have to be the judge if the loss of precision is acceptable.
Experience Tip. If you want to keep the same seating depth, but use mass produced bullets, you can sort the bullets. An easy way to sort the bullets (although not 100% reliable) is by using a bullet comparator and measure from the base of the bullet to the ogive. Sort into as many piles as necessary. Switching piles will require an adjustment to the seating die if you want to keep the exact same seating depth.
There are a couple different styles of dies used to seat the bullet in the case. The most common is the ⅞-14 threaded dies. Many of the brand die makers produce this kind of die (RCBS, Redding, Hornady, Lee, etc) This type of die screws into the top of the reloading press. Micrometer tops can be purchased that make it easier to accurately adjust the seating depth.
The overwhelming majority of short range Benchrest shooters use Wilson chamber style seater dies. This die is used in conjunction with an arbor press. Like the threaded dies, micrometer tops can be purchased.
Experience Tip: No matter which die you use, make sure the tip of the bullet does not touch the seating stem of die. The circumference of the stem should contact the ogive of the bullet. When finding consistent seating depths, all bets are off if the tip of the bullet contacts the seating stem.
Runout is a measurement that tells how crooked the bullet was seated in the case. There are many different concentricity gauges that measure runout. Almost all of them use a dial indicator that touches the bullet while the case is rotated in the device. The more the needle moves the more runout there is.
I use Sinclair’s bullet seating depth tool to find the .000” mark. I made a tighter fitting bullet seating depth guide by turning a piece of delrin down to the action size using a mini lathe. Over the years, I have learned how to feel when the ogive just touches the lands. This tool is used in conjunction with a worksheet (found in reproducibles). The worksheet keeps track of the .000” mark, round count, and throat erosion for a particular barrel.
My competition barrels only get fed custom bullets (BIB). Simply put; custom pills can be tuned to shoot tighter groups. For hunting rifles, I shoot a combination of custom (BIB) and mass produced bullets. Another reason I like custom bullets is that I never have to worry about inconsistent seating depths. However, a coyote can not tell the difference between a three-quarter inch rifle and a half inch rifle.
To physically seat the bullets, I like to use Wilson chamber seating dies with a K&M arbor press on all my cartridges. When possible, I order a blank Wilson die and have the gunsmith use the chamber reamer to cut the seating die.
I stopped measuring runout years ago. The Wilson chamber dies seat the bullets square with the case. The tiny amount of runout is a non issue for the short yardage competitions and hunting that I do. If I was a long distance shooter (600 yds or more) then I would pay more attention to runout.
Seating depth is an important piece to the tuning puzzle. Develop a system that allows you to confidently find the :just touching” point, then start adjusting the seating depth to find where your rifle shoots the best.
As with most things in the reloading world, the attention is in the details. Little things do matter. Connect the Dots is here to help you develop your own process to pay attention to these details. Until next time, enjoy the experience.