Hornady Lock n Load OAL Guage

One real advantage to reloading is the variety of bullets you can choose from, which allows you to reload exactly the correct bullet type to your chosen rifle sport. Manual manipulation of their seating depth is vitally important for accuracy and correct grip tension from the brass. One of the best ways of increasing the accuracy from your rifle is to alter the relationship between the bullet and the rifling in the barrel, in terms of distance from each other. Most factory ammunition will have bullets seated a fair way into the case to make sure they feed through a magazine correctly, but by seating your bullet out a little further you can lessen that jump between bullet and rifling and hopefully achieve better concentricity and alignment as the bullet enters the rifling. This simple step can be accurately measured with many tools.

Altering the Overall Length (OAL) of the cartridge opens up so many avenues for the shooter in experimenting with differing bullet types with regards to construction and shape. You may favour longer range shooting where a more streamlined and higher ballistic coefficient bullet is desirable or if woodland stalking at closer ranges is your norm, then a more typical soft point or round nose design may suffice. You will find that a certain bullet likes certain seating depths for best accuracy and velocity, so by experimenting with differing overall lengths, you will be doing yourself and your quarry a favour. The combinations of bullet and seating depths are endless, so be warned. It can send you a tad mad chasing the perfect seating depth, but by using the Hornady Lock-N-Load gauge, it really simplifies the process and achieves very accurate results too.

Ethos

This is one piece of kit that every serious shooter or handloader should own and it works in tandem with the Hornady bullet comparator device to take real measurements. These two precision items can mean the difference between realising your rifle’s true accuracy potential and not, as well as ensuring your reloading dies are set up correctly and more importantly safely.

It is a proven fact that most rifles shoot more accurately when the bullet is seated in the case just off the rifling lands. This means that the ‘ogive’ part of the bullet, the curved section of the bullet just ahead of the bearing surface area or shank, is seated just shy of the start of the rifling. This ensures that the bullet has less ‘jump’ from case to rifling that might upset its initial progressive flight and that the bullet enters the lands of the rifling concentrically, ensuring a uniform start. Also, by being seated off the lands, the chamber pressures can be drastically reduced, especially if running your loads at full throttle. A few thousandths of an inch difference in this measurement can result in fair accuracy or spectacular accuracy as the ‘sweet’ spot is reached - each rifle has one.

Up close

This Hornady OAL gauge looks like a chamber bore guide with a removable sliding inner section to which a cartridge case is attached. To start using the gauge, you will need to purchase what is called a modified case that fits your rifles chamber. This fits to the gauge via a threaded section at the tip. There are over 80 modified cases available and they cover the most popular calibres.

Next, select the bullet you intend to use in your reloads and slip it into the neck end of the modified case. The internal push rod is made from tough, glass-filled nylon and is held in place by a thumbscrew at the rear of the gauge. Loosening this allows the rod to be positioned to support the bullet and prevent it from falling back into the case body. Next, insert the gauge by sliding it into the chamber of the rifle until it is a snug fit. Do not ram it in, you just need a surface to surface fit for accurate results. After loosening the thumbscrew, you can then slide the push rod forward until the bullet makes contact with the lands of the rifling. At this point, you have reached the maximum OAL with that shape, calibre and ogive of the bullet in that rifle. Of course, if a different bullet was to be selected (round nose, soft point or especially VLD(very low drag), the contact length would alter and the OAL would change due to the differing bullet length and ogive to lands contact. It is precisely these differences that ensure that the OAL of any bullet combination is the most accurate within the confines of your own gun.

Armed with this information, you can now confidently transfer this measurement to your logbook as a permanent record for that case and bullet type combination. More importantly, you can use this invaluable measurement in setting up your seating dies when you actually reload.

This is where the Hornady Bullet Comparator comes to the fore as this device gives a reading that will give you a more precise and accurate result as it measures the ogive length to the base of the cartridge, not the tip of the bullet to base. You can also check bullet uniformity without a case with this tool, to ascertain the base to ogive uniformity of individual bullets and sort them accordingly. I have covered this before. The bullet comparator can be easily attached to the blade of your callipers with the thumbscrew provided and the use of the interchangeable insert bushings allows any calibre to be measured for the bullet ogive.

Results

Typical bullet seating depths for a .308 Win cartridge start with the maximum OAL of 2.80”, which is the typical short action length. This allows most bullet types to be seated correctly for use in magazines without hang-ups, unless it has been modified, you single load the rifle or the gun has an especially long throated chamber.

Using the cutaway of the old Tikka barrel, which is quite worn, to be honest, I tested several types of .308 bullets to show the differing overall lengths measured using these tools for a true ogive to rifling lands datum point from which you can work backwards to achieve the best depth/bullet jump for your rifle.

First up were the Sierra 125-grain Pro Hunters, which are flat-based, soft pointed bullets. The measurement was 2.3100” due to a short stubby nose profile, but as a result, the bullet barely seats in the case. The Nosler 150-grain Ballistic Tips measured 2.3000”, with the boat tail section seated down to the case shoulder. They measured nearly the same OAL as the 150-grain Accubond at 2.3295”, but the B-Tip was seated deeper into the case, taking up more powder space.

The very round-nosed profile of the Nosler 170-grain Partitions (with more forward ogive) gave a shorter OAL of 2.285”. Plus, most of the bullet ended up occupying valuable powder space within the case itself. By comparison, the super sleek 175-grain Nosler RDF bullets had an OAL of 2.2835”, but not seated so deep as a lot of the forward section never touches the rifling. Finally, the Nosler 220-grain came in at 2.2865” OAL. This was due to the ogive being closer to the meplat region, like the 170-grain version.

So, if you were loading a 150-grain Ballistic Tip with the bullet touching the rifling lands at 2.3000”, then start 50 thou off the rifling lands and work up in 10 thou increments. That way, you can look for pressure signs and then check the target groups for signs of shrinking or enlarging of the group size.

Conclusions

By becoming proficient with this tool or set of tools, you can drastically improve your rifles performance and tweak it just right to get the best accuracy. These measuring tools from Hornady provide data that can be catalogued and used as a reference in the future. This is also a great way to check on barrel or rifling erosion of the bore as you can see the changes in the OAL of your cartridge. You will also be surprised how far from the lands that some VLD and lead-free bullets need to be seated for safe and accurate results too!