Hornady Lock-N-Load O.A.L. Gauge & Bullet Comparator Kit Review

Hornady LNL OAL Gauge & Bullet Comparator One of the most addicting aspects of reloading ammunition is the specialized tools that are so readily available today that improve the process and help squeeze every bit of accuracy out of your firearms. Two products that I recently invested in are the Hornady Lock-N-Load OAL Gauge & Bullet Comparator Kit (you'll also need to pickup a modified case - usually will be displayed right next to these products on the shelf. These three tools used together help determine how a specific bullet best fits into your chamber by its Ogive (pronounced o-jive). The Ogive of the bullet is the plane that lies between the straight wall and the rounding taper. Each bullet differs in greatly in base to tip dimensions, between each manufacturers unique "style," the bullet type, and the grain/size. In fact it's common for variations of up to .025" to exist from one bullet to the next. However the Ogive is what engages with the barrel's rifling lands, and gives the reloader a more consistent standard of measurement.

Basing your seated bullets off the O.A.L. (Overall Length, from case head to bullet tip) is standard stuff, and while it will help keep you within SAAMI specs and inline with factory ammo, you could be missing out greatly in terms of accuracy and performance. Measuring off the Ogive will give you a more customized relationship between your desired bullet and your specific rifle's chamber. The best metaphor I can think of is imagine if you could customize the tread on your car's tires so specifically to your vehicle and the road surface so that it gave you an extra 3-5 miles per gallon. While seating depth won't effect velocity, a bullet seated to a precise length relative to YOUR rifle's barrel will noticeably improve performance.

*Note: you will also need to keep in mind your magazine length limitations.  If the O.A.L. of your cartridge after fine tuning using this process is greater than the wall of the box magazine or bottom metal, then you will have to single load each round into the rifle.

The O.A.L length gauge and modified case let you set up a bullet in a case with maximum overall length between your closed boltface and the barrel's lands. You may be asking, how the heck do I measure the length to the Ogive instead of the bullet tip?  Well, thats where the Bullet Comparator comes in.  It is an adapter that easily attaches to the blade of your caliper. It comes with interchangeable inserts for bullet diameters including .224" (5.56mm), .243" (6mm), .257", .277", .284" (7mm), .308" (7.62&8mm). When installed on a rezeroed caliper, it lets you measure a cartridge from casehead to bullet Ogive. That's the shorthand version. For those who aren't passed out on their keyboards or off surfing YouTube, I'll explain the whole process a bit more thoroughly. If you grasp the concept, you can skip to my review key points.

Hornady LNL OAL Gauge & Bullet Comparator

First you take your modified case and thread it onto the O.A.L gauge, then lightly push your desired bullet into the case to the point where it's seated deeper than normally. For example, I'll thread on a .308 win modified case and then insert a Sierra 168gr MatchKing bullet. Just don't push it too far were it falls into the case or else you'll have to push it out or fish it out. Next, remove the bolt from your rifle (or use the curved gauge if your rifle's bolt does not come off)  insert the O.A.L. gauge through the action (slowly) and into the chamber. You don't want to jam it with too much force that you unknowingly alter the modified case. When its gently snug, you then push the plastic inner rod of the gauge forward, which will push the bullet forward in the case and if you're sensitive enough you will feel the bullet engage the lands of your barrel's rifling. You can then tighten the thumb knob and lock that inner rod, and pull the gauge out of the action.  Again, if you use too much pressure you may lodge the bullet in the lands and will not come out with the gauge, and you'l have to start over.

So now you have your gauge with the modified case and bullet still in position, and then get out your caliper with the comparator and proper insert installed. You will have to rezero the caliper closed on the comparator first. With both tools in each hand, insert the bullet tip into the comparator, and adjust the caliper to measure off the case head as usual. Now instead of a reading for overall cartridge length from casehead to tip, you will have the exact distance between casehead and your bullets Ogive (exactly 0.00" using my .308 win and the SMK 168gr) Now's were the fine tuning comes it. That dimension tells me when my bolt in closed, the shallowest I can seat that specific bullet where it will be into the lands of the rifling. You will want to back off of this some, between 0.015" and 0.02" typically to start but every rifle/bullet combo will have a sweet spot. It's up to you to determine whether your rifle's barrel prefers that specific bullet closer or farther from the lands.

While this may seem like splitting hairs to some, the accuracy difference can be up to 0.5-1 MOA.  At longer ranges, using the Hornady Lock-N-Load OAL Gauge & Bullet Comparator Kit can be the difference between a fantastic group in one singular hole, or just a decent 1 MOA group. Based on my results, I find I will almost never buy a box of factory ammunition, as long as I have the brass and components I am able to make cheaper and more accurate rounds.

Firearms Insider Reviews - 8 Key Points

Claim to Fame: Measuring cartridge lengths across bullet tips is not a reliable or repeatable method for measuring your reloaded rounds. The O.A.L Gauge and Bullet Comparator solve that problem by measuring rounds from a reliable surface on the bullet, the ogive, to provide consistent, precise measurements of your rounds and improved accuracy.

Target Market: Reloaders both Novice and Experienced

FNBs (Features & Benefits of this product):

What other aesthetic options or finishes are available?: The O.A.L Gauge comes in either straight or curved orientation to best work with your rifle's action.

What others are saying?: “I decided to order this comparator when I purchased my Remington 700 SPS Tactical (.308). When I bought this rifle, I wanted to take my reloading a step further and dive into the world of precision hand loads. Up to this point, I was reloading rounds mostly for target practice and a few for hunting every year. So the reloading gear I own was sufficient enough to get the job done, but not for higher quality hand loads. But as I began realizing how challenging precision hand loading can be, I knew that I would have to reach out and get some reloading equipment that could help me get the job done.

Due to the fact that I had no experience with the tools needed for this type of work, I simply called into Sinclair International and spoke with one of their many highly experienced reloading techs. He couldn't have been more helpful in explaining about important tools, explaining how and why they worked. As you may have guessed, he suggested this comparator as an essential tool for the entire process." Brownells Review Price Point:

Bullet Comparator

O.A.L. Gauge

I need it now! Availability: Brownell's

Our Rating:

  • Comparator is offered in different price points per how many different inserts/calibers you need, the basic 6 insert kit covers the common calibers
  • The OAL Gauge is easy to operate and the thumb knobs are well crafted

  • Each modified case needed is expensive!

Score: 8.5 Great