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Sinclair International Hand Primer Review

Updated: Oct 20, 2020

Sinclair International Hand Primer Review

One of the more interesting topics handloaders have resurfaced is primer pocket seating in relation to accuracy. Does it improve accuracy? How much do primer pocket depths vary? Do primer cup heights vary? How accurate can a hand primer be in regards to consistent seating depth? In this article, I break it down for you.

Scope of the test

In the first part of the test, I checked for primer pocket depth consistency. This is three times fired Lapua brass. Moreover, the reasoning for this is because if primer pocket depths vary, and I seat a primer, I will get inconsistent readings for the consistency of primer seating depth. The tool I am using in the video below is an Accuracy One Primer Depth Gauge.

Now, since my primer pockets varied in-depth, I next cut them using a primer pocket uniformer all to -0.121-0.1215"

Below you can see just how consistent the primer pocket uniformer is:


Primers, depending upon lot, can vary in cup height. Some more than others. Therefore, I purposely set the Sinclair Hand Primer to seat only 0.001" below flush, without the primer actually crushing. Moreover, since my primer pocket depths varied by 0.0005"+/-, I wanted to make sure I was not crushing primers, or the actual height difference from primer to primer would give me false readings of how consistent the hand primer can be. As a result, my primers averaged 0.1195-0.119". Since my primer pocket depth is set at 0.1215-0.121", I have roughly 0.001" more of wiggle room before my primers touch the bottom of the pocket.

How consistent is the Sinclair International Hand Primer?

In the next video, I have already set the hand primer to seat exactly at 0.001" below flush.

Here, from a very small sample size, before I test a hundred cases, I wanted to show you the results from these five cases already.

Sinclair International Hand Primer Consistency

1. From one hundred cases, 93 were exactly 0.001" below flush, 4 other cases were 0.0005" below flush, and 3 cases measured in at 0.0015" below flush.

2. After reviewing the results and having a few that were not dead accurate; it could have been false readings from my Accuracy One, or it could simply be user error from not pressing down consistent enough. Either way, a 93% success rate with this tool is incredible. Statistically, I would view the 0.0015" and the 0.0005" as outliers in my sample size of 100.

Furthermore, statistically, we can check if they are indeed outliers without just claiming that they are by using the interquartile method and a box plot for simplicity:

The formula for the interquartile method to identify outliers: e ∉ <Q1 - 1.5 × IQR; Q3 + 1.5 × IQR>

Quartile Q1: 0.001

Quartile Q3: 0.001

Interquartile range IQR: 0

Outlier Results: {0.0005, 0.0005, 0.0005, 0.0005, 0.0015, 0.0015, 0.0015}

Pressing The Handle down more

Even further, I wanted to see if it would change the seating depth if I pressed down hard a few more times.

How the Primer System works

The primer system itself comes with punches for both small and large primers. The body, head, and punch housings are made of stainless steel, while the handle is machined from aircraft-grade aluminum.

In order to switch from large to small punches, it takes roughly about 1 minute to unscrew the die head, loosen the nut, and switch the rods

In order to adjust the priming seating depth, you have to turn the priming punch push rod. On a side note, it appears to have some sort of glue that looks like red Loctite, but it is not. It is called Vibra-tight. All you need is a pair of pliers to turn it.

One full turn will move it .050" at a time, so, it is suggested to go in small increments when setting your primer seating depth, and only requires the rod itself to be snug on the eye bolt.

Subjective Analysis

When I write an article, I try to close with some of my own personal thoughts. While the rest is solely based on the gear and what I find without any bias, I always try and let people know what I also thought of the product from my own point of view.

Sinclair International Hand Primer

Pros: Consistent, relatively affordable compared to other similar tools, easy to assemble/disassemble, easy to switch from small to large push rods, extremely durable, minimalistic, able to feel the pressure of primers being seated by squeeze, uses Lee shell holders, head locking mechanism keeps brass in place without moving, four shims provided to manipulate the shell holder head to the most comfortable position depending upon how you hold the priming tool.

Cons: Not able to adjust primer seating depth quickly, have to disassemble in order to set primer seating depth, need pliers to adjust primer seating depth, ergonomics of the handle made my hand personally cramp up after 100 rounds, if tightened too tight when priming, it can sometimes leave a faint ring around the headstamp. However, nothing is protruding from it. I don't think it can mess with anything, no primer feed tray.

If you are curious about consistent primer seating depth in relation to accuracy, check this out.

All in all, this is one sweet priming system! Moreover, as a disclosure, this item was sent out to me for testing. In order to do these articles, items are sent out, but monetary compensation is NEVER asked for in return for testing. This gives me the freedom to say anything I find without bias and gives me the freedom of not having any strings attached whatsoever to any companies willing to have their products tested out by myself.

On a further note, one of the big proponents of this website is including yourself. Please, if you have tested this priming system before, send in an email or drop a comment on your results. While this is what I found, results can vary from lot to lot with tools. Getting a larger picture of how a tool, bullet, powder, case, primer components perform from across the board is statistically more significant and offers a better idea to more individuals reading this review before investing in an item.

As always, shoot straight, be safe, and happy reloading! If you liked this article and think it was worth $1, please consider donating:

Blake has been writing reloading articles for four years and helping out within the community to further enhance reloading education. In his free time, he works within the community to help out new hand-loaders by educating them on the many variables that come with this wonderful hobby. His passion is solely based on helping others so that they may pass on that information to future generations, keeping the art of hand-loading alive.         

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