An Illustrated Guide To Using The Sinclair Priming Tool | Top Rated Supplier of Firearm Reloading Equipment, Supplies, and Tools - Colt

An Illustrated Guide To Using The Sinclair Priming Tool

An Illustrated Guide To Using The Sinclair Priming Tool

Sinclair's stainless steel Priming Tool (#749-007-603) is known all over the world as one of the best – if not the best – hand tools for priming cartridge cases. It offers superb feel, precision, and repeatability.

The Sinclair Priming Tool's unique features include the ability to seat primers either by "feel" or by "depth," and the ability to "lock" the case securely in the shell holder before seating the primer, further improving the seating operation's feel. The Sinclair tool's outstanding leverage provides control, equating to feel, like no other hand tool on the market. That control is amplified even more when primer pockets are squared to a fixed depth with a primer pocket uniformer. For those accuracy buffs who prefer to seat each primer to a specific depth (usually a few thousandths below flush with the cartridge case head), the tool stroke may be adjusted to "bottom out" firmly against the priming tool body, easily accommodating the fixed-depth technique. This technique should only be attempted by advanced reloaders with the skills, tools, and experience to get it right, as seating the primer too deeply can cause unsafe pressure spikes.

Locking each case into the shell holder seems, on the surface, to be overkill. Yet, seating a primer into a case that isn't securely fastened into the shell holder can be sloppy, neither starting or finishing with a crisp priming stroke. It could even potentially start the primer sideways. I've had this occur on occasion with other hand tools, where excessive space between the case head and shell holder allowed a primer to "sit" on its side. Locking the case accentuates the feel already enhanced by the tool leverage and uniforming of the primer pockets. For primer seating, I'm not sure it can get much better!

Let's work through the different set up procedures and adjustments for this tool and address the questions many of our customers ask when considering if it is right for them.  Are we ready to seat some primers? First, let's cover installation of the appropriate Primer Punch Housing Assembly, depending on what size primer you're using.

Shown are the Sinclair Priming Tool, additional Punch Housing Assembly (for both small and large primers), housing shims, and the Sinclair Priming Tool Shell Holder, which is sold separately. Notice the soft felt mat (#749-001-055) on our bench top. Be sure to use something similar because the Sinclair Priming Tool has several small, intricate moving parts that can (and will) very easily get lost in your carpet or garage floor. A cloth or mat helps prevent them from disappearing. Let's install the appropriate priming tool housing and shell holder…

Our cartridge of choice for today's tool setup is the classic "triple deuce," the 222 Remington. Remove the priming tool head by simply unscrewing from the main tool body.

Because the 222 Remington uses small primers, loosen the front Allen screw to free and remove the large priming tool punch housing, which comes factory installed.

Upon removal, notice how the "hardened pin" priming tool punch is lubricated and installed within its housing with return spring. This will help with re-assembly, as well as installation of the small punch assembly and additional lubrication if ever necessary. You will also discover four shims of various thicknesses and colors installed on the housing. These will be discussed in more detail later.


Reverse the procedure by sliding the shims onto the small priming tool punch housing assembly. Install and tighten the front Allen setscrew. Do not over-tighten.  It takes very little pressure to hold the housing in place. Over-tightening the setscrew against the priming tool housing can damage the intricate stainless steel screw.

Easy as pie, right? I've never been gifted with the coordination to be "crafty" with hand tools, but even I can handle prepping this tool! Now, let's install the appropriate shell holder for our "triple deuce."


With the priming tool head still removed, loosen and remove the two Allen setscrews located on each side of the priming tool head. Use caution not to lose these small setscrews.

Slide the shell holder in from the underside of the priming tool head, and then position the shell holder mouth to easily accept a cartridge.


Snug each of the Allen setscrews to secure the shell holder in place. Do not over-tighten these. - it takes very little pressure to hold the shell holder in place. Again, if you over-tighten these intricate screws, the threads will very easily strip out.

Sinclair Priming Tool Shell Holders are available for most standard cartridge families and are machined from stainless steel to exacting tolerances specifically for use in the Sinclair tool. Lee Precision's Auto-Prime Shell Holders may also be used in a Sinclair Priming Tool.  However, Sinclair shell holders are machined for exact fit, whereas the Lee product is stamped steel and may need a bump here or there with a Dremel tool to shape it to fit properly.


Load up a primer seating tray, such as the RCBS tray (#749-000-903) illustrated, with primers. In this instance, we've placed 100 primers in our tray and have appropriately shaken it to "flip" them for easy handling. After washing your hands, simply grab a primer and insert it into the priming tool housing. You don't have to worry about contaminating the primers – unless your fingers are dripping with oil! We plan to fire these rounds within days – after all, we're reloading so we can get out and shoot more, aren't we?

Insert a case into the priming tool shell holder and then turn the shell holder head until the case "locks" in place.

The case head locks into the tool head so well that you can actually lift the whole tool by the case! You may need to thread the shell holder head outward to gain clearance and properly install your first case. Once the first case is installed and locked in place, subsequent cases are easily removed and reinstalled by simply turning the shell holder head a quarter turn. It's that simple to loosen and lock – fast and effective.


Squeeze the priming tool handle to insert the primer into the case. I've found that a consistent, assertive squeeze provides the best primer seating feel. This enables you to better feel the primer bottom out, whereas a slow, methodical squeeze tends to lose the feel at the end of the stroke. After seating a few primers, individual users tend to quickly develop a technique that works best for them.

What about those little plastic shims? They are there simply to enhance our priming experience. Now that you are starting to develop a new priming technique after a few practice rounds, we'll use the shims to position our priming tool shell holder where it's most ergonomic. This is where we get a lot of blanks stares. Position what?


First, let's think about how we hold the tool in our hand when priming. We've seen folks wrap their fingers around the lever (illustrated above), while others use their thumb to operate the lever. It's a personal choice. I prefer to use my thumb.

Now, which way do you want the shell holder mouth to face? Since it only takes a 1/4 turn to lock in the case, having the ability to adjust direction of the shell holder mouth makes this tool a literal pleasure to use. I prefer the shell holder mouth to open toward me while operating the tool with my thumb, so I can easily slip the next case in, tighten the quarter turn, and prime the case.


Different shim combinations will position the housing so that the priming tool face will "lock" at different points around the head's circumference – wherever you want it! Find the combination that best suits your priming style.

Changing the primer "stroke" is the last adjustment we'll cover. Your tool comes from Sinclair properly set up to seat primers by "feel." For most users, this is more than adequate. If you're a really experienced reloader who has the appropriate measuring tools and equipment, you can use the tool to seat primers by depth. If you, like me, lack fine mechanical skills and the equipment, stick with the "feel" method. Otherwise, your adjustment may not be safe. If you are equipped to do it and want to try, here's the skinny:


Loosen the Allen handle setscrew at the bottom side of the priming tool body.

Next, remove the handle pin that secures the handle and pushrod assembly to the body. You'll notice the pushrod assembly head is threaded onto the pushrod and secured with Loctite. This keeps your priming tool pushrod head from possibly unthreading and changing your stroke length.

Ideally, the end or your primer "stroke" will have your handle flat against the priming tool body. This is where you would adjust, by trial and error, the pushrod assembly head to seat each primer to a pre-determined depth. Once you've established your depth, apply Red Loctite (#749-001-002) to the threads to fasten the pushrod assembly head, and reinstall the handle, securing the pin with the Allen handle setscrew. Not to sound like a broken record, but don't over-tighten the stainless steel screws.

I hope the above information provides some valuable insight, answers lingering questions you may have, and gives you  a better understanding of what our customers claim is "the best priming tool in the world." As always, don't hesitate to email or pick up the phone and call us at 800-717-8211.  Speak to one of our experienced reloading techs for even more valuable information. Our goal is to make sure you're armed with the best reloading tools for the job at hand, and to provide the support necessary to enhance your reloading experience, keeping it safe and enjoyable.

Geoff Esterline
Sinclair International