AR Projectile Sticking Explained: Freebore, Seating Depth, and Rifle Tuning

Posted by WADE C. on Dec 23rd 2025

AR Projectile Sticking Explained: Freebore, Seating Depth, and Rifle Tuning

Important Disclaimer: Projectile Sticking, Freebore Variability, and AR Platform Realities

If you have experienced stuck projectiles in the past, this issue will almost certainly occur with this particular load. Because of that, we want to be completely transparent about what’s happening, why it’s happening, and what we’re doing to address it.

We have received reports from a small number of customers experiencing projectile sticking. As part of our standard process, we measure cartridge overall length (COAL) across a broad sampling of barrels from manufacturers we trust and regularly work with. During that initial evaluation, no issues were identified.

After the first report came in, however, we began a deeper investigation.

What We Found: Freebore Is Not a Standard

The core issue comes down to freebore variability.

There is no true industry-wide standard for freebore. In practice, most reamer manufacturers settle on what they believe is optimal, and over time a loose form of standardization develops. That still does not guarantee consistency, especially in the AR platform.

To investigate further, we sourced multiple additional barrels with significantly shorter and tighter freebore. In those barrels, we were able to replicate the issue. This confirmed that when tighter chambers and shorter freebore are combined with the inherently dirty nature of the AR platform, projectiles can contact the lands and stick—especially as fouling builds.

Projectile “Creep” in the AR Platform (Yes, It’s Real)

Now let’s talk about projectile seating movement, often referred to as projectile “creep.”

This is common knowledge today for many experienced AR shooters: projectiles do move forward in semi-auto platforms. This is not speculation—it happens, and it happens on every cartridge run through a semi-auto system to some degree.

At Ally Munitions, this behavior is factored into our COAL decisions from the start.

Some projectiles are more susceptible than others, particularly those with more “slippery” ogive designs. Another major factor is rifle tuning. The rougher a rifle is tuned, the more projectile movement you will see.

It doesn’t matter if there’s a cannelure.
It doesn’t matter if tighter neck tension is used (which we do).
It’s still going to happen.

That’s the reality of the semi-auto world.

Why Proper Tuning Matters More Than Most People Realize

The single best thing you can do for your AR is to tune it to be as soft-shooting as possible.

This isn’t just about projectile seating—it’s about overall system health. A properly tuned rifle:

  • Reduces projectile movement

  • Reduces stress on internal components

  • Extends parts life

  • Improves reliability and consistency

A harshly tuned rifle increases forward projectile movement, absorbs tolerances more aggressively, and accelerates fouling-related issues.

Dirty Chambers, Reduced Freebore, and the Perfect Storm

As fouling builds in the chamber, freebore, and forcing cone area, those tolerances effectively get “absorbed.” In simple terms, you end up with less functional freebore.

Combine:

  • A dirty chamber

  • Short or tight freebore

  • A roughly tuned rifle

  • Normal projectile creep

And you have the perfect recipe for stuck projectiles.

What We’re Doing: Mod 1 Development

To address this, we’ve sourced a dedicated test barrel with much shallower freebore and different forcing cone angle cuts, and added it to our catalog of test uppers. This represents a worst-case scenario and allows us to test against real, measurable conditions.

We are currently testing a Mod 1 version of this load using a slightly shorter overall length.

The Trade-Offs

Shortening OAL introduces a balancing act:

  • Shooters with more generous freebore may not see the exact same precision results.

  • That said, deeper seating does not automatically mean worse accuracy.

Over the years, we’ve conducted extensive seating depth testing and have repeatedly seen projectiles seated deeper still produce excellent downrange precision. In some cases, precision remains unchanged—or even improves.

Our philosophy has always been the same: test real barrels, gather real data, and make decisions based on results—not assumptions.

What You Can Do Right Now

If you’ve experienced projectile sticking, the most important step is simple:

Keep your chamber and freebore exceptionally clean.

We recommend this for all ARs regardless. Fouling is a variable, and when variables change, accuracy and precision change with them. That said, we recognize that perfectly maintaining chamber cleanliness isn’t realistic for most shooters—which is exactly why Mod 1 is being developed.

A Note on Barrel Inspection

Whenever possible, we strongly recommend having your barrel borescoped before installation. We’ve seen more than a handful of chamber-related issues over the years, which is precisely why we inspect every barrel before listing it on our site.

Final Thoughts

This issue is real, reproducible, and rooted in chamber variability, projectile behavior, and platform realities—not guesswork.

We are actively testing solutions, and Mod 1 will be introduced in the next production run once validation is complete.

Our standards haven’t changed. If anything, this process reinforces them.

More data to come.