Can You Shoot 17 Hmr In 22 Mag
Can You Shoot 17 Hmr In 22 Mag The world of rimfire cartridges is filled with various calibers that often share similar parentage, leading to common questions about interchangeability. One of the most frequent queries among target shooters and varmint hunters is whether you can shoot .17 HMR ammunition in a firearm chambered for .22 Winchester Magnum Rimfire (WMR), commonly known as .22 Mag. While these two cartridges are closely related—the .17 HMR was actually developed by necking down a .22 WMR case—the physical differences between the projectiles and the chambers of the rifles themselves make them non-interchangeable. Understanding the mechanics behind why this is dangerous and ineffective is crucial for any firearm owner looking to maintain safety and performance on the range or in the field. 
Understanding the Physical Differences and Compatibility
To understand why you cannot simply swap these rounds, one must look at the specifications of each cartridge. The .22 WMR uses a straight-walled case designed to fire a .224 inch diameter bullet. In contrast, the .17 HMR is a bottlenecked cartridge that fires a much smaller .172 inch diameter bullet. Although they share the same parent case dimensions at the base and rim, the necking down process creates a completely different shoulder profile. Because a .22 Mag chamber is a straight cylinder designed for a .22 caliber bullet, a .17 HMR round would not sit securely or correctly within it.
If you were to attempt to chamber a .17 HMR in a .22 Mag rifle, the round might physically enter the chamber because the base diameters are nearly identical. However, the bottlenecked neck of the .17 HMR would have no support. Most importantly, the barrel of a .22 Mag rifle is rifled for a .22 caliber projectile. Shooting a .17 caliber bullet down a .22 caliber bore means the bullet would not engage the rifling. This results in a massive loss of pressure as gases blow past the undersized bullet, leading to extremely low velocity, zero accuracy, and a high probability of the bullet becoming lodged in the barrel, known as a squib load.
Safety is the primary concern. When a cartridge is fired without proper chamber support, the brass case can rupture. Because the .17 HMR case is necked down, the extra space in a .22 Mag chamber would allow the brass to expand violently and potentially burst, sending hot gases and metal fragments back toward the shooter's face or through the magazine well. This is why firearm manufacturers and ballistics experts categorically state that you should only use the specific ammunition stamped on the barrel of your firearm.
Ballistic Comparison: 17 HMR vs 22 WMR
Choosing between these two popular rimfire magnums usually depends on the intended application rather than interchangeability. The .17 HMR is celebrated for its incredibly flat trajectory and high velocity. It typically sends a 17-grain bullet at speeds exceeding 2,550 feet per second. This makes it an exceptional choice for small varmints like squirrels and prairie dogs at distances out to 200 yards. Its accuracy is often superior to the .22 WMR, as the high-velocity, polymer-tipped bullets are designed for ballistic efficiency.
On the other hand, the .22 WMR is often preferred for slightly larger game or closer ranges where "stopping power" is more important than a flat trajectory. The .22 Mag typically fires heavier bullets, ranging from 30 to 50 grains. While it is slower than the .17 HMR, the increased mass allows it to carry more kinetic energy downrange. For hunters targeting animals like foxes or coyotes at 100 yards, the .22 WMR provides a harder-hitting impact that can be more effective for a clean harvest.
| Feature | .17 HMR |
|---|---|
| Bullet Diameter | 0.172 inches |
| Typical Bullet Weight | 17 - 20 Grains |
| Average Muzzle Velocity | 2,550 - 2,650 FPS |
| Best Use Case | Long-range Varmints |
Mechanical Requirements for Conversion
While you cannot shoot .17 HMR in a .22 Mag rifle as-is, the fact that they share a parent case makes conversions possible in certain rifle platforms. Since the rim and base dimensions are the same, the bolt face and magazine of a .22 WMR rifle will often work perfectly with .17 HMR. However, the most critical component—the barrel—must be replaced. A conversion requires a barrel chambered specifically for .17 HMR with a .17 caliber bore and appropriate rifling twist rate.
In modular rifle systems, such as the Ruger Precision Rimfire or certain CZ models, swapping barrels is a relatively straightforward process for a gunsmith. However, even with a barrel swap, shooters must be cautious with semi-automatic platforms. The .17 HMR produces different pressure curves and bolt velocities compared to the .22 WMR. Many early semi-auto .17 HMR rifles faced recall issues because the light bottlenecked cases would sometimes fire out of battery or rupture. If you are considering a conversion, it is always safest to stick with bolt-action or lever-action platforms which are more robust against these pressure variations.
FAQ about Can You Shoot 17 Hmr In 22 Mag
Is .17 HMR just a smaller version of .22 Mag?
Technically, yes. The .17 HMR was created by taking a .22 WMR (Magnum) case and necking it down to hold a .172 caliber bullet. However, this change in shape makes the cartridges physically incompatible in each other's chambers.
What happens if I accidentally fire 17 HMR in a 22 Mag?
It is highly dangerous. The undersized bullet will not fit the bore, causing gas to leak around it. This leads to very low velocity and a high risk of a "squib" (the bullet getting stuck in the barrel). Furthermore, the unsupported brass case may rupture, potentially damaging the gun and injuring the shooter.
Can I use the same magazine for both calibers?
In many cases, yes. Because the base of the .17 HMR case is identical to the .22 WMR, many magazines designed for .22 Mag will successfully feed .17 HMR. However, you still must have the correct barrel installed for the caliber you are shooting.
Which is louder, 17 HMR or 22 Mag?
Both are significantly louder than a standard .22 LR. The .17 HMR often has a higher-pitched "crack" due to its higher supersonic velocity, while the .22 Mag has a slightly deeper report. Both require the use of hearing protection.
Conclusion
In conclusion, the answer to "Can you shoot 17 HMR in 22 Mag?" is a definitive no. While the cartridges share a common lineage and the same case base, they are distinct ballistic entities with different diameters and chamber requirements. Attempting to use them interchangeably is not only ineffective for accuracy and performance but poses a severe safety risk to the shooter and the firearm. Always ensure the ammunition you are using matches the caliber designation marked on your rifle's barrel. By respecting these ballistic boundaries, you ensure a safe and enjoyable experience at the range while maximizing the unique strengths that both the .17 HMR and .22 WMR bring to the shooting world.