Max Frame Length for Shoulder Holsters: How to Choose Yours

How do I measure my firearm for a shoulder holster rig?

To establish your required Max Frame Length, you must measure the physical dimensions of your specific firearm. Use a standard metal ruler or a tape measure to ensure accuracy.

Where to measure on the frame

Place the ruler along the top of the firearm’s slide or frame. Measure from the very front of the muzzle end to the very rear of the backstrap or beavertail. This measurement represents the total length of the frame that the shoulder holster rig must be able to contain.

Finding the measurement in manufacturer data

If you do not have the firearm in hand, locate the manufacturer’s technical specifications. Look for the “Overall Length” or “Frame Length” measurement. Note that “Overall Length” often includes the barrel; for a shoulder holster rig, the “Frame Length” or “Slide Length” is the critical value for determining the Max Frame Length requirement.

Verify the measurement in inches (in.). Most manufacturers provide these specifications in both millimeters and inches; ensure you are looking at the imperial measurement to match the rig’s specifications.

What happens if the Max Frame Length is incorrect?

Choosing a Max Frame Length that does not match your firearm dimensions leads to specific mechanical failures during use. These failures are dictated by whether the holster is too small or too large for the specific frame.

Before buying, determine your requirements by evaluating different holster retention levels.

Risks of an under-sized Max Frame Length

If your firearm’s frame length exceeds the rig’s Max Frame Length, the firearm will not seat fully into the holster. This creates a “print” risk where the rear of the slide or the grip protrudes from the carrier, making the firearm visible through clothing. Furthermore, the firearm may sit at an incorrect angle, causing the slide to hang up on the holster’s internal walls during a draw or during cycling.

Risks of an over-sized Max Frame Length

A Max Frame Length that is significantly larger than your firearm’s actual size results in a loose fit. Without a snug retention fit, the firearm can shift, tilt, or “wobble” inside the rig while you are moving. This movement can cause the firearm to shift toward the front of the holster, potentially causing the muzzle to point in an unsafe direction or making the draw path inconsistent.

What should I do if my firearm is between two sizes?

If your firearm measurement falls between two standard Max Frame Length options, you should prioritize the larger of the two available sizes. Selecting the larger capacity ensures that the firearm will physically fit into the rig without protruding.

Why you should size up

A holster with a slightly larger internal capacity can be adjusted or modified to provide a tighter fit, but a holster that is too small cannot be expanded to accommodate a larger frame. If your measurement is 8.2 in. and the options are 8 in. and 9 in., the 9 in. rig is the only viable choice to ensure the firearm is fully enclosed.

Improving the fit of a larger rig

If the larger rig feels too loose because your firearm is on the smaller end of the range, check the manufacturer’s instructions for adjustable retention features. Some shoulder holster rigs include thumb breaks or adjustable straps that can be tightened to compensate for extra internal space. If the rig has no adjustable features, you may need to ensure the retention mechanism is fully engaged to prevent the firearm from shifting.

Before ordering, consult the specific manufacturer’s size guide for that model to confirm how they define their Max Frame Length and whether they provide specific instructions for borderline measurements.

Reviewed by the TacticalVestPro editorial team. TacticalVestPro writes these guides from the 35 most-reviewed shoulder holster rig listings in our retail dataset, not from manufacturer copy.