Hornady Critical Duty 357 Sig FlexLock – Rapid Bottleneck Load

Description

The Hornady Critical Duty 357 Sig FlexLock puts the duty bullet into the cartridge that was designed for exactly this job. A 135 grain FlexLock at 1225 fps carries about 450 ft-lbs from a four inch barrel, and the 357 Sig gets there with a bottleneck case and a short, fast bullet rather than by leaning on pressure alone.

• Hornady Critical Duty 357 Sig FlexLock Overview
• 357 Sig Duty Ammo Ballistics
• Why The 135 Grain FlexLock Bullet Fits This Cartridge
• Specifications
• Pistols That Suit This Barrier Blind Bottleneck Pistol Load

Hornady Critical Duty 357 Sig FlexLock Overview

Hornady item 91296 loads a 135 grain FlexLock bullet to a nominal 1225 fps, producing roughly 450 ft-lbs at the muzzle. Twenty rounds per box.

Hornady publishes the curve from a four inch test barrel: 1225 fps and 450 ft-lbs at the muzzle, 1112 fps and 371 ft-lbs at fifty yards, and 1031 fps and 319 ft-lbs at a hundred. A four inch test barrel is what a duty pistol actually has, which makes the numbers unusually honest.

The 357 Sig was developed in 1994 by Sig Sauer and Federal to give a semi-automatic pistol 357 Magnum performance. It is a 40 S&W case necked down to take a 0.355 inch bullet, and the bottleneck shape is why it feeds so reliably.

The FBI protocol is a specific test sequence rather than a general endorsement. Ammunition is fired into calibrated gelatin bare, through heavy clothing, through steel, through wallboard, through plywood and through automotive glass at two angles, and expansion and penetration are measured in every case. Doing well across all eight is genuinely difficult.

357 Sig Duty Ammo Ballistics

At 1225 fps a 135 grain bullet produces about 450 ft-lbs, from grains times velocity squared divided by 450437. Compared to the 357 Magnum version of this load, which shows 487 ft-lbs from an eight inch barrel, the 357 Sig gives up very little from half the barrel length.

That comparison is the case for the cartridge in a nutshell. A four inch semi-automatic delivers nearly what a long barrelled revolver does, with more rounds in the gun and faster reloads.

Trajectory is flat by handgun standards. A light bullet at 1225 fps shoots close to point of aim well past twenty five yards, which is what earns it the description of flat shooting duty grade ammunition.

Recoil is sharp rather than heavy. The 357 Sig produces a quick, snappy impulse and a noticeably loud report, and shooters coming from 9mm usually need a little range time before they shoot it as well.

Why The 135 Grain FlexLock Bullet Fits This Cartridge

The FlexLock design solves two separate failure modes. A conventional hollow point driven through heavy clothing can pack its cavity with fabric and never open at all. Hornady fills the cavity with a soft polymer Flex Tip, which cannot pack and is driven rearward on impact to start expansion from the inside out.

The second is the jacket and core separating. That risk climbs with velocity, which makes it directly relevant in a cartridge built around speed. Hornady adds a mechanical InterLock band that grips the core and holds the two together, and that is where the weight retention comes from.

Barrier blind is the shorthand for the result. The bullet behaves much the same whether it reaches its target directly or through a windshield, a car door or an interior wall, and the FBI protocol exists to measure that exact spread of conditions.

The 357 Sig earned its reputation on glass in particular. A short fast bullet in a bottleneck case punches through a windshield with less deflection than most handgun rounds, and a 135 grain FlexLock bullet that also holds together afterwards makes the most of that.

Expansion is designed to be consistent rather than maximal. Hornady prioritises penetration depth, which usually means a slightly narrower mushroom than a bullet built purely for bare gelatin numbers, and a much better chance of reaching something important through an obstacle.

That is the whole brief for a barrier blind bottleneck pistol load: open when it should, hold together when it is punished, and reach the depth it needs either way.

Specifications

Pistols That Suit This Barrier Blind Bottleneck Pistol Load

Any pistol chambered in 357 Sig in sound working order will handle this load. That covers the Sig P226, P229 and P320 in the chambering, the Glock 31, 32 and 33, and the Smith & Wesson M&P357.

Many 40 S&W pistols convert to 357 Sig with a barrel swap alone, since the two share a case head, magazine and slide. If yours has been converted, confirm the barrel is correctly headspaced before running a 357 Sig duty ammo load through it.

Feeding is one of the cartridge’s strengths. The bottleneck shape guides the round into the chamber in a way a straight walled case cannot, which is a large part of why agencies that adopted it kept it.

Practise with the load you carry, at least occasionally. Point of impact and recoil both differ from cheaper practice ammunition, and the 357 Sig is expensive enough that many owners never fire the defensive load at all.

Ammunition availability is the cartridge’s real weakness rather than anything about its performance. A barrier blind bottleneck pistol load in 357 Sig is worth buying when you see it, because the shelves empty faster than they do for 9mm.

Flat Shooting Duty Grade Ammunition Availability

This Hornady Critical Duty 357 Sig FlexLock is in stock and ships from our Collegeville, Pennsylvania shop. MAG5 Firearms is a family owned FFL dealer, and orders of this flat shooting duty grade ammunition normally leave within one business day.

The revolver equivalent is the Hornady Critical Duty 357 Mag FlexLock. For the same bullet in more common chamberings see the Hornady Critical Duty 9mm 124gr FlexLock and the Hornady Critical Duty 45 ACP FlexLock. Full ballistics are published by Hornady.