Custom carbine packs a pistol cartridge PUNCH plus! | By Paul Markel
THE firearms industry is like any other with its ups and downs. Often a new product will surface and seem to be an answer looking for a question. I will admit that this was my first reaction when the .357 SIG cartridge surfaced in 1994. The brainchild of Federal Cartridge and SIG Arms, the new bottle-necked round was embraced by many and scoffed at by others. Although I was not convinced of its necessity as a pistol cartridge, it seemed to be a natural for a submachinegun or carbine. I still feel the same about the 10mm cartridge.
The specs from Federal Cartridge list the .357 SIG bullet at .356 of an inch, one thousandth more than the 9mm and one thousandth less than the .357 Magnum. The heritage of the .357 SIG can be traced back to April 1986 in Miami, Florida. Now stay with me for a moment.
The Miami Shootout, as it came to be known, took place between several FBI Agents and two homocidal bank robbers. To shorten the story, two FBI agents died and five were wounded. The after-action report put a large share of the blame on the 9mm pistol cartridge for not being powerful enough. The report led to the adoption of the 10mm pistol by the FBI and subsequently the reduced power 10mm "FBI Load". This in turn led Winchester and Smith & Wesson to develop the 40 S&W cartridge using the same bullet and a shortened 10mm casing (also, I feel, in response to the 41 AE/Kurt). The 357 SIG uses a necked down 40 S&W case. Are you still with me?
During the past several years my attitude toward the 357 SIG round has softened a bit. It is a hard hitting, fast moving round pushing a 9mm bullet to speeds nearer the old .357 Magnum. It does, however, produce a stout recoil particularly from lighter handguns. My feeling has been and remains that the 357 SIG is not a cartridge for beginners or those content to fire their guns during annual qualification only.
Although I have never been a velocity fanatic, it is hard to ignore a round that sends its .357 projectiles down range in the 1300 to 1400 feet per second (fps) range. Going back to my original desire to use the SIG round in a carbine, my wish just recently was realized.
Kurt's Kustom Firearms
Kurt Wala owns and operates Kurt's Kustom Firearms from his facility in Bushnell, Florida. Kurt's primary ware is the AR15, producing custom uppers, accessories, and complete guns. Kurt also does custom 1911 and shotgun work. The shop has a precision rifle division as well.
During my first discussion with Kurt I asked him about pistol caliber carbines. He mentioned that he had done quite a few including those in 9mm and 40 S&W. "How about 357 SIG?" I asked. Yes he could do that. Kurt advised me that the carbine configuration was brutal on brass and not to expect to reload empty cases. No problem. I don't reload 357 SIG. The brass just goes into a bucket for recycling. Regarding this point, I have spoken with several sources, including those in the ammunition business, who have expressed frustration over this cartridge from a reloading standpoint.
During further e-mails and conversations it was decided that I would work with a flat-top CAR-15 style carbine. The flat-top Picatinny rail would accept all Weaver-style mounts. For this project I had a specific sight in mind to work with.
The carbine that arrived from Florida was the Model P109 357 SIG. Kurt attached his 357 SIG upper receiver to a modified Olympic arms lower (note: lower was standard preban w/Colt-style magwell adaptor installed). As I had carried the M16A2 for some time as a Marine Infantryman, I appreciated the feel and the familiarity of the controls. I suspect many military vets will feel the same way. Taking hold of the pistolgrip and sending the bolt forward was like being reaquainted with an old friend.
As previously mentioned, the upper receiver is a flat-top Picatinny design. An adjustable flip-up front sight was included. For those wishing to use iron sights, an adjustable rear sight is also available for mounting. Wrapped around the barrel is Kurt's 4-Way handguard. A variety of different lights, sights, and lasers can be quickly mounted to the left, right, over, or under. The forearm has numerous air holes all around to promote barrel cooling. The muzzle brake/flash suppressor is a familiar design mimicking that of the M16A2.
A four position Rock River Arms stock is used to ease adaptibility, allowing the shooter to adjust it to fit against tactical body armor or other apparel. Fitted between the frame and the stock is a GG&G End Plate Sling Adaptor. This is a nice option as it allows the use of a tactical sling such as the Single-Point from Wilderness Tactical Products. The Single-Point sling allows the user to simply let go of the carbine to use both hands or to transition to a handgun. The gun falls naturally to the center of the body, hanging at the ready. A quick release buckle allows the gun to be removed rapidly.
Tactical Accessories
I wanted to work with a new optical sight for this project, so I chose the Mark 4 CQ/T 1-3x14mm from Leupold, which is a 1-3 power illuminated reticle. Designed specifically for close to medium range shooting, the CQ/T uses a "circle-dot" reticle for fast target aquisition. The scope is zeroed using normal windage and elevation knobs. The reticle can be used in the "off" or "on" modes with ten different brightness settings. The reticle's brightness can be set low enough to work with night vision devises. To attach the CQ/T to the P109 I used a dedicated flat-top mounting bracket from Leupold. Leupold designed the CQ/T to run on a single AA battery.
In addition to the sight I needed a good illuminator. I have been working with the M3 Tactical Illuminator from Insight Technology for a year now and have found it to be lightweight, super-bright, and simple to operate. The M3 slipped onto the 4-Way rail easily and locked tightly in place. To operate the sight while maintaining a good a good grip on the carbine, I attached a remote pressure switch from Insight. The process could not be more user friendly, taking only a few seconds to accomplish. The pressure switch itself arrives with adhesive backing and is ready to mount out of the box.
Test Ammunition
For this review I would test seven different loads from hollowpoint to full metal jacket practice rounds. The ammunition came from CorBon, Federal, Remington/UMC, Ultrmax, and Winchester. The P109's barrel is 16 inches with a 1 in 16 twist. With the exception of the heavy 150-grain Federal load, the tested ammunition averaged in the 1600 to 1700 fps (feet per second) range.
During a recent test of the Glock 31 357 SIG, the Federal 125-grain JHP averaged 1385 fps and the UMC 125-grain FMC 1383 fps. With the P109, the Federal load averaged 1715 and the UMC 1704 fps, an increase of 330 and 321 fps respectively. Does an extra 300 fps really make a difference?
As a rule of thumb, I believe most ballistic engineers will agree that speed is a major factor to reliable expansion from hollowpoint or controlled expansion bullets. Unfortunately, I did not have any ballistic gelatin to work with. I did, however, wish to test the carbine against soft body armor.
The test sample was a six by six inch square of NIJ level II Ultima Armor from Second Chance. For comparison purposes I chose the Remingtom JHP and the Winchester USA Brand FMJ loads.
I had tested this particular armor against 357 SIG JHP and FMJ rounds fired from the G31 pistol and both had been stopped by it. For this test I taped the armor panel to the chest of a plastic 3D Man target from Law Enforcement Targets, Inc. The first round fired was the full metal jacket from Winchester. Averaging 1623 fps, the FMJ round cut through the Kevlar fibers and impacted somewhere in the dirt berm behind.
I flattened out the armor sample and fired the Remington JHP load. This round had averaged 1630 fps during testing. The armor buckled and a hole was punched into the plastic chest of Mr. 3D Man. After a struggle, I pulled out the armor and found the bullet fully mushroomed and trapped by the Kevlar fibers. These findings should not be seen as an indictment of the Ultima armor. A carbine round traveling over 1700 fps is more than a level II threat. These findings do show that an extra 300 plus feet per second made a difference.
The Range: Day and Night
Zeroing the Leupold sight took only six rounds. Sitting down at 25 yards, the gun cut large, ragged holes in paper targets with each round impacting on the next. Five round test patterns at fifty yards averaged in the two-three inch range. As the P109 is a CQB gun I did not spend time benching it a 100 yards. Instead, I worked with the 3D man targets engaging them rapidly from standing, kneeling, and prone positions.
It was during this rapid firing that I was to discover the P109's one weakness. As the gun I received was the very first one made, the magazines sent with it were modified UZI mags. Out of the five magazines, three gave me problems, often double feeding. A discovery such as this, of course, the purpose of testing and evaluation. The two magazines that performed well would be the models for future production.
As night began to fall I started my low-light testing. Activating the CQ/T sight, I engaged targets using the illuminated circle-dot reticle. Raising the carbine to my shoulder, the sight came instantly into view allowing quick shot placement.
As the sun sank farther below the horizon and the stars began to shine, I made use of the M3 light. Rolling out from behind cover, I found that I could light up the targets and quickly hit them using the Leupold sight. The sight ring glows with an orange/amber color and I never lost it, even when using the bright tactical light. From distances of twenty-five and thirty yards, the M3 light provided good target aquisition and the CQ/T allowed rapid shot placement.
The Wrap
With the exception of the magazine glitch, the P109 performed solidy. During the time I tested it, I fired nearly 500 rounds of various ammunition theough the P109. Range sessions were performed during the day and night. I did take the gun to the field and trekked around the woods in search of varmints. The field time has me sold on the GG&G End Plate Sling Adaptor and the Single-Point sling. Yes, I was able to drop an Ohio Marmot with the Remington JHP load. From fifty-five yards a single round flattened it out nicely.
For agencies currently issuing the 357 SIG pistol and looking for a compatible long gun, the P109 has a lot to offer. Making use of the tried and true CAR-15 characteristics, mated with excellent tactical accessories, the P109 just might fill the bill.
