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Toolcraft Nickel Boron (C158) BCG Left Hand 556

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Toolcraft Left Handed Bolt Carrier Groups Ship FREE.

Your Left-Handed AR15 Build deserves the best quality BCG you can get - Toolcraft!

This quality Toolcraft bolt carrier group has all the outstanding specs of the right-handed Toolcraft BCG, but it's a lefty. Both the carrier and the bolt are the exact mirror image of a traditional right-handed BCG. Use this left-handed BCG in a left-handed build, or as a spare BCG for your complete left-handed rifle.

Nickel Boron is an extremely durable finish with self-lubricating properties so your AR15 cycles smoother and requires less lubrication. Toolcraft uses a Nickel Boron finish so durable that it is specified on Army 81mm and 60mm mortar tubes, Blackhawk helicopter hoists, and for hard use applications on some Navy ships!

IMO, this may be the ultimate finish for a hard working AR15 BCG. And it looks good too!

This is a .223/5.56/300 Blackout bolt carrier group.

Will not work with 6.5/6.8/308 etc.

See our views of Toolcraft BCGs here - Toolcraft Gallery

Bolt Left-Handed; Shot Peened; MPI
Bolt Material Carpenter 158 Steel
Bolt Finish Nickel Boron
Caliber .223 | 5.56 NATO | 300 Blackout
Extractor O-ring Viton; Mil Spec
Carrier Material 8620 Steel, Toolcraft Proprietary
Carrier Finish Nickel Boron
Carrier Design Left-Handed; Full Auto Style
Gas Key Material 4130 Steel
Cam Pin Material 4140 Steel
Cam Pin Finish Nickel Boron
Firing Pin Material 8740 Steel; Hard Chrome Plated
Manufacturer Toolcraft


Note: Some dealers are selling Toolcraft BCGs that have been finished after leaving Toolcraft. The finish on those BCGs would not be warrantied by Toolcraft. All Toolcraft bolt carrier groups sold by SpiceTac include the 100% no-questions-asked Toolcraft warranty.

Lifetime Warranty

Lifetime Warranty

Toolcraft products carry a lifetime warranty. Simply put - should any of our products fail, return it to us for a brand new replacement.

A note from Toolcraft

Toolcraft carriers are made from the best materials that can be purchased in the market today. Regardless of the coating you choose, the carrier that it protects is made the right way, with no compromise of standards using materials that are Made in the USA. There is the basic 8620 steel, a better grade of Gun Quality 8620 steel, an even better grade of Aircraft Quality 8620 steel, but then there is the best Aircraft Quality 8620 steel that is proprietary to Toolcraft only and no one else. These high standards of materials set us apart from the rest.

While some manufacturers have compromised the Mil-Spec standards of machining just to add to their profits, Toolcraft has stayed loyal to the Mil-Spec machining standards since the beginning.

All Toolcraft carriers are post-heat treat machined to remove any distortion that has occurred during the heat treat process. We first grind the outside rails that are in contact with the upper after heat treat. Next, we machine the inside bore where the bolt is doing the work. This ensures the gas rings are not damaged and that the weapon cycles and charges smoothly. These standards are not just met, but we exceed them on every operation during the machining processes and this effort gives our carriers a superior finish with no machining lines.

Toolcraft machines each carrier to last for thousands of rounds and that is why we can offer with confidence a Lifetime Warranty on our products. These standards have given each consumer the confidence that when they use a Toolcraft bolt carrier group in their weapon, it will do what it was created to do, round after round for years to come.

Customer Photos

Below: Toolcraft Black Nitride bolt up close showing Magnetic Particle Inspection (MPI) mark. Note: Markings on Toolcraft bolts vary. Sometimes they are marked, sometimes they are not.

 toolcraft-ar-15 bcg for sale

Below: Bet-your-life reliability (1100 rounds without cleaning) from this AR pistol build using Aero Precision Upper Receiver with no Forward Assist, Ballistic Advantage 11.3 Hansen 556 NATO barrel, Toolcraft Black Nitride BCG, Radian Weapons Raptor charging handle, and SBA3 pistol brace.  


Below: Following a 1100 round Toolcraft BCG review with Federal M193 and Wolf Gold. Dirty but reliable. 


Below: AR pistol build using a SB Tactical SBA3 brace, old-school cool 1913 picatinny quad rails and a Toolcraft Black Nitride Bolt Carrier Group


Below: Short AR15 (pistol build) with Toolcraft bolt carrier group and free float rail


Below: Scoped AR15 rifle for accurate long range shooting using reliable Toolcraft BCG


Below: AR-15 pistol build using M-LOK free float rails and Black Nitride Toolcraft bolt carrier group


Toolcraft FAQs

Common Questions About Toolcraft BCGs


What markings will my Toolcraft BCG have?

Generally speaking, the carrier will not have markings or a logo of any kind.

Toolcraft manufacturers carriers and sources bolts from U.S. suppliers. For this reason, the markings on the bolts vary from batch to batch. Sometimes they are marked MP or MPI but often they are not marked in any way. Sometimes the Carpenter 158 bolts are marked C158 but more often they are not marked in any way. All Toolcraft bolts are individually MPI tested whether they are marked or not.

Is the staking on my Toolcraft gas key screws heavy enough?

Toolcraft installs carrier keys using mil-spec procedures. This means proper surface prep, sealant and gas key screws torqued to the proper value (both over and under torqued screws can fail). Toolcraft then stakes each gas key screw to the mil-spec. There are a lot of overly staked carriers on the market and this is seen by some as a sign of quality. It is not. Over staking of gas key screws runs the risk of cracking the key in a way that can’t be seen with the naked eye.

Proper gas key installation is a process that involves several steps each done correctly. Toolcraft does it right and confidently offers a Lifetime Warranty on all their products.

What is the difference between Carpenter 158 and 9310 steel?

Carpenter 158 is the military specification (mil-spec) for bolts. 9310 is a more modern steel which can be up to 8% stronger than Carpenter 158. They are both premium steels with a long and successful history of use in AR15 bolts. Either will serve you well!


What finishes do they come in?

Finishes include Black Nitride, Nickel Boron, Chrome & Manganese Phosphate, Ionbond Diamond Like Coating (DLC), and Titanium Nitride.

What is the best finish for me to get?

This is a very subjective question and the simplest answer is that you can’t make a bad choice! Our biggest seller is the Black Nitride, and it is generally the least expensive. If you are looking to spend more, the Nickel Boron, DLC and Titanium Nitride all offer a very slick feel and easy clean up. The chrome & phosphate finish is perfect for traditionalists. For a more in-depth look at BCG finishes, see our blog post on AR15 BCG Finishes.

Do the Toolcraft Bolt Carrier Groups come assembled?


Do Toolcraft BCGs come with firing pins?

Yes, they do. They come ready to drop in to your AR15.

Do Toolcraft BCGs come with charging handles?

They do not, but charging handles can be added to your order.

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