The newly designed Ultra Low Mass Sharps Xtreme Performance Bolt (XPB) Carrier Group Complete comprises our patented Relia-Bolt™ and our Special Ultra Low Mass Balanced Bolt Carrier. The Ultra Low Mass Carrier is 2.3 ounces lighter than the Full Mass Carrier. 

This BCG is made specifically for competition shooters who want to lighten their recoil system. Forward assist cuts have been omitted to reduce weight. Sharps manufactured the Ultra Low Mass BCG from S7 tool steel, making it tough enough for those who want to utilize it in any demanding application. We combined this with our patented adjustable gas key (SARGS), which, when tuned properly, reduces felt recoil impulses and allows for faster recovery and follow-up shots.

The ULM BCG undergoes a 24-hour thermal cycle proprietary heat treatment and is finished with your choice of either the DLC (Diamond Like Carbon) Coating or NiB-X coating. As always, this carrier group displays the SRC logo machine cut, which is visible when the ejection port door is open. The product fits standard AR-15/M16/M4 rifles chambered in .223/5.56, Sharps 25-45, and 300 Blackout calibers.

Special Note: To account for the lighter weight, the Ultra Low Mass SAGRS starting adjustment should be approximately 1 1/2 turns counterclockwise from completely closed, then fine-tune accordingly.

Technical Specifications

Why S7 Tool Steel?

S7 has excellent shock absorbing properties which provide superior impact resistance when being utilized in the construction of Sharps Bolt Carrier Groups. S7 demonstrates high strength and toughness as well as a resistance to softening at moderately high temperatures, i.e. operating temperatures not exceeding 1000°F. 

The properties we as shooters look for in an AR platform BCG, are hardness and wear resistance.  S7 provides such attributes when heat-treated properly. Sharps has found that the key benefits from S7 tool steel are higher tensile strength and toughness which translate to longevity of use, i.e., a higher number of cycles the bolt can handle before it fails.

Technical Data on DLC Coating

• Weight: 8.8 oz    

• Batch MPI and HPT tested

• Tensile Strengths of 1550-1600 mpa, or 220,000-235,000 psi.

• Toughness over 200ft/lb Charpy C-Notch

• HRC of 46 yields a 15% increase in hardness at the same toughness comparing to Carpenter 158 & 9310.

Limited Lifetime Warranty

If any SRC Bolt Carrier or Relia-Bolt™ is found to have manufacturer defects, SRC will repair or replace it at no charge. Manufacturer defects include out of spec parts and defective parts.  Although our BCG is Mil-Spec, there are so many variables, sometimes a little troubleshooting, or fine tuning of parts may be required for proper functionality.  Before a part is replaced or refunded, SRC reserves the right to inspect and test part(s) in question to determine if it is defective. Please keep in mind that altering the product renders the warranty void.

Note:  Binary triggers will NOT work with the low mass carrier.