# HK MR556 A4 5.56x45mm 16.5in Black

**Brand:** Heckler & Koch
**Category:** AR Style Rifles
**Caliber:** 5.56 NATO

## Specifications

- **Caliber:** 5.56 NATO
- **Barrel Length:** 16.5"
- **UPC:** 642230269415
- **SKU:** UCBJ1QlAV

## Description

The HK MR556 A4 is a semi-automatic AR-pattern rifle chambered in 5.56x45mm with a 16.5-inch threaded barrel. It has an M-Lok handguard and ships in black. The magazine capacity is 10 rounds.

### Key Specifications
- **Brand**: HK
- **Model**: MR556 A4
- **Caliber**: 5.56x45mm
- **Action**: Semi Auto
- **Barrel Length**: 16.5 in
- **Color/Finish**: Black
- **Capacity**: 10

### Detailed Features
- 16.5-inch threaded barrel
- M-Lok handguard
- 223 Remington/5.56x45mm chambering
- 10-round magazine
- Black finish

## Frequently Asked Questions

**Q: What caliber is the MR556 A4?**

A: The MR556 A4 is chambered in 223 Remington/5.56x45mm.

**Q: Who makes the MR556 A4?**

A: The MR556 A4 is made by HK (Heckler & Koch).

**Q: What type of firearm is the MR556 A4?**

A: It is a semi-automatic AR-pattern rifle.

**Q: What is the barrel length of the MR556 A4?**

A: The MR556 A4 has a 16.5-inch threaded barrel.

**Q: Is the MR556 A4 barrel threaded?**

A: Yes, the MR556 A4 comes with a threaded barrel.

**Q: How many rounds does the MR556 A4 hold?**

A: It ships with a 10-round magazine.

**Q: Where can I buy the MR556 A4?**

A: Compare current vendor offers on this page.

## What Customers Say

*AI-generated insights from customer reviews*

The MR556 A4 is positioned as a premium AR-pattern rifle, and owners who buy it are typically drawn to the HK engineering and build quality. The gas-piston operating system sets it apart from direct-impingement AR rifles, and owners frequently cite cleaner operation and cooler barrel temperatures during sustained fire as practical benefits.

The 16.5-inch barrel length is slightly longer than the typical 16-inch spec and draws occasional comments from buyers who notice the difference. The M-Lok handguard is considered functional and modern. The 10-round magazine capacity is a common purchase compromise for buyers in restricted states, and some owners note acquiring additional magazines separately.

The price point is the most polarizing aspect of the MR556. Owners who are satisfied generally say the fit, finish, and reliability justify the cost over time. Critics argue the premium is hard to quantify against comparable AR platforms. The trigger is generally acceptable but not considered a standout feature of the platform.

## Pricing

**2 offers available**

| Vendor | Price |
|--------|-------|
| Grabagun Com | $3749.00 |
| Guns Com | $3749.99 |

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*Data from [GunsNation](https://gunsnation.com)*