The Munitionworks Mod J SPR Part II - The Oregon Desert

When it comes to precision gas guns chambered in 5.56 that blend boutique craftsmanship with practicality and affordability, the Munitionworks Mod J SPR continues to impress me even after 2 years of faithful yet abusive service in my hands. Building on my earlier impressions and 2 years of faithful service, this Part II review focuses on real-world use throughout the years and roughly 5,000 rounds, both at my regular range sessions, as well as my favorite training facility - Thunder Ranch. In addition to that, I’ve also recently been able to take some extended range testing at Leupold’s private range in the Oregon desert, where we got a good chance to test out some new ammo and push the rifle to its limits in terms of practical accuracy.  

More Rifle Reviews @ TFB:

• TFB Review: The Munitionworks MOD J - The Modernized SPR
• TFB Review: Springfield Armory Coyote Brown SAINT Victor V2 5.56 NATO
• TFB Review: REVAMPED Saint Victor 14" Pin/Weld
• TFB Review: BCM ARMK2 RECCE 14

The Munitionworks Mod J SPR Part II - The Oregon Desert

The Mod J SPR remains one of my favorite rifles in my permanent collection. It’s a boutique rifle that doesn’t break the bank and doesn’t try to reinvent the wheel when it comes to features. Joe and the Munitionworks team have carefully engineered a rifle that merges high-quality parts, hand assembly, thermal fit barrels, and attention to detail without the premium pricing seen in many competitors. Joe tests all of his rifles before they leave his facility, and even sends along a proof card that he signs, the casings from the rounds he fired to achieve that group, and a bible as well.

Assisting in the accuracy department was the new budget-friendly American Quality Ammunition 77-grain OTM rounds from AmmunitionToGo.com. This ammo, while maybe not as hot as some other 77-grain offerings, is not only reliable but meters consistently and gives me the accuracy I needed to keep up with other DMR-style rifles chambered in 6 ARC and 6.5 Grendel. If you’re looking for some great performing 77-gr OTM ammunition that doesn’t cost nearly $1 a round, I’d go check out the ammo here, as it’s only about $150 for 200 rounds.

The 1:7 twist barrel of the Mod J is optimized for stabilizing heavier 77-grain bullets, paired with a solid but comfortable new adjustable stock trigger that all contribute to sub-MOA accuracy from the bench with both the ammunition and the rifle. This rifle doesn’t chase flashy features; it delivers reliable, repeatable precision that appeals to serious shooters looking for real-world capability. Along with the suppressor, the whole rig weighs in right at around 11lbs - not a rifle for those who haven’t been doing their cardio, but neither is the original MK12.

Thunder Ranch and The Oregon Desert

The true test came at Thunder Ranch, where the Mod J SPR was pushed beyond benchrest precision into dynamic tactical shooting scenarios. The focus here was on fundamental skills—shooting on the move, quick reloads, and precision shots from unconventional positions, and we got to do this both at Thunder Ranch and at the Leupold Range. The Mod J SPR maintained zero with exceptional consistency between these two virtually back-to-back trips, even through rapid firing sequences, rough handling, and regular transport.

A critical factor in the setup’s success was the American Quality Ammunition 77-grain open tip match rounds from AmmunitionToGo.com. Offering match-grade performance at a wallet-friendly price of roughly 60 cents per round, this ammo has impressed me with its reliable accuracy when compared to more expensive 77-grain options like ADI and Federal SMKs. The 77gr OTM bullet performs exceptionally in the Mod J’s 1:7 twist barrel, consistently delivering tight groups at distances from training close to the extreme long range. This combination further pushes the Mod J towards the more value-oriented side of the spectrum and gives you a balance of affordability and performance that’s hard to beat, especially for shooters who like reaching out to distances beyond 300 yards.

In addition to the 77-grain ammo, I also shot a ton of PMC X-Tac M193 55-grain ammo from my personal stash and found that while my results weren’t as consistent at longer range, anything 500-yards and in was easy work, especially on the full-size 5’8” targets that are placed at ranges from 100 out to 700 yards on the Thunder Ranch Adam Brown range. However, at the Leupold Private range, I noticed that at ranges out to 1000 yards, almost necessitated the use of the 77-gr OTM ammo as it was simply more predictable at those extreme ranges.

Final Thoughts

The Munitionworks Mod J SPR continues to prove itself as an outstanding 5.56 precision rifle for medium to long range when paired with the right ammo, like the budget-conscious, high-quality 77-grain OTM ammo. Valuable time spent at both Thunder Ranch and the Leupold ranges with their long-range target arrays emphasized that this rifle is not just for bench shooting but is ready for demanding practical applications and field use.