MTM Case-Gard RLLD-50-10 is the first pick for shooters who load several magnum calibers, so you can keep one box for most of them. If you want the best ammo box for a 300 Win Mag, the choice depends mostly on how many rounds you carry and where the box goes. This article covers four MTM boxes, sorted by size: 20, 50 and 100 rounds. Each one has a different job, from a pocket case to a bulk box for the shop shelf. For more detail, see Best Guns for Hog Hunting: Five Air Rifles to Consider.
Start with capacity, because the box size decides how many trips or how much storage you need. A 20-round box fits a jacket pocket, while a 100-round box stays at home. The 50-round boxes sit in between and suit most field trips.
Each box lists the calibers it fits, so check your cartridge against that list before you buy.
Key takeaways
Start with the capacity you need: 20, 50 or 100 rounds.
Check that the calibers you shoot appear on the box’s fit list.
Pick a lockable box when the ammo travels or sits where others can reach it.
The RLLD-50-10 is the first pick for owners with several magnum calibers.
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How we picked: from products sold on Amazon for this need, compared by what their makers state and what buyers report in their reviews.
The Picks at a Glance
Product | Best for | Capacity | Item weight | Item dimensions l x w x h | Buyer rating | |
|---|---|---|---|---|---|---|
MTM Case-Gard RLLD-50-10 | owners with mixed magnum calibers | 50 ml | 0.27 g | 7.2″L x 4.2″W x 4.1″H | 4.8 of 5 (982 reviews) | |
MTM Case-Gard H50-R-MAG-24 Deluxe | hunters who transport ammo | 50 load | 25.54 g | 7.86″L x 4.52″W x 4.71″H | 4.9 of 5 (924 reviews) | |
MTM Case-Gard J-20-LLD Slip-Top | carrying a few loads in a pocket | 20 load | 4.54 g | — | 4.6 of 5 (710 reviews) | |
MTM Case-Gard R-100-MAG-10 Deluxe | bulk storage at home | 100 load | 0.27 g | 7.73″L x 8″W x 4.47″H | 4.7 of 5 (592 reviews) |
Buyer ratings as shown on Amazon on October 13, 2026; they change.
MTM Case-Gard RLLD-50-10: Best for owners with mixed magnum calibers
MTM Case-Gard RLLD-50-10 is the first pick for owners with mixed magnum calibers. Its fit list is long enough that one box can hold rounds for several of your rifles.
The maker says these cases have been the first choice of rifle enthusiasts since 1968. The body is polypropylene that will not warp, crack, chip, peel or expand. For you, that means the box keeps its shape over years of use, so the rounds stay protected in the same case.
The fit list includes 264, 300, 330, 338 and 458 Win. Mag.. If you own a 300 and a 338, one box can carry rounds for both, so you do not need a separate case for each rifle. The snap-lock latch keeps the contents from spilling when you carry the box.
Each box measures 7.2 by 4.2 by 4.1 inches, so you can plan shelf space before you buy more than one. The boxes stack, which keeps a few of them in a tidy pile at home. The maker guarantees the box for 25 years.
Pros
One box for many magnum calibers
Buyers say it is well built, sturdy and durable
Buyers say it holds a good number of rounds, including large reloads
Buyers say it is good value for the money
Cons
Each box holds 50 rounds, so a 100-round load needs two boxes
It is not water resistant, so it suits dry storage better than wet gear bags
If you want a larger box for storage at home, the R-100-MAG-10 Deluxe is the better fit.
MTM Case-Gard H50-R-MAG-24 Deluxe: Best for hunters who transport ammo
The H50-R-MAG-24 Deluxe is the pick for hunters who carry ammo to the field. It is a 50-round rifle box that the maker describes as lockable and built for transporting ammo, which makes it a good fit for a truck, a camp, or a trip where the box leaves your sight.
The maker says the box is lockable and designed for ultimate ammo protection and ease of transporting. For you, that means the box can stay closed and locked in a vehicle or a shared camp.
Bullets sit point down, and four special fingers hold them in place. The maker says this design keeps most bullet tips off the bottom of the box, which prevents tip damage that can change bullet flight. For a hunter, that means fewer dented points after a bumpy ride.
The fold-down carrying handle lets you carry the rifle and the box in one hand. The maker says a full 50 rounds of magnum ammo can weigh a lot, so this matters on a long walk in.
Pros
Lockable, so the ammo stays secured on trips.
Fold-down handle carries the rifle and box together in one hand.
Bullet tips are kept off the bottom of the box.
The maker lists a 25-year guarantee.
Cons
It holds only 50 rounds, less than the 100-round R-100-MAG-10 Deluxe, so a bulk supply will need more boxes.
If you mostly store ammo at home or load several magnum calibers, the MTM Case-Gard RLLD-50-10 Flip-Top is the first pick for owners with mixed magnum calibers and is a better starting point.
MTM Case-Gard J-20-LLD Slip-Top: Best for carrying a few loads in a pocket
The MTM Case-Gard J-20-LLD is the pick for carrying a few loads in a pocket. It holds 20 rounds in a slip-top box that the maker says is designed to ride in a jacket or shirt pocket.
The maker states the box is made of clear, see-through polypropylene and lists 300 Remington Ultra Mag., 300 Weatherby Mag., 300 and 338 Win Mag, and 7mm Remington Mag. among its fits. For you, the clear walls mean you can see which rounds are inside without opening it, and the fit list tells you whether your caliber belongs here.
The maker also says the box is made in USA and is ideal for keeping special loads separate. In daily use, that makes it a good home for a handful of hunting or match loads you do not want mixed into your main supply. The box is not water resistant and has no lock, so it suits a pocket or a shelf better than a truck or a place where others can reach it.
Pros
Keeps special loads separate from your main supply
Buyers say the box is sturdy and well made
Buyers say it holds a good number of rounds and keeps them organized
Cons
20 rounds runs out fast, so a long hunt means refilling it
Buyers say the lid fits loosely on some boxes
Buyers say it is too small for some larger cartridges
If you carry 50 or 100 rounds on a trip, look at the MTM Case-Gard H50-R-MAG-24 or the MTM Case-Gard RLLD-50-10 instead.
MTM Case-Gard R-100-MAG-10 Deluxe: Best for bulk storage at home
MTM Case-Gard R-100-MAG-10 Deluxe is the pick for storing a large supply of magnum ammo at home. It holds 100 rounds in one box, so a full load stays in one place.
The maker lists a lockable box with bullet tip protection and a strong handle. A lock matters most when the box sits in a shared closet or garage, where others can reach it.
The box is made of rugged polypropylene with a scuff resistant textured finish. It is stackable, with a mechanical hinge and a load label, so you can use shelf height instead of floor space. The 10-year guarantee gives you a long period to use it.
At 7.73 inches long, 8 inches wide and 4.47 inches high, it takes more shelf space than the first pick.
Pros
Holds 100 rounds in one box
Comes with a 10-year guarantee
Made in USA
Lockable, with bullet tip protection
Cons
Larger footprint, so it takes more shelf space
Not water resistant, so a dry closet or garage suits it better than a damp basement
Hunters who carry ammo into the field should look at MTM Case-Gard H50-R-MAG-24 Deluxe instead.
How do you pick the right size and lock?
Start with the cartridge. A box protects a round only if the case fits its cavity, so match your caliber to the fit list before you compare anything else. The maker lists 300 and 338 Win Mag among the fits for the 20-round MTM Case-Gard J-20-LLD. The 50-round RLLD-50-10 also lists 264, 300, 338 and 458 Win Mag.
Check the overall length too. Each box gives a maximum overall length, which is the longest cartridge it will hold. The 100-round R-100-MAG-10 allows 3.24 inches with the bullet up and 3.75 inches with the bullet down. Measure your cartridge from base to bullet tip and compare it to that number.
Pick capacity by use
The size you need depends on how you carry and store your ammo. A 20-round box is built to keep a small batch in a jacket or shirt pocket, which suits a few special loads. The J-20-LLD holds 20 rounds.
For a trip, the H50-R-MAG-24 holds 50 rounds. Its fold-down handle is designed to let you carry the rifle and the ammo box in one hand.
For storage at home, the R-100-MAG-10 holds 100 rounds in one box. It is a bigger box, so plan for the shelf space.
Choose a lock when it matters
Choose a lockable box if the ammo travels or sits where others can reach it. The H50-R-MAG-24 is a lockable box. The R-100-MAG-10 is lockable too.
The J-20-LLD has no lock. If it goes in a pocket or on a trip, keep it out of reach of others.
Which box to start with
The MTM Case-Gard RLLD-50-10 is the first pick for shooters with several magnum calibers. The maker lists 264 / 300 / 330 / 338 / 458 Win. Mag. among its fits, so one box can hold loads for more than one of those calibers.
Decide on capacity first, because box size sets how many trips or how much storage you need. The MTM Case-Gard J-20-LLD is designed to keep 20 rounds secure in a jacket or shirt pocket, which suits a few special loads for a day in the field. For a shelf at home, the MTM Case-Gard R-100-MAG-10 holds 100 loads in one box.