Thunder B vs Blank Kit V2: Cost, Reliability, and Cold-Weather Performance (2026)

Full disclosure before we start

I designed the Blank Kit V2. This is not a neutral article. The whole point of the product is that it does something the stock Thunder B does not do well, so obviously I have a bias.

But this is not a hype piece. If you play airsoft casually, the stock Thunder B might genuinely be the better call for you — and I will explain when. What I want to give you is the actual numbers on cost, reload time, and cold-weather behavior, so you can decide for your own use case instead of listening to me tell you my kit is amazing.

Prices and comparisons are for the US market as of early 2026.

TL;DR

• Cost per throw: Thunder B ~$2.91, Blank Kit V2 ~$0.34
• Reload time in the field: Thunder B 20-30 seconds, Blank Kit V2 ~10 seconds
• Cold weather: Thunder B slows significantly below ~10 °C; Blank Kit V2 unaffected
• Break-even point on the higher upfront cost: ~35 throws
• Availability: Thunder B ships from many US retailers; Blank Kit V2 ships only from breytac.com (US warehouse in Dallas)
• Failure rates in our testing: Thunder B ~50%, Blank Kit V2 ~20% — neither is perfect
  

If you throw grenades often, the math points at the Blank Kit V2. If you throw one every few weekends, the Thunder B has a lower barrier to entry and is easier to grab from a retailer you already order from.

What each product actually is

The Thunder B is a compressed CO2 "time" grenade made by APS. It ships as a reusable metal core plus a consumable outer shell that cracks open on impact. You fill the shell with talc or plastic BBs, twist in a fresh 12g CO2 cartridge, snap the shell around the core, and it goes bang when it hits the ground.

The Blank Kit V2 is not a grenade on its own. It is a conversion kit for the Thunder B core. It replaces the CO2 cartridge with a 9mm PAK blank cartridge, which is the same round used in starter pistols. The core is the same; the propellant is different. That single change is what drives every other difference in this comparison.

The Thunder B is available bare from Evike at around $26.95 for a set of 3 cores, so ~$9 per core. The Blank Kit V2 is $80 alone (if you already own a Thunder B core) or $100 in the bundle that includes a fresh Thunder B core.

So on day one, before you have thrown a single grenade, the Thunder B is roughly 9x cheaper. This is why the cost-per-throw calculation matters — the whole argument for the Blank Kit V2 rests on operating cost.

The cost per throw math

Here is where the two products actually diverge.

Thunder B per-throw cost

Blank Kit V2 per-throw cost

The Blank Kit V2 is about 8.5x cheaper per throw. But you paid more upfront, so the honest question is: how many throws before that upfront difference pays back?

Break-even math: $80 (Blank Kit alone, assuming you already own a Thunder B core) divided by $2.57 (savings per throw) = ~31 throws to break even. If you are starting from zero and buying the bundle, it is ~35 throws.

Translating that into game time: 35 throws is about 3 to 5 CQB days for an active operator who throws grenades on breach entries. For someone who plays once a month and uses grenades sparingly, it is closer to a full season. If you only touch airsoft twice a year, the Blank Kit V2 will still pay for itself, but slowly.

Reload time in the field

Both are impact grenades. Both need to be reloaded during a game. But the reload procedures are different.

Thunder B reload sequence:

1. Twist the two shell halves apart
   
2. Remove the spent CO2 cartridge (careful — it may still be pressurized)
   
3. Refill with talc or BBs (optional)
   
4. Screw in a fresh CO2 cartridge
   
5. Snap the shell back onto the core
6. Rearm the striker
   

Realistically, that is 20-30 seconds under pressure, and requires you to be carrying loose talc/BBs, spare CO2, and spare shells in your loadout.

Blank Kit V2 reload sequence:

1. Remove the spent cartridge from the kit
   
2. Insert a fresh 9mm PAK cartridge
   
3. Rearm the striker
   

That is about 10 seconds, and the only consumable you carry is the cartridges themselves — small, cheap, no fragile plastic shells or shifting powder.

Does 10-15 seconds matter? Depends on your play style. During a CQB entry, it can be the difference between deploying two grenades on a floor and deploying one. During a casual afternoon, it does not matter at all.

Cold-weather performance

This is where physics kicks in, and where the Thunder B has a real problem.

CO2 canisters lose pressure as temperature drops. Below ~10 °C, a 12g cartridge does not deliver the same force as it does at room temperature. In the Thunder B, this means slower detonation on impact — sometimes the grenade lands and simply sits there for several seconds before the shell cracks, sometimes it does not activate at all. In winter airsoft, this is well documented across community forums and worth searching if you want independent confirmation.

The Blank Kit V2 uses a pyrotechnic charge inside the 9mm PAK cartridge instead of compressed gas. That charge is not temperature-sensitive in any meaningful sense for airsoft field conditions. It works the same at 25 °C and at -5 °C.

If you only play in summer, this is irrelevant. If you play year-round or in northern regions, it is one of the two strongest arguments for the Blank Kit V2 alongside cost per throw.

Reliability — the honest numbers

Neither product is 100% reliable. Impact grenades are fundamentally fragile devices with many variables (angle of impact, surface hardness, temperature, humidity, condition of the trigger mechanism). No system on the market delivers guaranteed detonation on every throw.

In my own testing and from customer feedback:

• Thunder B: roughly 5 out of 10 throws succeed on first impact under mixed conditions. Higher in warm weather on hard surfaces. Much lower in cold or on soft ground.
• Blank Kit V2: roughly 8 out of 10 throws succeed. Consistent across temperatures. Most failures trace back to the striker mechanism needing a manual check between game sessions — a 10-second visual inspection at the end of each day.

20% failure rate is still not zero. Anyone selling you an impact grenade with claims of "100% reliability" is lying to you. What the Blank Kit V2 delivers is a meaningfully better failure rate at a meaningfully lower cost per throw, not perfection. If you throw 10 grenades in a session, expect about 2 to not activate on first impact. Pick them up and try again, or leave them for the ref.

Availability and shipping

Thunder B is stocked by most US airsoft retailers — Evike, Airsoft GI, and smaller specialists. If you already order from them, adding a Thunder B to your cart is one click. Physical stores sometimes have them in stock too.

Blank Kit V2 ships only through breytac.com. We operate a warehouse in Dallas, TX for US orders, which means standard US shipping is fast (comparable to Evike's ship-out times in our experience, though you should factor a day or two to be safe on release runs).

Thunder B wins on breadth of availability. If you are already loyal to a specific US retailer and want to avoid adding a new vendor to your list, this is a real factor.

A word on legal considerations

9mm PAK blank cartridges are the same rounds used in starter pistols and are generally legal to purchase and use in the United States for airsoft, training, and starter-pistol applications. To date, no US customer has reported any legal issue purchasing or using them for the Blank Kit V2.

That said, I am not a lawyer and this is not legal advice. Blank cartridge regulations vary by state and sometimes by county — a few states have quirks around purchase age, storage, or transport. Check your state and local regulations before ordering. The BATFE resource pages are a reasonable starting point.

When the Thunder B is the right call

• You throw fewer than 30 grenades per year
• You want the lowest possible upfront cost
• You want to buy from a US retailer you already use
• You play only in warm weather
• You want physical retail availability

If you match most of these, the Thunder B makes sense. Do not let anyone (including me) talk you into overspending on a kit that will not pay itself back for your play frequency.

When the Blank Kit V2 is the right call

• You play weekly or more
• You play year-round or in cold climates
• Reload time matters to your CQB style
• You want the lowest possible cost per throw over the season
• You already own a Thunder B core and are frustrated with the shell + CO2 cost cycle

If you match most of these, the math tips toward the Blank Kit V2 relatively quickly.

What our customers actually say

We ship to operators across the US, EU, and UK, and the feedback pattern is consistent: strong reliability once the striker is set up correctly, low maintenance overhead, and the cost savings become obvious after a few sessions.

Some quick signal from verified reviews:

• One US customer reported that swapping to the kit was straightforward, that they had to source 9 mil blanks locally because the 9mm PAK was less common in their area, and that our customer service walked them through it. Product worked as advertised.
• A regular player who owns two kits and orders more mentioned the cost per use being their deciding factor, and instant activation on impact being what keeps them ordering.
• An Italian operator ran the kit through a five-hour CQB event in a hotel scenario, threw 13 rounds, and flagged one specific caveat worth passing on: the striker plate needs a visual check between reloads if you have been throwing hard. Miss that check and the next reload can misfire. This is exactly the maintenance point I mentioned above.
• A French customer flagged that the outer aluminum shell can be slightly tight on some CO2 spoons — mostly cosmetic, but worth mentioning if you are trying to run the kit and stock parts interchangeably.

Not everything is perfect. But nothing on the market that goes bang on impact is perfect either. What we optimize for is the fewest surprises, the lowest running cost, and reliability where the CO2 system falls apart.

Bottom line

If you play regularly enough that grenades are a real part of your kit — CQB entries, milsim breach ops, weekly team drills — the Blank Kit V2 recovers its upfront cost inside a handful of game days, then keeps saving you money for every session after. Cold weather stops being a coin flip. Reload is fast enough to matter in a stack.

If you play a few times a season and one Thunder B is going to sit on your loadout for months, the stock system is fine. Buy it from Evike, keep spare CO2 in your rig, and skip the conversion. That is the honest answer.

If you have decided the math works for you: Shop the Blank Kit V2 →

Already have a Thunder B core? Save $20 by going with Blank Kit V2 alone → and using your existing core.

For reload logistics and mounting: pair with the Cartridge Holder → and Blank Kit Holder → for fast field reload.