September 28, 2021
By James Tarr
If you want to do ballistic impact/terminal performance testing of cartridges, back in the day people would shoot bullets into water jugs or water-soaked phone books or even, if you’re old enough to remember, clay blocks. These days, the standard is FBI-spec 10% ballistic gelatin. That is what the FBI, other law enforcement agencies, and ammunition manufacturers use when performing terminal performance tests. Gel blocks are the standard tissue simulant.
The downside? You have to find bulk gelatin, make them yourself at least a day ahead of time, and they have a short life outdoors (they are actual gelatin blocks) especially if there’s any heat. Gelatin is organic, and gel blocks are very temperature unstable. Plus, depending on what kind of gelatin you acquire, they can be cloudy, making retrieval of fired bullets a slow and annoying process.
Enter Clear Ballistics LLC’s blocks. Clear Ballistics sells various blocks, but here I will be talking about their “10% Ballistic Gelatin FBI Block”. This block is 16-inches long, six inches tall, and six inches wide. Each one weighs roughly eighteen pounds.
Despite the name, these blocks have no gelatin in them, at all. They are polymer, which allows them to be made clear. The manufacturer has chosen a polymer which they say performs exactly like FBI-spec 10% ballistic gel. They can be shot dozens of times, and when they get too cloudy or beat up you can melt them down and reform them into new blocks—up to ten times, according to the manufacturer.
They are very convenient to use, and unlike true gel blocks which you have to mix up and then refrigerate overnight, these are ready to use right out of the box. That convenience might be their biggest selling point, although you pay for that convenience. As I write this, Clear Ballistics has them on sale for $70 apiece, but normally they run over $120 each depending on the retailer (I bought mine through Brownells). And I honestly recommend buying two and placing them end-to-end, as quite often bullets will penetrate more than one block.
These blocks are clear, making it easy to find your bullets and spot the bullet track, and temperature-stable from 32F-100F. They are completely synthetic, which means they won’t rot, and you can store them indefinitely.
The bad news? Despite what the manufacturer claims, extensive testing by both Police1.com and Federal Ammunition has shown that these blocks do not perform the same as true FBI-spec 10% ballistic gelatin. They’re often close, but results do vary, depending. If you’re just having fun in your backyard looking to see how well your carry ammo performs that’s one thing, but it’s another if you’re a small police department using these blocks to evaluate potential duty ammo.
Compared to actual calibrated gel blocks, the Clear Ballistics blocks seem to be less dense—bullets penetrate more deeply and expand less. Just how much depends on the bullet and the caliber, but it is not a standard percentage.
I still recommend these blocks if you want to do ballistic testing as they are better than anything other than true gel blocks, and far more convenient than those, but be advised your results will vary when compared to shooting into actual FBI-spec gel blocks.
A few hacks if you want to start doing some gel block testing:
- Set your blocks on something you don’t mind seeing damaged. Don’t put them directly onto a table. Gel blocks flex forcefully when shot (enough to crack wood), and sometimes bullets veer down into whatever they’re resting on. I use a double layer of 2x6 lengths under my blocks.
- When testing rifle or shotgun ammo, blocks sometimes bounce right off the table onto the ground from the force of the impact. Having a bottle of water nearby to wash them off will help you spot the bullets. You might want to mark the front and top, so you know how to reorient the block back on the table.
- You’ll want a tape measure to measure penetration.
- You’ll need a knife to dig the bullet out. It doesn’t have to be long (a three- to four-inch blade is enough) but as you’ll be prying, don’t use something delicate or expensive.
- Want to get rid of the wrinkles on your Clear Ballistics block for the ultimate in viewing pleasure? Try a hair dryer.