by Tom Gaylord
Writing as B.B. Pelletier

Part 1

This report covers:

  • Loading
  • Loading takes time
  • Loading a pellet
  • Velocity JSB Exact Jumbo
  • Eley Wasps
  • Longer pellets failed to work
  • JSB Exact RS
  • Evaluation so far

Today I fire the pellet adaptor with several pellets to both find out what it can do and also to get familiar with its operation. Let’s get right to it.


Several things have to happen to load the adaptor. First I use a cotton swab to wipe the carbon from the previous shot off the inside of the case neck. Then I wipe the outside of the cartridge neck and shoulder with a rag.

The primer is removed with a small Phillips head screwdriver pushed through the case mouth. Remember that the primer pocket was enlarged to accept a 209 shotgun primer, so it’s much larger than a conventional primer flash hole. There is no primer pocket anymore — just a huge hole with an o-ring inside.

That o-ring must be lubricated every time or the primer is too hard to insert. To do that I put some airgun oil on the tip of a clean cotton swab and wipe the o-ring once. I used Napier airgun oil that comes packaged with a lot of British airguns. It works well for this.

Next I load a pellet. I will describe the pellet preparation in a moment, but know that they don’t come straight from the tin.

The primer is the last thing I insert. If the o-ring is lubed, the primer goes in easily, though it isn’t loose.

Loading takes time

I timed myself several times, and getting the adaptor ready for a shot takes 90+ seconds. That doesn’t include the time it takes to load the adaptor into the rifle, which does take more time, because I’m shooting this in an AR-15. Single-loading cartridges in an AR is fiddly at best. But the adaptor fits well and always fired, so reliability wasn’t a problem.

Loading a pellet

This operation is the trickiest of all. You have to stuff a lead pellet tail-first into a brass cartridge case mouth. They don’t want to go, and if you use brute force you will simply damage one side of the pellet skirt.

What I did was use a flat steel plate to roll the skirt of the pellet on my desk top. The skirt is the widest part of the pellet, so the pellet naturally centers itself as you roll it on the flat desk top with the steel plate. You are sizing the edges of the skirt down to fit into the case mouth, and with a little practice, you get the hang of it. A die you could shove the pellet through would be far more precise, but I don’t have one.

Velocity JSB Exact Jumbo

I tried the 15.89-grain JSB Exact Jumbo pellet first. No particular reason for that. But this pellet has a relatively soft skirt that did size down, once I got the hang of it.

I shot 5 shots rather than 10 for this test because of all the time to prepare each one. On this first try, though, I shot 6 pellets. The reason I shot 6 instead of 5 is the first shot went 385 f.p.s. and shot 2 went 695 f.p.s. The difference was in how deep I seated the pellet, so before I give you the average velocity, let’s look at that.

The first pellet I seated until the domed head was touching the case mouth evenly all around. It looked good, but gave me the 385 f.p.s.

Jumbo seated 1
The pellet skirt wants to cock the pellet when you seat it. You have to use some force to seat it correctly.

Jumbo seated 2
This may look good, but the pellet isn’t seated deep enough to give good velocity.

The first shot was with a pellet seated to the point where the head just touches the case mouth all around. It looks good, but doesn’t give as much velocity as a deeper-seated pellet gives.I accidentally deep-seated pellet number 2, because it’s hard to control your thumb pressure when seating.

Jumbo seated 3
This deep-seated pellet gave both the highest and the most consistent velocity.

Now, let’s look at the velocity of the JSB pellet. Six shots averaged 605 f.p.s., but that includes the first shot that only went 385 f.p.s. After I started seating the same pellet deep the next 5 shots looked like this.

Shot……Velocity (f.p.s.)

These 5 shots averaged 651 f.p.s. Yes the total spread is 99 f.p.s., but that’s better than the 310 f.p.s. if we include shot number one. I am surprised I got even this much consistency. I was expecting a variation of 250 f.p.s. or more. At the average velocity this 15.89-grain pellet produces 14.96 foot-pounds of muzzle energy.

Eley Wasps

Someone suggested I try Eley Wasps in the adaptor. They have very large skirts, so the rolling had to be longer and harder, but I got them to fit. I deep-seated all of them and here are the results.

Shot……Velocity (f.p.s.)

Wow! The spread for Wasps was 281 f.p.s. That’s more in line with my past experience with primer-powered pellets. The difficulty is fitting these large pellets into the adaptor. There is very little uniformity, because of the way I am sizing the skirts, so that’s where the velocity variation arises. No doubt a sizing die would be much more uniform.

At the average velocity of 512 f.p.s. Wasps generate 8.44 foot-pounds at the muzzle. I doubt they are going to be very accurate.

Longer pellets failed to work

I tried both H&N Baracuda Match and RWS Superpoints, but both pellets have skirts that are too long for the adaptor. They simply would not enter past the two dimples in the adaptor case neck. What I needed was a lead pellet with a thin skirt that was also short.

JSB Exact RS

The last pellet I tried was the 13.34-grain JSB Exact Jumbo RS. This pellet is both light and has a short skirt. But they surprised me! Let’s look.

Shot……Velocity (f.p.s.)

My gosh! The spread for RS pellets was 378 f.p.s. The “average” velocity was 336 f.p.s. I have no hope whatsoever for this pellet and I’m not going to post the energy, since not one pellet came close to the “average” velocity..

Evaluation so far

This test is turning out pretty much like I imagined. Unless these pellets have any accuracy, I think these adaptors are a failure. But there are folks who swear by them, so let’s wait.