I read once that the older Baronfig Squire pens accepted some gel ink refills. Imagine my surprise when mine did not. Apparently somewhere along the way things were redesigned and the Squire lost the ability to accept a standard gel ink refill. It is non-reversible, but the pen will accept the old refill once the mod is completed.
To do this mod you will need:
- A Baron Fig Squire
- 1/8th drill bit for wood
- Skewers and masking tape
- Pentel Energel Pen- you need the refill and the spring
- Patience
- Craft knife
I went through the process of stuffing every gel ink refill I own from Pilot G2 to Pentel Energel to Zebra Sarasa into the pen, and each and every time, blocked. I poked around with a skewer, and found that there is a lip down inside the tip area that holds the narrow tube that holds the pen’s tip. It is snug to stop the refill from rattling around. Since I really like the Energel Pro for sketching doodling and general writing, I measured it against the Schmidt P8126 refill I usually use for the Squire. There was exactly 1mm difference in the diameter of the tubes, and the Energel refill’s tube was roughly 1/8th of an inch.
I decided to do this mod by hand, for many reasons but I did not want to take a chance of removing too much material and damaging the Squire beyond use. I’m not kidding when I say the Adrift is my favorite Squire. I grabbed a brand new 1/8th drill bit intended for wood and taped it to a wooden skewer, yes, masking taped it to a skewer. Again, this was to force me to use a light hand and prevent me from binding up the bit into the metal. 
The skewer also allowed my short bit to reach deep into the pen. It is important to point out that you drill the INSIDE of the pen, NOT from the tip in. So drill inside out. While I do not recommend it, if you chose to use a drill press for this mod, you’d need an extra long bit. 
I bored the inside a small amount then test fit. Then repeat that until I had bored out roughly ¼ inch or 5mm deeper. I attempted to use the Squire’s spring. It didn’t work with my Energel refill. The Energel spring did work. Even when I went back to the original refill I still needed the Energel spring. The Energel refill will need to be cut between 76 and 78mm from the base of the ink reservoir, not the tip, depending on how far you would like the tip to emerge.
Results? It works perfectly with the Energel refill. The metal part of the Energel tip fits perfectly into the Squire and there is no rattle or more movement than you usually see with a Squire. It’s smooth in deployment, the knock works perfectly and man that gel ink is great.
You might wonder why I went with the Pentel Energel Pro over say a PaperHate Inkjoy or Uniball Signo or even the Sharpie SGel or Zebra Sarasa refill. I really like the Energel Pro for sketching but also writing. It is also the only refill available in a 12-pack. I can buy singles or 2-packs of all of the mentioned refills but I really wanted a 12-pack. When I’m sketching, drawing and even writing a lot, I drain gel ink pens. Buying a 12-pack feels the most economical and ecological. I know a lot of people will buy entire pens and just use the refill. I feel wasteful doing that, so I’m going to stick with buying refills for this pen.