CA is the perfect solution to your issue with the stress cracks.

Stress cracks occur due to the wood separating at a spot where grains diverge. One set wants to go one way and the other set the other way. They can occur at any time in any species of tough-grained wood like out stocks are made from. Even if you were able to squeeze them together again, the load there would most certainly fail, especially under shooting conditions. However.....they can be arrested.

There's a good chance that doing nothing here won't aggravate these fissures. They've probably been there for a while but might have migrated slightly and that's when you discovered them. That would be my bet. Chances are good that what you see there is not going to travel much more, if any at all. Still, you need to keep an eye on 'em.

If you do decide to address them, the goal would be to somehow insert water-thin CA into the largest part of the fissures. CA will travel everywhere and penetrate into the depth of the fissure walls, setting there in the walls and locking them together against further movement. "Locking down" the travel of the fissures is the goal. Right now, however, the problems is that those fissures are really small and inserting even the smallest applicator I've seen (basically a needle) would be difficult. So, here's my suggestion.

1) Do nothing right now. Watch for any additional travel. Measure accurately the existing cracks and record them in your file on that rifle (I'm sure you have one.) Once and a while measure again and compare. An accurate photo helps a lot. If it moves further, look at #2.

2) Ok. You decide to address the fissures. The goal here is to get the CA into the fissure but finding an applicator to get into the fissure would be difficult. And, applying water-thin CA is messy if it gets on your stock surface. It can be addressed but it's a lot of work. You want to somehow get the water-thin CA into the fissure without bothering the stock surface and the original finish. The way to do that is simple. All you would have to do is first of all purchase some water-thin CA and the smallest applicator you can find. Go to a hobby store. They will have all three viscosities of CA along with very tiny plastic applicator tips designed to insert the adhesive into tight areas for hobbyists. These tips are disposable, btw, and cheap.

Now, once you've acquired those items, all you have to do is find a tiny drill bit that is just slightly larger than the CA tip you have. Drill a test hole in some scrap and make sure the tip will insert into the hole you've drilled. Once you're satisfied, you'll drill a whole in the largest part of the two fissures and to the depth of the fissure. DON'T go all the way through! Stick a piece of paper into the fissure to figure out how deep it is and only drill to that depth. Support the stock well, then simply and very carefully insert the CA with the tip installed into the hole you drilled and apply a tiny amount of pressure. The CA will flow readily into the fissure, traveling end to end. DON'T try to force it in because it'll overflow and you'll be back to fixing the surface. Also, don't try to "fill" it, either. Just apply enough so you know it's in there. Water-thin CA is really "leaky" and will move on it's own. CA doesn't dry, it cures. Moisture in the stock wood will take care of that (don't add any!) and if you try to wipe it away or get it on your fingers you'll see just how fast it happens. The goal here is to install a tiny amount of water-thin CA into the fissure so it locks down any further travel. Let the stock sit overnight. I know, I know, it's 'instant' glue! But because of the tight quarters there won't be a lot of air moisture getting in there so you'll have to wait until it cures up which won't be instant. DON'T use a "kicker" here, either. There's too little space for that to work, too.

If you have to, address each fissure at different times so you can keep the stock level and flat keeping the CA off the stock surface while the CA cures.

Now, you've got a tiny hole to deal with which won't be difficult at all. After the CA is cured, simply pick up a small container of MinWax filler material. You'll find it in the stain isle of any good home center. It comes in a bunch of different colors. These fillers are designed for very small repairs and is a clay-like material. Buy two colors if you must to match your stock as closely as possible. Darker is better than lighter, btw. Dark fillers will more handily cover your tracks. Just force the filler into the remaining fissure surface and your small hole and buff it up. In a few days it'll harden and you shouldn't even be able to see where it is when you're done.

I know this sounds like a very complicated and long-winded explanation of a simple process but I just wanted you to have enough info to plan your attack and create a successful repair.

If you need any further info, just post your questions and I'll be happy to clarify anything I've typed here.

Rome