Devcon works great, just make sure you're accurate with your mixing ratios, weight it out before you mix it. A lot of gunsmiths use marinetex as well, I hear it's more forgiving on mix ratios. Release agent on EVERYTHING lol. Hornady unique works very well in the last 3 rifles I've bed.
You can check out Pro-Bed 2000 for being available in quantities that won't have you wasting/throwing out a bunch of Marine-Tex (recommended by McMillan and popular) or DEVCON (who make both aluminum and titanium based compounds if you're concerned about iron/rust). It's mix ratio is 1:1, and it is THICK. That makes it very easy to work with if you are OK with that consistency.
My favorite is Pro Bed 2000 (Score High) by a mile.
Used Devcon steel putty for many years, which is also excellent, but no looking back after using Pro Bed. I still use the little Devcon combo tubes for bedding bases or small fills.
Pro Bed and Devcon have always finished nice per strength, smooth fit, no shrinkage.
What gives Pro Bed the nod is how easy it mixes without air traps/bubbles, ideal manageability (not too thick or too thin), and how nicely it fills and sets up - working time is 2X longer than most, so 60 to 90 minutes depending on room temp.
Limiting to 45 minutes of work time can be like disabling a bomb.
I've used most of the common ones. My current go to is Hy-Poxy H-800 stainless filled. It has an 8100psi compression strength which is near the top of the epoxies available, but is remains flexible enough to not crack or shatter.
All seem to work fine. If I need to do a colored job, I just use Acra Glas gel and color to suit.
Edit: I will not be using what I said below for a couple reasons. See my post further down.
Original post.
Devcon 10760 (titanium base) is what I will be using. It is overkill and 10610 (aluminum base) would have worked for 2/3rds the price, but I found a place that would ship the 10760 to Alaska and the convince of not having to keep looking (combined with the cool factor of overkill using Devcon's hardest use epoxy) was worth $30 to me.
Weigh and corrosion concerns kept me from getting the 10110 (steel base). I know the 10170 is lighter, though probably not but a few grams for how much I will be using. The corrosion concerns are completely theoretical, but I spend time around salt water and know I would needlessly worry about it, so I did the OCD thing.
My favorites are Brownell's Steel Bed, MarineTex, and Devcon 10110, I've gotten great results with all three. The Steel Bed is the most forgiving compound I've used.
So, I failed to do good research on the differences between Devcon 10760 (Ti), 10610 (Al), and 11010 (steel). My Ti Putty arrived a few days ago, and today being my first day off in the past six days I was reading over the directions and noticed the pot life was only 20 minutes on the box. So I looked up the technical data sheet (something I should have done earlier) as I had made several assumptions.
Edit: it appears Technical Data Sheets are actually hard to find for many epoxies, so I don't feel as dumb for not looking these up before. I encountered the TDS by accident to start with. End edit.
In terms of chemical resistance, the Ti puty is hands down the best. For bedding a rifle it has several flaws in comparison to the steel putty and the aluminum putty. Here are some that stand out to me.
Pot life
Steel: 45 min
Ti: 20 min
Al: 60 min
Specific gravity (density)
Steel: 2.33 g/cubic cm
Ti: 2.36 g/cubic cm
Al: 1.58 g/cubic cm
The Ti has higher max operating temperature, but I don't thing the difference between 120 C and 177 C counts for anything on a bolt gun.
The Ti has better resistance to petroleum products, but not enough to make up for short cure time, heavier weight, and minor increase in shrinkage.
Should have verified my assumptions. Time to do some more research.
Edit: The difference in shrinkage is probably too small to really matter. Pot life is probably the most significant difference. Weight just negates what I had assumed would be the primary advantage of the Ti. It looks like Marin Tex Grey has a density of 1.7 g/cubic cm and pot life of 30 minutes. I cannot find specific numbers on shrinkage. It sounds like any of them will work. I will probably go with Marine Tex Grey or Devcon Al for weight reasons. Clearly both work well for lots of people. End edit.