Wonderful. Yes you are correct, I am not saying it is impossible, it is quite possible. And with some time, you WILL learn stuff about what happens to that gun when it goes bang, even if everything goes wrong.
You have the mill / lathe and drill press. You're in business. This other stuff is cheap.
Ok, 8 years ago I would have said that programming would have been easier to learn back in the 70's or 80's on something no longer available to buy. That has changed, and now I would absolutely advocate that little gizmo I posted the link to. Not only will it be so damn much fun you won't believe it, but it's as easy and as straightforward as programming is going to get. And, it doesn't cost an arm and a leg. I recommend that device since it has good resale value, and allows you a learning and debugging experience that you will never get on a PC. Any more, PC's suck for learning to do programming. At the beginner level anyway. It isn't that programming is difficult, but, nothing today is documented AT ALL, and you are google searching all the time to find every tidbit of information. That company there produces datasheets just like the old days. Yes, that datasheet for the processor thats included on the board is 1000 pages. But the info is in there. You don't need to find some obscure website to get info. And it's not like you need to read every single page and every word. You need to know the basics of each section that pertain to you, and you need deeper information when things don't work as expected. But the info is there, and its easy to find.
Your accelerometer is just one way to collect data. But like almost all methods, it's an analog device. Meaning, it will give you voltages between 0-5Vdc as a result. You need to catch those really fast, and you need to catch them as a number (Analog to Digital Conversion ADC). An oscilloscope is the easiest way. However, in some cases, it is not the best way. It sure is nice to have a scope for all the work on the circuits, and it doesn't have to be the fastest thing in the world. But when I did this, I did not collect usable data nearly as well with a scope as I did with a processor. I also didn't use an accelerometer, though I'd probably use a few now if I was to do it over again. I made my own devices. Be that as it may, you'll need to try all ways before it's all over. That 18Fxxx chip on those boards I linked has A-D converters on it. You simply set them up and read the values from ram. Easy as pie. The controller I'm working on right now will do 5 at one time, and sample them >1,000,000 times a second. For a small controller, that's unheard of. My chips were <$5 each. Fyi, I have no use for the A-D on them. It just happens to come with it, as it does many other things. That same chip is sold with more pins and will sample 9 simultaneous A-D's. at that speed, you would be able to have 4 2-axis samples simultaneously (4 sets of sensors on the barrel at the same time), and with a typical bullet ride of 2ms, lets say conservatively you could sample those 2400 times while the bullet is in the barrel. So, a super fast scope really not only isn't necessary, but, isn't going to give you this level of data collection cause this data you can actually get out of the chip and save, then move to excel or a database if you wanted to.
I would be willing to point you in the right directions (or what I think are right) but I will not do the work for you and will tell you that up front. I don't have time to invest. But I'd be happy to offer ideas as time permits. And I can give you shopping ideas that'll really help keep the cost down and fun factor up. Fun being what this is all about anyhow!
As long as you don't get discouraged, you'll find this a great experience. There's various forums full of folks who'll help with about any problem.
In the interest of not starting some flame war, I'd suggest we move this from the forum to email. Mines in my profile I think...
A scope will have a limited number of inputs. One of your inputs will be used just to tell the thing when to catch data. That is one limitation. Scopes with 4 channels or more are expensive. Scopes >100Mhz start to get expensive too. This is why your buddy said it would be an expensive undertaking. You don't need a super expensive scope, and that is why I say get a used one cheap. It might not have todays features, but people have built some pretty kewl stuff with scopes of 20 years ago. Many can be had because they are no longer young enough to be certified. They are essentially scrap to the company that is using them where they need certification with paper to back it up. It has nothing to do with them not working, it just means that nobody will stake their life that the numbers from it are dead on correct.
If you go to microchip.com, you can go TODAY and download FOR FREE, Mplab8.70. That software will allow you to simulate any processor they make, and actually run the code and sample apps, as well as pretend there is actually a device there connected to sensors and all sorts of crap, all within an integrated development environment (IDE - Program for making programs let's say). You can do that for $0.00 tonight. The new IDE is under development and that is what I use right now. I'm working on a project at the moment using a brand new type of processor (to me, not that old to anyone else really) and using the new IDE in its current Pre-release state and I love it. It will not simulate like the old Mplab will though. And for that 18F chip, it may be easier to begin with what already works.
I'll tell you this as incentive. I have personally gotten about a half dozen people started in micro-controller apps, all of whom have had virtually 0 prior experience with the stuff. Each has gone on to do projects of their own with 0 help from me or anyone else, and the stuff has worked for what they do. People from all age categories 15-60, but all folks like yourself who will stick their nose to the grindstone and learn the stuff.
Begin by making an LED flash on that board. From there, you'd be surprised how close you are to reading movement of barrels.