You are referring to this:
https://data.bls.gov/cgi-bin/cpicalc.pl
I use this often myself, but we have to remember two things:
These are the official government numbers. It is in the government's best interest to keep the CPI as low as possible. The formula for calculating CPI has changed since the 1970s-80s. I've read many times and places recently that, if that website used that early formula, it would be showing upwards of 15% rather than the current 8.5% it is claiming.
The official CPI is derived by comparing the prices of a "market basket" of goods and services that most American consumers buy on a regular basis, e.g. common groceries, rent, energy (gas prices are not included because they're too volatile) entertainment, etc.
I highly doubt that the price of firearms and ammunition are included in that market basket. As an example, I recently found the receipt for a gun I bought in 2017. That gun has inflated in price 52%. I recently bought projectiles for reloading; those are up almost 200% since about 2 years ago. I put some firearms accessories on backorder about 6 months ago. I recently got. notice that those items are still on backorder, but that the price had increases 35%.
I have a box of 100 22LR from the 1990s with a $3 price tag on it. According to the official CPI calculator, $3 in 1990 works out to $6.70 or 6.7¢ per round. I haven't even seen cheap bulk box ammo in that price range in years. The cheapest 22LR at Luckyguner.com is 13.8¢ per round. Cabela's still carries the identical 22LR ammo, in the same packaging even, at 12¢ per round.
So, using the real world comparison, ammo prices are about double what they should be when compared to the government's official numbers.