I think that every one here knows by now to use low pressure loads for safety and to keep stress on the wood to a minimum. Accidents happen and guns fail, but why take a chance with loads which were never used when the gun was brand new? The NID was designed to deal with higher pressures because the Flues and earlier designs were not able to handle them and for all intents the NID was the last designed US gun and other than the Model 21 maybe the only one to shoot modern shells without major concern. When shell makers had to raise pressures, to work autos, the double gun was left behind by the shell makers. Sales were too few to warrent any major improvement in design for most makers. Either the old guns could handle the higher pressures or they became the Miners, Flues and Klunkers too weak to shoot safely with factory fodder. Have your gun checked, barrel walls measured and use basic common sense.
IF only one of the big box sporting stores, stocked low pressure shells for the masses to buy, it would be a public service. In fact if one ammo maker got smart they could corner the market in sales in a heart beat. Federal should make their paper shells in 12, 16 and 20, loaded to low pressure levels. Market them as "trainer loads, low recoil loads, vintage loads or classics loads". Bring them out in 2 1/2 or 2 9/16" with 1 ounce in the 12, 1 or 7/8 ounce in 16 and 7/8 in 20. Price them at or below 5.00/box retail, the shooters would buy them by the case. In fact I would personally buy 30-40 flats. Keep the pressure to say 6,500/12, 7,000/16 and 8,000/20 and they would have a winning combo. With modern powders, paper hulls and wads to work with these are reasonable to acheive. Anyone know if Federal looks at this BBS?
