Been reloading bottleneck rifle cartridges, and including .270 Winchester, with H4831 and H4831SC for over 40 years.
There is nothing inherently wrong or dangerous with a compressed propellent charge... provided the resulting load is not overpressure. Slower burning powders frequently require a compressed charge. In the .270 Winchester case, this includes H4831 and H4831SC.
The "SC" is an acronym for "short cut", which refers to H4831 extruded kernels cut shorter to better fit into standard cases like the .270 Winchester (as opposed to magnum cases). H4831SC also meters better than the original, with less chance of a kernel being cut by a powder measure. The ballistics and load data for H4831 and H4831Sc are identical.
As others have noted, IMR4831 load data is NOT identical to the Hodgdon product.
Regarding H4831 and 130 grain bullets, back in the day... 62.0 grains was considered a maximum safe charge. Some rifles and some brass would take that without excessive pressure. Over the years, as loading manuals became more conservative (or watered-down, depending on your viewpoint), the maximum charges have been lowered.
While I've had a couple of .270 Win bolt action rifles that have shot that load well, I currently load 60.0 grains H4831SC with the 130 grain bullet. It's not maximum in my rifle with my components, but it is a slightly compressed charge in Hornady brass.
The case capacity of various brands of brass differ and this affects pressure. Federal, for example, was generally thicker brass with less capacity than Winchester, and could not be loaded with the same charge. I once used PPU .270 Win brass that required a safe charge in Winchester brass to be lowered a full 2 grains.... with corresponding loss of velocity. These case capacities can vary over time and manufacturing date.
Various brands of bullets also have their own characteristics based on design, ogive, hardness, etc. These affect pressure too.
The manufacturers creating the loading data and doing the testing, are dealing with their own individual rifles and/or test barrels, under their own testing conditions including brass and seating depth, with bullets of their own making or choosing. And after finding what is maximum safe under SAAMI pressure standards for those specific components and equipment, they back off as a safety margin. Few manuals provide any specific pressure information on their loads - Hodgdon is a rare exception.
As you are reloading for your own rifle and components, consider the manuals a starting guide. I would advise against starting with any maximum load out of any loading manual... reduce 3% and work up. With a 60.0 grain charge, that would be 58.0 grains.
Compressed charges are not in and of themselves dangerous, so long as they are appropriate.
PS. Heavily compressed charges of ball propellant are a bad idea. Compressed ball powder can fuse in unpredictable fashion, resulting in either dangerous hangfires or inconsistent pressurization.
As an example, back in the day (1956), the new .458 Winchester Magnum was factory loaded at close 2200 fps with the 500 grain bullet, to achieve the mythical 5000 ft lbs of energy for marketing purposes. The ball propellant used was very heavily compressed, and firing the cartridges 10 years later resulted in a number of the above-mentioned anomalies: both hangfires and "bloopers". This was probably due to a combination of the compression and storage under conditions of heat and humidity. The Winchester factory ammunition was reduced to 2050 fps spec, and many lots barely broke 1950 fps in typical rifles with 22-24" barrels.
