I have had advice from numerous folks that I can use 45 or 46 grains of H4350 behind 175 grain bullets in my commercial 1955 Husqvarana 7x57.

The Hogdon site, however, says 37 grains is a maximum load.

Who is right?

I have used up to 44 gr in an 1895 Chilean Mauser with mild pressure. My rifle is in like collector grade mint condition and I would never use a load in it that I thought would be any where near excessive.

The Speer #12 manual has a max of 45 grains for all 3 of the 4350s.
The Hornady #4 manual has 44.3 grains of IMR4350

Hodgdons data is pitiful for this round. I suspect if you use it you will get badly sooted cases from the neck not sealing off.

Use a chronograph for sanity. The loading manual will give you a good idea of what constitutes a sane maximum velocity, so start with a minimum load and work your way up.

The load you mention is a good load for modern rifles such as yours. What bullet are you using? You still need to drop 10% and work up to it watching pressure signs. This is a 30-06 pressure load.
Matt

Another suggestion might be to get a copy of Ken Water's Pet Loads.
I worked up to several of his suggested loads for the 7X57 and found them to be 100% true to what he wrote, and the same applies to many other cartridges he worked with...

Just checked my Speer and Nosler manuals. Speer lists 45 grains of both H and IMR 4350's for max loads with the 175gn grand slam and match bullets. The test rifle was a ruger M77 with a 22" barrel. Velocity of just over 2400fps. They list 41 grains as a starting load with both powders, and both got almost identical velocities again at around 2200fps. Speer says they test the 7x57 to 30-06 pressure (50K CUP).
Nosler tested their 175grain Partition with IMR4350, but not with H4350. They list a max of 45 grains. Velocity was just over 2500fps from a 22" barrel.
I have seen this load of 4350 (from H and IMR) printed in several different places. It almost seems like a "standard" and well proven load. Don't know about any other 57mm cased cartridges, but 45 grains of H4350 works great with the 115 grain Partition in the 257 Roberts. The Roberts is another round hampered by low SAAMI spec pressure limits. The above mentioned load is also in the 30-06 pressure level though. Always work up your loads in your rifle. Don't start at max. You never know. The primer, case capacity of you particular lot of cases, the particular bullet you are using- all can effect pressure. I'd find a loading manual with the bullet your using and go from their. Take what folks like us here on the internet forums say very cautiously and use a loading manual!

Hogdon may have been lawyering up in consideration of some of the old rifles floating around.
This is where it's handy to have several load books so you can get a consensus.
My Hogdon book, which is kinda old, shows a max of 44grs for the 7x57 but then it has a second set of figures for "heavy loads" for Ruger only. I would assume that means any modern bolt action rifle.

The worst of the old rifles floating around have to be the 7mm Remington Rolling Blocks.
They are not really chambered like a modern 7X57 and if they let go it is all right in front of your nose.

Check it out in YOUR rifle by starting around 41 grains and working up in 1 grain increments until you start to see some pressure indications. Do this seating the bullet out as far as your rifle will allow without jamming the bullet into the rifling.
The assumption here on my part is that the throating is as deep as most military 7x57s, and they normally are. roger

Chronograph. Seriously, get a chronograph, pressure and velocity ARE correlated. If you are getting 280 or 7 mag velocities out of your 7x57, you do not have a "special" chamber or "extra long throat". At best you'll get stunningly short brass life, the worst case... hopefully only the rifle is ruined.

Contrary to internet wisdom or bravo sierra, a 175gr NP at 2350fps will actually kill a cotton tail, or a good sized elk for that matter.