At the risk of revealing my ignorance, and in preparation for .35 Rem reloading:

Why do published .35 Rem loads top out around 35,000 c.u.p, when published .375 Win pressures top out around 50,000 c.u.p.?

Both are chambered in Marlin 336s. In the case of the .375 the chamber wall thickness is less than in the .35, right, or am I misinformed? What's up?

Because that's the way John Browning designed the .35 Remington, and that's the way Winchester engineers designed the .375.

The .35 Rem., also known as 9mm Browning in Europe as I recall, was originally designed for the rifle built by FN in about 1906 that became the Model 8 and later 81 Remington. It was later chambered in the models 14 and 141 remington designed by a Remington engineer named Pederson. This rifle is somewhat marginal in strength and not so durable as many others. It does not take to hot-rodding. The 8 & 81 are recoil operated, and if loaded significantly hotter that designed pressure will be battered, reportedly even to the point of breaking the back out of the receiver.

The .375 Winchester was designed for a significantly strengthened model 94 action which is capable of withstanding the higher pressure.

The SAAMI specifications for the cartridges are as you stated because of the various guns they are chambered in, not just the arlin action. Without checking references, as I recall the MAP for the .375 Winchester is actually 52,000 PSI.

And before anyone says the 9mm Browning is a pistol cartridge (actually two different ones) that is correct. Europeans do not get so specific in describing cartridges as we do.

Winchester had little choice but to raise proof pressure because they needed to to increase the performance of the 375. Had they stuck to lower pressure, performance would have suffered. Also, while it is true that the beefed up the 94 to handle it, it was never really a problem with a Marlin 336. While it would be possible to load a 35 higher in a 336 the main concern here is case strength because even the strongest action can be damaged if case ruptures. The 375 is a curious round but it never achieved what they wanted it too. The 35 is too good of found to lay to rest. The 30-30 has a fairly weak case too and is limited by it no matter what gun you shoot it in. While is i possibly to resize and use 30-30 brass in a 375 it should be avoided because 375 brass in thicker in base.

Makes sense. Thanks guys.

I believe the Marlin receiver is rated at 42,000 cup for the 30-30 . So that would be a guideline for how hot you would want to load your 35 rem. Your brass should have no problems at this pressure.

Go to marlinowners and maybe even here at beartooth. And search for A person with alias "35remington" has done massive/extensive research on the 35 Remington and has a lot of load data for +p 35 Rem loadings. He has produced a 2 or 4 part editions with various bullets and loadings.

Remember that the Marlin 336ER was chambered by Marlin in .356 Win which has significantly higher pressures than a 30-30 and there was no receiver changes to the 336ER compared to either the standard 35 Rem or 30-30.

From this data, it appears that a 35 Rem can easily and safely be loaded to higher pressures to equal the 30-30 or even higher. As pointed out above the 35 Rem factory loadings must be down loaded because they may be used in older semi-auto rifles.

Go to marlinowners and maybe even here at beartooth. And search for A person with alias "35remington" has done massive/extensive research on the 35 Remington and has a lot of load data for +p 35 Rem loadings. He has produced a 2 or 4 part editions with various bullets and loadings.

Remember that the Marlin 336ER was chambered by Marlin in .356 Win which has significantly higher pressures than a 30-30 and there was no receiver changes to the 336ER compared to either the standard 35 Rem or 30-30.

From this data, it appears that a 35 Rem can easily and safely be loaded to higher pressures to equal the 30-30 or even higher. As pointed out above the 35 Rem factory loadings must be down loaded because they may be used in older semi-auto rifles.

I have read that the basic 336 design is good to about 50,000 PSI and as noted the 336ER in 307 and 356 had no changes in action design. Still, you need to be careful with 35 because case is not that strong and high pressure could lead to its rupture. You could load a 35 a lot heavier but you can shorten case life a lot too.

Thanks guys. This is helpful, and will influence my comfort with and development of these loads. I believe this .35 Remington to be a very underestimated cartridge, and am always amazed at it's versatility. A Speer 180g JFN at 2400 FPS is nothing I'd sneeze at in any camp. Thanks for the guidance. Any other help is always appreciated.

Yes a 35 is a very capable round when hand loaded. Well above a 30-30 and with a 220 FN it would play well on elk, moose or even bear at closer ranges in timber. When I bought my 30-30 over 30 years ago I really wanted a 35 Marlin but all they had was 30-30's at the time on sale for 79 bucks new and it was hard to pass up. I even have a Remington 742 BDL in a 308 that I got new for 139 back then to a few years later. Guns were cheap back then. Back in early 80's I could have bought a new 1894 44 mag for 99 bucks. I wish I had.