In reloading for my Marlin .35 Remington, I'm nearing listed max with AA2520. I've got zero signs of having a warm load, besides recoil and report. I'll be on my 3rd loading of these cases, and have not had to trim a case yet. This is in contrast to my .303 #5 enfield, which is pretty hard on brass with average loads. Are there pressure signs which are more common to lever guns? My primers look good and extraction is easy. Don't want to stress my rifle or myself though!

In this kind of lever action, with rear locking, by the time you get a pressure sign, you are already way too hot. With a front locking bolt like in the BLR, things are normal.
Your .303 likely has a generous chamber, so don't set the shoulder back when you resize. That way your brass will last longer, but the Enfield is a rear locker too.

You will see primer change if you get close to the top end. But I'm guessing that you will easilly reach max loads with no change. The lever gun is stronger than a lot of people think it is. That said, there are some oldies that are not safe with modern loads.
What Slamfire said is quite true, just don't read too much into it. Experienced lever gun loaders know that even with the 30-30 you can see pressure sign as you aproach max loads. Been there done that in a M94 Winchester. But, every model gun has different limits and in a gun with as long a run as some Winchesters and Marlins, there are major strength differences within the model. As an example my 70's vintage model 94 can exceed max by a fair margin before showing pressure in the form of slightly flattened primers, my 1910 model 94 will slightly flattend primers with factory loads.
Read those primers carefully! When I say flattend, I am NOT refering to the type of flattenning routine in some bolt guns. Stop when the flattening is just beginning to appear, your margin of saftey is not as safe as a front locking bolt gun.
Neck sizing will help your brass on the 303, probably a lot. It would probably pay you to have the headspace checked. And yes, it was common for the chambers to be cut a little large to allow for mud and crud, but I'm a little surprized that it's on a #5.
I suggest you email Steve Redgewell from his site, www.303british.com for more info.

While the Marlin is a strong gun, I'd quit when you reach factory velocities or 100fps over. For what your going to gain in a 35Rem it's not worth a grain of salt.

I agree there is no need to push a caliber beyond what it is designed for. There are a couple powders listed that give a little more velocity than AA2520. When I use up my stock of AA2520 I'll try some Reloder 7. The rifle shoots very well with the AA2520.
Regarding the #5 I get a bright ring around my case head after the 3rd reload.
These are necksized, half a grain under listed max. I'll have the headspace checked, the rifle has a "0" bolthead and may be due for a tighter one. It is quite accurate with this load. Factory rounds including Hornady Light Mags give no pressure signs. Thanks for the input. I'll restrict my handloads for the #5 to once fired or new brass and back off a half grain. No need to hot rod these rifles, I have a scoped .338 Ruger to reach out with. Incidentally the Light Mags shoot very well in the .303.

I was gonna say that "pressure signs and lever guns don't belong in the same sentence". As usual though, I learned something. Thanks to John Y. I shoot an Marlin 1895LTD .45/70 using the data from Hodgdon and just don't feel the need for more speed with this round.

303, regarding your #5 w/ bright rings on cases of the 3rd loading, you might check the insides of your cases with a 'feeler'( maybe a bent paper clip). Feeling for any indentation on the inside walls of any cases will tell you when to retire that case before it fails from incipient case seperation.

Another thing you can do with your 303, once you have determined your chamber dimensions, is to check what bolt head you have. There are differant sized bolt heads (1 thru 4, I believe) to accomadate slight headspace differances. - Dan

dan
The bolt head number 5 is rumored to exist, never seen one though.

Hey 303hunter, The best Pressure Detection method I've found for the lower SAAMI Pressure cartridges is Pressure Ring Expansion(PRE). Case Head Expansion(CHE) is not usable at these low Pressure Levels, but PRE always works.

Basically shoot a box of factory ammo through your firearm. Measure(and Average) the PRE on those cases with a 0.0001" capable Micrometer, by locating the high spot on the Pressure Ring. Use that Average PRE as your Comparative Benchmark Standard.

Either Full Length Resize or Partial-FLR those cases. Then do your load development in those same cases. When you get the same PRE as you got on the factory rounds - STOP.

You should get good PRE data for Loads 1 through about 10 at those lower Pressure levels.

You can get RCBS 0.0001" capable Micrometers from www.wideners.com for $21. A 0.001" capable Caliper just isn't accurate enough.

Not to argue with the other folks at all, but for me, I've found this method much more accurate and reliable than going by a subjective Primer appearance. That does not mean to ignore the Primers however.

Always use every Pressure Detection method available to you and STOP when they indicate that you should.

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Good hunting and clean 1-shot kills, Hot Core

Find an accurate load you can live with for your lever action rifle. I would say don't push your luck loading for any lever action designed rifle. Stay below maximum loads listed to stay on the safe side. Lever action rifles can explode more violently than a bolt action rifle. Lever actions will not group as well as bolt action rifles. You may be tempted to put just a little more powder in the case to se if the group will shrink more. Consentrate on symetrical reasonable sized groups and medium weight powder charges. If your lever action rifle will give you 1 1/2 groups at 100 yards that is considered good groups. You can test all powders listed for the cartridge your shooting in your lever action rifle along with adjusting the seating depth to get the very best groups possible. Brass preperation is more important than velocity. Lever actions were designed to give you extra shots if needed and should be limited to 150 yard shots. They were designed to be light to carry and fast handling in heavy wooded brushy hunting venues. They were not designed to fire hot loads and you will only damage them if you do fire hot loads. The action will stretch and not function at all in short order.