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I am preparing to load my first cast bullet loads for my 308. I realize i need to stay under 1600fps per the bullet manufacturer but does the pressure curve matter much here? It might get to 1600 but do it too suddenly and smear my bore. Or not?

Planned on h4198 and or trailboss...

I fooled with a lot of Trailboss when it first came out...it was always adequate but never the best. One mans's opinion. 4198's or RL 7, but most of my experience is with .30-40, '06, 8x57, 32-40,38-55, 45-70.
You might keep an open mind on 'fast' powders, sometimes if your bullet is a tad small for your throat/groove, you can save yourself the heartache of leading with a swift kick in the ass with fast powders and perky primers.
Again, one man's opinion.

Thanks

Not a writer.
In my 308 I've been up to 2450 fps and routinely run 2200 with The NOE version of the Saeco #315 180 gr gc bullet sized to .3115. These are powder coated and water quenched out of the PC oven. Before the PC cycle they run around 15 Bhn. I have used several powders for those loads over 2000 fps, Varget, N202, H4350 and H4831sc. The pressure curve you talked about would favor slower powders in this project.
I've taken several whitetail does with this load, never recovered a bullet, even on a couple that went end to end.I intend to fun some air cooled versions of the same bullet to see how they work. If it ever cools off around here.

This is without gas checks. Just learning to cast and trying different bullets first

It's been shown here before, but...if you're going to get into casting a lot of really good information here: http://www.lasc.us/CastBulletNotes.htm

Too many unknown factors to allow a prognosis. Bullet fit? Bullet alloy and hardness? Gas checked?

Have you read one of the iterations of the Lyman cast bullet manual? If not, do so.

All that said, 1600fps is a walk in the park. 4198 may be your friend, maybe not. I would prefer 4227, RL7, 5744, or my all time fave 4759 but that stuff ain't no more. Trail Boss will get you there but pressures spike quickly when you push it past cowboy action type loads. I don't care for it one darn bit and accuracy always sucked compared to other powders. YMMV though.

As a rule of thumb without going through all the rigamarole of chamber casts and bore slugging, size it to .310", lube it well, and pick a powder from the manual that'll give the desired velocity, and see what happens. At that speed it shouldn't lead unless you're doing something particularly offbeat.

Do yourself a favor and get a neck expander die from either Lyman or RCBS that will expand the neck to accept the larger bullet and bell the case mouth slightly to ease insertion of the bullet. Fairly critical, that. Those dies are cheap. Using a standard neck expanding plug just doesn't cut it- something has to give and it won't be the brass. Your carefully crafted relatively soft cast bullet will suffer as will your accuracy.

Well the plan is to shoot a 150 ish grain bullet at 1500 to 2000fps eventually. Didn't know this stuff was so complicated.

I have been handloading for 15 years but i guess i need to do more research

Not gas checked. 309 diameter

cra1948s recommendation of the lasc is good as is flintlocks on fast powders.

For moderate velocities in numerous 30 cal rifles, and 165g and up weight bullets, i have had very good luck with 4227, 2400, 5744, and sometimes Unique. My best accuracy seems to be around 1500 fps.

If these are over the counter bullets, it may help to get a size that is large enough for you to tailor the diameter to match your rifle. Cast bullets is a whole nother hobby that is fun but requires some work and fiddling around. It helps to have a neck expanding die so you dont shave lead seating a bullet.

No doubt others will chime in with great suggestions.

Not gas checked throws a monkey wrench into the works. Practical upper limits of plain base bullets falls short of your 1600fps goal. There may be/are excwptions but you gotta have your ducks in a row and even then it's not terribly likely that?accuracy with no leading will result.

Plain base .30 bullets: to me spell 1400fps and less and powders like Unique and Bullseye. That's not a bad place to be though. Accuracy is to be expected, and after all a bullet only has to be moving fast enough to punch through both sides of a paper target. Hunting? Yeah it's possible and in the hands of a steely eyed woodsman a light load like that will knock a deer ass-over-tin cups. I'm not always that guy and so I prefer my cast .30 hunting bullets to have a little more moxie.

Ok. These bullets are able to have a gas check attached so maybe i will do that as well

Mr Galt, I would defer to the Gnoaaah on this stuff, but to me a gas check bullet, sans the gas check, is a recipe for failure much above 1,000 fps. There are a lot of sharp edges back there exposed to a theoretical 2,000 degree flame...most alloys melt around 700 ish. As long as your eventual goal is hunting velocities, go with the gas check from the get-go. You need not spend a fortune to begin with...Lee push-thru dies are your friend. You don't need some high dollar lubrisizer until you know what you're doing, and maybe not then. I am not a powder coater, never will be, but if the PC guys are telling the truth about accuracy, then that may get you where you want to be.

Ok. Thanks

👍👍👍

I second the motion on the use of gas checks. One thing, and as I don't know what configuration your bullet has, but if it is a fairly straight sided ending in a round nose, try inserting it the bullet nose first into the muzzle of the rifle. If the nose is engraved by the rifling or is a snug fit, then the bullet should shoot well. I've noticed that bullets that are loose or a sloppy fit accuracy usually sucks big time. Since the powder maker is it's infinite wisdom no longer make SR4759 (thank you bean counters) I've gone to Accurate 5744 for my general cast bullet shooting. I reserve Unique for light gallery loads. I generally reserve 2400 for my .357 and .44 magnum loads.
Paul B.

I use unique with 165grain bullets for my358 winchester. About 1600 fps.

castboolits.com is a great reference for cast bullet ("boolit") shooters.

Many variables for accuracy in a rifle. Rifling twist, groove diameter, throat diameter, bullet hardness, powder, velocity etc.

I would recommend getting a good assessment of your barrel first. Do a "pound cast" (look it up) technique to accurately measure the THROAT diameter of your rifle/chamber ( 0.000" or 0.0000")

Then lube your bore, and tap the bullet you wish to use through your breach, out to the muzzle. Record GROOVE diameter (0.000", or 0.0000").

Use a tight fitting patch or bronze bore brush, and measure your rifling twist. (1-10"? 1-11"? 1-12"? other?)

A very good starting point for accuracy is to size the cast bullet to THROAT DIAMETER (maybe 0.0005" smaller than throat diameter)- or just small enough diameter to just fit the throat of the chamber. If too big, it won't fit. Too small, it will FIT, but won't give you best accuracy.

You will probably read that you should size your cast bullets to 0.001-0.002" over groove diameter. This is a good start, but is not really what you should target your bullet sizing diameter. This APPROACHES throat diameter, and may even match it (it the diameter matches it, you got lucky). You really want to target fitting just so it snugly fits into the throat. This will save you time in seaching for best accuracy with cast bullets.

watch your MV. Use gas checks. If your twist is 1-10" , you will likely see best accuracy around 1600 fps. If 1-12", you may be able to get good accuracy up to 1800-1900 fps, pending bullet alloy. If you are looking for "high velocity", you should seek even a slower twist of 1-13" or 14" twist, this may get you up to 2400+ fps with accuracy. The issue you run into is "threshold velocity" or "threshold rpm" (look that term up for cast bullets).

castboolits.com has a lot of this info on the website. One person's posts who you should read over there is "Larry Gibson". He has done a tremendous amount of work with high velocity cast bullets and slower rifling, due to the threshold rpm / velocity issue. It is essentially when the softer cast bullet strips from the rifling as it is pushed too fast for the barrel's rifling.

The SAECO 315 ("Eagan bullet") is a good bullet design, as is the 311041. "Ranch Dog" designed molds are excellent hunting bullets, and accurate, and have a large meplat ( flat nose for good energy transfer). Night Owl Enterprises (NOE) make excellent molds of proper diameter. Arsenal Molds is another excellent mold maker, and they will cut the mold to your requested diameter for no extra charge.

Good luck. Throat diameter is the key measurement.

Yup, all that and more. Which is why I said to get Lyman's book and read it.

I've been loading plain base cast bullets for my .35 Whelen for many years, my use was limited to plinking only. When I first started I was using SR 4759, when that powder was discontinued I switched to Unique. 15gr. of Unique and bullets weighing 200, 210, 215 and 225 grains it didn't make any difference 15gr. of Unique was a load that shot very well accuracywise. Cast bullet loading adds what can be a fascinating new dimension to ones shooting, lots to research and experiment with.