substitution for compressed powder charges

Would substituting a standard primer for a magnum primer work to reduce compressed charges in a .308? I noticed that when I set my ogive at a certain measurement, and compressed charges tends to make your ogive a little longer than what you want, especially when working up a ladder. Each .3 increments tends to make the ogive longer by a couple thousandths on compressed charges. A magnum primer can give more speed / pressure than a standard primer, so you would reduce your charges anywhere from .3 to .8 grains if using a magnum primer, correct me if I am wrong.

I'd probably back off a grain or so and come back up 0.3 grain and a couple of rounds at a time if I was within 0.005" or 0.010" of the lands to begin with. If I was 0.050" off the lands, I wouldn't worry about it.

What powder and bullet combo? And what seating depth? Can you seat the bullet out longer?

Switching to magnum usually equals about .3 to .5 grains powder, give or take.

Sorry Chad for leaving out powder type, It's IMR-4064, maybe Varget also, not sure. I know both of these will fill cases easily. I like to load close to the lands to experiment with as well.

Which bullet are you using?

I have loaded up some loads for the .308 and 167 Scenars / 4064 and worked up a ladder to get max velocity. 4064 tends to fill the case more because of the long kernels.

Have you tried Varget?

Compressed loads tend to push the bullet out a bit after sitting on the shelf for a few weeks, at least with the 0.002” neck tension I use, so I try to avoid them. Full is good, over full, not so much.

Yes, Varget is my go to powder, but it won't hurt to experiment with 4064. It's reason I asked if using a magnum primer would work instead of a standard primer because you will eventually need to reduce charges to avoid the bullet push issue. I measured right after seating, ( ladder charges) and the higher charges (slightly compressed ) shows longer ogive than the lesser charges ( not compressed ).

I tested magnum primers with 175 SMK's and Varget. The groups opened up from 1/2 MOA to 1 MOA even after redoing ladder tests more than once trying to find a sweet spot. fwiw - my usual load is 43.5 gr of Varget with a F210. The mag primers generated the same velocity at 43.0, just as a reference in your tinkering.

However, I only tried Varget, so other powders may produce different results. Will watch your tests with some interest and hope it works for you, truly. Some folks have reported better results in 308 with mag primers, so it is worth trying.

The bullets not remaining at the intended seating depth is reason enough for me not to use a compressed charge.

Although not normally an advocate of crimping centerfire cartridges, when seeking to load compressed charge ammo, usually in a quest for speed, a light crimp will solve the bullet push issue. Most of us don't do it, but most factory loaded centerfire rifle ammo is crimped. Some of it shoots quite well. In order to get a consistent crimp, particular attention must be given to trim length. In the event you try it, be advised that pressure and corresponding velocity will be a bit higher, so back off a bit and work back up.

Can you crimp bullets that don't have a canelure?

You can with a Lee FCD.

Yep. You can also put a light crimp with a standard seating die. I prefer the FCD. I would not advise a full blown roll crimp with no canellure. If you have a collet style puller and pull a bullet from most any factory loaded round you will be able to feel the noticeably higher neck tension from the factory crimp, whether it has a canellure or not.

Have you tried using a drop tube? I use it for my 223 with Varget and 77 TMKs. It give me just enough space to seat the the bullets where my gun likes it.
https://www.midwayusa.com/product/1012691876/forster-blue-ribbon-powder-funnel-with-long-drop-tube

I did use a drop tube, it reduces it some but still compressed with IMR -4064