300 WM seating depth/208 gr. A-Max

[Sargesniper]

Just starting to load for the 300WM and would like your best seating depth recommendation. I have not fired the rifle as of yet. Rifle is a Rem.700 Long Range with 26" Varmint BBL. Not sure how well these bullets will shoot. Any suggestion will be appreciated.

 

[gohring3006]

Just start at mag length and try it. You might be surprised, I was in my 300 Weatherby.

 

[Sargesniper]

Just start at mag length and try it. You might be surprised, I was in my 300 Weatherby.

If i load to mag length it will jam the lands. I would prefer to load a little off.

 

[MagnumManiac]

If i load to mag length it will jam the lands. I would prefer to load a little off.

This is my advice to ALL users of a new rifle.
Take a NEW case that has had the neck sized, get a dremel or grinder with a .039"/1mm cyt off disc, and cut 2 slots opposite each other in the neck, clean up all burrs, size it again and place a bullet lightly in it and chamber it carefully. Lift and lower the bolt handle a few times, then slowly and carefully withdraw it with finger pressure from your opposite hand on the case so it doesn't drag the chamber wall or action from the ejector pressure, then measure it. Whether you measure from base to tip or base to ogive doesn't really matter at this stage.
This measurement will be for THAT bullet, you must do this with EVERY DIFFERENT bullet you intend to use.
I would start with the bullet .030" from the lands, then closer in .010" increments. You may find tge sweet spot, if you don't, I would try further away, up to .050"-.060". Once you find the sweet spot, you can go up and down in .005" increments and see if it tightens the groups any.
I always test powder first with the bullet at .030" from the lands, this always works for me for initial work up.
Some of my hunting rifle chambers cannot get anywhere near the lands, so mag length determines seating depth.

Cheers.
gun)

 

[Sargesniper]

This is my advice to ALL users of a new rifle.
Take a NEW case that has had the neck sized, get a dremel or grinder with a .039"/1mm cyt off disc, and cut 2 slots opposite each other in the neck, clean up all burrs, size it again and place a bullet lightly in it and chamber it carefully. Lift and lower the bolt handle a few times, then slowly and carefully withdraw it with finger pressure from your opposite hand on the case so it doesn't drag the chamber wall or action from the ejector pressure, then measure it. Whether you measure from base to tip or base to ogive doesn't really matter at this stage.
This measurement will be for THAT bullet, you must do this with EVERY DIFFERENT bullet you intend to use.
I would start with the bullet .030" from the lands, then closer in .010" increments. You may find tge sweet spot, if you don't, I would try further away, up to .050"-.060". Once you find the sweet spot, you can go up and down in .005" increments and see if it tightens the groups any.
I always test powder first with the bullet at .030" from the lands, this always works for me for initial work up.
Some of my hunting rifle chambers cannot get anywhere near the lands, so mag length determines seating depth. Cheers.gun)

Thanks for the tip, been doing this exactly as you state. Works well when done as you said.

 

[Bart B]

After a "sweet spot" is determined for where to seat the bullet relative to the rifling, what will you do several dozen or hundred rounds later when the rifling's eroded away and is further down the barrel increasing that lot off ammo's distance bullets jump to the rifling?

300 Win Mag's erode the barrel's rifling advancing it about .001" for every 15 rounds fired.

 

[Sargesniper]

After a "sweet spot" is determined for where to seat the bullet relative to the rifling, what will you do several dozen or hundred rounds later when the rifling's eroded away and is further down the barrel increasing that lot off ammo's distance bullets jump to the rifling?

300 Win Mag's erode the barrel's rifling advancing it about .001" for every 15 rounds fired.

I suppose I would either chase the lands or bump the load up or both.

 

[MudRunner2005]

300 Win Mag's erode the barrel's rifling advancing it about .001" for every 15 rounds fired.

By your estimate, that means your average .300WM loses 0.010" of throat per 150 rounds of barrel life...I'm definitely not an expert on barrel life and throat wear, but that seems excessive.

 

[Bart B]

Use the right tools and techniques to measure your barrels throat erosion, then you'll know for sure.

My .308 Win barrels eroded about .001" for every 30 to 40 rounds of barrel life.

 

[MudRunner2005]

Use the right tools and techniques to measure your barrels throat erosion, then you'll know for sure.

My .308 Win barrels eroded about .001" for every 30 to 40 rounds of barrel life.

I do have the right tools and know the proper technique.

I wasn't questioning you, just saying that sounded like a lot of wear for such a short round-count.

 

[MagnumManiac]

After a "sweet spot" is determined for where to seat the bullet relative to the rifling, what will you do several dozen or hundred rounds later when the rifling's eroded away and is further down the barrel increasing that lot off ammo's distance bullets jump to the rifling?

300 Win Mag's erode the barrel's rifling advancing it about .001" for every 15 rounds fired.

As I thought you would already have known the answer and the question is rethorical, the answer is fairly simple.
Because the sweet spot is a combination of distance to the lands, velocity and barrel time, the easiest way to stay in the node is to bump powder charges, when velocity drops, back to the original velocity.
Many years ago, I would chase the lands, but this only works for about 1 season, throat erosion gets too much at the end of a season, so I would set back and re-chamber, sure this worked, but It was costly. Nowadays, a barrel can last 2 seasons without being set back and re-chambered.
Your assessment on throat erosion is on par with my own measuring, .040" after a full weekend match of more than 200 rounds is common, depending on what powder is used. Double base powders seem to be kinder on throats than single base powder.

Cheers.
gun)

 

[FEENIX]

Just starting to load for the 300WM and would like your best seating depth recommendation. I have not fired the rifle as of yet. Rifle is a Rem.700 Long Range with 26" Varmint BBL. Not sure how well these bullets will shoot. Any suggestion will be appreciated.

Not sure if it works for your rifle but this the one I have for my SAKOM995 with 24" barrel 1:11" ...

It's .040" off the lands; 73 IMR7828SSC, CCI250, WW brass, 2800 FPS, <.5 MOA @ 200 yards.

Not really sure if this is the sweet spot as I only loaded 9 just to establish a base line from another load development but I left it alone since I wasn't going to hunt with it anyways.

Good luck!

 

[Sargesniper]

Not sure if it works for your rifle but this the one I have for my SAKOM995 with 24" barrel 1:11" ...

It's .040" off the lands; 73 IMR7828SSC, CCI250, WW brass, 2800 FPS, <.5 MOA @ 200 yards.

Not really sure if this is the sweet spot as I only loaded 9 just to establish a base line from another load development but I left it alone since I wasn't going to hunt with it anyways.

Good luck!

Thanks FEENIX, that is about what I am getting (a little more @ 3.601 actually) for my starting point. I won't get out to shoot for a week. I am waiting on my powder to arrive from PV. I'll load this weekend and be ready for next week. This won't be a hunting rifle so length won't have to fit the mag. well.

 

[jammer300]

I am seating the 208gr AMAX .050 off the lands in my Savage model 111, 300 winmag, 24" barrel 1:10". I am using 69.8 grs. of IMR7828SSC, WLRM primers, Federal brass with an average velocity of 2780fps. I average 1" groups @ 200 yards