seating depth for .300 WinMag

[SuburbanHunter]

When I was handloading for my .270 I seated the bullet barely off the lands and they worked really well.

Now I am reloading for my new .300 WinMag. I have made and fired some test loads and am getting marginal accuracy (1.75" @ 100) so far. My best load so far is:

Federal brass,180 gr. Nosler Partition, 72gr IMR4350, CCI 250 Primer

I was told that the magnum cartridges need to be farther off the lands than standard cartridges. The reason I was given was that it takes a little extra time for presure to build and that the extra 'jump space' allows that to happen. The guy that was telling me this recommend 100 thousands off the lands. That sounds weird to me that a .270 would like to be almost kissing the lands but the .300 WinMag would like some space. I thought the idea was to get the bullet into the rifling as soon as possible so it would be lined up with the rifling as good as possible.

What do you all think? Where do you seat bullets on you magnums relative to the lands?

 

[danr55]

Hi and welcome to Hunttalk.. Your question is about as good as asking what is the best caliber for deer... I personally like to set my cartridges at the maximum length listed for the cartridge. By setting the bullet too close to the lands, you cause the chamber pressure to rise faster and higher than it would if it were seated back a bit farther. So my advice is get a StoneyPoint Cartridge gage and set your overall length to the spec rather than for the individual rifle. I've been loading for a long time and I've never found a rifle that would shoot less than 1 MOA with the right load and the right care.

That's not true. There was one. A Browning stainless stalker in 300 Win Mag. Tried everything. That rifle just did not like me.

 

[gundog]

Danr55's advice is pretty sound. Seat to max overall length and forget it. The real trick is finding a good bullet/powder combo. Years ago I played around with seating depths and found that with most hunting rifles little was to be gained by adjusting depth. It is important for the benchrest boys where even minimal improvement is huge.

Danr55 may be able to provide more insight but I've seen several instances in heavy recoiling guns where bullets were seated to touch the lands (no crimp) and after the second shot the bullet was being "engraved" by the lands when the new cartridge was pushed into the chamber.

 

[SuburbanHunter]

I am currently seating the bullet so that I am at Max Overall Length as per the the Speer manual.

I have played with powder & charge weight and still 1.5 moa is the best I can do.

I guess I don't understand why seating close to the lands on my .270 made such a huge difference in accuracy without any high preasure indications yet I am advised not to do it with the .300 WinMag.

Not arguing you understand, just the "engineer" (small 'e' cause I don't have a degree) in me needs to understand it better.

 

[gundog]

IMR 4350 would not be my first choice for powder. I'd look at IMR 4895, 7828. or 7828SSC. Try different bullets if changing powder doesn't work. Guns can be finicky..
I don't see any reason why you can't seat the bullet close to the lands if that's what you want to do. As long as you stay within the reloading manual recommendations pressure shouldn't be a problem.
Out of curiosty, what brand of rifle are you shooting. Are you shooting for a 3 or five shot average. What's the spread on the first two shots.

 

[T Bone]

Don't mean to sound stupid here, but 1.5 MOA is plenty good for big game hunting.....

 

[Gunner46]

Ok...........Here's a thought. Just for consideration.

I have a Rem 600, 308 Win. Never shot worth a hoot. 2"- 2 1/2" groups were BEST I could get. Hunted with it for many years, cuz inside 100yds or so it did just fine.

When I broke my back, and had surgery, I was laid up at home for a couple + months. Between Mom, wifey, and mom-in-law, I needed an escape. TA-DA!! Glass bed the little carbine. I just bedded the receiver and about 3 " of the barrel channel, relieved the Mfg pressure point at the front of the forearm to free float the rest, striped/ and put an oil finish on the stock. Less than $25 and many blissful qiuet hours ( I could only stand up for a few min. at a time).

WORLD of difference !! Went to MOA, with just about any load I cooked up. Settled in on a 180 Nosler BT at around 2450 fps that prints 3 shot holes which can be coverded by a nickle, sometimes a dime!

Who Knows?

 

[Pygmy]

T-bone... My sentiments exactly....

I have some hunting rifles that group 3 shots in less than 1/2 inch at 100 yards, and I have some that won't do that well..

My PET , and the rifle that I have killed the most game with, from woodchucks to Alaska moose, from point blank to 400 yards, is a M70 in .280 Rem that groups around 1.5" or a little more at 100 yards... I had to work to find just the right combo to get the groups that small....Still, I seem to kill everything I shoot at with that rifle...

 

[T Bone]

Pygmy,
You crazy guy, don't you know its impossible to kill elk or moose with anything less than a .338?

It's fun to fart around with rifles, but the thought keeps coming to mind to go to one rifle like the lowly 30-06 and use the rest of the money to go hunt.

 

[SuburbanHunter]

Thanks to all for the information and opinions.

I know that 1.75 is plenty good for hunting. But this rifle is glass bedded, free floated and has had a trigger job. All done before I bought it. I really want to understand and get as close to the potential of this rifle as possible and I just think it/and I can do better. . Its a Win Model 70 Classic and my only big game rifle.

 

[gundog]

If the barrell is fully free-floated try putting a little upward pressure on the barrel. You can build a pressure point in the barrel channel with layers of small pieces of electrical tape---strictly a trial and error proposition. Are your groups circular or are they "stringing" out as the barrel warms?

 

[Pygmy]

Suburban.. I understand, and agree that you should be getting better groups..

I'll just throw out a couple of things to try...

Powders...With the 180 Nosler, I've had very good accuracy with R-22 and H4831 in the .300 Winnie... Another bullet to try is the 180 Speer Grand Slam..

Have you tried other bullet weights..??.. Some rifles just don't like certain weights..My .280 throws 150 grain bullets all over the target, but groups acceptably well with 160 or 140 grainers with the right powders..

Try some 200 grainers...They are an excellent weight for the .300 mags..

Although I feel it is a waste of perfectly good powder capacity, you can go the other way and try some 165 grainers....They make a decent deer bulet in the .300 and would work on the bigger stuff with stoutly constructed premium bullets..

 

[Curly]

I have two .300 Win mags and reload for them. I don't think the seating depth with make a big difference........you may be able to shrink the group a little by fine tuning the seating depth but I'd look for a different powder first if I were you.

I think 4350 is a little on the fast side for a 180 grain. I found H1000 to be really good with 180 grain bullets. During load development I'd recommend seating to an OAL of 3.34", then once you get a load that will shoot best you can try different seating depths. (Maybe your load with IMR4350 will prove to be the best you can get with your rifle, but I'd be surprised if you couldn't do a little better with a slower powder.)

With that said, my best load on one of my rifles has on OAL of 3.45" and is 0.030" from the lands. (The rifle has a very long throat.) It also shoots almost as good a group at 3.34" OAL.