One of my buddies believes I am making a bad choice converting my .338WinMag Ruger into a long-range target rifle. He recommends I go for a .300 WinMag, which only has 3.7gr more case capacity and a lower BC. This doesnt make sense to me. I have read the BC of a .338 WinMag is .410'ish. Have you guys found any with higher BC's?

ballistic coefficient is a combination of several factors, the least of which is caliber, with the exception of the 50BMG perhaps. and thats due to shear weight and cofiguration of the projectile rather than caliber.
if you consult the bullet manufacturers reloading manuals or their websites, you will see BC's listed for their products. from that you can come to your own conclusions.
i shoot a 338 regularly, and though i'm not recoil sensitive, the thought of shooting them from a bench for anything over 20 rounds does'nt appeal to me. and if its a ruger m77 mk2 with the sporter stock, that has even less appeal.
better to get a 308 allready configured in my opinion. you'll spend a lot less and have just as good results.

Richard hit the nail on the head with his thoughts about recoil. Shooting a .338 mag all day from a rest might be the real chore. If your just punching targets the 308 delivers all the performance you really need. Even the 6.5 by 284 is a better choice.

You'll see some folks using a 300 Win mag, but most are shooting lighter recoiling rigs. You don't need to deliver a lot of energy to a long range target to make a hole in it.

Sierra sells a .338 300 grain Matchking that has a BC of .768 at velocities over 2300 fps and .750 under 1800 fps which is really impressive, but so is the recoil.

If your looking for a long range shooter you might consider the 338 Lapua it was designed just for that purpose. Here's a couple of places to check it out.

http://www.snipercentral.com/338.htm

http://www.accuratereloading.com/338lmag.html

Here's a summery of .338 long range cartridges by Chuck Hawks you might want to read. It'll give you a better picture of the big .338's.

http://www.chuckhawks.com/super_338_Mags.htm

The problem with using these extremly high BC bullets in the 338 Win mag is with the 300 grain bullets your limited to velocities under 2500 fps with a .338 Win mag and that severely limits trajectory. Here's a chart on different bullets and velocity to look at. Scroll down near the bottom and look at the heavier bullets.

http://www.accuratereloading.com/338wm.html

There are several 6.5 and 30 calibers with higher BC's than .410. Check out Sierra's Website and their Match king bullets. Here's the link. By clicking on the green description of the bullet it will give you the BC's for different velocities.

http://www.sierrabullets.com/index.cfm?section=bullets&page=rifle&displayAll=1&brandID=1

Thanks faucett you really helped me out alot. I wish there were more members like you man. I'll look into that Sierra Matchking. Im guessin since it is 300gr it may be originally for the .338 lapua. But the WinMag can hold up to 83 grains of powder easily so I should be able to achieve 2500fps+ with that. I candle any recoil it dishes out, especially if I can get .768 BC. For some reason recoil seems to be worse from the bench that from the prone. I thought it would be worse prone, being that the shooter is in a more stable position. Who knows. Thanks for the info!

Check with Sierra on the twist rate needed. Some of their long-range target bullets require faster-than-normal twist rates to stablize.

I'm with the rest, think you'd be better off with something much smaller. Even the fast-twist .22s will do some pretty amazing things with 69-80gr. bullets at long range.

Ballistic coefficient is only part of the equation; albeit an important one.

Bullet drop is determined by time of flight to the target.
Wind drift is determined by time of flight and ballistic coefficient.
Time of flight is determined by muzzle velocity and ballistic coefficient.

It's worthwhile to run the numbers on a good ballistic program. It's entirely possible to give up too much velocity in search of a high BC with a small or moderate capacity cartridge and wind up with more drop or windage than you might get with a lower BC and a higher velocity.

The 300 SMK requires a 10 twist and most if not all factory 338s are 10 twist....

The 300 SMK requires a 10 twist and most if not all factory 338s are 10 twist....

Like jwp says - Rugers web site shows they currently use a 1 in 10 twist for their .338 Winy.

However, running the .338/300 SMK at 1.95" length through the Greenhill formula calculates a maximum required barrel twist of 1 in 8.8" at a muzzle velocity of 2,800 fps or less!

Simply put.....A 1 in 10" barrel twist should not be fast enough to stabilize a .338/300 SMK - You'll need an 8.8 or faster twist (i.e. lower number).

Thanks faucett you really helped me out alot. I wish there were more members like you man. I'll look into that Sierra Matchking. Im guessin since it is 300gr it may be originally for the .338 lapua. But the WinMag can hold up to 83 grains of powder easily so I should be able to achieve 2500fps+ with that. I candle any recoil it dishes out, especially if I can get .768 BC. For some reason recoil seems to be worse from the bench that from the prone. I thought it would be worse prone, being that the shooter is in a more stable position. Who knows. Thanks for the info!

I know what you mean about recoil biggun. I shoot several big boomers including my favorite 8mm Rem mag and several friends 300 Ultra-mags. I built my own lead sled that has support behind the buttstock and uses up to two bags of lead to cut recoil. Shooting the big 8mm mag is like shooting a 243 with this setup and no bruises.

http://i136.photobucket.com/albums/q172/faucettb/Preditor%20masters/280Rem-1.jpg

You can also get a past Magnum recoil pad that straps on you and really helps out a bunch for those big boomers.

Like jwp says - Rugers web site shows they currently use a 1 in 10 twist for their .338 Winy.

However, running the .338/300 SMK at 1.95" length through the Greenhill formula calculates a maximum required barrel twist of 1 in 8.8" at a muzzle velocity of 2,800 fps or less!

Simply put.....A 1 in 10" barrel twist should not be fast enough to stabilize a .338/300 SMK - You'll need an 8.8 or faster twist (i.e. lower number).


With all due respect to the Greenhill formular the need for a 8.8 twist is not correct. The recomended twist by Sierra for the 300 SMK is a 10 Twist. I have a 338 Laupa with a 10 twist and it shot a 3 shot .8" group at 300 yards with a 325 grain rebated boatail bullet made by Wildcat bullets in Canada and that bullet is longer than a 300 grain SMK

With all due respect to the Greenhill formular the need for a 8.8 twist is not correct. The recomended twist by Sierra for the 300 SMK is a 10 Twist. I have a 338 Laupa with a 10 twist and it shot a 3 shot .8" group at 300 yards with a 325 grain rebated boatail bullet made by Wildcat bullets in Canada and that bullet is longer than a 300 grain SMK

I guess sometimes it just comes down to that fact that some things look one way on paper and another in testing. But I would agree with jwp, if Sierra says a 10 twist works, thats what Id go with. Besides, they made the bullet. Thanks for the info guys:)

With all due respect to the Greenhill formular the need for a 8.8 twist is not correct. The recomended twist by Sierra for the 300 SMK is a 10 Twist. I have a 338 Laupa with a 10 twist and it shot a 3 shot .8" group at 300 yards with a 325 grain rebated boatail bullet made by Wildcat bullets in Canada and that bullet is longer than a 300 grain SMK

jwp,

Well.....I believe you, But Don't jump to conclusions too quickly.

I'm guessing that your 338 Laupa is close to or exceeding 2,800 fps so you can get away with a slower 1 in 10 twist. The 338 Winy isn't going to make 2,800 fps with a 300 grain bullet. So guess I'll still raising a caution flag here. Sorry guys, I hope for biggun's sake the Greenhill numbers are wrong.

jwp,

Just had an idea to check formula:

If you'll post the muzzle velociy of your Laupa with that 325 bullet and the length of that 325 bullet, I'll run these numbers and we'll see what we get with your rifle!?

Ray I am not jumping to conclusions at all. I am aware of several whom have shot the 300 SMK out of a 338 win and and a10 twist barrel. I am a long range shooter and belong to several boards and I can assure you that a 8.8 twist is not needed for a 300 SMK. Sierra list load data for the 300 SMK in the 300 Win Mag and the test rifle is in fact a 10 twist..Sierra Edition V page 649

Ray I am not jumping to conclusions at all. I am aware of several whom have shot the 300 SMK out of a 338 win and and a10 twist barrel. I am a long range shooter and belong to several boards and I can assure you that a 8.8 twist is not needed for a 300 SMK. Sierra list load data for the 300 SMK in the 300 Win Mag and the test rifle is in fact a 10 twist..Sierra Edition V page 649

OK.....Just thought it would be a easy check to do.

Ray I am not jumping to conclusions at all. I am aware of several whom have shot the 300 SMK out of a 338 win and and a10 twist barrel. I am a long range shooter and belong to several boards and I can assure you that a 8.8 twist is not needed for a 300 SMK. Sierra list load data for the 300 SMK in the 300 Win Mag and the test rifle is in fact a 10 twist..Sierra Edition V page 649

Now would it be safe to load the 300gr SMK in a .338 WinMag case? Idk if the cartridges are the same length. Im not sure but I think I read somewhere that the .338 Lapua is made from a necked-down .416 Rigby case?? Id like to use that bullet if possible, of course if I can get it over 2500fps. But Im thinking I might consult Sierra about running the 300gr in a faster twist like 8.8". Would it be worth the effort to get a barrel with a faster twist, say from ER Shaw or Lilja, if I run that 300gr load? How would that twist affect accuracy with that load, or better yet the inaccuracy of lighter bullets?

.768 @ 2300 fps and above
.760 between 2300 and 1800 fps
.750 @ 1800 fps and below

That's Sierra's listing of BC's for the 300gr MK.

I think you'd be pressing your luck in trying to get the 300 gr to 2500 fps in the 338 WM. I base that on just looking at achieved velocities with the 225 & 250 grainers. With the 225, you can expect to get 2800 - 2850 or so, and with the 250, 2650-2700 or so. That's with 25 gr bullet weight difference, and a 150 fps difference. Taking 50 gr difference in bullet weight and comparing to the 250 grainer and assuming a linear relationship, you should expect 300 fps difference, or 2400 at best. But it probably isn't going to be linear....it's probably going to be less than 2400 fps. Std length magazine and throat dimensions assumed of course. If you have a long magazine and throat, you might get there, but think you'd still be pushing or exceeding pressure limits.

Those are some impressive BC numbers on that bullet though.

Now would it be safe to load the 300gr SMK in a .338 WinMag case? Idk if the cartridges are the same length. Im not sure but I think I read somewhere that the .338 Lapua is made from a necked-down .416 Rigby case?? Id like to use that bullet if possible, of course if I can get it over 2500fps. But Im thinking I might consult Sierra about running the 300gr in a faster twist like 8.8". Would it be worth the effort to get a barrel with a faster twist, say from ER Shaw or Lilja, if I run that 300gr load? How would that twist affect accuracy with that load, or better yet the inaccuracy of lighter bullets?


You can do as you wish as far as barrel twist, but I can assure you that there is no way in this world that I would ever consider a 8 or 8.8 twist barrel in 338 Cal. No one uses that fast of a twist. The 338 Whisper doesn't and that is a sub sonic round...
With a 24" barrel Seirra list 2400 FPS with the 300 SMK, your rifle may do as well, worse or a little better it is impossable to tell until you try it...

The Greenhill formula is helpful, but it is not the end-all and be-all of ballistics. There are a bunch of combinations that shouldn't work (per that formula) but do.

To be fair it was derived a long time before a bunch of the cartridges and bullets that we use today.

If your twist rate meets the recommendations of the formula, it almost certainly will work. But, there are a lot of things that will work, even though the formula suggests they will not. Usually they're pretty close to the suggested twist rate though.

Also it will depend on the individual gun to some extent, when you really get on the edge. Not unheard of to vary a bit with the weather, also.

Why not just use a 6.5-284. That seems to be the hot caliber for long range shooting right now.

Why not just use a 6.5-284. That seems to be the hot caliber for long range shooting right now.

Yeah, Ive heard alot about that round, supposedly one of the best 1000 yard rounds out there. But my rifle is already chambered for the .338 WinMag.

Thats nothing that a new barrel couldn't fix :D

Thats nothing that a new barrel couldn't fix :D

Say I wanted to have my gun setup for the .338 Excalibur. I know that a new barrel that is chambered for it would work, but would I be able to load the magazine with the Excalibur rounds and cycle the action normally?