300 Win. Mag.


January 4, 2003, 02:26 PM
Started this thread on Art of the Rifle,TFL back in October and, after extensive experimentation with H450 & 200 gr. bullets (both Sierra and Nosler part.), still not satisfied with accuracy. Plan to try Barnes X 200 gr. but would like to get reasonable group w/above bullets before trying the Barnes.

H450 works great in my 30-06 w/190 gr. bullets but apparently not in this particular rifle/caliber.

Rifle is a post 64 mod. 70 and I have bedded the action, floated the barrel and lapped the bolt lugs, which yielded some improvement but not much. Most 5 shot 100 yd. groups are over 2.25"....by some fluke shot one five shot 1.1" group which I have been unable to duplicate and one 5 shot group, four of which measured 15/16").

Have just about decided H450 is not the powder for this particular rifle and bought some H 4831SC, Retumbo and IMR 7828 to play with.

Quite a bit of info available on 4831 and 7828, not so much on Retumbo. Anyone done and accuracy work with the above powders?

Thanks for your input.


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January 4, 2003, 02:48 PM
while i have not expiremented with 200gr bullets.
i have had exellent results in my .300mag with 168gr. & 180gr.
bullets , useing both H4831 and IMR4350.

January 4, 2003, 03:25 PM
My rifle was mediocre with150 gr. Nos. Part. in the accuracy dept.
This is one reason I am trying heavier bullets, seem that many others have better accuracy from the 180' & 200's. Also, I am contemplating possibility of using this rifle for some heavy duty hunting if all works out, so need as heavy a bullet as I can get decent results from. I may load up some of my old 150 gr. loads and see if accuracy has improved any w/bedding, floating, etc. done on the rifle.

Used IMR 4350 with the 150's and got better accuracy than I have been able to get with the H450/200's so far. Have never tried 4831 but plan to give it a try.

The Retumbo starts out at a case full and goes on up to a compressed load on Hodgdens web page.

Thanks for the reply.


January 4, 2003, 03:42 PM

lots of loads and results listed there

I'm going to start with RL-22 for my 7 mag and 300 WM

Bruce H
January 4, 2003, 07:36 PM
In early 1973 I purchased a new Mod.70 in 7mm Rem Mag. I proceded to do my absolute best to get it to perform properly. I loaded many and varied loads to no avail. i tried bedding and all the usual accuracy improvement tricks. Tried different scopes and just about everything else. Finally gave up on it and traded it on another rifle in the same calibre. Allready had too much stuff to change rounds. Still have the one I traded for and it still shoots as well as I can hold it. There are some rifles that the only fix is a new barrel. Might be worth a look as barrels aren't really that expensive any more.

January 4, 2003, 07:36 PM
I had good luck with Accurate3100 and 200 grain speers out of my Win mod 70 SG 300WM. May not be the best powder but I have got 1" or better groups consistently. IMR4350 and RL22 have also shot well, 1" or a little bigger. I am in the process of experimenting with 200gr. Nosler Partitions and RL22. Im looking forward to seeing what I can get out of it.

January 4, 2003, 07:59 PM
redneck 2:
Thanks for the link.


January 4, 2003, 08:16 PM
Not quite ready to give up on the barrel yet!, but this is a possibility, of course.

This rifle will shoot 1.5 moa w/150's, which is sufficiently accurate for a hunting rifle, but it's the only one I own that will not do moa if I do my part. Has become a challenge, if you know what I mean. Besides, if I don't get something worked out soon, this bbl. will be worn out and will have to replace it.:)

Have never used Accurate powders nor the RL22. I do notice lots of folks using the RL22 in the 300 Win Mag, so it must work.

I have used 4350 a lot, in 6mm Rem., 30-06 and works good in another 300 WM and so-so in this one. As Bruce said, may have a barrel problem??

Thanks, guys, for the feedback.


January 4, 2003, 08:31 PM
Buddy of mine swears by 4831 in the Win Mag. Not sure what his bullet weight of choice is.

January 5, 2003, 12:41 AM
hps1, have you had the bbl recrowned?

I had a post-64 model 70 heavy (new 1991 or so) in 308. The rifle wouldn't shoot but 1-1.5 moa. I had the bbl chopped and recrowned after some load tweaking the thing was 1/2moa on a bad day.

About a year later I ran into the exact same thing with a Remington Sendero in 300WM and had about the same results after the recrown.

January 5, 2003, 02:25 AM
74 grains RL-22, 190 gr. Sierra Match, loaded to 3.375" OAL, very accurate out of my Model 70 Classic Super Grade. (Once I bedded the barrel, that is...)

January 5, 2003, 07:28 AM
have you tried the "Ladder method"?? If you're not familiar, I'll find the link

I've never had to re-crown, but I think before I'd try lotsa different powders, I'd start with

varying loads (ladder)

different bullets (I don't know that Partitions will give a lot better than 1 1/2...) may need Scirocco's, A-Max or Ballistic Tips


but absolutely the first thing would be to put shims in the forestock and put some upward pressure

January 5, 2003, 08:26 AM
In the .300 Win Mag, more than likely your problem is OAL.

IIRC, the max OAL listed for the .300 Win Mag is around 3.362. This insures that the bullet is seated in the case far enough so that the loaded cartridge fits the magazine.

Unfortunately, it also leaves a heckuva long jump from throat to rifling.

I had this problem, too. Started our with 168 grain bullets and RL22. Shotgun pattern at 100 yards. The rifle is a Winchester Laredo.

Tried different charge weights. No difference.

Then, I started reading about the peculiarities of the .300 Win Mag cartridge. Made up a dummy round with a long bullet, started it into a case by hand, blackened the bullet with a marker and chambered and extracted.

By measuring the distance to the ogive and to the beginning of the rifling, I found that my max OAL for that cartridge in my rifle was 3.515. So, I made up some rounds:

175 grain Sierra MatchKing
71.0 IMR 4831
Federal Large Rifle Match primers (Note: NOT magnums)
Winchester cases, once fired.
Cartridge OAL 3.510; no crimp used.
Necks inside reamed with RCBS reamer prior to loading.


At 100 yards, three rounds--.337 inches.

Average of ten, three round groups was .388 inches.

Note: I do NOT rapid fire this rifle. Max rate of fire: 1 round each three minutes, nine rounds at a time, with a minimum of ten minutes rest each nine shots. While rifle is warm, after each nine rounds, one solvent patch followed by three clean patches with a coated rod and bore guide. Stand rifle up in rack with the bolt open for best cooling.

NOTE: These results were best for my rifle--yours might and probably will vary. My load is below listed maximums--however, reduce and work up carefully, especially loads that seat the bullet close to the lands. Neck turning often decreases bullet pull and pressures; be careful, though, that case neck tension is sufficient to hold the bullet firmly for uniform ignition. Watch carefully for pressure signs; measure cases at case web after each firing while working up your load, and watch for expansion or incipient head separations.

Good luck. I hope you enjoy your rifle as much as I do mine.

January 5, 2003, 01:59 PM
First off, thanks to Cratz2, Pointman, CampX, redneck2 and Powderman for your suggestions.

I failed to list my goals in this endeavor. I am considering using this rifle & 200 gr. premium bullet (Nos. Part. or Barnes X depending upon attained accuracy) to take an Eland if all works out as planned. Since this caliber is on the light side for intended purpose, I want to be 100 % sure of bullet placement even though the Eland presents a large vital area target, and, of coarse seek maximum energy, as well. Have plenty of time to tweak the rifle/load and am enjoying the challenge and appreciate all of the different views and ideas.

H4831SC is one of the powders I plan to try, have heard good things about it in the 300.

Crown appears to be good. Giving an even "star" powder mark on the crown but since crown is blued hard to see so may drop by my gunsmith and have the 11 deg. crown put on it. If nothing else will make the "star" easier to see.

Have tried to make only one (mechanincal) change at a time in order to learn where the problem is, but this sure drags things out.:(

RL22 seems to be a very popular 300WM powder. No one in this area carries it, however. If all else fails, could order some.

The bedding on my Mod. 70 was the pits, too. Have removed the "hot glue bedding", some wood, then re-bedded w/accraglass; free floated barrel and test fired. Some improvement, but not there yet. Next trip out plan to shim between forend and barrel in a couple of stages to see if this helps any. Also lapped the bolt lugs. One lug was contacting only about 10% and the other about 60% before lapping.

Isn't the ladder method of load development great!? I used this in developing my H450 loads and found three flat spots in the ladder. One moderate and two different ones in the max. load
area. Chronographed all loads tried and got some very good SD and extreme spreads on a couple of loads but they still did not shoot. Read this to mean there is a mechanical problem but have had a load or two in the past that were extremely low SD/ext. spread that did not shoot in other rifles.?

Interestlingly enough, in my rifle & these H450 loads, I could see no measureable differnce in accuracy between the Nosler part. and Sierras, but , have not really achieved acceptable accuracy with either one yet.

Shimming forend was the next mechanical experiment planned....hopefully next week.

Thanks again for the help.


January 5, 2003, 02:29 PM

My rifle chamber gives a cartridge overall length of 3.516" w/sierra 200 gr. BTSP to the lands. Have experimented some with oal and will do more once I find a promising load.

Unfortunately, since this is a hunting load, am limited by my magazine length of 3.48" so cannot get as close to lands as I would like. Barnes states that bullet jump distance is critical to accuracy with their X bullets and I know it is definately a factor w/others, as well.

I have an extremely good batch of WW cases that weigh out very close, neck turned and uniformed primer pockets/flash holes. Polished expander button in sizing die and am getting .001 to .002" bullet runout w/standard Pacific seating die, so feel that only thing left in ammo dept. is oal and trying different powder.

Since I am seeking maximum, or at least near maximum energy, have been watching case head expansion closely. Best results so far has been right around 2800 fps with the 200 gr. Sierras. Your load looks like it would be between 2800 & 2850.....have you run it thru a chronograph?

That is great results you achieved w/your rifle! Sure is rewading when it all comes together, isn't it? I'll be happy w/moa on mine.:)

Thanks for the input.


January 5, 2003, 10:06 PM
Actually, I have averaged 2910 fps from my rifle.

An easy (but somewhat pricey) solution for your rifle is a custom barrel. For the maximum possible accuracy with any given load, I would send it off to Kreiger. Send along two or three dummy cartridges, no powder or primer, seated in the exact configuration you would like. You will have to decide if you want to have the bullet tight into the lands, a bit of spacing (say, .005 to .010 off the lands), or even freebore.

For 200 grain bullets, I would specify a twist of 1-9.75 or better to stabilize the bullet well.

You would probably want a SAAMI spec chamber for a hunting rifle.

Good luck in your quest for accuracy. Also, if you don't want to drop the money on a Kreiger, you probably know of other barrel makers who will do just as well. Pac-Nor in my neck of the woods does good work. Don't forget to have the action blueprinted as part of the rebarreling procedure.

January 6, 2003, 02:01 PM

The second best group I have had was a 200 gr. Nos. Part. @ 2896 (5 shot avg. vel.) SD of 14.9 so probably will not do well @ longer ranges.

Did get a (as in one ) 1.1" hundred yd. 5 shot group w/Sierra 200 gr. BTSP @ 2805 Av. vel w/ SD of 6.1.

May need to do a little more work on this load before getting too far afield.

One thing I noticed in your post is the cleaning after 9 shots. I am firing one fouling shot before starting the session, then letting barrel cool down between shots to "barely warm to the touch" but am not cleaning until after session (up to 30 rounds). As one might expect w/near max. loads, getting fairly heavy copper fouling so this could be a factor I had not addressed.

You did not mention changing barrels in your rifle so assume your great groups are w/factory barrel.? Is the Laredo a heavy barrel or sporter weight?

If I decide to re-barrel, have had great luck with Mark Chanlyn's barrels. He and Krieger both apprenticed under Boots Obermeyer as I understand it and the three still get together and buy their steel, so materials are identical. Dave Sullivan (Westwind Rifles, Erie, Co. did an excellent job on my match rifles w/these barrels. I know of Krieger's stellar reputation as well; it would appreat the Obermeyer is also an excellent mentor!

Thanks for your help.


mark mcj
January 6, 2003, 03:02 PM
I've had good results with H1000. Seemed to work quite well in fact. Not .388" for 30 rds., but it worked well.

January 6, 2003, 03:55 PM
mark mcj::

I may have to try H1000 next time I find a can. Also RL22 looks pretty good in the books and others have reported good results with it.

Thanks, Mark.


January 14, 2003, 10:40 PM
Just back from the range & things are lookin' up.

My rifle does not like 200 gr Barnes X bullets.

Found that the best H450 load got better when loaded to max. magazine length of 3.47 OAL. Got group down to 1.030", so may do some more work on this one.

Nothing spectacular w/ IMR 7828 or H 4831 SC group wise,
but , Retumbo looking good! Using ladder method and starting @ Hodgden's starting load worked up to within one grain of their maximum load w/Sierra 200 gr. BTSP, WW cases and Fed 210M's. Had 5 shots form a .730" group at top end of the ladder w/2872 average vel. Definately plan on more experiments in this area. Maybe if loaded a little longer.................

Thanks to all for your suggestions.


January 14, 2003, 10:53 PM
My Ruger #1 is a 200th year model, #1-B. It too has a very long throat, and no silly magazine to worry about:neener:

I run Nosler 180 Partitions at an OAL of 3.59", backed by Reloader 22 and Federal 215's, a hot primer. The powder charges are within Alliant's guidelines, but they aren't conservative, and the velocities are faster than you'll see most references list. It does have a 26" barrel. Were I to take it deer hunting, I'd load the 180 gr Ballistic Tip.

Accuracy is outstanding, though like any rifle with a pressure bedded barrel, it is sensitive to how it is held.

I tried some Nosler/CT 180 gr Fail Safes, with 72 grains of R22, and it too shot beautifully. Velocity was 2950 fps.

It is my favorite rifle

Al Thompson
January 15, 2003, 08:18 AM
Let me ask a silly question - is the scope on the rifle a verified one? I.E., one that has produced small groups on another rifle? 90% of the accuracy problems that I've seen on rifles is scope related.

January 15, 2003, 12:30 PM
Hi Al:
The rifle has had three scopes on it, all gave same results.
(Started w/6x Redfield, then 3-9 Leupold, currently has a 4.5-14x42mm Burris FF II).

I do not understand everything I know about the reasons that the H 450 loads did not shoot well in this rifle. Only got one promising group with that powder (Had SD of 6.1 and extreme spread of 12.8 fps for five shots.) It did produce a 1" group, but never repeated in many attempts until OAL was increased.

The Retumbo looks like a winner in this rifle, however. Seems to have a real sweet spot @ near maximum loads (which is what I am looking for) and haven't had a chance to play with OAL, yet.
Interstingly enough, the Retumbo group (5 shots = .730" @ 100yds.) was in an 8 shot ladder string with 3.5 gr. variation in charges (46.0 SD and 99 fps extreme spread for the five shots). Velocities (& group size) showed a distinct flat spot near the top of the ladder. Still 1 grain under max. load and no pressure signs, so will increase a tad next trip.


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