.300 Win Mag vs. .300 Remington Ultra Mag

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LR Sarge

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I am new to forums, but not new to guns. It was nice to read through the rules for writing, and it seems this would attract a group of American loving people that deeply appreciate the rights that are self evident, yet need to be defended and paid for in blood.
With that said I have a question, and I hope to hear from some savvy reloaders that are familiar with big .30s. I am reading all over that the .300 WM has 2 inherent accuracy hurdles. A short neck in the case and the belt that the bolt headspaces against. I bought a 30" Pac-Nor "Super Match Grade" barrel with 3 lands and 3 grooves, 1-10 twist, and I had it chambered in the .300 WM. My goal is ultimately to get a 208 gr. Hornady Amax bullet up to 3100 fps for the purpose of staying super sonic for 1 mile. Looking at reloading manuals, it appears as though I will be stressing cases in the WM to achieve this, even with the 30" barrel and Retumbo, or H1000. The recurring themes I read about with the WM are the potential accuracy issues. Because of that, I looked at the RUM. It looks as though the RUM case alleviates the head space issue on the belt, and it has a longer neck to help with bullet alignment. What I don't like is the crazy long free bore (.4") that the RUM needs to help in achieving the added 200 + fps. With all that said, here is the question... Could I use the RUM case, and load to WM specs to overcome the potential accuracy struggles of the WM case, while keeping from burning up the barrels any faster than the WM is likely to? If I have to load hotter than WM specs it wouldn't be by much. I know that I cannot predetermine what bullet my rifle would like, but with my 30 moa scope base, and a total vertical adjustment in my scope, the 208 gr Amax at 3100 fps both stays supersonic for a mile, and stays within my adjustment range in my optic. Any thoughts?
 
LR Sarge said:
I am new to forums, but not new to guns. It was nice to read through the rules for writing, and it seems this would attract a group of American loving people that deeply appreciate the rights that are self evident, yet need to be defended and paid for in blood.
With that said I have a question, and I hope to hear from some savvy reloaders that are familiar with big .30s. I am reading all over that the .300 WM has 2 inherent accuracy hurdles. A short neck in the case and the belt that the bolt headspaces against. I bought a 30" Pac-Nor "Super Match Grade" barrel with 3 lands and 3 grooves, 1-10 twist, and I had it chambered in the .300 WM. My goal is ultimately to get a 208 gr. Hornady Amax bullet up to 3100 fps for the purpose of staying super sonic for 1 mile. Looking at reloading manuals, it appears as though I will be stressing cases in the WM to achieve this, even with the 30" barrel and Retumbo, or H1000. The recurring themes I read about with the WM are the potential accuracy issues. Because of that, I looked at the RUM. It looks as though the RUM case alleviates the head space issue on the belt, and it has a longer neck to help with bullet alignment. What I don't like is the crazy long free bore (.4") that the RUM needs to help in achieving the added 200 + fps. With all that said, here is the question... Could I use the RUM case, and load to WM specs to overcome the potential accuracy struggles of the WM case, while keeping from burning up the barrels any faster than the WM is likely to? If I have to load hotter than WM specs it wouldn't be by much. I know that I cannot predetermine what bullet my rifle would like, but with my 30 moa scope base, and a total vertical adjustment in my scope, the 208 gr Amax at 3100 fps both stays supersonic for a mile, and stays within my adjustment range in my optic. Any thoughts?
Click to expand...

I would just go 300 Win Mag since you already have a barrel chambered. Shoot it and if you aren't satisfied, go the other route. But I'd just go to something in 7mm like the 7mm Mashburn Super Magnum. It uses 300 Win Mag brass I believe.
 
My machinist has the reamer for the UM and it has not been assembled so nothing is lost so far but an extra chambering. Do you know if the belted cases are capable of shooting as tight as non-belted cases? Can you load a UM down without destroying accuracy?
 
Loose powder burns unevenly and an Ultra Mag has tons of space in the case. I wouldn't load it down. Just get your smith to headspace onto the neck of the 300 Win Mag instead of the belt. Problem solved. You can also just resize the shoulders to headspace on the neck...which will naturally occur once you've fired brass into your rifle's chamber anyway.
 
And what do you think about the shorter neck on the WM? I would love to shoot .5 moa because at 1 mile that is still an 8.5 inch group. Needless to say 100 things can go wrong between muzzle blast and dead taget at 1 mile...
 
The 300 Win Mag has a great reputation of long range capability. But the specific bullet that you want to load may indeed act twerky in that neck. Maybe someone else will chime in.
 
LR Sarge said:
I am reading all over that the .300 WM has 2 inherent accuracy hurdles. A short neck in the case and the belt that the bolt headspaces against.
Click to expand...

I wouldn't pay any attention to anyone making those claims.

LR Sarge said:
My goal is ultimately to get a 208 gr. Hornady Amax bullet up to 3100 fps for the purpose of staying super sonic for 1 mile.
Click to expand...

That's my bullet of choice for .300 Win Mag. Here are some 5-shot groups I shot with that bullet using a Remington action, Krieger barrel and AICS stock. I neck size and bump the shoulder back a couple of thousandths. I don't think I was anywhere near 3,100 fps with the load shown though. I'd have to check my records.

71.6gr_reloder22_208gr_amax.jpg
 
I would see what you can do with the Winnie first.

I personally don't think the WSM will work, they barely work with 180 gr. bullets much less anything longer. The standard for the WSM was I think a 150 gr. bullet to minimize case intrusion and the resulting loss in powder capacity.

As already mentioned I wouldn't be happy either with a RUM case downloaded to Winnie velocity. That's a big old case and I think you should find a load giving a decent fill percentage.
 
browningguy I tend to agree with you on the down loaded RUM. Likely to get radical chamber pressure variations and a vertical shot group. I am already chambered for the WM... Maybe I should stick with that unless I am willing to pump my RUM loads to full RUM pressures, in which case I'll be buying barrels every 600 rounds
 
1858... How many shots are you getting our of your brass? What velocity are you coming in at? It's the 1 mile capacity that has me licking my chops. The farthest I have shot is 1000 yd with an M24 chambered for the .308 and we were using machinegun ammo... 150 gr. Not worth our time really, but it sure got me wanting more yards between me and the target.
 
If you want to shoot a mile with a SS projectile try the 230gr Berger Hybrid. You mentioned a 30" barrel so 70gr RL-25 will get you 2809fps at the muzzle safely.

Using QuickLoad v3.8 to get my numbers.
 
centurion20000 I love the high BC of that bullet (.743), and I am reading that with the RUM, one guy is getting 3050 fps with H1000. I don't know if he is showing any pressure signs at that intensity, but that sounds like it would arive at the target with killing energy leftover. The rifle I am building is intended to serve a practical purpose, so delivering energy on target is another imparitive. Thanks for the info!
 
I shoot a clone of the the Navy/Army round the Mk248/mod1. It uses a re SMK. Accuracy hovers around 1/3 MOA but this is a top to bottom custom rifle. This round is the development behind the recent change over of the Army. They are swapping their Remington 700 .308's out for the .300WM. Their round is still super sonic at a mile unless I am mistaken. It shows very similar statistics to a.338LM. out to 2000 yards. The .338 still a clear beast with better statistics, but the .300WM kept them from using the 338 because engagement past the 300's reach will be with artillery or a 50 BMG. I will did up the write up it is interesting and the specs of the mk248 mod1 are widely found on the Internet.
 
I have both rifle calibers and I would work with win mag first as others have suggested. Finding the right combo of powder and bullet is important as can be seen from the armies development. As an aside I have been working up a hunting load for my 300wsm with 180g ttsx bullet. I am getting 3190 fps (chrono) from 73g of superformance powder. I was not looking for that much velocity but that load is what closed up my groups. I was amazed with the velocity and lack of primer or case damage.
 
You can't predetermine what bullet the rifle will like but you CAN steer the odds. If you want to shoot the 208's, then I would make sure that the reamer is ground with that bullet combo in mind. Having the freebore/leade properly set with the reamer makes all the difference in the world.

What's the story on the reamer that you have? Do you know what the specs are on it? It could be that the reamer will make the 208's a less than ideal choice. Again... just something to consider.

As for the 300WM, yes it does indeed have a short neck, which is why the 308 Norma/30-338 was (and still is in some cases) so popular. As for the belt, you're mindfudging it... like the others have said, you can get great accuracy by just headspacing on the shoulder.

I would start with some solid brass like Norma or Nosler, properly size the cases and then have your gunsmith chamber the rifle to those cases. That'll ensure a nice tight fit. You gunsmith SHOULD have already discussed this with you.

I have a friend with a Remington 5R in 300WM and judging by the velocity numbers he's getting, I think your goal is FAIRLY reasonable. Especially with a 30" tube. It'll just depend on the powder. You should be able to get pretty close though.

As for the accuracy troubles... if the rifle is built properly... the only accuracy troubles you'll have will be your own. :) Good luck with your build.
 
Thank you all for the responses! I did make the decision to go with the .300 WM. I am still a little skeptical of being super sonic for 1 mile with it, but I am sure I can accomplish good accuracy at that distance. My machinist gets his reamers from PTG (Pacific Tool and Gauge) I have looked for their specs and have been unable to find them.
What I have typically found is that bullets under 208 gr are unable to stay supersonic to a mile because of the lower B.C. The down side to the heaver bullet is lower muzzle velocity and limited adjustment between scope and base. My smith did make it clear that he was willing and able to chamber whatever load I wanted to go with. His suggestion (which I agree with) is to adjust the head space to the shoulder, and cut the leade .020 longer than the ogive contact, and work forward and back until I find the sweet spot. The completed build with have a blueprinted Remington 700 long action, over bored (.705) to accommodate an oversized PTG bolt (.703) Sako extractor, PTG .30 recoil lug, Badger Ord. 30 MOA scope base, Badger 30mm 1 piece (base) steel scope rings, McMillan A5 stock with thumb wheel, I haven't decided on which bottom metal I am going for, Nightforce NXS 8-32x56. The barrel is a stainless steel, super match grade, 3 land-3 groove 30 inch #8 Pac-Nor. I am also attaching the Surefire SOCOM762-RC. I am looking forward to giving you guys some updates as I progress with this build.
 
LR Sarge said:
1858... How many shots are you getting our of your brass? What velocity are you coming in at?
Click to expand...

I've reloaded the same Winchester brass six times with no signs of issues. As I mentioned, I just bump the shoulder back about 0.002" with a Redding die and neck size so the body of the case isn't being worked much shot to shot. Annealing the necks really helps with accuracy too. I'll have to check on velocity but I think it was around 2,800 fps from the 26" barrel.

Your planned build sounds very similar to the rifle I built (and sold recently). It was an awesome rifle but once I bought an AI AWM in .300 Win Mag I didn't see the point of having both.


Strongbad said:
If you want to shoot the 208's, then I would make sure that the reamer is ground with that bullet combo in mind. Having the freebore/leade properly set with the reamer makes all the difference in the world.
Click to expand...

The 208gr A-MAX likes to be close to the lands which is typical of secant ogive bullets. I had very good success at 0.020" off. I started to get really good results once I began sorting the bullets base to ogive.
 
ive got a 300wsm a 300h&h a 300 win a 300wby and a 300 ultra. All are capable of great accuracy. More a matter of how good the gun and barrel and your load is then it is in any inherent accuracy advantage of one over the other.
 
My machinist gets his reamers from PTG (Pacific Tool and Gauge) I have looked for their specs and have been unable to find them.
Click to expand...

Your smith should've been provided a drawing of the reamer when he was supplied the reamer. That is typically how PTG does it. They do however keep records. You can probably call them and tell them who they sent the reamer to, and they can pull it up in their system. Going off of that, I believe they should be able to pull up which reamer they supplied then probably fax or email over a reamer print. I know when I had my last reamer made, when I called to ask about it, the lady on the phone was able to confirm the specs in short order.

The 208gr A-MAX likes to be close to the lands which is typical of secant ogive bullets. I had very good success at 0.020" off. I started to get really good results once I began sorting the bullets base to ogive.
Click to expand...

Agreed. I'm just saying that there is also an optimal length for the round once assembled and preferably you want the bullet seated further out (unless you want a repeater and need it to fit the magazine). So the reamer needs to be made with that in mind. Basically what I'm saying is that if you want to load it for use as a benchrest style round, single shot, you'll want an OAL around 3.70". Otherwise if you want it to feed from the magazine, you'll want an OAL around 3.50". The reamer should take that into account. Will it completely ruin everything if it isn't? No, but it's not ideal... and if you want to shoot at a mile... you're going to want ideal.
 
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