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Old April 27, 2019, 12:36 AM   #1
m&p45acp10+1
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.300 Win Mag?

I have my first .300 Win Mag. It is a Ruger Magnum Precision Rifle. It is chambered in .300 WM The twist is a 1 in 9. I picked up Hornady FL dies, and Hornady brass. I have CCI Large Rifle Bench Rest primers, Federal Match LR, and Magnum LR, as well as a brick of S&B large rifle primers as well. I have H4831 powder. I will be picking up some 178 ELD Match, as well as some 200 grain ELD Match as that is what the closest place has on the shelf.

I will get to the point now. I have never loaded .300 WM so am I going to need the Magnum primers, or will the BR2 primers work? Also any suggestions for bullets, and powder would be great.

(Note I am not a novice reloader. I have been loading for more than 10 years. I load for several rifle calibers, and several hand gun calibers. I have 2 manuals. I am not asking for pet loads. I need info on powders, and primers mainly. )
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Old April 27, 2019, 02:57 AM   #2
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Use magnum primers because of the case volume. I tried lr primers it didn't work out so good. Powders 4831,4350,h1000,7828,7977,rl16,rl23,rl26 are good powders. With a twist rate of 1-9 it should like bullets of 190gn and heavier.
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Old April 27, 2019, 08:39 AM   #3
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Use magnum primers because of the case volume. I tried lr primers it didn't work out so good. Powders 4831,4350,h1000,7828,7977,rl16,rl23,rl26 are good powders. With a twist rate of 1-9 it should like bullets of 190gn and heavier.
That has been my experience with 300 WM and 7mm Rem Mag. Large case volume so I run with a LR Mag primer to make sure I get good uniform ignition.

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Old April 27, 2019, 09:08 AM   #4
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Thanks for the information. I have the Mag primers. Now I am off to the store to pick up some bullets. There was a lot going on when I picked up the rifle, and somehow I managed to not pick up any bullets. The only .308 bullets I have right now are 110 grain JSP for my .30 carbine. I doubt they would hold up to .300 WM full bore loads.

I am off to the LGS, and I saw some 178, and 208 ELD Match at Acadamy so I will pick up a box of the 208 to start with. Then next time will try heavier.

I was tempted to get .3338 LM but it seems like too much over kill for my wallet, and the fact of the matter is most of my shooting is at 100 yards. That is as far as it goes on the local range. The closest place that had long range was in Liberty Hill. The range is still open. The long range rifle course is as of the last time I heard closed. So the next closest place is 2 hours of driving each way. I did not want to spend that much on a rifle, and ammo I will only be shooting one or two times a year max.

This rifle is strictly for fun, and targets. It is way too heavy,and cumbersome to hunt with. I have plenty of rifles that are more well suited to hunting if I get the urge to do that.
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Old April 27, 2019, 01:05 PM   #5
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"...magnum primers because of the case volume..." Magnum primers have nothing to do with the case volume. They're about the powder used and nothing else. Absolutely nothing to do with the cartridge name.
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Old April 27, 2019, 03:17 PM   #6
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T.O. look at Hodgdons site. Why is it their data for a 30-06 with 4350 powder calls for a LR primer. Then their data for a 300 win mag with the SAME 4350 powder calls for a LRM primer.
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Old April 27, 2019, 05:25 PM   #7
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I've loaded the .300 win. Mag. with H4831 and Winchester's long discontinued WMR power and usually the 200 gr. Nosler Partitions and the standard WLR primer. Accuracy has been excellent and although WMR is supposed to be temperature sensitive, point of impact at 100 yards when checking the sight at the Whittington center was unchanged from when I worked up the load during Tucson's very hot summers. Temp at Raton was about 20 above zero IIRC. Velocity at load work up was 2880 FPS average and groups from .375" to .55" The load has worked in three of four .300 Mag. rifles I own.

There was an article in Handloader Magazine back when they would take submissions from us peons where a man was working up a load for his magnum rifle and ran out of magnum primers. He sent his wife back into town to get more from the LGS (I'm thinking Jensen's) and she came back with standard primers. The upshot was accuracy improved and even velocity was a bit higher. I guess they moral of the story is maybe one should try both.
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Old April 27, 2019, 05:47 PM   #8
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O'Heir is famous for bad advice.

When you try to burn more powder you need hotter "Magnum" primers. In some instances, with some LR primers you can still use standard primers. I found that Winchester large rifle primers worked just as well as magnum primers in my 300 WSM. But those are among the hotter burning standard primers and the short, fat case with less powder than 300 WM made it easier to ignite. You might get decent results in 300 WM, but with that much powder, in that case I'd bet you get better results with magnum primers.

You're going to be using this for target shooting, not hunting. Or so I assume with a 15 lb rifle. I'd be looking at the 210-230 gr high BC bullets from Berger or Hornady. The 220 gr ELD-M bullets made by Hornady will probably be the least expensive option and a good place to start.

Since you have 178 and 200's use them, but if you really want to take advantage of what you have you need to go heavier. Not sure about which powders to use. The same powder that works well with 178's probably won't be so good with 220-230 gr bullets.
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Old April 27, 2019, 06:00 PM   #9
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1-9 twist is on the faster side for a 300WM. I'm thinking that you will find your barrel likes 200+ gr bullets. I have a Rem 700 Sondero in 300WM (1-10 twist) and it's not very consistent with bullets <190 gr. My go to bullets are the Hornady 208 Amaxes and H1000 powder.
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Old April 27, 2019, 08:37 PM   #10
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JMR40 the rifle is for targets, and fun only. With the scope and rings, and a full magazine I am going to say on the conservative side of things it is a bit over 20 pounds. It feels like a ton.

I will start with the 208 grain ELD-M first. Nosler seems to think the best powder for that weight for accuracy is 4381. In my testing with 8 calibers of rifles the advice that they give has been spot on for powder. I have had to adjust charge weight a bit, but the powders they say work best have been spot on.
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Old April 27, 2019, 11:28 PM   #11
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M&P,
Shooters from overseas use LR primers in 7mm Rem Mag, 300 Win Mag. Especially New Zealand, Australia.
They claim to get lower ES/SD with the regular primers.

If your planning on shooting in cold weather, yeah, i'd definitely recommend the magnum primers.
Also magnum primers for hunting rifles. But that's just me wanting the insurance it's gonna go bang when i want it to.
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Old April 29, 2019, 05:02 PM   #12
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Well I have a pack of LRM primers so for the sake of testing I used them. Results were very encouraging. 69.5 grains gave me quarter to half MOA. If the wind had not been blowing the target board back and forth I am sure there would have been one single hole. The rifle shoots like a pup. The heavy weight, and the brake work well.

Now I will have to start accumulating components. I will give the lighter bullets a trial later on. I will have to start stocking up on bullets, brass, primers, and powder.
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Old April 29, 2019, 06:36 PM   #13
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If you stay with 4831sc get a 8lber.
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Old May 2, 2019, 07:57 PM   #14
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I will be getting an 8 pounder when I can afford one. I have 2 pounds now. Will pick up 2 more this weekend as well. It works so well with the 208 grain bullets I am going to leave well enough alone. I may for the sake of testing try the match primers with the load to see if a drastic change in POI happens. The load performed well to plus of minus half a grain either way. I went right in the middle with the load that works well. A 10 shot group ate up a half inch bull's eye at 100 yards. I am beyond happy with it so far.
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Old May 3, 2019, 01:57 AM   #15
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I'd get 8 lbs too.
Of Reloder26!!!

Just say'n...
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Old May 3, 2019, 06:57 PM   #16
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Magnum primers make a larger volume of gas than standard primers do. The original idea was a larger capacity case (a magnum case) needed that to achieve adequate start pressure, hence the name "magnum primer", even though the cups are the same size. However, there are two factors that mitigate the need for a magnum primer even in larger cases: an easily ignited powder, and a very high load density that leaves little empty space other than what is between the powder grains.

The only way I know to tell which one you need is to try both with your load. Whichever one gives you lower velocity SD is the one you want, as it is igniting the powder more consistently. However, you will probably shift your sweet spot a little in switching primers around and may need to followup a change with a little additional powder charge tuning.
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Old May 4, 2019, 12:52 PM   #17
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I will do a minor test by using the same load with changing the primers. I have CCI BR2, Federal LR Match, S&B LR, and Winchester LR. I have 50 Federal LRM left in the sleeve I purchased last week. I know POI will likely shift. I want to see which one will give me the closest to where the rifle is now zeroed at.

I do not have a chronograph. I may end up getting one some later day. I do not have to go chasing numbers. I let the groups tell me the load my rifle my shoots best.
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Old May 5, 2019, 07:40 AM   #18
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I did some chrono work testing both standard and magnum primers in a .223 AR-15 using W748 ball powder. Some shooters claim better accuracy when using mag primers with a ball powder. I put this claim to bed , and by the end of the day I observed NO difference in accuracy or velocities. As for my 300WM, never tested both. 300WM rounds are expensive and i'm not interested in potentially introducing another variable into my loads. I can state that I DO in fact notice lower SD's (standard deviation) within my velocities with my subsonic .308 and my BPCR 45-70. Not anything substantial, but I did notice a difference in the numbers.
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Old May 6, 2019, 11:49 AM   #19
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JMR40 has it right but at 100 yards for target range, any bullet its happy with will do fine.

1-9 twist would seem to lend itself more to 200 and lighter.

I have had good results with Horandy ELDs if that is what you are shooting (too many acronyms these days)

I have one rifle (7.5 Swiss ala 308) that likes 125 Gr bullets a lot (1-10)

Only issue is keeping enough charge to get the expansion good on the case, more needed on a 300
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Old May 7, 2019, 11:38 AM   #20
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I had a 9 pound 300 Win Mag hunting rifle with a 26" 1:13 twist barrel that tested MOA at 1000 with 180, 190 and 200 grain match bullets. IMR4350 over RWS standard LR primers with max loads.

1:12 twists were in my four 30-338 Mag target rifle barrels shooting about 6 grains less of the same powder for the same bullet weights leaving about 100 fps slower. They tested about half MOA at 1000.

All bullets are not perfectly balanced when they leave the barrel. The faster they spin upon exit, the more they will jump off the bore axis. Which is why some folks got best accuracy with 7.62 NATO M80 ammo using 1:14 twist barrels.
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Old May 10, 2019, 12:26 PM   #21
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Well bart, if your 30-338mag shot so good why didn't you bet on it

https://yarchive.net/gun/rifle/30-338.html
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Old May 11, 2019, 10:07 AM   #22
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Quote:
Originally Posted by old roper View Post
Well bart, if your 30-338mag shot so good why didn't you bet on it
Because the 30-338 shot better scores overall in other matches at different places. Gale McMillian new that and did not admit it. Had he acknowledged that, I would have bet. Note the USMC teams practised at Quantico and knew the wind conditions better. And all the Army successes at the nationals with 30-338 ammo didn't matter.

Another reason was he refused to take my bet that Win 70 receivers were 2 times stiffer than Rem 700 receivers. Said he didn't want to take my money. Having measured both, it was a sure win for me.

McMillian building 30-338 rifles to compete against his 300's is questionable for valid accuracy comparisons. The Army should not have allowed that. And he is ignorant of (or wont admit) the 300+ fps velocity increase the 30-338 has over the 30-06. Nor the 100 fps difference between 300 and 30-338.

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Old May 11, 2019, 08:05 PM   #23
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I got rained out for testing today. The rain did let up, but the water 4 inches deep the entire walk to the 100 yard target boards. So I will see if it is better next weekend. I did manage to pick up a pound of H1000 I loaded up some test loads with 178 grain ELD-Match. I have 3 primer types to test out. Winchester standard. Federal Match, and Federal Magnum.

Last week I tested out 12 with Winchester LR primers, and the same load as the rest. I have no chrono so no readings from that. The groups were the same. POI did not seem to shift. At this point I am the weakest link in the chain.
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Old May 12, 2019, 06:15 PM   #24
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Hey, we all tend to be that. One day I can put 10 in a 3/8 hole and the next week its nice to get sub 5/8 x 5.

Ticked I was getting under 1/2 MOA at 240 yards but was only brave enough for 5. I got a range pass there now so I can do the 300 meter range when I feel up to it (brave).

100 meter range has a shed and overhead heaters for winter. Drive is a bit longer but all highway.

I don't do much about primers. I just picked CCI (readily available in the bulk box and the bench rest guys tend to them) and stuck with it.
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Old June 5, 2019, 10:24 PM   #25
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Standard primers will work. Magnum primers will probably work better. If you’re running compressed loads magnum primers will definitely be a better choice. It’s worth noting though that when such cases as the .375 hh, 300 hh, all the original weatherbys based on the hh case, and others, there was no such thing as a magnum primer. There were just primers. The federal 215 large rifle magnum primer was developed specifically in conjunction with the development of the massive .378 weatherby.

T O’heir is mistaken. While very slow burning powder is indeed served well by magnum primer, case volume has everything to do with the reason for magnum primers. Case in point being that the .378 wby uses powders of similar burn rate to what works well in a .270, but there really no need for mag primers in a .270. It’s not about the powder burn rate as much as how much powder you’re setting off.
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