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Old April 16, 2014, 08:55 PM   #1
psalm7
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.300 WM

Im loading a .300 Win Mag at max load in the Sierra reloading manual 74.6 gr IMR 4831 , 175 gr Match king HPBT , Remington magnum primer . The test rifle in the book had a 24" barrel mine has a 26" . I get group at 100yards with all holes touching . The only sign of preasure is a wrinkle in the primer like around the fireing pin where factory loads there is just a dent . Should this be a concern or not ? When I used to shoot bench rest some of the shooters would have primers ruptured or even fall out when they took the empty case out . Question is what do folks that have been reloading a while think or look for ? My rifle is a Remington 700 .
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Old April 16, 2014, 10:26 PM   #2
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Yes, the wrinkle in your primer around the firing pin hole is a sign of concern for overpressure. You are quite close to having a "pierced primer" event.

Not good for your bolt face or firing pin.

Try a slower powder, IMR7828SSC is what I would recommend as a starter.

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Old April 17, 2014, 11:21 AM   #3
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RL22 and H4831sc are two more good ones in the win mag.
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Old April 17, 2014, 02:28 PM   #4
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I primarily use H1000 for my 300WM. I use pretty hot loads (Mk248 mod1 clones) and have yet to have pressure marks.
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Old April 17, 2014, 03:42 PM   #5
Bart B.
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I'd want to see pictures of that dimple.

It might be caused by pin tip shape and oversize hole in the bolt face.

Is the factory load used for comparison a Remington magnum primered one?

Push out that primer then see if it's mushroomed out past it's diameter. If so, the pressure may be too high. Make this comparison with a factory equivalent round.

Last edited by Bart B.; April 17, 2014 at 03:49 PM.
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Old April 17, 2014, 04:01 PM   #6
green_MTman
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there is a clear cut way to know if your over pressure

1.have a micrometer
2.check the case head of a shell that has been fired but is clearly not over pressure,like the shell fired at minimun load.measure the case head to a 10,000th of an inch which only a micrometer can do.calipers for bullit seatting or checking case trim lenth only measure to 1,oooth of an inch.write down your measurement

3.mic the case head of the case that might be over pressure.after firing the case head will expand a certain amount but should not expand more than .0005 (5 ten thousanths of an inch).
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Old April 17, 2014, 04:48 PM   #7
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Measuring case head expansion only gives reliable data if all cases were made from the same lot of brass formed to the same dimensions with the same hardness. That doesn't happen. I've shot proof loads (67,500 cup) with cases showing the same head expansion as other cases from normal factory loads at SAAMI normal safe (52,000 cup) maximum pressure specs.

With the case diameters at the head ranging from 3/10 to 6/10 inch at typical measuring points, it stands to reason the larger ones will expand less for a given peak pressure. And all cases with the same diameter head point do not all have the same peak pressure spec.

Last edited by Bart B.; April 17, 2014 at 06:39 PM.
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Old April 17, 2014, 05:32 PM   #8
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My Winchester M70 craters primers with factory ammo or reloads. Problem is a slightly oversized firing pin hole in my case. Could also be a weak firing pin spring in the OP's rifle although I'm thinking possibly an overmax load.
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Old April 17, 2014, 06:34 PM   #9
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For the reasons stated above cratering alone may not be due to excess pressure. Back off a couple of grains and see if it still does it.
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Old April 17, 2014, 06:34 PM   #10
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All holes touching in 300WM?


I can do that some of the time with 223 and 6mmBR, but but 300WM rifles, even the ones I build with premium barrels... 3 shots under and inch is as good as I get.
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Old April 17, 2014, 07:36 PM   #11
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Im not tech savy when it comes to posting pics . Factory loads do not show the wrincle on the primer . A slower burinig powder sounds like the cure . I like the way this laod shoots but I cant risk damaging this rifle . Yes Clark this rifle is amazing it shoots well with factory ammo . When I started loading it with the 175 match kings I was surprised . I will save the 4831 for my 25-06 and try the 7828 . Thanks all .
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Old April 17, 2014, 09:31 PM   #12
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If you're wanting best accuracy with max loads, note IMR powders 4350 and 4831 gave best accuracy with 300 Win Mags using 180 to 200 gr. bullets when it was popular in matches. Sierra Bullets uses that 300 to test most all their 30 caliber bullets heavier than 180 grains. Their best match bullets go into about 1/4 MOA in their 200 yard range.

I don't think a slower powder is a good solution compared to cutting the powder charge you use about a grain. It's already a grain or so under most max load data.

Last edited by Bart B.; April 17, 2014 at 10:41 PM.
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Old April 17, 2014, 09:44 PM   #13
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I was going to chime in but having read all that Bart said I have little to add. Go read his comments and pay attention. He's right on.

Also, one thing to remember is that primers from Federal, Remington, Winchester and CCI as well as Wolf are not all made of the same metal alloy.

So one being softer may show "pressure signs" more than another one even when the loads are the same.
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Old April 17, 2014, 11:24 PM   #14
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Bart B.,

I had good results with 7828 under 168gr Win/Nosler CT Ballistic Tips in 300 Win Mag.

A friend needed a general purpose hunting load for Idaho, so we used what components I had on hand and I was pleasantly surprised at the results. Velocities were not particularly impressive (still faster than a 30-06 though), and accuracy was deemed acceptable. Deer, elk, and black bear attested to the terminal ballistics of the load.

I do agree that cutting powder back until the pressure sign goes away is a completely viable option. I don't believe that soft primers would be the issue unless there was also an oversized firing pin channel as all large rifle and large rifle magnum primers are rated for pressures over 60k psi, although a bad batch isn't outside the realm of possibility.

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Old April 18, 2014, 06:33 PM   #15
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Im trying both options . I would think since I,m talking near max loads a little more sign of pressure would be expected over factory loads right ? I noticed Graffs had plenty of bullets but not alot of powder .
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Old April 18, 2014, 07:38 PM   #16
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Virtually all factory loads are already at maximum safe pressure.
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Old April 19, 2014, 08:00 AM   #17
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I shoot a .300 win mag and have used all of the powders recommended above. I have a couple of comments:

IMR7828ssc gives good accuracy in both the 168 and 200 gr. bullet weights I used (Barnes and Nosler). Velocity over the chronograph was, frankly pathetic.

IMR4350 is too fast for high velocity. Match shooting isn't hunting, so accuracy trumps velocity when shooting paper (to some extent).

I like Alliant RL22 for the 168 gr. bullet and it gives me true win mag velocities. H4831 and IMR4831 are both good choices. H1000 and RL25 are too slow IMO for anything lighter than a 200 gr. bullet.

A good point was made regarding primers. I am pretty particular about my rifle primers and find the Federal to be the best for me. Different primers can have a large affect on pressures.

Bullet seating depth can be another issue with regard to pressure. Be sure you aren't jamming the bullet into the lands. (Hard to do with the long throat on a .300 win mag though)
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Old April 19, 2014, 10:54 AM   #18
psalm7
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loaded 73.5 IMR4831 and worked out great . No swelling around the fireing pin and seems a little hotter than factory loads . I don't have a chrono but acording to manual should be around 2950 fps where the max load of 74.6 was 3000 fps . I use IMR 4350 in my 25-06 I think it would burn to fast for what I want in a .300 Win Mag . Thanks every one .
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Old April 19, 2014, 12:15 PM   #19
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That sounds like a winner to me.

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