Smokin hot load in my 300 Win Mag

[General Lee]

So I recently got my custom 300 win mag finished and man I love the results. I am seeing 220 grain Sierra Match Kings whippin out there at 2850 fps pushed by 70.1gr of IMR7828. My chamber is cut extremely tight and it is making super smokin loads. From what I am reading in all the books I am exceeding the max velocity from any powder for this bullet. The only signs I see of excess pressure is some deformed primers here and there. I see no case damage at all and primer pockets are remaining tight.

 

[Walkalong]

Well, there is no free lunch. I would look at everything very carefully.

 

[Grumulkin]

The published alleged "maximum velocity" means very little. That's why I don't use a chronograph for load work-up.

Pray tell, what do you mean by "deformed" primers?

 

[NCsmitty]

Is the velocity based on actual chronograph results?
www.hodgdon.com is showing the starting load of 70.0gr of IMR7828 at 2541fps with the 220gr Sierra RN.
I question the reported velocity of your load. If you're using a chronograph, are you setting up too close to the muzzle blast? It's best to be at least 15' with a heavy caliber like that.

I'm glad to hear that you are happy with your new rifle, and the 300 Win Mag is a great cartridge.



NCsmitty

 

[General Lee]

I used a buddy's high end chronograph. I honestly don't know what chronograph is good or not, but he is the guy who built my gun and he doesn't go cheap on stuff. The results are different from what you are seeing in normal cartridges because my chamber is match sized. I actually small base sized a piece of brass and sent it to Manson reamers and he built a specific reamer for that cartridge. the chamber is extremely tight and would not even fit brass fired out of another weapon. There is very little expansion thus causing the higher velocity. I am 100% confident the readings are correct after shooting 10 rounds and all of them being very close to one another.

I meant some of the primers are slightly flattened out. I am also using regular primers and not magnum with this load.

Might I add the accuracy is also fantastic on this. The gun can shoot quarter inch groups at 100 easily. I have hit at 600 repeatedly on a 15 inch circular plate. I am looking forward to putting up paper at 600 and even 1k.

 

[Slamfire]

If you are exceeding published values than you are exceeding published pressures.

There is no such thing as a free lunch.

You can exceed SAAMI pressures quite easily in centerfire bolt guns and not have pressure indications.


First indication is brass that does not last long. Primer pockets open up because the cartridge base is being spread out due to high pressure. Another issue is cracking. Structually the rifle is designed to carry a maximum load. If you exceed it the first thing you are likely to see, and it may be a while, are fatique cracks. If the bolt/receiver is being stressed above yeild, there are a finite number of cycles to fatique failure.

I have buds who are shooting 6.5 Grendels or turbos in semi auto actions. I don't remember if the action is an AR15 or AR10 action. Anyway the cartridge thrust exceeds the design limits of the action and they are experiencing cracked bolt lugs.

For them, the bolt is a consumable. They are willing to spend a couple hundred bucks for a new bolt.

That is something you need to consider when you push things at pressure levels that probably exceed the design limits of your rifle.

 

[General Lee]

Ouch... I am definitely not looking to break anything. I am just looking to get the best accuracy out of the gun. These numbers honestly kind of worried me when I saw them. The chamber in this gun makes starting loads my max load.

 

[Clark]

This is a 7mmRemMag case head, which is the same 1925 300 H&H mag case head that the 300 Win Mag uses.

The primer fell out with a load that Quickload thinks is 107 kpsi.

This was not in a work up, but a quantum leap.

 

[unwise11]

If I were you I would decrease a bit because I've seen that rifle and it would be a shame to mess her up, not to mention you could seriously get hurt..

 

[blarby]

The OP has about another 4.9 grs of leeway.

Push lightly forward sir, but you are still in the safe zone.

Nice rifle

 

[sonick808]

quickload shows a velocity of 2713 for a 24" barrel based on your components. 2767 with a 26" barrel.

It also shows a max pressure of 54134 at pmax; you're very close to the limit of 62366.

Consider yourself near or at the max. Perhaps even exceeding it; quickload is far from perfect,and only gives rough numbers.
If you're truly pushing 2850fps, you're probably near completely maxed, evidenced by the flattening primers. On any given Sunday, you're pushing it.

Be very careful out there


These numbers from quickload should be taken with a large grain of salt.
YMMV
etc etc disclaimer