Load density 7mm mag

[TimberHunter]

Found a good accuracy level at 56 grains of IMR 4451. ES over 3 shots was 13 so decent.

Comparing load density to other powders on Nosler’s website, I believe I’m somewhere around 75% load density. Is there any issues with this low load density? Majority of my reloading (308 and 270win) is 93%+ load density


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[lennywd87]

Found a good accuracy level at 56 grains of IMR 4451. ES over 3 shots was 13 so decent.

Comparing load density to other powders on Nosler’s website, I believe I’m somewhere around 75% load density. Is there any issues with this low load density? Majority of my reloading (308 and 270win) is 93%+ load density


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My best guess would be consistency, maybe a wide SD, I’d assume maybe you’d get a flyer here and there. If a compression load is most consistent do to the load density. Then I’d assume going the opposite direction would counter that. Assuming that the less full the case is the more ways the powder could lay in the case. Sounds like it’s working for you though.


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[Rob5589]

I would definitely check es/sd with more than 3 rounds.

 

[TimberHunter]

Will do, but wondering if I should go back to the drawing board and select a powder with higher load density


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[Piscatory_4]

What weight bullet?

 

[TimberHunter]

What weight bullet?

Sorry about not including that

162 SST seated to book OAL


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[wind gypsy]

I've never experimented with low case fill ratio loads. I've read that you can have issues with steep downward shots if the powder is not tight against the flash hole.

 

[TimberHunter]

I've never experimented with low case fill ratio loads. I've read that you can have issues with steep downward shots if the powder is not tight against the flash hole.

When you say low fill ratio do you mean 75%? I’m about half way between what Hogdon recommends as min/max


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[wind gypsy]

When you say low fill ratio do you mean 75%? I’m about half way between what Hogdon recommends as min/max


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Yeah, I was using case fill ratio interchangeably with your use of load density. 75% is low.

 

[lennywd87]

I should explained this earlier. At 75% you have 3/4 of the case full, on a 7mm mag that’s a pretty large case. You powder could be laying against the primer and not the bullet, against the bullet and not the primer, against both or neither depending on how the gun was sitting before you shot. Say you had it standing up on a gun rack, riding with the barrel in the floor board or laying flat across the back seat in a gun case. Low load density will create more variables within the case during the firing process. As said above a larger group testing might reveal this compared to 3 bullets. 10 is a good place to start figuring SD of velocities. The lower the SD the better, shoot for

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[TimberHunter]

I should explained this earlier. At 75% you have 3/4 of the case full, on a 7mm mag that’s a pretty large case. You powder could be laying against the primer and not the bullet, against the bullet and not the primer, against both or neither depending on how the gun was sitting before you shot. Say you had it standing up on a gun rack, riding with the barrel in the floor board or laying flat across the back seat in a gun case. Low load density will create more variables within the case during the firing process. As said above a larger group testing might reveal this compared to 3 bullets. 10 is a good place to start figuring SD of velocities. The lower the SD the better, shoot for

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Thanks for the info. Being this would be a long range hunting rifle, the rifle could be in many difference positions when it’s fired, hypothetically leading to accuracy/velocity issues.

I’m going to see if I can find a powder with a higher case fill ratio. Nosler is the only one that I know of that published case fill %. Looks hard to get near 90%+ fill

Other powder I have on hand are IMR 4064, BLC2, H4831SC, H4350, IMR 4350, H4895, RL15, RL23, IMR 7977 and benchmark. IMR 7977 or H4831sc will likely me my next try


IMR 7977 shows loads between 64-69.5 with 69.5 being compressed. That may be my best bet for high case fill if it will shoot accurately

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[wyo2track]

Unless you really just like burning up powder and bullets, you're giving up waaayyy too much performance in a 7 mag loading it like that. Of the powders you have listed on hand, I'd go right to the IMR 7977, it'll really fill up the case with powder, good density. Next I'd try the H4831SC; buddy of mine shoots that with 160's and is in the mid 60's for powder charge and around 3050 for muzzle velocity. Check out the Hodgdon Reloading Data Center. Right now you're barely above 7mm-08 levels.

 

[Rob5589]

I have always had great success with my 7 mags and R22. R23 is supposed to be pretty much the same but more temp stable. I have some but have not yet tried it. I will after my 22 runs out. I'd try out the 23 if it were me.

 

[lennywd87]

Accuracy over velocity for me and most I’m sure unless you can get both, usually sacrifice one for the other though. Compressions for consistency, but of course work your way up to it. Most nosler loads I’ve used ride the razors edge for max load in smaller calibers like .243, but a person might be able to work past their max. I’m consistently working past max in my Lee manual. Manuals are a reference guideline set within SAAMI safe and sensible suggested limits that applies to all factory rifles, but every rifle is its own animal and some have longer legs than others. Pretty soon you’ll be using a drop tube


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[brad407210]

If you want to do an extreme spread test with low density loads like 4451 you can try tipping the rifle straight up, then slowly lower into a level position to shoot through the chrono then tip it straight down with the next round and slowly bring it back to level to shoot through the chrono. It's not perfect but will get a pretty good idea of what the worst case scenario could be in the field shooting up or down hill. H4831/4955 to H1000/7977 has been the range I've had the best luck with in my 7mm using 160's, but I used to run 140's with 4451 that shot great, I was just missing out on some velocity potential. There is a point where low density loads can actually cause pressure spikes, my understanding is that a primer blast that shoots over the top of powder can ignite it all quicker than when it's lighting it from one end to the other. I'm not sure what exact load densities this applies to, but if you're concerned about that just include some tipping up/down shots into a pressure test on a hot day and see what it does to your pressure signs then stick to a load that is safe no mater how the powder is laying in the case.

 

[Harvey_NW]

I worked up a load with H4831SC and 168 VLD's in my last 7mm mag and the load density wasn't great but I wasn't running book COAL. Had much better luck in the past with H1000 so I would put my efforts into testing the IMR7977 since it's supposed to be very similar.

 

[TCrea72]

I’m new to reloading and this was an interesting read since I plan to start with 7mm.