Is This Excessive Pressure??

[CanardNoir]

Anybody question the tradeoff in accuracy for a 17-25 fps gain in velocity?

At the upper end of the equation - F = 1/2 m X v(sq) - you could be better off (or just as well off) with better accuracy & less velocity, if you're shooting above 6,000 ft in altitude - simply because, "...it's not what you shoot, but where you hit, that really matters."

 

[Jerrys kid]

I would appreciate hearing your comments on these pic's.

Fired from a 7mm Rem Mag loaded with 78.0gr of RL33 pushing a 175gr Nosler Accubond LR at 2,922fps.

I am seeing some cratering on the primer but it doesn't look flattened-out and hasn't spread out. I don't see any marks on the case either.

What do you guys think...does it look safe or excessive?

The second pic (lighter-shiny brass) is loaded with 79.0gr of RL33. The cratering is a bit more pronounced but not by much.

The extra grain of powder is only giving me an extra 13fps so I would go with the 78.0gr if you guys think it's OK.

Whatdaya Think?

Both look fine to me. I have factory federal premium 308 shells that have primers flat! I load 72 grains retumbo over Berger 180s in my Remy. No pressure issues. Great accuracy.

 

[BLK]

You got it right CanardNoir. There are many, many shooters who try to get that "max load" only to realize they are giving up accuracy for a load that has a 100fps less velocity that shoots same hole at 100 yds. Most of the serious ones catch on like finally did. Put it in the bread basket and they are a humane and quick kill.

 

[Nitroman]

Why wonder, when you can know: https://www.shootingsoftware.com/pressure.htm

 

[Stiletto150]

my .02 cents. I have been working up loads for a 270-4831sc and 300-H1000. in the 300. 3 different brass, and 2 different bullets (copper and lead). In all caliber and bullet combinations. My accurate load is usually .5-1 gn. less than when pressure starts appearing. And have had similar velocity losses as you. Most of my testing has been at 70-80F. One thing I haven't tested which I know may happen in the field is cooking the second round and the bullet shift after firing. I have however seen significant velocity changes end up at the same POI when using a chrono in my testing.

 

[Nevmavrick]

Primers are very inaccurate when trying determine pressures, especially when trying to compare different brands.
I believe the ones you are using are CCI 250s, especially with as slow a powder, and as much, as you are using.
250s are a hard primer so hold up pretty well under pressure.
Your velocities are a good indication that your pressures are max, though not max enough to hurt anything. A good working max. After accuracy tests, you'll probably be using this rifle for hunting. That's in the winter and at higher altitudes. Pressures will drop a bit, so you'll have fewer problems.
I would drop the charge back by .2 grains...twice. In other words...78.0, 77.8, 77.6, then 78.2, and 78.4, and check the accuracy.
I would probably move the OAL a bit with the same loads. I don't know what the "jump" is, so I would measure THAT, too, so I can judge better.
I would consider the 79.0gr load max, so I would stay below that.
I don't know what the max deviation, or SD, either one, is so I would keep an eye on that as I was shooting.
I am one of those lucky people that can shoot for accuracy and use the chronograph at the same time. FWIW, I use an Oehler M33, that I've had for over 30 years, and checked many times to see that it stays the same.
You've got your load close, so just need to test accuracy.
Have fun, and "eat meat."
Gene

 

[Ingwe]

Primers are very inaccurate when trying determine pressures, especially when trying to compare different brands.
I believe the ones you are using are CCI 250s, especially with as slow a powder, and as much, as you are using.
250s are a hard primer so hold up pretty well under pressure.
Your velocities are a good indication that your pressures are max, though not max enough to hurt anything. A good working max. After accuracy tests, you'll probably be using this rifle for hunting. That's in the winter and at higher altitudes. Pressures will drop a bit, so you'll have fewer problems.
I would drop the charge back by .2 grains...twice. In other words...78.0, 77.8, 77.6, then 78.2, and 78.4, and check the accuracy.
I would probably move the OAL a bit with the same loads. I don't know what the "jump" is, so I would measure THAT, too, so I can judge better.
I would consider the 79.0gr load max, so I would stay below that.
I don't know what the max deviation, or SD, either one, is so I would keep an eye on that as I was shooting.
I am one of those lucky people that can shoot for accuracy and use the chronograph at the same time. FWIW, I use an Oehler M33, that I've had for over 30 years, and checked many times to see that it stays the same.
You've got your load close, so just need to test accuracy.
Have fun, and "eat meat."
Gene

Thanks for that reply!

Actually I am using Federal 215's though

 

[james wadkins]

I'd say they look pretty good. Going to a grain more for 14 fps tells me you're close to Max. No problem with bolt lift?

 

[wildcat westerner]

Since you like this load hot and are quibbling over a single grain of powder and 13 fps. I suggest you get this firing pin bushed. You'll not have to worry about blowing a primer once the operation is complete.

Gene S.

 

[Ingwe]

No bolt lift issue at all but I think that I will limit the charge to 78.0 to be safe for when I shoot under a hot sun

 

[Pdvdh]

Choot'em!

 

[Mark Warner]

What was the outside temp, 65, 95 degrees, was your ammo and or your rifle hot from sitting in your truck when you started shooting. Pressures change, when prairie dog shooting in the warmer months I have always painted my ammo cans white to keep my ammo cool and almost always had stainless steel barrels to reflect the sun. Blued barrels will always hold heat longer. Just a thought!

 

[Swiftkill]

Why not drop a grain or two for three rounds and see if it goes away or it is ...like he said a sloppy firing pin hole. You can try a harder primer too.

 

[DavidleeCole]

I have some on my 300 whby mag that done the same thing. I was ok as that was the first sign of pressure. After a ladder test I found that OCW was 1.4 grains less. If you do stay with that load keep an eye out for other and watch for early sings of case head separation.