.30 cal vs. 7mm

What action and throating did Berger use to obtain their data? Long throat and generous OAL, or a tight SAAMI-spec chamber? If you know much about hand loading and internal ballistics, you'll know that when a bullet uses soft lead (like Nosler) and large bearing surface (like the NPT), you generate more pressure than if you use a bullet with a harder gilding metal alloy and smaller bearing surface (like the VLD).

You and I both know that most of the data out there for the 7RM isn't representative of what can be reached in a modern, strong bolt-action rifle. How about you work up a load with the 230gr Berger in your .300WSM, and chronograph it with a reliable chrono, and I'll report on real-world velocities from my 7RM and 7WSM using 162gr A-Max and 180VLD. Loads must be free of traditional pressure signs. Deal?
 
Jordan Smith said:
What action and throating did Berger use to obtain their data? Long throat and generous OAL, or a tight SAAMI-spec chamber? If you know much about hand loading and internal ballistics, you'll know that when a bullet uses soft lead (like Nosler) and large bearing surface (like the NPT), you generate more pressure than if you use a bullet with a harder gilding metal alloy and smaller bearing surface (like the VLD).

You and I both know that most of the data out there for the 7RM isn't representative of what can be reached in a modern, strong bolt-action rifle. How about you work up a load with the 230gr Berger in your .300WSM, and chronograph it with a reliable chrono, and I'll report on real-world velocities from my 7RM and 7WSM using 162gr A-Max and 180VLD. Loads must be free of traditional pressure signs. Deal?
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Yes, we both know the 7mm rm has been watered down to 61k psi and most published loads don't even hit that. My nosler #1 shows 3150fps with a 160 pt and 3k with a 175. "Modern" data isn't close to that. The problem is that this is a forum that people of all experience levels frequent and when someone, who obviously knows little about ballistics, asks about 7 vs 30 cal I do not think it does any good to show them fps that really just isn't there from the manufacturers. And heaven forbid if they don't reload. Good luck with the factory stuff. HSM for the 180gr is loaded to 2850fps. Not sure if anyone else loads bergers.

I'm curious to see the new Berger reloading manual. Should be lots of good info in there.
 
Yup, I'd like to get my hands on one, as well.

Anyway, it's been a good discussion, but I think it's only fair to let the OP and anyone else reading know that the 7RM is capable of more than what the meager factory loads, and even lots of the hand load data currently in production, offer. That was my intent- to show both sides of the coin. Yes, factory loads and many loading manuals show the 7RM hitting no more than ~2800fps with a 175-180gr bullet, but the cartridge is capable of much more when loaded to the same pressure as other modern cartridges, in modern bolt-action rifles.

Regarding your concern with people of all experience levels reading this forum- this is the internet. Take it for what it's worth, since the info you get here is often worth what you paid for it ;)
 
joe-nwt said:
And what would the diameter be of a square bullet?
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OK, weight in pounds/ diameter X diameter which is the same thing. Point is; diameter X diameter represents the area of a square of those height and width measurements not the area of a circle of that diameter.

The formula should have been done weight in pounds/Pi R squared.
 
Neither does the formula take mass into account, so the weight in pounds should have been divided by the velocity of gravity, so weight in pounds /64.35/Pi R squared. Now my head hurts and I have to lay down for a while.
 
Dogleg said:
OK, weight in pounds/ diameter X diameter which is the same thing. Point is; diameter X diameter represents the area of a square of those height and width measurements not the area of a circle of that diameter.

The formula should have been done weight in pounds/Pi R squared.
Click to expand...

Boomer said:
Neither does the formula take mass into account, so the weight in pounds should have been divided by the velocity of gravity, so weight in pounds /64.35/Pi R squared. Now my head hurts and I have to lay down for a while.
Click to expand...

Well as long as everyone uses the same formula, we still end up with numbers that we can use to compare one bullet to another, no?
 
I'm shooting a Rem Titanium with a 24inch magnum contour barrel with 1-10 twist. I had forgotten that before i pillar bedded and free floated this gun i believe i was actually was getting 3000fps with a 165 accubond. The stock also had the pressure point on the front of barrel at this time. When i bedded the action i tried the same load i was previously useing ... of course it didnt work, I believe it was 63.5 gr of H380. Not only did it not work it was all over the fking place, no consistency at all. I had to slow the load down substantially to get the same accuracy. My load is now 60gr of H380. Im getting the same accuracy ... around 3 quarter inch at 100 yards. I was thinking that maybe now that the pressure point at the end of the barrel is gone there is more vibration thus have to slow the load down to control the harmonics ?... Im open to any thoughts on this

Id like to stick with Hodgson powder being its less sensitive to tempature

I know that this isnt really what this thread is about but since were on the topic ...
 
Dogleg said:
US or Imp wouldn't matter much as long as it was a ten gallon hat. That way it would mesh with the metric system.Simpler math should be better even if its wrong.
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:)Don't mind me, ;)just twisting your tail a little. Bit of a side issue but the difference between a US & Imperial gallon was graphically brought home in trade school hydraulic calculation questions years back that I got wrong:redface:.
 
Let me get this straight: The imperial ballistic coefficient metricated yeild better penetration on a 10 gallon cowboy.....wait, no....I'll get it yet.....hold on......where's that damn pencil sharpener.....
 
:redface:Pardon me for getting side tracked but it still pains me when I think of some of the easy calculation questions I lost marks because of the difference in gallon size. Oh well, water under the bridge at this point in time, but for what it's worth, if I recall correctly, a U.S. gallon is 231 cubic inches and the imperial 277:p.
 
joe-nwt said:
Let me get this straight: The imperial ballistic coefficient metricated yeild better penetration on a 10 gallon cowboy.....wait, no....I'll get it yet.....hold on......where's that damn pencil sharpener.....
Click to expand...

You're getting it, just remember that the metricated cowboyhat coefficient is calculated at 2000 telephone poles per hour. Then it all makes sense.
 
pilot2001 said:
I'm shooting a Rem Titanium with a 24inch magnum contour barrel with 1-10 twist. I had forgotten that before i pillar bedded and free floated this gun i believe i was actually was getting 3000fps with a 165 accubond. The stock also had the pressure point on the front of barrel at this time. When i bedded the action i tried the same load i was previously useing ... of course it didnt work, I believe it was 63.5 gr of H380. Not only did it not work it was all over the fking place, no consistency at all. I had to slow the load down substantially to get the same accuracy. My load is now 60gr of H380. Im getting the same accuracy ... around 3 quarter inch at 100 yards. I was thinking that maybe now that the pressure point at the end of the barrel is gone there is more vibration thus have to slow the load down to control the harmonics ?... Im open to any thoughts on this

Id like to stick with Hodgson powder being its less sensitive to tempature

I know that this isnt really what this thread is about but since were on the topic ...
Click to expand...

IMHO, an accurate rifle will shoot any reasonable load pretty well. If something is done to a previously stable rifle that makes it finicky, or worse, causes it to shoot poorly, with a load that previously performed pretty well, it suggests that the change was not an improvement. You of course have to be the one who decides if giving up 80 fps in velocity by reducing your load by 3.5 grs to maintain the level of accuracy you're after is worthwhile, but to my way of thinking, I'd sooner have the extra velocity provided I could get it safely. That said, I'd be inclined to use the rifle for a while, and see if the level of accuracy you've observed with the 60 gr load holds up over time. If the rifle shoots during the cold part of the winter, but acts up in the spring as the weather warms, you should consider replacing the pressure point. If you shoot more than one load in the rifle, and it proves challenging to tune the loads for accuracy, you should probably replace the pressure point now.

I like ball powders for their higher loading densities, but Hodgdon's ball powder is not temperature stable, so not only will you loose about 80 fps by reducing your load 3.5 grs, but you could loose and additional 30 fps if you shoot that load in the cold. Only Hodgdon's Extreme line of powders are temperature stable, and while those powders are stable in heat, which is an important consideration, they loose energy in the cold. I did find that Hybrid 100V was a good performer in the cold in the cartridges I used it in. Unlike the Australian manufactured Extreme line, Hybrid is manufactured in the States by St. Marks Powder, a subsidiary of General Dynamics, and is tested for stability in the cold, by air bursting large charges at high altitude and measuring the over pressure.
 
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