7mmRM velocities

[Koda]

What is max distance.
That helps to know.

Practically speaking he'd like to shoot out to 400yds and probably will never mess with trying other bullets once he has a handload so I'm hoping he will pick one that he can grow into in case he wants to shoot farther someday.

 

[Koda]

Also whether using the Berger calculator, JBM, or whatever, I do my stability calculations using standard sea level stats. I don’t want a load that must be shot above 5,000’ to be stable.

So Im on the right track using the coast range I hunt in years I dont draw my Eastern Oregon tags, but it sounds like I should just use sea level whenever checking a bullets stability.

 

[BigGame]

So Im on the right track using the coast range I hunt in years I dont draw my Eastern Oregon tags, but it sounds like I should just use sea level whenever checking a bullets stability.

Yup, that’s my view. Another reason is that actual density altitude can be even lower due to conditions at the time. For example, I’m in the Portland area at an elevation of 250’, but at this moment the density altitude is actually about -600’ (600’ below sea level). I think testing stability at standard sea level conditions is a good practice.

 

[Koda]

I think testing stability at standard sea level conditions is a good practice.

Agree and with all the above. Ive always estimated stability in the coast range where I hunt since its lowest of my Eastern hunts but it makes sense to estimate it at sea level.
Im not certain the coastal towns are gonna like me zeroing my rifle on the beach though... kidding.

Now Im back stuck at home again waiting for the snow to melt off in the coast range again, so I can tune my own handloads and get some practical practice in.

I think I have what I need now to offer advice to my friend and think the 132HHT will be best for a 9.5 twist but will see what he picks. These old traditional twist rates really limit mono selections.

 

[kneedeep]

A paper on the plastic tip effect. As above, the JBM calculator is the one you want to use.

https://www.researchgate.net/publication/267157150_A_Stability_Formula_for_Plastic-Tipped_Bullets_Part_1_Motivation_and_Development_of_New_Formula

Love the information biggame. To the point and easily understood. Always glad to see you jump in the conversations.

Kneedeep

 

[Muddyboots]

I think I have what I need now to offer advice to my friend and think the 132HHT will be best for a 9.5 twist but will see what he picks. These old traditional twist rates really limit mono selections.

This will be an interesting discussion with anyone with zero experience with Hammer bullet PDR effect since heavy is preferred for elk. Maybe show Hammertime reference discussions?

 

[Koda]

This will be an interesting discussion with anyone with zero experience with Hammer bullet PDR effect since heavy is preferred for elk. Maybe show Hammertime reference discussions?

Unless hes been holding out hes also new to shooting and hunting, some beginners luck has set the hook. I don't think he has any prior preferences or bias.... This whole experience has been interesting and enjoyable to be a part of. Hes asked me about handloading because he can never find the same ammo anymore. I warned him it was a rabbit hole yet here we are....
I was hoping his rifle had a faster twist in case others questioned him using a lighter bullet as we know hunter peer pressure about "best bullet" can be really overwhelming... IMO, I don't think it matters that much which Hammer he picks. I myself would have no problem dropping an elk with a 130gn bullet of any make and I know the extra velocity will make up for it. I will let him know he can ask questions here though I'm not certain if hes an internet forum type and I don't like to steer people the way I do things I like to present all the options and let people decide which direction they want to go. With hobbies that helps me know who's really into it and especially when finding new hunting partners I know I can rely on.

 

[BigGame]

Koda, your comments/question on stability without the plastic tip modification (Berger calculator) vs. with the plastic tip modification (JBM calculator) reminded me of something I pulled together a while back. I realize you're past that point now, but I'll see if I can get a graphic to load on the topic, if interested.

If you can see the image below, it's showing the following:
For a given example bullet (given atmospherics, velocity, etc.), the basic Miller stability model without accounting for the plastic tip (Berger calculator) is represented by the BLUE LINE - see how the model predicts that to achieve 1.50 stability factor you need a twist rate of about 9.2. The ORANGE LINE represents the model after incorporating the plastic tip adjustment (JBM calculator) - see how the model now predicts that to achieve 1.50 stability factor you're fine with a twist rate of only about 10.2. (The gray line is a different model adjustment particular to hollow nose match-style bullets.)

This gives you a sense of how different the results can be using the two calculators, if your bullet has a plastic tip. It also gives you a sense of how we might waste our idle hours when the hunting season ends.

 

[Koda]

This gives you a sense of how different the results can be using the two calculators, if your bullet has a plastic tip.

I can see the difference in the chart. What if I subtracted the tip length from the bullet length using the Berger calculator? (Im guessing this is why Hammer includes that data)


I just need something simple to use. When I subtract the tip length the Berger calculator shows the bullet is very stable 1.92SG. The JBM calculator includes the tip measurement so I assume it knows to subtract that measurement and it reads 1.72SG (sea level, same 132HHT). Both of these values are well enough above 1.5SG (I'm assuming is the minimum...) but they are different. Im not certain how to know which one is more accurate or if it matters as long as its above the minimum 1.5SG?

 

[andron]

Koda, I would trust what the Hammer site shows. these will run in a 10 twist, and my 280 AI runs them 3300+ with 3 different powders, not a 7 Mag but you should be able to get around that with the right powder choices

 

[Koda]

Koda, I would trust what the Hammer site shows. these will run in a 10 twist, and my 280 AI runs them 3300+ with 3 different powders, not a 7 Mag but you should be able to get around that with the right powder choices

I do trust what Hammer shows, turns out I wasn't entering the bullet data correctly in the stability calculators.

Im running a 140gn Hammer in my 280ai at 3200 so Im sure we can hit at least that with a 130 in the 7RM but its been hard to find powder he wants available. We'll see what we can get with H4350 to start.