Berger to introduce 7mm 195 gr EOL Hybrid Hunting Bullet

[Swamplife]

Any idea as to how much powder capacity you expect to lose with the change in depth? Is it worth having a special reamer made or would you let it ride with it throated for the hybrid?

I took a guess and throated my 7LRM long and the bearing/boat tail junction on the 195's are .040 up from the neck/shoulder junction. So in my case I'm loosing nothing. If your reamer is set for 180vlds or hybrids. I don't think the lost will be much, especially if you have the 180's set with the bearing/boat tail junction above the doughnut area. If you don't have a reamer yet, then add .070-.080 to the 180 Hybrid freebore recommended for your caliber. If your already throated for 180's, I'd run'em first before making a change. The 7LRM has a neck lenght of .387 so I have a lot of room to play with. With some other shorter neck cases you won't be able to throat for 195's and still have enough case neck to safely run 180's up close to the lands. So there would need to be a compromise if you wish to run both 180's and 195's. Me personally I don't like to be restricted to one size bullet and that is why I selected a cartridge with such a long case neck to begin with.


Darren

 

[mrb1982]

Makes sense. I am going for a 7/300 rebarrel so I ask about the reamer because if the smith's reamer is already alright then I wouldn't worry about working up another reamer. It will be a little while before I get this project rolling too far. I need to get through hunting season in early October before I can start working the gun over.

 

[Edd]

It does't matter what the case size, shoulder angle, neck length, or the placement of the bullet is, a seating depth change of .062" will change the case volume approximately 1 grain.

 

[chuckhammer]

It does't matter what the case size, shoulder angle, neck length, or the placement of the bullet is, a seating depth change of .062" will change the case volume approximately 1 grain.

I'm told the concern isn't with the reduction in case capacity but rather the change in combustion behavior when the bullet shank is seated below the neck. It supposedly spoils the formation of the ideal combustion flame front at the neck. Someone here can probably give the history behind this theory. I believe the benchrest folks adhere to it consistently.

 

[Swamplife]

It does't matter what the case size, shoulder angle, neck length, or the placement of the bullet is, a seating depth change of .062" will change the case volume approximately 1 grain.

So your saying, if the smaller diameter of the boat tail or the larger diameter of the bearing surface is moved .062 into the case. They will both take up 1 grain. That doesn't make sense. If it's only boat tail moving into the case, it will take up less space than if it is bearing surface moving into the case. So placement of the bullet does matter. Also that theory will vary if using flat base, rebated boat tail or standard boat tail projectiles.


Darren

 

[Edd]

If it's only boat tail moving into the case, it will take up less space than if it is bearing surface moving into the case.

It's going to be tough to move the boat tail without also moving the bearing surface.

 

[Swamplife]

It's going to be tough to move the boat tail without also moving the bearing surface.

I see what your saying. I was thinking more of case powder capacity being effected by pushing it deeper in the case shoulder as compared to still having the bearing suface in the neck after seating it .067 deeper, like in my case. Is that the volume measurement for .284? Because it doesn't seem like that would hold true for 223 thru 458.


Darren

 

[Edd]

Is that the volume measurement for .284?

Yes

it doesn't seem like that would hold true for 223 thru 458.

Moving a 223 bullet 1/16" would make about .6 gr difference and on a 458 it would make about 2.6 gr difference.

 

[chuckhammer]

Yes


Moving a 223 bullet 1/16" would make about .6 gr difference and on a 458 it would make about 2.6 gr difference.

Yep, it goes with the square of the caliber ratio, same as sectional density (for identical bullet weights).

 

[Lefty7mmstw]

Any velocity data?

next time out trebark.... we were pressed for time and barely let the barrel cool enough to keep shooting it... It shot to the same or slightly higher el as the 180 hybrid (2880 fps)and a bit below the 140 ab/bt load (3340 fps) so I'd bet she's 2900 fps plus but the Oehler 35 will tell me for sure soon....

 

[Lefty7mmstw]

Any velocity data?

http://www.longrangehunting.com/forums/f126/7mm-stw-reloading-thread-112532/index81.html#post1113095

a pic of the group @ 79 grains of rl33...

 

[Swamplord]

I used the 28 Nosler case dimensions in Quickload to determine that seating the 195 gr Berger to 3.340" impacts case h20 capacity by roughly 2.1 grs

Then I went and 40* AI'd the case and increased top of body/shoulder junction diameter from .5275" to .540". (.010" case taper) that change reflected a gain of 2.8 gr case capacity ,

28 Nosler AI 40* with a throat to seat the 195 gr bullet coal at 3.700" will gain approx 4.9 gr + or - a bit...

case h20 capacity up to neck/shoulder junction is 98.1 gr compared to the reg 28 Noslers 95.3 gr



.........

 

[chuckhammer]

Swamplord, can you share the line of QL code for the 195 Berger you used?

 

[barefooter56]

To all,
For anyone who has read the article on the ACCURATE SHOOTER/ 6MM BR website. We have some clarifications for you.
Twist rates :
minimum = 1-9
optimum = 1:8.3 ( 1--8)
G7 BC = .387
G1 BC = .754

This bullet is still in the testing phase and has not officially been launched. We sent this bullet out for some public testing to make sure we had positive feedback before we move forward with an official launch. We want to see how this bullet performs in different chamberings so please let us know if you have any issues and what cartridge you are loading for.
This bullet was made for hunting purposes. We realize that there will be shooters who will use these bullets for target shooting ( F-CLASS ). However we are not certain how they will perform. If things are successful we would like to eventually release a target version of this bullet.
Thank you,