How much jump for 300gr 338 Berger Hybrid????

[RayDog]

Just checking to see how much you guys are jumping them or what to make them shoot for you. I have a new barrel on my TRG and want to test these.
I'll be loading longer than mag length I can see. I'm touching at a AOL of 3.815" with an ogive of 2.965". Thanks for the info

RayDog

 

[onlyfineknives]

Re: How much jump for 300gr 338 Berger Hybrid????

Hi RayDog,

Sorry for the delay, but I just saw your post.
I'm shooting a Surgeon XL in a AI CIP stock with a krieger 26" barrel. I load the bergers for magazine length loading with 91.5gr of Retumbo. I'm touching at 3.695 and loading to 3.670 for a .025 jump. This gives me 2725 fps with very low es and .4 moa out to the 500yds I have tested it at. I can take the load to 2800 pretty easily, but the accuracy and es is not as good.
Hope that helps, and I would be curious to hear what you end up with.

Shannon

 

[Fuzzball]

Re: How much jump for 300gr 338 Berger Hybrid????

If you mean for best accuracy, you really need to check with your own rifle about that.

 

[onlyfineknives]

Re: How much jump for 300gr 338 Berger Hybrid????

Just to clarify, my question is what RayDog ends up finding as his best jumping distance for best accuracy in his gun.

Thanks,

Shannon

 

[cali_tz]

Re: How much jump for 300gr 338 Berger Hybrid????

the seating depth of the bullet will affect not only because of the jump, but also because there is more or less force holding the bullet in place, right?
What effect does the total length of neck to bullet contact have on the whole equation?

 

[onlyfineknives]

Re: How much jump for 300gr 338 Berger Hybrid????

In general, the more bearing surface of the bullet in contact with the neck, the greater the neck tension. Also, if the bullet is seated deeper in the case, more of the bearing surface has to "pass through" the neck creating friction for a longer time which increases neck tension (or bullet pull however you would like to term it).

This is one disadvantage of having a short throat allowing this bullet to be magazine fed. While it feeds great from the magazine, the bullet is approximately 1.8 inches long which puts quite a bit of it below the case neck. This not only increases bullet pull, but takes up case capacity which increases pressure.

My best seating depth & charge weight for my setup only gives me 2725 fps with my gun. It can be pushed faster, but the accuracy is not as good. Part of the reason for this is not only the harmonics of my gun, but also because of having to seat the bullet so deep in the case for magazine feeding.

Hope that helps

 

[cali_tz]

Re: How much jump for 300gr 338 Berger Hybrid????

Thanks. So in your case seating the bullet deeper, so as to be able to magazine feed, caused your muzzle velo to drop, probably because of the higher neck tension.

 

[onlyfineknives]

Re: How much jump for 300gr 338 Berger Hybrid????

In most cases, increases neck tension increases pressure which increases velocity.

The main reason that my velocity is a little lower is that I have a very long bullet seated deep in the case in order to magazine feed. The bullet is occupying more case capacity which effectively increases pressure causing me to reduce my load accordingly.

I have run 2800 with some light pressure signs, but the added velocity wasn't worth the accuracy loss that I got with my gun.

It's always a balancing act of some kind, because you're working the long bullet with the higher bc, against the ease of magazine feeding, factoring in your barrel and reamer specs, etc.

So to recap - in order to seat the bullet deeper to magazine feed, it increased pressure, which caused me to back off the load for pressure (and accuracy) issues.

 

[cali_tz]

Re: How much jump for 300gr 338 Berger Hybrid????

got it... understand that you reduced your load to offset the higher pressure from smaller case volume and higher neck tension.

 

[onlyfineknives]

Re: How much jump for 300gr 338 Berger Hybrid????

thats it