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Topic: Base to Ogive consistency  (Read 460 times) previous topic - next topic

Base to Ogive consistency

I think I remember somebody mentioning this a while back.
As I am going to be using my next 5lbs of H4350 (same lot) and my next 3 boxes of Berger 140VLDh (same lot) Things should be good for a bit.  I have prepped my brass and went overly numbers.  I have about 12 Berger's left from an old lot, they are approximately,

old bullets btog are .732
new bullets are btog  is .749
and I have two boxes of 140VLD target, btog is .743
Dang you Berger lol
Before I try and match my velocity node to the new bullets, any idea how much I should reduce my charge weight just for the seating depth?
I also have to adjust for the new powder lot I will be using, but no pressure signs at all at my current 41.2gr load.
Next barrel is going to have large purchase of bullets and powder in one visa card purchase to make things much more simple lol.
I Opened up two different boxes of different lot numbers of 143 ELDx, the btog is the same.

Re: Base to Ogive consistency

Reply #1
Did you by chance contact Berger and ask what their manufacturing tolerances are?
See you at the range.

Re: Base to Ogive consistency

Reply #2
LeadHammer,

If I read you right, the new bullets have a longer btog so you'll need to seat deeper to maintain the same ogive to lands.

Therefore you need to reduce charge weight in order to maintain the same velocity.

I can run this through QuickLoad for you. Not that it's vital but what brass are you using?

Gotta get ready for a late business meeting now, happy to run it first thing in the morning.
Chris

Re: Base to Ogive consistency

Reply #3
Exactly right Chris. 
Hornady brass. Fed primers.
I would think just a few grains would do it.  This is where a Labrador would be nice.

Edit:  My dumb a$$ forgot to say thanks.


Re: Base to Ogive consistency

Reply #5
I made the assumption you load to a COL of 2.800" just give QuickLoad something to chew on.

At that COL with 41.2 gr H4350 and the Berger Hybrid 140 gr bullet, QL predicts a velocity of 2667 from a 24" barrel.

Seating to 2.783" QL predicts a velocity of 2674 with 41.2 gr H4350.

Dropping the charge to 41.1 gr H4350 returns the predicted velocity to 2667 fps.

So, lose 1/10th grain :)

Happy to run it again if you want to provide actual COL.

Chris

Re: Base to Ogive consistency

Reply #6
I made the assumption you load to a COL of 2.800" just give QuickLoad something to chew on.

At that COL with 41.2 gr H4350 and the Berger Hybrid 140 gr bullet, QL predicts a velocity of 2667 from a 24" barrel.

Seating to 2.783" QL predicts a velocity of 2674 with 41.2 gr H4350.

Dropping the charge to 41.1 gr H4350 returns the predicted velocity to 2667 fps.

So, lose 1/10th grain :)

Happy to run it again if you want to provide actual COL.



Thanks Bike.
Hornady brass
140 Berger VLDh
Federal standard primes
BTOG of 2.155"
OAL of 2.81"
Velocity is tested at 2710, and matches out to 600yds via ballistic app.
24" barrel
42.1 gr H4350
Sorry I hope I provided all the info needed this time.  Appreciate it.

Re: Base to Ogive consistency

Reply #7
OK, I must have had something typed in wrong the first time, here goes with new data:

42.1 gr H4350, COL 2.810, velocity 2714

42.1 gr H4350, COL 2.793, velocity 2720 (new bullet seated deeper to maintain distance to lands)

42.0 gr H4350, COL 2.793, velocity 2714 (charge dropped to regain same velocity as with old bullets)

Chris

Re: Base to Ogive consistency

Reply #8
Wow, that is kinda amazing.  Thanks for the info, makes me want to get Quickload!

Re: Base to Ogive consistency

Reply #9
I've been amazed at how well QL correlates with observed measurements. I mostly use it to help me stay out of the over-pressure weeds to start with. Let me add, I don't consider QL a substitute for common sense and carefully monitoring for said over-pressure.
Chris

Re: Base to Ogive consistency

Reply #10
I've been amazed at how well QL correlates with observed measurements. I mostly use it to help me stay out of the over-pressure weeds to start with. Let me add, I don't consider QL a substitute for common sense and carefully monitoring for said over-pressure.

I absolutely agree.  What did it say my pressure was?

Re: Base to Ogive consistency

Reply #11
56694 psi

SAAMI max is 63091.

You'd hit max at about 43.4, QL says "DO NOT LOAD".
Chris

Re: Base to Ogive consistency

Reply #12
56694 psi

SAAMI max is 63091.

Wow, the Berger's bearing surface is so much different than the ELDx.  My 41.2 (VLD) load seems so easy on the brass vs 41.8 load.( Eldx pressure)
I will leave the Berger load alone as it shoots very well and the brass is happy.

You'd hit max at about 43.4, QL says "DO NOT LOAD".

Re: Base to Ogive consistency

Reply #13
So I had decided that I had enough components to separate my new lot of H4350 tests with the new Berger VLDh 140's.

I set up at 200 meters at my local range, mostly to do a velocity test to see if the powder matches. I got lucky as the new powder was an average of 1 ft per second off!!! Considering I use a Shooting crony I can't get any closer of a comparison.
My load is 41.2, so I made six of those, but I also loaded up four at 41.1, and four at 41.3. With no wind and it not being too cold, (-6c) I had a great afternoon at the range. Anyway here are a few photos. Next outing will be with the new projectiles, hopefully that goes well too.




Re: Base to Ogive consistency

Reply #14
Berger says they use the same die for all bullets of that lot. Once the die wears out, goes beyond tolerance, they replace it and start with a new die and therefore a new lot of bullets. At least that's how I understand it. I called them Friday about this as my new Loy of 6mm Hybrid Target bullets were .010" longer and the BTO was .009" longer.
RPR 6.5 Creedmoor
Bergara 6 Creedmoor