Hodgdon Reloading Data Center?

[Raythemanroe]

I was looking up data for a 210g bullet for a 300 win mag using Retumbo and they only show 208g then 220g info..Okay so I was checking both to look for a safe middle ground and the pressure on the heavier 220g was less then the 208g with the same charge wtf?

 

[spclark]

Entirely possible I suppose. Pressure's influenced by a number of factors, including but not just bullet weight.

I've found that bearing surface length is a reliable indicator of pressure differences in bullets of the same weight class. Could it be that that 220 has less bearing surface than the lighter projectile? Thinner jacket maybe?

 

[jo191145]

Very common with book data.

RUMOR has it Hodgen stops its data at the last accuracy node found. Of course that's for their test barrels etc. but I've seen lots of folks find best accuracy/velocity with H powders right at book max.

Bottom line, book data is just book data. Helpful to get you on the playing field but just a rough quide to the game. JMO

 

[watercam]

Bullet construction plays a major role in pressure results. If the lighter bullet has a thicker jacket, longer bearing surface, is a Partition or A-frame type, pressure results may be higher than a heavier target or conventional cup and core bullet. Cast bullets show less pressure than jacketed, etc..
I have had excellent results in most of the fifteen calibers I load for using Hodgdon data. In my two match rifles I am consistently about .5 grain below max with the powder/components I use and velocities seem to match up well.

 

[jo191145]

watercam

I agree with your post. I think what Ray is asking is why book data doesn't always end with the highest pressure possible for any given set of components.
For instance I notice a couple of years ago when IMR-8208XBR made the scene some cartridges now posted max pressures for that powder significantly higher than any other previous powder loads. Personally I put it down to marketing hype but I'm a skeptic at times. ;D
Or in rays case, why one weight combo was tested to "lets say" 50,000psi and the next weight stopped at 40,000psi.

Just my way of thinking perhaps but max pressure is max pressure. In a perfect world all the numbers in that column should be the same. No expert on pressure testing by the book tho.

 

[Raythemanroe]

There max pressure for the 208g was 61,300 psi and the 220g was 52,400 psi !

 

[Raythemanroe]

jo191145 , exactly what I'm thinking! If the max pressure they are willing to print is 60,000 psi, then why did they stop at 52,000 psi on the next load?

 

[Raythemanroe]

Now that I'm thinking about it, the 220g probably cause a case capacity issue

 

[jo191145]

Now that I'm thinking about it, the 220g probably cause a case capacity issue

That's a very real possibility Ray dependent on cartridge capacity and the normal shallow (magazine) seating depths of book data.
As a guy who shoots a lot of point blank Benchrest cartridges I can attest we have found ways of cramming that extra powder in ;D

If you look through Hodgen or any other loading data you'll find plenty of other scenarios where capacity isn't an issue. Also need to pay attention to CPU's and PSI's. Theres a smattering of both in Hodgens site. CPU's are the old measuring system and some of the loads on Hodgens site reflect the fact they haven't been updated in many many decades. Mostly Win powders from my recollection but I'm sure there are others.

 

[Raythemanroe]

I have been notified that one is psi and the other is cup there still both showing the same max charge and probably due to case capacity

 

[jo191145]

My bad Ray. I never noticed you specified a cartridge. If I had and had looked it up,,,,,,,,,,,,,,oh well.