Do you extrapolate???

AJC1

AJC1

Member
Joined
Jan 14, 2020
Messages
12,326
Location
St Marys Georgia
I extrapolate data a lot, but I have some rules. I don't do multiple data point guessing. I will find the exact bullet I'm using and extrapolate a starting charge, or I will use a well known powder on a bullet I'm not completely sure about. The second is more common as berry's and a lot of bullet makers don't publish data. I've done it with every rmr or everglades I've loaded.... this guy is nuts, and the video is for fun.... the real question is do you have rules to extrapolate data, and what are they....
youtu.be

170gr RCBS cast bullets swc loaded with Alliant 410 powder 357mag.

Using Alliant 410 powder in a 357 Magnum using a 170 grain RCBS semi wadcutter cast bullet 7 grains 7.3 7.6 7.9 and 8.2 grains do not go under 8 grains of th...
youtu.be youtu.be
 
I Interpolate a lot more than I extrapolate; however, if you don’t venture outside the linear portion of the curve you should be safe.

Just need to understand pressure/velocity relationships are NOT linear.

There are certainly choices to be made, I use many sources for data before I make a decision and generally land pretty close to expectations.
 
Well, since I always start the process from a use-case perspective, I look for combinations that will deliver a particular result, not just a functional solution. Start with, What do you want to put a hole in? and work backwards from there.
Example: I want to aerate cans and bottles at rock throwing distances.
Any projectile moving 550fps or faster will get the job done.
Any projectile larger than BB will get the job done.
Any firearm that has a close range sight and is man-portable will get the job done.
Not really a lot of figuring required. Let’s look in the safes and pick something, then find an inexpensive, easily replicated, well documented load known to perform well in that platform for the task at hand. Done. 👍
 
jmorris said:
I Interpolate a lot more than I extrapolate; however, if you don’t venture outside the linear portion of the curve you should be safe.

Just need to understand pressure/velocity relationships are NOT linear.

There are certainly choices to be made, I use many sources for data before I make a decision and generally land pretty close to expectations.
Click to expand...
Well said, that's pretty much what I do.
I don't like to extrapolate because, when I do, I'm usually already above that linear part of the curve. When I have to it's done very carefully.
I interpolate a lot with different weights of bullets that have no published data for a particular powder.
 
jmorris said:
I Interpolate a lot more than I extrapolate; however, if you don’t venture outside the linear portion of the curve you should be safe.

Just need to understand pressure/velocity relationships are NOT linear.

There are certainly choices to be made, I use many sources for data before I make a decision and generally land pretty close to expectations.
Click to expand...
What he said…….Y’all be careful out there. :)
 
When the 327 Fed. Mag cartridge first came out I wanted to use a 120 grain 32-20 lead bullet, no data. Not much data at all! So I used 100 grain XTP published loads, modified the load for the heavier bullet (and the fact that it was lead). If that's extrapolation, I've done it to that extent.

I didn't watch all 20 minutes of this video, but did view a few sections. His method... it's a definite no for me.
 
I have mainly abandoned extrapolation and interpolation and now Gordon's Reloading Tool. Sometimes I will do a quick extrapolation as a starting point and then put that value in for a computer model on GRT and modify. Sometimes I get what I expected and sometimes I don't.
 
I do extrapolate at times but do a lot of research first. Quickload has been good at getting me going in the right direction. Burn rate chart helps a little with similar powder starting charges, but one must be careful. JMW
 
  • Like
Reactions: mcb
Mr_Flintstone said:
I have mainly abandoned extrapolation and interpolation and now Gordon's Reloading Tool. Sometimes I will do a quick extrapolation as a starting point and then put that value in for a computer model on GRT and modify. Sometimes I get what I expected and sometimes I don't.
Click to expand...
It's the same idea in computer modeling. I push people to get and use this tool as often as possible. I try and keep the mental side sharp as a sanity check "does this computer output make sense" my Puter is almost fixed so I'll be back to modeling like a boss the soonest.
 
AJC1 said:
It's the same idea in computer modeling. I push people to get and use this tool as often as possible. I try and keep the mental side sharp as a sanity check "does this computer output make sense" my Puter is almost fixed so I'll be back to modeling like a boss the soonest.
Click to expand...
Just remember: according to the best computer models possible, Miami has been under water for 15 years.
 
Blue68f100 said:
I do at times but always start on the low end and workup after a lot of research. Wildcatting is a little easier these days with all the tools available.
Click to expand...
If your wildcating I consider that level 3. The first is figuring out a loads with unknown bullets, level two is sorting out unlisted powders and third is wild cating.... the fourth and final is unlisted powders.
 
Levels according to AJ? :)

The less you know about the caliber/powder/bullet, the more complicated it gets.

Why not put forth an example and ask if we have done that? The answer is likely yes for many of us here, a little for others, and a hard no for some, but I'd like to see examples for posters to respond to.
 
Walkalong said:
Levels according to AJ? :)

The less you know about the caliber/powder/bullet, the more complicated it gets.

Why not put forth an example and ask if we have done that? The answer is likely yes for many of us here, a little for others, and a hard no for some, but I'd like to see examples for posters to respond to.
Click to expand...
They are possibly 4 examples not exactly in an applicable order... all risks moderated by research, knowledge, and skill with a pinch of humility 😁
 
AJC1 said:
If you’re wildcating I consider that level 3. The first is figuring out a loads with unknown bullets, level two is sorting out unlisted powders and third is wild cating.... the fourth and final is unlisted powders.
Click to expand...
I messed around with the 25-303 and 35-303 many decades ago when I was shooting British rifles. They were cheap back then and once you invest in an action wrench you own it. Swapping barrels on an Enfield No1, No4, or No5 is easy. Setting headspace can be a breeze or a stone cold stitch. The rifle decides.
I had online buddies in Oz and Taz who were really helpful but we were using totally different powders and bullets. I never blew up a gun but I stuck a couple of bolts real good once or thrice.
I was young and stupid. That’s not an excuse. It’s a fact. 😎
 
I have different cases... I have different typs of primers...I have different powders and I have several types of bullets. First, I would go to my Lyman reloading manual and try to match all up with the "recepie"in the book. This seldom worked. Then I would go to the powder mfgr's website and do the look up. This seldom worked either. I usually had one or two of the components, but not a full house.

I would match up what I had, then go to the closest match with what I had on hand using the book or website. I did change loads up or down to see what works.

I've never checked a case volume by water. Reading here and other gunboards there are wide swings of opinion on primers, usually based on what the OP is trying to do. Most primers are interchangable unless you walk a fine reloading line. I don't chase one hole groups out to 1K yds. I've used SPP in rifle and LRP in pistol...all go bang and I really don"t notice a difference on the target. I don't buy magnum primers, unless that's all that's available. I didn"t do max loads, usually 75-80% or where the target showed best grouping. I had thought about looking for a "node" but...time and components. I tended to replenish the same as what I used, but I did buy some new to me components.

I didn't load for max velocity; I didn't have a crono for the last 38 yrs, but I was happy or not out to 200yd on my available range, and shorter distance for pistols.

I don't know if that's "interpolate" or "extrapolate", I do know it's not running to the LGS or online supplier to match a published "recepie". I do know that what I did worked in my guns and was close enough for me.

The shooting OP's opinion is the only one that matters.
 
Last edited:
I sure do . Over the years I've discovered that when starting working up a new load , the Starting Load is usually not where I end up at and often will not cycle semi-auto's .
The Maximum Load isn't where I want to start either ... and usually I don't use the Max Load either .
I'm usually looking for accuracy .
So ... where to start ... in the middle , extrapolate between min. and max !
And a lot of times ... just slightly above or below the middle is the Sweet Spot !

Extrapolation is fun and should not be confused with ... Exfoliation , which may or may not be fun !
Gary
 
You must log in or register to reply here.

Similar threads

Landric
  • Locked
Wanted: Load data for .32 H&R/.32 Long and Trail Boss
Replies
1
Views
585
Randy1911
R
K
  • Locked
Help Verify Approach for Loading for 9x18 Mak 93gr Hi-Tek Coated
Replies
3
Views
795
Dudedog
Dudedog
badkarmamib
  • Locked
Which manual(s) to start?
2
Replies
34
Views
2K
mr wack
mr wack
R
  • Locked
201gr SWC are 216gr
Replies
3
Views
328
RSVP2RIP
R
Zak Smith
  • Locked
Seeking soft-shooting 3Gun .308 load
Replies
10
Views
1K
Zak Smith
Zak Smith
Back
Top