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How many rounds to develop a load?

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Unread 04-04-2009, 08:39 AM
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Join Date: Jul 2004
Location: Texas
Posts: 7,189
Re: How many rounds to develop a load?

Originally Posted by Nobody View Post

Been a member for sometime though I rarely post. Do a lot of reading though.

I have a 264 Win Mag Sendero II. It's got a 1/9 twist, standard Remmy trigger though it's all been worked over by Clarence Hammonds. I'm trying to develop a load for it using 140 SMKs. I'd called Sierra and gotten a load range of something like 55.?grs - 62?grs of IMR7828. I can fire a couple of rounds and have them touching and the next three rounds are 3/4 of an inch out. Typically, I start at mid-range - I feel that's a safe thing to do though with 264s you gotta' be careful because they generate pressure spikes with even slight changes to load weight.

Anyway, I've got through like...25 rounds and I'm still no where near where I think this gun should be. My question, as the title suggests is, how many rounds should I reasonably expect to have to shoot while developing a load?

And by the way, if anybody has a good, safe load using IMR7828 or IMR4831 please let me know.

Thanks in advance.
I use a chronograph for the process of eleminating bad loads and don't worry about group
size in the begining.

It goes something like this=

First I select the bullet I would prefer to use.

Then I look at loading data for powder that has maximum performance and velocityat 100%
case density.

Next I load 3 rounds ,each with different powder charges starting midrange and moving
up to Max listed load by .5 gr increments.

Repeat the process with the next best powder listed.

Now its off to the range to test the loads. Make a log and keep very good records on all the
test loads (Even the bad ones) they will come in handy later on.

Start with the lowest loads and work up using the crony.

I eleminate based on bad SDs sometimes with only 2 shots and save the other rounds for
fowling shots or pull the bullets and reload to save the brass from to many firings.

Once you find good Standard deviations then zero in on powder charge,seating depth,primer,
even bullet type (Same weight).

With out good SDs you will never have good groups at long distances because this is the load
burn consistancy and with velocity changes vertical and horizontal stringing will drive you crazy
even if everthing else is good .( Like bedding ,barrel twist ,trigger pull ,ETC.

This process has saved me many rounds of testing and lots of brass over the way I use to do
my load development.

So now I some times luck out and find a realy good load after only25 or 30 rounds down the
tube but sometimes tweeking to get the very best load can add another 20 or so rounds to
the process.

Be patient and it will come.

Just the way I do load testing
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Unread 04-04-2009, 06:28 PM
Platinum Member
Join Date: Jan 2005
Location: OK
Posts: 2,132
Re: How many rounds to develop a load?

Did Clarence give you a report on what he found in the bore?

Was the chamber and throat concentric with the bore? doubt it but maybe you got lucky. Was the rifling defect free, from end to end? I assume he skim coated the action to stock and recrowned the muzzle? Lapped the lugs?

It helps to know some of the challenges you need to overcome.

Before I did any load work I would do my best to brake in the factory tube. Minimum 10 shoot and cleans 20 would be better.

I would pick an accurate bullet, work with that and 2 sutable powders to start.
Find your max oal to touch lands and back off .025". Load up 7 rounds of each with a powder charge that falls dead center between book starting charge and max charge. With a bone clean bore fire two foulers off the target and the next 5 for group, clean and do the same with the load of a different powder.

If one powder shows promise, work with the charge weight up or down a 1/2 grain or seating depth .010 in or out.

If those 25 or so bullets don't give you a direction to head, re load the brass, neck sized only and use the exact same oal and powder weights as the original 2 loads. Sometimes the neck sized brass will shoot in the same load that wouldn't shoot in a piece of new brass, somtimes it may be exactly the opposite.

This will give you a good start to a promising load, If you get to 200 rounds and nothing meets your needs, get a new barrel!!! OR save yourself the frustration and get a new barrel now.
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