“Your groups are too small” vs barrel life

[nksmfamjp]

If I get the Hornady theory of group building, it sounds like shoot larger sample sizes to more precisely determine the accuracy of the load in the barrel.

So, you need to shoot something to find pressure, right. So you have to shoot ~30 to determine this, especially shooting non-std cartridges, oal's and jump distances.

Then you would shoot 20-50 round groups to set powder charge for the bullet. Then seating depth. Then primer type, Then neck tension, then crimp, then primer depth, then repeat for several bullets to get match level results.

Doing all this for several bullets and what are we talking 1000 rounds of barrel life? How much is left for match shooting. Does this mean I can develop on one barrel and apply results to the next 2-3 barrels? Maybe.

The other side develops off 3-5 round groups, gets to a load in under 300 rounds, but struggles with things like load tune at long range, load tune range to range, other issues. The one thing this group doesn't do is chase results and then running out of barrel life.

How do you combine the 2 to get a "best value"?

 

[Mike D Texas]

It really depends on your standards for the rifle. If you have a 1/2MOA expectation from the rifle, if even 2-3 round groups exceed that, you are wasting time, components and barrel life if you keep shooting.

If your expectation is 1 MOA then there may be validity to more shots.

 

[DUCKMAN11]

I don't think the hornady method does anything but sell more bullets! 2 shots is all you really need for a particular load. If it won't shoot sub moa with 2 shots.....3 ain't gonna make it better. Yes your sample size will be larger therefore your data will be more accurate. But im not shooting groups to shoot groups. I'm developing a sub moa hunting load.

I'm finalizing an 80gr ttsx load in my 25-06. I did a 10 round pressure ladder starting with a medium load of H4350 and imr4350. I went up in .5gr increments past max charge without pressure signs. I found a large 1gr node 1gr over max book pressure. there's 20 shots.

Imr4350 was faster so I've loaded 3 of each powder charge from 1gr over max book to where I stopped before. There's 30 shots....10 .1gr increments for 3x

50 total so far. Would have been 40 had I known imr4350 would give me more speed or I only had 1 powder.

Found an accuracy load at 1.7gr over max book. Shot a 3 shot clover leaf.

CBTO has remained the same throughout testing. I Might do seating depth testing but I doubt it. Just depends if I can replicate the clover leaf load without changes.

Neck tension is at .004" and won't change.

I'm not saying it's dumb to do all the primer and tension and seating depth and everything else you mentioned for "benchrest accuracy". Those guys are shooting for groups or score. As a hunter I'm shooting for hamburger. You can definitely dive off in the weeds on tuning a load!! But knocking a .1" off a group at the expense of consumables for a hunting rifle is unnecessary.

 

[Grizzman47]

20 to 50 round groups? I've never heard of a person doing this.

What's the source of this info?

Barrels are unique. A load worked up for one barrel has no certainty of delivering acceptable performance in another. One load isn't even likely to give optimum performance throughout a barrel's life due to throat erosion.

 

[memtb]

20 to 50 round groups? I've never heard of a person doing this

That was "sort of" addressed in part of the thread over in the "Long Range Hunting & Shooting" section……"A Compliment to the Forum and a Little Humor"! memtb

 

[willfrye027]

I am in the hornady camp on this one, but I think you are missing a couple of their key points. When you actually shoot a statistically relevant group size (20+), it turns out that changes in seating depth and powder charge are either very minor and insignificant, or nonexistent at all. This is with modern cartridge design and their bullets (applies to others of similar ogive design), but has been broadly applicable for me.

Knowing that, it is better to change powder and/or bullets rather than constantly tinker with seating depth and powder charge. If a few different combinations are not achieving results; you cut losses and rebarrel. Keeping in mind that a true 1/2" gun is a unicorn in all but benchrest disciplines.

In my current 25 creedmoor barrel I arrived at a final load in about 30 rounds. 10 to find pressure, and then two different 10 shot groups to confirm it was a shooter. It will do 10 shots into 1" without fail, 600 rounds down the barrel and nothing has changed. I could cherry pick some tiny 3-5 shot groups that look impressive but the reality is that it's a 1" gun across many conditions and range days which is very good.

The hornady method results in LESS rounds to find a load, done properly. This means more rounds actually shooting and practicing which makes for a better shooter in the long run.

If you are in disbelief (i was), try shooting two 10-20 shot groups with a completely different powder charge or seating depth. You will find any difference to be small, and not repeatable assuming you are below max pressure with both loads. If you shoot a pressure ladder at the same POI, you will even find that the group size is remarkably close to the group size of your final load..