Is collet better than full length?

[Bart B.]

essayons21's shown us a good lookin' 3-shot group.

Is that the worst your load shoots? If so, that's impressive.

Does your load shoot that well for 20 shots?

It often happens that folks get better accuracy by neck sizing when their conventional full length sizing die's expander ball bends the case neck too much. Using a full length sizing die that doesn't need an expander ball as it's neck diameter is 1 or 2 thousandths smaller than a loaded round's neck diameter. RCBS and Redding both make these dies that use bushings of different diameters to size the neck.

 

[essayons21]

Of course thats one of my better groups The point I was trying to make is, you can get extreme accuracy out of inexpensive Lee collet dies.

Here's one of my ladder tests (5 shot groups), this is about average. I shoot off a bipod and rear sandbag, so there is a bit of shooter error in there as well.


These are a few targets with factory ammo, and one handload, all shot on the same day.



My first, and so far only group at 550yds


All done with $19.99 Lee Collet neck-sizing die.

 

[Bart B.]

essayons21, any rifle and ammo combination will shoot 3 shot clusters like yours once in a while; it's how often that's important for accuracy.

But your picture with six targets each with 5 shots can be used to see what the near 100% confidence accuracy level your rifle's ammo produces accuracy wise with you shooting it. But this assumes you used the same sight settings for each group.

Take each target and center its scoring rings on a clean one, then pencil point the center of each 5-shot group. You'll end up with a 30 shot composite. Measure the widest two points and that's what your accuracy is near 100% of the time. Each individual 5-shot group only represents what the accuracy is about 17% of the time. You will probably see that the largest 5-shot group is smaller than the 30-shot composite.

 

[essayons21]

I understand the issue with 3-shot groups not being very representative of accuracy. However, consistently producing the same 3-shot groups, with the same POI, is a quick, easier, and cheaper way to determine load and rifle accuracy, and it is less affected by factors such as changing wind and temperature, and barrel heat.

If all 6 groups were with the same load, you would be correct in your statement about creating a 30-shot composite. However, as I mentioned it was a ladder test to determine OCW. You can see the POI move on the targets as the powder charge increases.

Instead of 20-30 shot strings. I shoot 10-shot strings to determine load consistency, I feel that more is redundant as the groups rarely widen any after 10 shots, and it takes forever at the range to let the barrel cool. Even shooting a 1.125" varmint taper barrel, the POI will slightly change as the barrel heats.

Here's a picture I snapped using the same load at the range after I found my OCW (46.7gr IMR4064). From left to right, 5 fouling shots, 10 shot group, 3 shots an hour later to verify fouled, warm barrel zero.


I don't remember the exact measurements on this, but I think its somewhere in the neighborhood of 3/4" for 10 shots including the low right flyer.

EDIT: This is a great discussion but way off topic... it deserves its own thread.

 

[Bart B.]

essayons21, here's why I shoot at least 15 but usually 20 shots per test group:

If your barrel's heating up really causes a change in point of impact, it's not properly stress relieved or has a bad fit to the receiver. Good barrels properly fit don't change point of impact as they heat up.

 

[essayons21]

What is the context of that graph? ... I'm curious to see any associated data.

I've never seen a barrel that has no POI shift from a fouled cold bore to hot. Even national match winning rifles with lilja, hart, and brux barrels still have some shift, even if it is measured in fractions of an inch. This is why benchrest shooters shoot fouling shots through even a dirty barrel.

 

[Bart B.]

The context of that graph is it shows the chances that a given number of shots in a group measured different ways actually represents the accuracy it has. Military arsenals shoot dozens (hundreds?) of shots per group then calculate the mean radius. 7.62mm NATO match ammo has to have a mean radius of 3.5 inches; about 10 inches extreme spread. National Match lots have been down to about 2 inches mean radius.

If point of impact does shift when good barrels heat up, it definitely is "fractions" of an inch; very small fractions. It's been my experience that there's more shift (vertically) from powder fouling in the first few shots from a clean barrel increasing muzzle velocity than barrel heat.

Here's what a whippy 30-inch long Palma rifle barrel does when it gets hot. Shots 1 and 2 were made after a fouling shot was made. The next 8 or so left at a bit higher muzzle velocity due to the barrel getting fouled, then velocity stayed about the same. So it's natural the faster ones will drop less and print higher. All shots fired about 20 to 25 seconds apart with chronograph screen 10 feet from muzzle; 155's leaving at 3080 fps, 21 fps spread.

At 100 yards, this group would have been about 2/10ths MOA.

Some years ago, a friend shot his .308 at 600 yards testing bullets. Several 10-shot groups, each starting from a cold barrel, shooting a shot about every 30 seconds. Those groups ranged from about 1.5 down to .7 inches. He shot another one, 40 shots with a different load, starting with a clean barrel, they all went inside 2 inches at 600 yards.

 

[Clark]

Bart, have you been carrying that group in your wallet?

 

[Bart B.]

Clark asks me:

Bart, have you been carrying that group in your wallet?

No. It's too big. "Wallet" groups shouldn't be more than half an inch across outside edges of the bullet holes.

 

[Clark]

You know, Bart, you could get better groups at closer range.
Then it would fit in your wallet.

 

[Walkalong]

Fly at 100 yards. One shot, one kill.

 

[Bart B.]

Clark comments:

You know, Bart, you could get better groups at closer range. Then it would fit in your wallet.

I agree, but I wouldn't carry one with less than 20 shots in it.

That good lookin' 3-holer you posted looks like eight 5-shot ones I made a few years ago at 50 yards winning a smallbore prone match with a 400-40X score. Got to keep shooting to break the record but my 3rd shot on the first bull fired as the wind gusted from the right; calling it on the left side didn't help either as it just missed the X-ring at 9 by the width of a fly's leg. I used a fly's leg stuck on Walkalong's target as a dimesnional reference.

 

[twofifty]

Great discussion guys, much learning for me here!