Thread: Shorter Barrel 223 data

Only 30 mm offence in length. While this could make a small difference to velocity achieved with some loads, internal barrel and chamber dimensions, tolerances and finish could be more impactful as you suggested T’man.


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Originally Posted by grandpamac

Greetings,
You would expect a difference of around 30 fps between the two barrels with the longer one the faster all else being equal. All else is seldom equal though. The round count, if known, would be interesting as would has either been chopped?
GPM.

The shorter barrel is brand new, round count is currently 50. The round count on the longer barrel is about 400 (although some of the recorded velocities go back to its "break in" period).

Im thinking of now running a test on the new short barrel to see if the accuracy improves over its break in. I was thinking to load 100 rounds of cheaper components. Shoot a 10 shot group. 10 also of factory as a control. Blast off 20 rounds at gongs/hares etc. Shoot the 10 round tests again. Blast off 20. Test 10. Blast off 20, test 10. This would take the barrel to just over 200 rounds, which is when "the internet" says it should be fully broken in and shooting at its best (for a cheaper factory grade barrel). Thoughts on this guys?

Cheap components would be bulk Hornardy 55s over 748 powder. Id be interested to know if statistically speaking a 10 shot group is enough @gimp etc ??

The barrels are both at factory length. They borescope like factory barrels, nothing like a cut rifled and highly lapped custom grade barrel

I have a new barrel with 92 rounds on it. Precision for 10rd groups appears to be identical now vs when I started shooting it (at about 40 rounds). (Not .223 !!)

Originally Posted by Tentman

Cheap components would be bulk Hornardy 55s over 748 powder. Id be interested to know if statistically speaking a 10 shot group is enough @gimp etc ??

10 shots tends to give you a reasonably good idea of the true mean radius in my experience

Originally Posted by gimp

I have a new barrel with 92 rounds on it. Precision for 10rd groups appears to be identical now vs when I started shooting it (at about 40 rounds).

What is the barrel manufacture?

Originally Posted by Tentman

What is the barrel manufacture?

Brux

Originally Posted by Tentman

The shorter barrel is brand new, round count is currently 50. The round count on the longer barrel is about 400 (although some of the recorded velocities go back to its "break in" period).

Im thinking of now running a test on the new short barrel to see if the accuracy improves over its break in. I was thinking to load 100 rounds of cheaper components. Shoot a 10 shot group. 10 also of factory as a control. Blast off 20 rounds at gongs/hares etc. Shoot the 10 round tests again. Blast off 20. Test 10. Blast off 20, test 10. This would take the barrel to just over 200 rounds, which is when "the internet" says it should be fully broken in and shooting at its best (for a cheaper factory grade barrel). Thoughts on this guys?

Given that bullet-barrel interactions are only one part of the puzzle of dispersion, and bullet quality is another part - possibly larger - this test may not demonstrate anything as far as "testing if accuracy improves"


To see a difference (improvement) in precision of the order that you might reasonably expect (0 - 10 % change in mean radius?) from barrel "break in changes", you'd likely need massive sample sizes to have confidence in the result even if you used good quality bullets and ammunition. What you might demonstrate is that there is no meaningful difference that can be established, so people shouldn't worry about it

Here I am derailing another thread getting on this topic, but it is really sensible to think in terms of "requirements" and meaningfully test whether the system meets those then move on, rather than thinking about precision optimisation without an acceptance threshold


For example these 3 10rd groups (of 3 different powders loaded with the same bullet) are all different sizes, however the precision of all 3 is functionally more or less the same - 0.05-0.06 MRAD mean radius.




I don't actually care if one is "better" than the others. The test is - do they meet requirements? They all do, for precision - the predictive O95 is 0.2 - 0.24 MRAD, but the error bars mean we can't say there's actually any difference. Either of these values meets my requirements threshold - neither of these values produces a meaningful difference in hit probability at long range. I can select the load that meets my other requirements. If they all do, great. Only 1 of these 3 powder loads met all of my requirements. It is the first group below the aiming point dot. Load development completed - off to kill things and compete.

Originally Posted by gimp

I have a new barrel with 92 rounds on it. Precision for 10rd groups appears to be identical now vs when I started shooting it (at about 40 rounds). (Not .223 !!)

No, you cant do that. Its cruel. Reveal.

Here is some velocity data with 2x 16" .223 and my 18" - 3 different loads, all 10rd averages

62gr bullet


Load 1 Load 2 Load 3
18" (mullerworks) 2902 2863 2955
16" 1 (tikka) 2813 2772 2854
16" 2 (trueflite) 2811 2796 2836