NECK BUSHING TEST 30BR

[gunsandgunsmithing]

@Bill Norris test made me want to test a 0.323” bushing. I had already tested 0.325 and 0.324 bushings, wth 0.324 being the best. Today I compared 0.324 and 0.323.

30-BR, 0.332 Neck, 17 twist Krieger, long range stock (15.2 lbm total weight).
ARC Nucleus action with a Trigger Tech Diamond trigger at ~ 10 oz.
Lapua 6BR brass skim turned to 0.012” max thickness.
Brass annealed after every firing, has been shot 12 times.
35.5 gr VV N130, 118 gr 7 ogive Bibs, CCI 450, seated 0.004” jamb, using a Wilson seater.
70 F, no mirage, 7 mph switching tail wind.

I shot four, 4-shot groups so I wouldn’t have to process my brass again before my next match. The 0.324” bushing is still the king for my rifle, long live the brass!

I'd double check your neck and chamber clearance dimensions.
.012x2=.024
Plus minimum of .308 bullet diameter=.332...or zero clearance.

 

[6ShotsOr5?]

I'd double check your neck and chamber clearance dimensions.
.012x2=.024
Plus minimum of .308 bullet diameter=.332...or zero clearance.

I think I should have said turned to 0.011”. Thanks.

 

[danyboy]

@Bill Norris test made me want to test a 0.323” bushing. I had already tested 0.325 and 0.324 bushings, wth 0.324 being the best. Today I compared 0.324 and 0.323.

30-BR, 0.332 Neck, 17 twist Krieger, long range stock (15.2 lbm total weight).
ARC Nucleus action with a Trigger Tech Diamond trigger at ~ 10 oz.
Lapua 6BR brass skim turned to 0.012” max thickness.
Brass annealed after every firing, has been shot 12 times.
35.5 gr VV N130, 118 gr 7 ogive Bibs, CCI 450, seated 0.004” jamb, using a Wilson seater.
70 F, no mirage, 7 mph switching tail wind.

I shot four, 4-shot groups so I wouldn’t have to process my brass again before my next match. The 0.324” bushing is still the king for my rifle, long live the brass!

Why substrat .290" instead of .308" when calculating group size?

 

[danyboy]

Bill, the next time you're testing, you may want to try this. Once I find something that shoots dots at 100, I load 15 rounds and shoot a group. This is a good indicator of not only how stable the load is but also how stable your 'zero' (center of the group) is.

For what it's worth... -Al

Why substrat .290" instead of .308" when calculating group size?

 

[AlNyhus]

.290 is the size of a single bullet hole in this target paper. The .290 becomes the 'standard' to subtract when measuring group size rather than the actual bullet diameter. -Al

 

[6ShotsOr5?]

.290 is the size of a single bullet hole in this target paper. The .290 becomes the 'standard' to subtract when measuring group size rather than the actual bullet diameter. -Al

Thanks Al, learned something there. Do you have similar hole dimension info for other calibers?

 

[liljoe]

Just measure a single bullet hole. Down on the sighter. Here is an example. This one won't measure .243"
Joe

 

[liljoe]

Here is another one to compare. Same target. Which one is in tune?

 

[RGRobinett]

Here is another one to compare. Same target. Which one is in tune?

Different paper "grades"(types) and [surface] finishes result differing hole sizes - per Al & Joe,, simply measure a single hole and subtract that measurement from the outside edges of your group. RG