NECK BUSHING TEST 30BR

[RegionRat]

I think that if you do a statistical analysis, you will find that there is a high confidence level that there is no difference in these groups. When variances are small it takes a lot of data to say that A is different than B. Mother Nature is a bitch.

You have a point to a degree. In most sport shooting or where testing experience is low, most folks get confused when their results don't repeat and the reasons are as you suspect. Outdoor accuracy and precision testing is always subject to the climate and the tune.

When we are talking about short range BR, several of the top shooters may win on any given day due to a combination of luck with the winds and to the point you are making.

In Bill's case, he will follow up with enough tuning tests to know the difference because of his experience.

 

[Bill Norris]

Bill - I think what he's asking is akin to had you fired 4 x 5-shot groups using solely the .324" bushing load, would the target have looked about the same? Or would all 4 groups have looked just like the single .324" bushing group on the target you posted (i.e. all very tight)? In other words, might some of the size variance in the groups shown simply be due to shooter error (or some other variable) besides neck tension?

This is a difficult question to answer. It is not uncommon to find "discussions" at shooting forums about 3-shot groups versus 5-shot; or questions regarding just how many shots are necessary for a group to have some statistical relevance. Personally, I've been doing seating depth testing using 3-shot groups for a long time now. In my hands, 3-shot groups for that purpose seem to be just as telling/revealing as 5-shot groups, because I test exactly as I shoot in matches, from a bipod, and it's not uncommon for me to jerk the trigger on occasion when doing 5+ shot groups, thereby wrecking the group I was shooting. So using larger group size is often more about testing my consistency, rather than the load development itself.

I would imagine with the 30BR off a solid front rest that you are able to shoot groups like the .324" bushing very consistently, so if you had fired 4 x 5-shot groups solely using the .324" bushing load, there would have been 4 very tight round groups on the target, rather than one tight group and three that had opened up a bit as seen with the other three diameter bushings.

Thanks for posting these results! I have always tried to target somewhere in the neighborhood of 1.5 to 2 thousandths neck tension with my F-TR .308 Win and .223 Rem loads. After seeing your results, I'm thinking a little more experimentation with neck tension might be in order.

Thank you very much for the explanation. I normally do 3 shot groups as well. I just thought on this test I'd try 5-shot groups just in case I did pull one or feel something funny on the rest. As it turned out I feel all shots were as consistent as I am capable of shooting.

 

[Bill Norris]

You have a point to a degree. In most sport shooting or where testing experience is low, most folks get confused when their results don't repeat and the reasons are as you suspect. Outdoor accuracy and precision testing is always subject to the climate and the tune.

When we are talking about short range BR, several of the top shooters may win on any given day due to a combination of luck with the winds and to the point you are making.

In Bill's case, he will follow up with enough tuning tests to know the difference because of his experience.

Thank you for the vote of confidence Bro. I do plan to test this further to see if it duplicates but in different temps and conditions. I don't have a tuner on this rifle.

 

[RegionRat]

I'm looking forward to the range and match reports.

As many words as the Queen's English has, there are still too many that have multiple meanings. I meant "tune" as in the whole recipe and system, regardless of the use of a barrel tuner or not. Your follow up testing will cover the points chkunz mentioned. He wasn't wrong, but there is also practicality and experience at play.

 

[gunsandgunsmithing]

Some say if u jam neck tension don't matter.

Think their opinion through a little bit. Neck tension determines the amount of jam you can attain...within reason. Right? And jam is a big factor in starting pressures ands pressure curves..Right?

 

[Bill Norris]

Think their opinion through a little bit. Neck tension determines the amount of jam you can attain...within reason. Right? And jam is a big factor in starting pressures ands pressure curves..Right?

Rightly so.

 

[sqrlgtr]

Just out of curiosity, what is your necks turned too, assuming their turned?

 

[Bill Norris]

Just out of curiosity, what is your necks turned too, assuming their turned?

Turned to .098 My loaded round neck dia is .3275. Chamber is .330.

 

[sqrlgtr]

Turned to .098 My loaded round neck dia is .3275. Chamber is .330.

Thanks, almost same as mine (turned .010 neck dia .327 with .330 chamber) and I settled on the .325 bushing. I have several firings on my brass now and had thought about testing bushing size, but still getting great accuracy so probably want gain anything. I know want never know tell you try it....

 

[Olde Man]

Bill what is your velocity on your 34.7 load?

 

[AlNyhus]

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

 

[JimPag]

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

Ya but Al. Your shooting one of Craig's barrels. Thank God I have 3 left with very low round counts and one blank. Never saw a Kostyshyn that didn't shoot lights out. LOL.

 

[AlNyhus]

Ya but Al. Your shooting one of Craig's barrels. Thank God I have 3 left with very low round counts and one blank. Never saw a Kostyshyn that didn't shoot lights out. LOL.

They weren't always straight but they always shot! -Al

 

[Dusty Stevens]

Ya but Al. Your shooting one of Craig's barrels. Thank God I have 3 left with very low round counts and one blank. Never saw a Kostyshyn that didn't shoot lights out. LOL.

My 30br has one and yes it does.

 

[Bill Norris]

Bill what is your velocity on your 34.7 load?

I have not chronoed it but I will next time out

 

[Bill Norris]

A

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

Absolutely. I have shot 10 shot groups with the .324 bushing that were sub quarter inch.

 

[AlNyhus]

Ya but Al. Your shooting one of Craig's barrels. Thank God I have 3 left with very low round counts and one blank. Never saw a Kostyshyn that didn't shoot lights out. LOL.

It hurt to turn one of my last Kosty's into a f-form barrel for our WolfPup. But it was past it's prime and sacrificed itself for a higher cause.....

Good shootin' -Al

 

[6ShotsOr5?]

Shot these four 5-shot groups @ 100 yds. today checking neck bushings. Even with the forgiving chamberings neck tension is vital to tight groups. This was with my go to load in my 30BR with the .324 bushing being the usual for loads.

112 GR. BARTS FB/M 1.585 O M 2.275 COL T/L B S .202
POWDER 34.7 GR. H-4198 PRIMER FED 205M
SEATED @ 1.575 O M 2.265 COL .010 OTL
N/T TEST .326 .325 .324 .323 BUSHING

@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!

 

[Ccrider]

^^^^^^If you get the best tune with a particular neck tension, you may or may not see better results from changing the neck tension. Looking at the horizontal group, I would bet that is more due to the load being out of tune for that particular neck tension, or gun handling one.

 

[Bill Norris]

^^^^^^If you get the best tune with a particular neck tension, you may or may not see better results from changing the neck tension. Looking at the horizontal group, I would bet that is more due to the load being out of tune for that particular neck tension, or gun handling one.

Absolutely thanks Bro, my point in my initial post.