NECK BUSHING TEST 30BR

[Bill Norris]

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

 

[mikecr]

You might try adjustment of LENGTH of your bushing sizing (for a finer adjustment).
The area of force applied is easier to control than force changes

 

[6bra1k]

425 seems to have less vertical......
i would consider more work there

 

[stevenpoplin]

You might try adjustment of LENGTH of your bushing sizing (for a finer adjustment).
The area of force applied is easier to control than force changes

So your suggesting only bushing a portion of the neck that the bullet occupies?
Or more of the neck than the bullet occupies?

 

[Bill Norris]

You might try adjustment of LENGTH of your bushing sizing (for a finer adjustment).
The area of force applied is easier to control than force changes

Yea I normally only size a portion of the neck.

 

[mikecr]

So your suggesting only bushing a portion of the neck that the bullet occupies?
Or more of the neck than the bullet occupies?

IMO, you should never size a length exceeding seated bullet bearing, as that would greatly increase tension but also greatly increase tension variance. Nothing is free.
I'm talking about adjusting the actual length of that partial sizing for tuning. This, with a development plan, -instead of excessive neck downsizing.

Let's say your Berger recommended full seating testing lead to a CBTO that puts .200" bearing in necks. You can powder develop with .125" length of bushing neck sizing at a reasonable ~1-1.5thou interference. Later adjust sizing length to potentially dial in better.

 

[BartsBullets]

425 seems to have less vertical......
i would consider more work there

That’s what we call wind sensitive in short range.

 

[BartsBullets]

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

324 looks pretty stout for Five shots. .
Bart

 

[AlNyhus]

Thanks for posting this, Bill. Balancing neck tension/neck clearance/seating depth in the 30's is often overlooked but very important.

Good shootin' -Al

 

[RGRobinett]

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

"And there, you have it." (Louis Lotorto as the Emperor of Austria, in Amadeus) . . . the second KEY to thirty caliber success . . . RG

 

[gunsandgunsmithing]

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

Are you jamming the bullet into the lands a fair amount. I find most small 30's to like a pretty hard jam and most people I know shoot them this way. Point being, more neck tension may be affecting how much actual jam you have vs a bigger bushing, in addition to any benefits of the neck tension on tune.

 

[AlNyhus]

"And there, you have it." (Louis Lotorto as the Emperor of Austria, in Amadeus) . . . the second KEY to thirty caliber success . . . RG

Amen!

As we've witnessed, neck tension can turn a 'ho-hummer' into a 'Holy s&!t...this thing shoots! -er'

"In theory, there is no difference between theory and practice. But in practice, there is." - Yogi Berra

Good shootin' -Al

 

[Bill Norris]

Are you jamming the bullet into the lands a fair amount. I find most small 30's to like a pretty hard jam and most people I know shoot them this way. Point being, more neck tension may be affecting how much actual jam you have vs a bigger bushing, in addition to any benefits of the neck tension on tune.

I didn't jam with this test because I wanted to see the results @ .010 off the lands. Some say if u jam neck tension don't matter. The rifle shoots tighter normally with jam. I recently shot this 5-shot group below with .009 jam.

 

[SVT_Tactical]

Fine shooting

 

[Bill Norris]

Fine shooting

Thank you Bro.

 

[chkunz]

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.

 

[Bill Norris]

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.

Please explain your findings.

 

[chkunz]

Please explain your findings.

Bill, I do not understand what you are asking me to do.

 

[Bill Norris]

Bill, I do not understand what you are asking me to do.

I'm just not sure exactly what your were saying in your statement. how did you arrive at that conclusion? No big deal at all.

 

[Ned Ludd]

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.