Bullet choice vs bushing choice

[Okanogan]

I'm am thinking trying to string multiple bullet choices along during load development may lead to questions not often posed in our community.

Case in point new 6.5 SAUM. I have tired Berger 156 EH which seem happy with a .292 bushing for my AGD brass. I have also tried Berger 140 EH which seem to really prefer .291 bush though they seem to tolerate a .292 bushing if I didn't mind the bullet dropping 1/4-3/8" into the neck before it starts to hold tension. Today I got a box of 153.5 Target hybrids that I want to try out. They fell through the .292 sized brass and wouldn't hold tension with the .291 bushing. They seemed fine with my .290 bushing. I get that the Hornady bullets seem to have varying resistance to the .292 bushing I was using and that it might suggest I should be using a .291 bushing for everything if I wanted to be conservative/ safe. All the above is new virgin ADG which seems pretty consistent, and different similar bullets of the same box seem to seat pretty much alike perhaps with-in 0.001 tolerance so I am not suspecting the ADG brass but rather differences in the bullets as I change design.

I was under the impression that selecting a bushing was mostly dependent on what the case wall neck thickness was. That isn't what I have seen with my recent load development efforts and I'm mostly concerned because the differences seem to come from the same bullet manufacturer, which surprises me. Anyone have similar experiences, particularly with the 6.5M 153.5 target hybrids which seem to be the worst offender for me?

 

[Tiny Tim]

Is the "tail" just ahead of the boat tail on the target hybrids "tapered a little? If so, that may explain it going in a little farther before gripping the neck. I believe your assertion that bushing size ought to be dictated by neck wall thickness and "spring-back". I could see one bushing size difference, but 2 on virgin or once fired seems odd, especially with a consistent bullet manufacturer. Certainly someone more knowledgeable than i will chime in.

 

[Mikecr]

If you really think it's a problem with bullets, why don't you measure them and confirm it..

 

[Okanogan]

For the 153.5 Hybrids, it is two bushing sizes on virgin ADG brass. It isn't just the boat tail, the entire bullet will fall into the case if I use the .292 bushing I was using for the 156 EH. I sized some brass to accept the 153.5 and they shot well today so I don't think the 153.5 Hybrids are a problem. I just have never had to pick bushing size to suit the bullet rather than the brass before. E.g., I'm used to changing out bushings when I go from Norma brass to Lapua brass for my .308.

As for measuring the bullets, I figure my accuracy in trying to mic it is probably +/- 0.001 so I just assumed the prescribed bushing size would be slightly more accurate than my ability to measure. The bushing sizes seem okay to me because I can notice a difference each time I reduce one step in size.

I was just wondering if anyone else had encounter similar situations.

Not really germane to the thread but I think Long Range Ballistics volume 2 indicated that the level of neck tension wasn't a big factor in ES/SD. While this may run counter popular belief, if it's true I should just be able to run the smaller bushing during resizing and get by with either bullet.

 

[Mikecr]

Well if you did measure the bullets, you would find it's not the bullets -and that bullets make no difference to bushing selection after all.

You can measure loaded neck ODs right?
Then bushing makers suggest -2thou of this, and that's what you have, right?

 

[Okanogan]

Measuring case necks with seated bullets and taking 0.002 is what got me to the .292 bushing I used for the 156EH. That bushing worked just fine for the 156EH and still does. It will not work with the same virgin brass for the 153.5 Hybrids.

I mic'd the 156 EH bullets and got 0.264 - repeatedly. I mic'd the 153.5 hybrid bullets and got 0.2635- repeatedly. Does that account for 2 bushing size differences to get the 153.5 hybrid to seat- no. I probably measured wrong because 6.5mm bullets are all the same diameter, right?

What I measure doesn't mean as much to me as whether or not the bullet will stay seated properly. Rightly or wrongly, it takes a smaller bushing for me to get the 153.5 Hybrids to stay seated. Will that hold true for the next box of 153.5 hybrids? I'll find out when they arrive because they shot well enough I ordered more.

 

[cohunt]

have you measured the OD of the bullets yet?
are you turning brass necks?
other way to do it is to use a bushing 1-2 thou less than what you want then use a mandrel to open it back up to exactly the right diameter

 

[Mikecr]

Ok, we may be getting there.
The really weird part is going .292 through .291 bushings and it's still not enough to grip the 153.5gr bullets.
Even the bullet, seemingly out of spec, is not 1thou out. You confirmed that much.
So there an unknown going on with your bushing sizing.
What kind of neck expansion is in play?

 

[Okanogan]

I just loaded up some more 153.5 Hybrid and some 156 EH for the range tomorrow. My current theory is that it is probably a number of factors. I mic'd numerous 153.5 and 156 loads after they were seated in virgin ADG brass, The largest 156 EH case neck reading was .294 which would have led to my original bushing choice of .292. However, I did get case neck readings on the 156 EH loads down to .293.
The 153.5 Hybrids were a different story, I never got a reading above .293. I got numerous readings at .292 with some numerous also at .2915. I'm thinking part of the story is ADG brass and part of the story is the 153.5 Hybrids being slightly smaller diameter. I also think the ADG brass is harder and may not always spring back the same. I actually had a problem getting some of the 153.5 bullets to seat in the re-resized brass which may allude to spring back issues, especially with twice re-sized virgin brass.
I have not turned the necks on the brass. Last time I tried, I screwed up the brass beyond its original variation. I opened all the original virgin brass with a K&M mandrel before I resized it the first time.

 

[cohunt]

Have you tried measuring neck thickness?

 

[Tiny Tim]

Sounds like neck wall thickness variations combined with different bullet sizes. Can you measure neck wall thickness? Is all of your brass from the same lot? Perhaps you have different lots and you have the worst possible tolerance stacking combination? Neck turning may clear this up. I use the Sinclair tool. Works well and relatively quick.

 

[Okanogan]

I have not tried measuring neck thickness. All the brass came from the same ADG lot and for the next 100 rounds or so it'll continue to be virgin brass. I have previously tried measuring neck wall thickness on other cases but found I got poor repeatability with just my standard calipers. I'm trying to avoid going the neck turning route as I did poorly on it in the past and think it would take something like 21st century set up before I could do a decent job at it- and for what ADG brass costs, I don't want to experiment with it.
Current plan is get some smaller bushings for the few times I have further seating problems with the 153.5 Hybrids. For the 1st time at the range, the Hybrids seem to offer some potential on paper and if they continue to do so without a lot of extra effort, then I'm happy enough to work around what seem to be some quirks with my set up/ components. I would definitely rather be shooting than turning necks.
View attachment 195991

 

[twister]

you need a ball micrometer to get good neck measurements.

Is your bushing floating? Have you measured your sized necks to see if its consistent?

 

[Okanogan]

I don't have a ball micrometer so didn't attempt to measure neck thickness. I measured necks with seated bullets and they varied as noted above. I'm sure the bushing is floating as I back it off and can just hear a little rattle when shaking the die.