Bushing Sizing Question

[Sheldon N]

So I'm working on fine tuning neck tension in multiple calibers using Redding full length bushing dies and am running into the issue where my resulting neck size is smaller than the chosen bushing would suggest. I know this is something that Redding indicates can happen when you size down more than .008 - .010 in one step, but I'm not sizing that much but am still seeing the same outcome. Here's what I've got on two different calibers, no expander ball used just the bushings.

308 w/ unturned Lapua brass, annealed every firing: Loaded round .338, Fired case .341. .337 bushing gives a .3355 neck size.

280AI w/ unturned Remington brass, annealled every firing: Loaded round .311, fired case .315, .309 bushing gives a .307ish neck, with some variation case to case.

Do any of you observe this same phenomenon?

Its got me heading towards reinstalling the expander ball for the 280AI to give a more consistent inner diameter and neck tension since I'm not turning necks.

 

[Dusty Stevens]

Let me go with just one here. On your 280ai you get a 307 nk after sizing but loaded its .311? Does a 310 bushing still give you 311 loaded? With as many variables are involved in brass and bushings i dont think you have a problem just go bigger if you have too much tension. You have plenty of clearance so just roll with it.

 

[jcampbellsmith]

I have a range of bushings and if the bushing I pick sizes too much, I try the next larger bushing. I don't get too concerned about the measurements. I focus on getting case necks that will securely hold the bullet.

Regards JCS

 

[msinc]

The whole purpose of these type dies is to size the brass the least amount possible and to get lower neck tension. If you just want a tight bullet why not use regular dies??? Trying to make the bullet tight in the neck has another problem with these dies. Biggest problem for using these type dies to me is that if you go too tight the die puts inconcentricity into the case. I have a 208AI and I got a bushing die from a guy who just said "I don't like it"...it came with 307, 308, and 309 bushings. All proved too tight. As I understand it you mike the neck of a loaded round {in my case .311"} then choose a bushing .001" under that {.310"} anything more and the neck was .002" out of whack to the case.
Suggest you try a bushing .001" under what the loaded neck mikes and check for concentricity...once the cases were knocked out of whack a bush type die will not correct them. At least mine wouldn't, I had to resize in a regular die first and then go back to the bushing setup.

 

[Shynloco]

The whole purpose of these type dies is to size the brass the least amount possible and to get lower neck tension. If you just want a tight bullet why not use regular dies??? Trying to make the bullet tight in the neck has another problem with these dies. Biggest problem for using these type dies to me is that if you go too tight the die puts inconcentricity into the case. I have a 208AI and I got a bushing die from a guy who just said "I don't like it"...it came with 307, 308, and 309 bushings. All proved too tight. As I understand it you mike the neck of a loaded round {in my case .311"} then choose a bushing .001" under that {.310"} anything more and the neck was .002" out of whack to the case.
Suggest you try a bushing .001" under what the loaded neck mikes and check for concentricity...once the cases were knocked out of whack a bush type die will not correct them. At least mine wouldn't, I had to resize in a regular die first and then go back to the bushing setup.

Agreed! AS an aside, I've gotten into the habit of annealing my .308 brass AT LEAST, every third shooting to make sure the "spring back" feature of using neck bushings is alive and identical in each piece of brass.

 

[Sheldon N]

Yes, I've already been moving towards larger bushings on both calibers in the hopes of having a lighter neck tension. With the 308 I'm using a bushing just .001 under a loaded round and it's only a .004 reduction from a fired round, but I'm still ending up with a neck that gives me .003 in tension which is more than I want. The next step up would be to use a .338 bushing... the same size as a loaded round.

On the 280AI it might make sense to go up to a .310 bushing, however I wonder if perhaps I'd be better off spending the money on something like a Lee collet neck sizing die (two step sizing, collet for the neck and Redding full length w/ no bushing for bumping shoulders), or perhaps just use the expander ball. My main goal is consistent neck tension, and I wonder if these might end up being better for that since I'm not neck turning and the RP brass isn't known for having the most consistent neck thickness.

 

[lawman29]

Another idea: Get a Sinclair expander die and an expander mandrel and neck mandrel for your calibers. After sizing brass run 5 through expander and another 5 through neck. Load and test.

 

[bugman]

Yes, I've already been moving towards larger bushings on both calibers in the hopes of having a lighter neck tension. With the 308 I'm using a bushing just .001 under a loaded round and it's only a .004 reduction from a fired round, but I'm still ending up with a neck that gives me .003 in tension which is more than I want. The next step up would be to use a .338 bushing... the same size as a loaded round.

On the 280AI it might make sense to go up to a .310 bushing, however I wonder if perhaps I'd be better off spending the money on something like a Lee collet neck sizing die (two step sizing, collet for the neck and Redding full length w/ no bushing for bumping shoulders), or perhaps just use the expander ball. My main goal is consistent neck tension, and I wonder if these might end up being better for that since I'm not neck turning and the RP brass isn't known for having the most consistent neck thickness.

The first thing is to recalculate/consider some of what you stated above about the 308. If you are "using a bushing just .001 under a loaded round", then you DO have @ .001 neck tension.....if (big if) the measured OD of the sized neck is truly .337 and the measured OD of the loaded neck is truly .338. Don't concern yourself with the fact that a fired neck OD is .341 because you have no control over the neck chamber OD. Besides, that .004 difference is pretty good.

Here are a few things to at least consider....none of them alone will give you a quick and easy answer.

1. bushing inside diameters often vary from the number that is stamped on the bushing. Sometimes another new bushing with the same stamping (or a friends) will give you a different sized neck OD. Inverting the bushing can often give you a different sized OD. You can see how just these things alone might help you find the tension you want.
2. it is hard to really get into fine tuning neck tension if you are using calipers. A micrometer is needed for really accurate numbers, if that is what you seek.
3. annealing can help keep your neck tension more consistent over repeated firing by keeping spring back within bounds.
4. if you are not going to turn, Lapua brass will usually trump Remington brass for more consistent neck brass thickness. When you seat that bullet, all the neck thickness differences get pushed to the outside surface.....maybe this is causing some of your inconsistent seated neck OD numbers?
5. the hard truth is that people go thru the hassle of turning necks to make neck tension more controllable and more easily adjusted. It is your decision to not turn, but you can't expect the same measurement consistency as people that do turn.
6. FWIW, I agree with an earlier poster who said you should just roll with it. Get this tension issue as close as you can, and then spend your energy on charge weight, seating depth, component tests, etc.

Jack

 

[Sheldon N]

The first thing is to recalculate/consider some of what you stated above about the 308. If you are "using a bushing just .001 under a loaded round", then you DO have @ .001 neck tension.....if (big if) the measured OD of the sized neck is truly .337 and the measured OD of the loaded neck is truly .338. Don't concern yourself with the fact that a fired neck OD is .341 because you have no control over the neck chamber OD. Besides, that .004 difference is pretty good.

Here are a few things to at least consider....none of them alone will give you a quick and easy answer.

1. bushing inside diameters often vary from the number that is stamped on the bushing. Sometimes another new bushing with the same stamping (or a friends) will give you a different sized neck OD. Inverting the bushing can often give you a different sized OD. You can see how just these things alone might help you find the tension you want.
2. it is hard to really get into fine tuning neck tension if you are using calipers. A micrometer is needed for really accurate numbers, if that is what you seek.
3. annealing can help keep your neck tension more consistent over repeated firing by keeping spring back within bounds.
4. if you are not going to turn, Lapua brass will usually trump Remington brass for more consistent neck brass thickness. When you seat that bullet, all the neck thickness differences get pushed to the outside surface.....maybe this is causing some of your inconsistent seated neck OD numbers?
5. the hard truth is that people go thru the hassle of turning necks to make neck tension more controllable and more easily adjusted. It is your decision to not turn, but you can't expect the same measurement consistency as people that do turn.
6. FWIW, I agree with an earlier poster who said you should just roll with it. Get this tension issue as close as you can, and then spend your energy on charge weight, seating depth, component tests, etc.

Jack

Thanks for the reply... I'll try to respond to the issues you raised.

Overall, the main reason for my post was my confusion/frustration with NOT getting the resulting neck tension that I should be getting given my bushing selection. You say that I have .001 neck tension because I'm using a bushing that's .001 smaller than a loaded round (.337), but what I'm actually getting is .003 neck tension (.335 neck). I only bring up the dimensions of a fired round so that you know how much I'm stepping down with my chosen bushing.

To your specific points...

1. I've measured the ID of all my bushings for all calibers, they are all good. The .337 bushing is maybe actually a .3365 bushing, but close enough.
2. I've got a good set of calipers that are giving me consistent measurements in all my reloading processes, I do trust the numbers. I wouldn't try to use them to measure thickness of brass case neck walls, but for measuring OD of an entire case neck they work fine.
3. All this brass is annealed every firing, as noted in my OP.
4. I definitely think about this... has me leaning towards using the expander ball on the Remington 280AI brass to push inconsistencies to the outside of the neck. For the more consistent 308 Lapua brass I'm more comfortable fine tuning with bushing selection and no expander.
5. Now that's the heart of the issue.... me trying to avoid neck turning.
6. Already spending energy on the other things and feel that I've got a decent handle on most of them. Neck tension is the forefront issue I'm working on currently.

The overall crux is that my bushings are giving me a resulting size that is roughly .0015- .002 smaller than the bushing size itself.

I haven't seen other people comment on this so was curious if this was common or if I'm getting unusual results. If this is uncommon perhaps I'm doing something wrong with my annealing making the brass too soft, or potentially some other cause?

 

[Brians356]

1. I've measured the ID of all my bushings for all calibers, they are all good.

That surprises me. I have a large number of Redding bushings, and most of them gauge considerably tighter than their nominal sizes, up to a full ~.001" smaller. I gauged them all using pin gages, which have themselves been checked with two different .0001" micrometers. As far as I'm concerned no Redding bushing can be used blindly at face value.

The .337 bushing is maybe actually a .3365 bushing, but close enough.

That's what I'm talking about. Being as "little" as .0005" too small is unacceptable, and in my experience they are often even farther off than that.

 

[/VH]

Sheldon N,

I am thinking that the inconsistent neck wall thickness of your unturned brass is causing some of the issue you are having as you force the variance to the inside with the bushing and then back to the outside with the bullet. Then firing in a concentric chamber places it back to the inside.

 

[Nude nut]

I purchased bushing dies with the intent of neck turning I have all the neck turning equipment just havent taken that step yet.
I went through the same issues with them as many do that you read in forums this is what works for me with unturned lapua 308 brass
first polish the expander ball or replace with carbide expander ball.
My process,
With expander ball.
Deprime with .340 bushing
Anneal
Sonic clean
Size with .338 bushing trim brass to length
Polish inside neck
Dip neck in graphite or spray oneshot
Size with .337 bushing it barely touches neck just enough to push everything to the OD
Prime load charge and seat bullet I put my projectiles in ziplock bag and spray oneshot in there pull out to dry before seating.
With sizing I also have just sized down with bushing die and used sinclair expander die and mandrel with good results.
Works for me might not be your cuppa tea but im not a high volume reloader.

Cheers Trev.

 

[Nude nut]

Sorry forgot to mention this is for nk sized brass.

Cheers Trev

 

[Sheldon N]

Sheldon N,

I am thinking that the inconsistent neck wall thickness of your unturned brass is causing some of the issue you are having as you force the variance to the inside with the bushing and then back to the outside with the bullet. Then firing in a concentric chamber places it back to the inside.

I guess I should clarify... the Lapua .335 sized diameters are without a bullet seated. Once I load a bullet in the case it goes back to being .338 OD. The Lapua brass seems pretty consistent with neck thickness as I measure around different points on the loaded neck. It's the Rem brass that's got more of an inconsistency in thickness.

 

[savagedasher]

I only shoot bullets that like to be jumped so neck tension is never a issue. Larry

 

[/VH]

I have a large number of Redding bushings, and most of them gauge considerably tighter than their nominal sizes, up to a full ~.001" smaller.

brian356,

Are the bushings that gauge considerably tighter coated?

 

[/VH]

I guess I should clarify... the Lapua .335 sized diameters are without a bullet seated. Once I load a bullet in the case it goes back to being .338 OD. The Lapua brass seems pretty consistent with neck thickness as I measure around different points on the loaded neck. It's the Rem brass that's got more of an inconsistency in thickness.

Sheldon N,

FWIW, with my out of the box Lapua 6.5x47 brass, neck wall thickness typically varies .001" to .0015".

 

[mikecr]

308 w/ unturned Lapua brass, annealed every firing: Loaded round .338, Fired case .341. .337 bushing gives a .3355 neck size.

Ok your attempted downsizing is 4thou and you're ending up with ~1.5thou too much.

280AI w/ unturned Remington brass, annealled every firing: Loaded round .311, fired case .315, .309 bushing gives a .307ish neck, with some variation case to case.
Do any of you observe this same phenomenon?

Your attempted downsizing is 6thou and you're ending up with ~2thou too much.

This happens to me with some combinations, and while not a desired end result, I think it's common enough to consider a couple bushing sizes on ordering. On many occasions 5thou & greater means greater downsizing than stamped on the bushing. This is due to greater angles created in the sizing. That is, the brass is turning inward at a greater angle, and brass angled (in new form) springs back less to previous parallel form.
Speaking of spring back, you divulged two spring back contributors to your results: constant annealing, and no expansion.
Where you were ~1.5thou greater in sizing result, normal spring back of nearly 1thou would have put you only ~1/2thou greater sizing than desired. With normal expansion + normal spring back from that, you likely would have ended up right at 1thou under(as expected).
Where you were ~2thou greater in sizing result, the same applies, AND you're attempted sizing was higher than 5thou anyway, so a larger bushing was in order to begin.

With normal ~1thou under interference, you'd adjust tension with LENGTH of neck sizing.
There is absolutely nothing wrong with bushing dies. It just takes a bit of thought, and sometimes a bit of trial & error to set them up correctly. But then again, it's that way with all dies. Right?

 

[Dusty Stevens]

I like the CRT bushings for all that i dont use a carbide one for

 

[Sheldon N]

Thanks mikecr, that's really great info and some good perspective to consider. Thanks also to the others who've provided valuable input.

I'm leaning towards both adding larger bushings to get the desired sizing, and might also try some load testing with a polished expander vs no expander. I imagine there's not going to be much effect on concentricity to have the expander just kissing the case neck on the way out, and it might help with the any neck thickness inconsistencies. Results on paper will tell the story, ultimately.

Of course this is all just a step on the pathway to the inevitability of neck turning.