Redding bushing die

[RustyRick]

I just got my first competition Redding Dies for my 7mm RM.

So how do I decide which bushing to purchase.

My fired cases are measuring .3125

 

[dok7mm]

You'll need to measure loaded neck diameters, not fired brass diameter, and then pick a bushing .001" to .003" smaller depending on how much neck tension you desire. .002" would be a good starting point. Because neck thickness can vary .001" or more, from thin side to thick side, you need to measure at several points around loaded neck and take an average. The fired neck measurement of .3125' plus .001" will give you the approximate diameter of your chamber's neck. If you have to reduce neck size more than .005" (from fired dia. to .002" neck tension) you may have to have an intermediate bushing to ensure consistent neck tension.

 

[flashhole]

You need to look at more than what you measured.

Is the case neck wall uniform to within .001" all the way around. If no - you should consider neck turning to establish a consistent neck thickness so every piece of brass will be the same. You can't expect good results unless you have addressed the important variables.

The jacketed bullet should measure .284". Your bushing should reduce the interior dimension of the neck wall by .002" - .003" so as to establish a uniform neck tension on the bullet. Again ... the only way to get interior neck tension uniformity is if the neck wall thickness is uniform and the same for all cases.

What is the neck wall thickness of your brass and are you satisfied with its uniformity/consistency case to case?

 

[RustyRick]

For what's it's worth. I measured 10 rounds with Berger VLD-H all seated with my brand new Redding die. Each one measured .307

then I measured 10 shot empties. That were also seated with the same bullet.
0.3125
0.3120 0.3125
0.3100
0.3200 0.3300
0.3110 0.3130
0.3100 0.3120
0.3150 0.3125
0.3125
0.3150 0.3120
0.3130 0.3135

That's how they stack up.

On a side note. I'm amazed that - fire formed the outside dia should be identical. If there is wall thickness differences. That should be on the inside. But the out side should all be the inside of the throat.

 

[dok7mm]

RustyRick, you will find differences in fired neck diameters, even with neck turned brass, due to varying brass spring back. That being said, you will have far better results at longer ranges with uniform neck tension. This can be enhanced by sorting your brass by measuring neck thickness with a ball micrometer or turning case necks to a uniform thickness. A regular annealing schedule will also help you keep consistent neck tension. I'm not sure you are ready to go this far down the rabbit hole with your loading. To answer your original question, you need a .305" bushing for .002" neck tension if your measurements are correct. It also appears your chamber neck is around .315" or .316" , again if your measurements are correct. SO, you are going to be reducing your FIRED neck diameter down to .305" or roughly .010" total reduction. You cannot reduce this far with 1 bushing and expect to get any kind of consistent neck tension from shot to shot. This is a fairly common problem with larger factory chamber necks. To get consistent reductions, you simply have to use two (or possibly three) bushings to get to your final neck size. In this case, first a .310" and last your .305" bushing. It's a PITA, but will give better results than doing it in one step. I use only Redding Comp dies and have had excellent results, but I'm running tighter necked chambers than you. IF, your final sized necks measure .305" consistently, you are good to go, depending on your accuracy requirements. THEN, to improve at longer ranges, there's always more needed. Good luck!

 

[Bart B]

For what's it's worth. I measured 10 rounds with Berger VLD-H all seated with my brand new Redding die. Each one measured .307

then I measured 10 shot empties. That were also seated with the same bullet.
[
On a side note. I'm amazed that - fire formed the outside dia should be identical. If there is wall thickness differences. That should be on the inside. But the out side should all be the inside of the throat.

Both the outside and inside case neck diameters on fired cases will not be the same for each. They'll all vary a little bit. There's no need to measure fired case neck dimensions; it's meaningless to the reloading process. Only the size of the resized and loaded case is what counts.

,,,,, you will have far better results at longer ranges with uniform neck tension. This can be enhanced by sorting your brass by measuring neck thickness with a ball micrometer or turning case necks to a uniform thickness.

I've handily got sub MOA many-shot test groups at targets 3000 feet away with a .0015" spread in case neck wall thickness. There's several other dimensional issues on the case, bullet and barrel a lot more important that neck wall thickness. Some are never addressed by most folks.

 

[dok7mm]

Bart, it is not meaningless to measure fired neck diameter IF you don't know what your chamber neck diameter is AND you are using bushings to resize necks. The OP appears to have a chamber neck .010" over his target resized neck of .305" and Redding experts will tell bushing users not to reduce necks more than .005" in one step as it can cause inconsistent neck tension. I know his approximate chamber neck BECAUSE he measured his fired case necks and I added .001" for spring back, therefore, I recommended he use at least one intermediate bushing, as per Redding instructions. He may have excellent results. His call as to how much accuracy he wants. I only addressed case wall thickness in reference to flashhole's post, but I agree with him. The PO asked a simple question and somehow it got to how well you shoot @ 1000. My apology to RustyRick

 

[Bart B]

I don't think anyone knows what his 7 Rem Mag's chamber neck diameters are. SAAMI specs state .317" at the shoulder and .316" at the mouth, + .002". Specs for loaded round neck is .315" +.002", Compare those to the numbers he got measuring his fired cases; noting that some were over those diameters. Is his chamber within specs?

Never had any problems sizing down 30 caliber case necks that were .341" diameter after firing down to .334" in a loaded round using dies with their necks at .333" diameter. That's a .008" reduction.

 

[dok7mm]

Good for you. Your results don't necessarily apply to every rifle/brass combo, so excuse me for opting to use Reddings' recommendations. In reducing a 7RUM neck by .009" in one step, I was getting very erratic pressures and velocities. A call to Redding solved my problem, when they told me to try the intermediate bushing. That is the info I passed on to the OP, in case he had a problem that mirrored mine.

 

[Bart B]

Did you measure bullet release forces to verify inconsistent neck tension?

Did Redding mention any of the other two causes of big spreads in pressure and velocity? Two of them have nothing to do with the ammo.

 

[dok7mm]

Bart, Platinum is not a synonym for PERFECT or SUPERIOR. If you want, open a thread and I'm sure someone will be glad to indulge in a ******* match with you 24/7, as that seems to be what makes you happy. I try to offer suggestions to members, based only on my experience with topics I know something about. You seem to comb thru the threads, looking for a reply that you can demolish with your vastly superior intellect and volumes of knowledge, secure in the believe that nobody could possibly have input that equals yours. In the interest of harmony, I will avoid posting on any thread you subscribe to in the future. Fair enough?
SORRY LEN, he had it coming, IMO

 

[Bart B]

Bart, Platinum is not a synonym for PERFECT or SUPERIOR. If you want, open a thread and I'm sure someone will be glad to indulge in a ******* match with you 24/7, as that seems to be what makes you happy. I try to offer suggestions to members, based only on my experience with topics I know something about. You seem to comb thru the threads, looking for a reply that you can demolish with your vastly superior intellect and volumes of knowledge, secure in the believe that nobody could possibly have input that equals yours. In the interest of harmony, I will avoid posting on any thread you subscribe to in the future. Fair enough?
SORRY LEN, he had it coming, IMO

Most ridiculous and erroneous post I've ever seen. Anywhere.