Bushing size question

[Jcub]

Hey fellas,

I have a .280 ackley and I'm creating some match brass.

I have 100 pieces of .280 Norma that I fireformed, it's OD with a loaded round is .313.

My 50 pieces of once fired Nosler brass is with a loaded round .310.

I would like to us both of these lots together, I'm going to turn the necks, then anneal them. Would turning the necks of the Norma brass to be the same as the Nosler be too much?

What bushing should I use?

 

[dok7mm]

What is your chamber neck measurement, your Norma case neck thickness and your Nosler case neck thickness ? You could turn your Norma brass .0015" (per side) for the .003" you are looking for and have same nk thickness all around, but you will still have a thick & thin side on your Nosler. Best to stick with one brand of brass at a time as they will have different capacity, even within the same brand. After you decide, you can pick a bushing 1-3 thousands smaller than loaded neck depending on how much bullet tension you want.

 

[Jcub]

I have a Sammi spec reamer

 

[dok7mm]

If you don't have a reamer print, you can come close by measuring a couple of fired case necks from your rifle and add .001 to get your chamber neck dimension. You will need a tubing mic to measure case nk thickness @ 4 quadrants of your case necks ( or some other type of nk gauge ). The reason for knowing loaded nk diameter and chamber diameter is that you may have to have an intermediate bushing if you end up neck sizing more than .004". This is almost a given if you turn necks for a Sammi neck.

 

[dok7mm]

If you are determined to turn neck turn your brass, Google German Salazar/ neck turning basics

 

[Jcub]

I really appreciate all the info. Ive read a few of his articles, but it's always good to re read it.

Will you educate me on an intermediate bushing size?

 

[dok7mm]

Sure, say your Norma loaded round is .313 and your chamber neck turns out to be .318" and you want the standard .002 neck tension. That means you are sizing down from .317" (don't forget the springback ) to .311" (.002" below loaded nk dia ). From .317" to .311" is too far to take nk down in one step. It will cause your .311 target size to become .309 or.310" -- below what you wanted --- and cause very eratic amounts of neck tension. If you have a similar situation after you measure chamber nk and loaded rd nk, you must use a two step bushing method. In this case, we would neck size first w/ a .314 bushing and then your .311 bushing.

 

[Jcub]

That makes a lot more sense!

 

[dok7mm]

Was hoping it would. I would still advise you to stick to one brand of brass per load work up. You can always use your second batch to work up what may become a similar load. See which is the best in your rifle and consider increasing your supply of whatever brass is most consistent for you. Hope this got you a bit clearer on what you're up against. After you get some solid measurements, as discussed, you may find your chamber neck too loose to make more than a light skim nk turn on your brass. Regards, David 11B 40 RVN '68-70

 

[Jcub]

It did! I really appreciate it.

I had planned on only skimming anyways, but noticed that the nosler brass was thinner. Just wondered if it would be worth it to try to trim to its diameter. I'll just buy more norma brass and Fireform it.

 

[Jcub]

Always good to talk to another infantryman.

 

[Bart B]

I see no problem using the same load with different makes of cases. Same charge weight a grain or two below max in my 308 Win cases 150 to 175 grains in weight all shot about half MOA through 300 yards. Same charge weight in my 30 caliber magnum cases of 220 and 235 grains weight shot 3/4 MOA at 1000.

Turn both lots of brass to neck thickness enough to clean up most of the thinnest lot. Use a bushing .002" smaller than loaded round's neck diameter. Both lots will shoot with equal accuracy with the same charge weight. But zeros will be about 1 MOA different in elevation at long range. Increasing the clearance between case neck and chamber neck by turning neck walls thinner doesn't degrade accuracy nor bullet alignment to bore center.

Shoot at least 20 shots per test group to get meaningful results. If your rifle starts walking shot impact as it heats up, the receiver face is probably not square with the barrel axis.

 

[Jcub]

Thanks for the response, but that wasn't really my question.