Bushing die and semi auto

[tangolima]

My first bushing die is in 6.5cm. It works beautifully loading for a bolt action rifle. Neck bushing has a just right bushing to size the neck so that the expansion ball is eliminated. Good for accuracy and brass life.

I recently have been tinkering with an ar-10 in 7mm SAUM. Hornady bushing die set was on sales. After their free bullet rebate, it is only slightly more expensive than ordinary full-length sizing die set, so why not? I need every help to prolong the brass life as they are expensive.

After 1st test fire, I realized variation to this perfect plan. Semi auto tends to put dents on the brass. The neck may "cave in" when hit something on its violent journey out of the action. Bushing die only size the outside diameter of the neck, and it can't push out dents.

I have no other choice but to put the expansion ball (comes with the die set) back on. But it defeats the purpose of a bushing die.

What would you do?

-TL

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[FrankenMauser]

Use an undersized expander ball (like 6mm or 6.5mm?) to get "close" to round, and the necks should return to round in the bushing, unless creased.

[tangolima]

Originally Posted by FrankenMauser

Use an undersized expander ball (like 6mm or 6.5mm?) to get "close" to round, and the necks should return to round in the bushing, unless creased.

Thanks. I have been thinking along similar direction.

Push regular 7mm expander ball into fired brass to push out dents. It won't expand the neck as the it is oversized before sizing.

Remove expander ball.

Size with bushing die.

What do you think?

-TL

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[stagpanther]

Are the dented necks pretty consistently appearing on many/most of the fired cases? You might have an issue with the extractor flipping the case back into the deflector when being ejected.

[tangolima]

Don't know for 100% yet. It is mostly the brass hits the ground mouth first, I think.

-TL



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[FrankenMauser]

The standard expander should work.
Seems reasonable.

[tangolima]

Alright. I will give it a try. Thanks.qq

-TL

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[Unclenick]

If the dent is so severe that you can't get an expander in, slip a small flat-bladed screwdriver in and pry it or push it enough so the expander can do the rest.

If you want, you can also get a Sinclair mandrel die body and an appropriate mandrel and mount it in the press to expand the case as a separate operation. This is often done on a separate press (an inexpensive single-stage press or sometimes at a spare position on a turret or a progressive press). The idea is that you don't interrupt the flow of the loading procedure by having to stop and remove the expander before you can proceed to sizing and loading.

[Shadow9mm]

Never understood the hype behind bushing dies. Why is eliminating an expansion ball "good" for accuracy and brass life?

If you use an expander ball that is pulled through, you wind up with a round hole that is straight in line with the ram/die/case.

If you use a bushing die, you are squeezing in the neck from the outside. So now the outside of your neck is perfect, but why does this matter, what matters is the inside where the bullet goes, right? just because the outside is perfect that does not mean the inside is. I always understood you needed to turn necks to ensure a consistent neck thickness if you were using a bushing die, is this not correct?

so some questions

How many firings are you expecting to get out of this brass?
How many extra firings do you expect to get because you are using a bushing die instead of a traditional full length die?
How much of an accuracy increase are you expecting to get using the bushing dies?
Granted this is a semi-auto, what are your accuracy expectation for the gun itself.

Personally I use small base dies for my semi auto, and scrap the casings after 5 firings, assuming I have not lost them yet. If I had an annealer I might shoot for 10 firings.

[Unclenick]

Originally Posted by Shadow9mm

Why is eliminating an expansion ball "good" for accuracy and brass life?

The answer to the second question is that it works the brass less. If you remove the expander from your standard sizing die and measure the hole in the case, you will see it is undersized (aka, has too much bullet interference fit, or "neck tension"). This is necessary because the SAAMI and CIP standards allow a range of neck wall thickness tolerance, and since the die maker doesn't know whose brass you will be using, the standard sizing die has to be made to size the outside of the neck enough so the thinnest brass the tolerance allows for will still be sized below the expander OD. Most brass is not as thin as the minimum spec, so all that brass is then made smaller than it has to be. Exacerbating this problem is that a shooter with a maximum chamber neck OD has that neck grow more than usual, and that means having to size down far enough to allow not only the thinnest neck but also the maximum spring-back when sizing down for the expander. It's a lot of brass working.

Originally Posted by Shadow9mm

If you use an expander ball that is pulled through, you wind up with a round hole that is straight in line with the ram/die/case.

Not usually quite so, and this addresses the first question about accuracy. Expander balls are notorious for bending the neck axis out of line with the case body axis. This old YouTube video demonstrates it by showing neck runouts on cases from a die with an expander versus a Lee Collet Die, which sizes a neck against a mandrel and thus does not pull an expander through a case's neck.

Incidentally, the Lee Collet Die's mandrel addresses the ID sizing concern, and you can thin them or order them thinner from Lee. You can size the case body in a Redding body die or in a bushing die with the bushing removed. Either way, it leaves the neck alone for the Collet die to handle. You end up with two sizing steps but with very straight cases.

A neck bushing die usually does a good job of leaving a case straight, but you do have to sort your brass so you get the same neck ID at the end of the process.

[tangolima]

I think it has been well established that expander ball is a major contributor to bullet run-out. Normal full-length sizer first over squeezes down the neck to cater for the min neck thickness then expand it back to spec. Full-length sizer with neck honed is considered the best solution, with bushing die probably the 2nd best.

Correct the neck thickness needs to be consistent. Neck turning may be necessary. Mandrel die is alternative.

Putting 10 rounds from cold bore into designated 1moa target is my goal. The closest I have gotten is 7 rounds into 1.1moa. With 1moa guarantee in the barrel, I hope I will get closer.

I hope I can get at least 10 firings out of the brass. It costs $2 each.

Why bother? Well... Sein oder nichtsein, das ist hier die Frage.

-TL

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[Shadow9mm]

Originally Posted by tangolima

I think it has been well established that expander ball is a major contributor to bullet run-out. Normal full-length sizer first over squeezes down the neck to cater for the min neck thickness then expand it back to spec. Full-length sizer with neck honed is considered the best solution, with bushing die probably the 2nd best.


Correct the neck thickness needs to be consistent. Neck turning may be necessary. Mandrel die is alternative.

Putting 10 rounds from cold bore into designated 1moa target is my goal. The closest I have gotten is 7 rounds into 1.1moa. With 1moa guarantee in the barrel, I hope I will get closer.

I hope I can get at least 10 firings out of the brass. It costs $2 each.

Why bother? Well... Sein oder nichtsein, das ist hier die Frage.

-TL

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So I understand run out, but I don't put much stock in it as I feel it has almost no effect on accuracy for the vast majority of shooters. F-class john did a great video on run-out testing https://www.youtube.com/watch?v=6m8Y6ZmSBiU He went from minimal runout to extreme runout. While there was a notable difference in accuracy, the differences in runout was extreme, and the worst group was still sub MOA at 1000yds. With normal runout from regular dies I would expect a negligible difference in accuracy.

Mandril dies work the brass a 2nd time, same as an expander ball, but generally maintain concentricity better so your kind of back to square 1.

That is an excellent accuracy goal IMHO, much more difficult than most people realize but definitely obtainable.

10 firings is gonna be a stretch imho, good luck.

Why bother? My point is this, why do the extra work and spend the extra money for a real world benefit you cant quantify?

You switch to bushing dies, how much accuracy does the extra concentricity buy you?

You switch to bushing dies how many more firings do you get with the same load?

Seems to me the issues you are fighting are a Pyrrhic victory.

[Shadow9mm]

Originally Posted by Unclenick

The answer to the second question is that it works the brass less. If you remove the expander from your standard sizing die and measure the hole in the case, you will see it is undersized (aka, has too much bullet interference fit, or "neck tension"). This is necessary because the SAAMI and CIP standards allow a range of neck wall thickness tolerance, and since the die maker doesn't know whose brass you will be using, the standard sizing die has to be made to size the outside of the neck enough so the thinnest brass the tolerance allows for will still be sized below the expander OD. Most brass is not as thin as the minimum spec, so all that brass is then made smaller than it has to be. Exacerbating this problem is that a shooter with a maximum chamber neck OD has that neck grow more than usual, and that means having to size down far enough to allow not only the thinnest neck but also the maximum spring-back when sizing down for the expander. It's a lot of brass working.



Not usually quite so, and this addresses the first question about accuracy. Expander balls are notorious for bending the neck axis out of line with the case body axis. This old YouTube video demonstrates it by showing neck runouts on cases from a die with an expander versus a Lee Collet Die, which sizes a neck against a mandrel and thus does not pull an expander through a case's neck.

Incidentally, the Lee Collet Die's mandrel addresses the ID sizing concern, and you can thin them or order them thinner from Lee. You can size the case body in a Redding body die or in a bushing die with the bushing removed. Either way, it leaves the neck alone for the Collet die to handle. You end up with two sizing steps but with very straight cases.

A neck bushing die usually does a good job of leaving a case straight, but you do have to sort your brass so you get the same neck ID at the end of the process.

Uncle Nick.

So given it is a lot of brass working, how much of a real world practical effect does it have. How many extra firings can you expect to get using a bushing die?

So I have seen several videos on neck runout over the years. here is one from Erik Cortina https://www.youtube.com/results?sear...cortina+runout. And here is one from F-class john https://www.youtube.com/watch?v=6m8Y6ZmSBiU&t=262s. My conclusion at this point is that, with typical runout from normal dies, most shooters will not see any real world benefits from additional concentricity.

Sorting brass by ID seems rather impractical. What if you only have 100 or 200pcs of brass and you wind up with 5 different sizes of brass ID. To me the only realistic options seems to be neck turning if you want to be able to use all your brass.

[tangolima]

With black Friday discount and free bullet rebates, bushing die set with vernier seater costs only slightly more than full-length set. It can be used as a full-length when needed. So why not?

I may not gain much but it won't hurt either.

-TL

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[stagpanther]

I'd offer my less-than 2 cents from my 30 BR experience that using an arbor press and dies-- and a stand-alone mandrel die to compensate for not using the standard expander ball when sizing--has proven very effective for me for not only minimizing neck/bullet run-out but also setting consistent neck tension on the bullet which can be verified by the pressure gauge when seating the bullet. It's a bit of pain making the brass, but once made to "snugly" fit the chamber's dimension 30 BR brass has a reputation for lasting virtually forever. I don't know how much obsessing of neck/bullet run-out for conventional "loosey-goosey" cartridge-to-chamber fit is going to make (I suspect it helps anyway), but in a close-tolerance fit between the case and chamber the concentricity has a significant influence in the inherent accuracy of the 30 BR in my experience.

[243winxb]

An ar-10 in 7mm SAUM will need the correct neck tension/bullet hold of .002" or more.

Bushing should not size down neck more then .008" Ok to use expander. Choose a bushing that produces light drag, when the expander is pulled thru the lubed neck.

Brass life will be longer, by not over working the necks. More then 20 loadings on 243 Win Brwss.

Size only 1/2 of the neck. 243 & 6.5 CM.

Using Redding Type S FL sizing die allows testing with & without an expander. If wanting to try the Lee collet neck die, remove the decapper & bushing from the S die to only size the body.

[Rimfire5]

Not sure if it matters to brass life.

I have never used a bushing sizing die.
I load with Lapua brass religiously and use a standard seating die with .223, 6.5mm CM and .308s.

I get from 20 to 23 reloads from Lapua brass with all those calibers and the primer pockets get loose before the necks split. Changing sizing dies wouldn't help the primer pockets.

But I do not load near Pmax, so that could be a factor.
The few times I have loaded near Pmax to maintain velocity or kinetic energy, i found that the primer pockets wore out after fewer reloads.

[tangolima]

Originally Posted by 243winxb

An ar-10 in 7mm SAUM will need the correct neck tension/bullet hold of .002" or more.



Bushing should not size down neck more then .008" Ok to use expander. Choose a bushing that produces light drag, when the expander is pulled thru the lubed neck.



Brass life will be longer, by not over working the necks. More then 20 loadings on 243 Win Brwss.



Size only 1/2 of the neck. 243 & 6.5 CM.



Using Redding Type S FL sizing die allows testing with & without an expander. If wanting to try the Lee collet neck die, remove the decapper & bushing from the S die to only size the body.

Bullet hold of .002" means 0.002" difference in diameter, right? I think I have 0.003" to 0.004".

AR is hard on brass neck, because of its ejector arrangement. During extraction, the neck bangs on the "teeth" of barrel extension lugs and dragged along. That puts a dent on the brass mouth and longitudinal marks on the shoulder and neck. Calibers smaller than .264 tend to have split necks pretty early, between 5-8 firings. Annealing helps but only marginally. I basically give up on .223 and .243 win as brass are practically free. 6mm ARC takes more care as it costs more even converted from Grendel brass.

7mm saum is totally different game. Brass costs way more. 10 firings is minimum, 20 would be nice. I would annealing each time, on top of the bushing die.

-TL

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[stagpanther]

Tango--do you know to what specs X Caliber used as a chamber reamer? It's not unusual for higher-end custom barrels to be reamed with a particular cartridge/bullet in mind; and it's possible your chamber could be optimized for longer range bullets you might expect in 1000 yd F class since that's where I would expect significant market demand for the 7 SAUM to be. Just speculation on my part.

[ocharry]

tango.....i agree with stag about the extractor causing the dented case mouth....i would bet it is hanging onto the rim to long and driving the mouth straight into the case deflector

i had the same problem with my grendel...look at the case deflector and see if you have brass tracks on its face...also look at the rim of the case and see if there are fang marks or scratches on them from the case coming off the extractor

if its not to much trouble take the ejector out of the bolt and put a case in there under the extractor and see if there is any resistance of the case coming off the extractor....should slide right off with no resistance

my grendel would smash every case coming out of it..big flat on the mouth..and it would cause misfeeds and eratic ejection...my rifle was really bad...i asked the guys on the grendel forum and to a man they all went for the extractor...so i took it out and did some polish work...that help but it was still hanging on to long...so i really defanged the dang thing and polished it up again .....and presto chango ...no more eratic ejection and no more dented case mouth....thing runs like a sewing machine now....and no brass tracks on the defector...so i dont think the brass is touching the defector at all now...like it is supposed to be.....give it a look see....

just some thoughts

[tangolima]

Originally Posted by stagpanther

Tango--do you know to what specs X Caliber used as a chamber reamer? It's not unusual for higher-end custom barrels to be reamed with a particular cartridge/bullet in mind; and it's possible your chamber could be optimized for longer range bullets you might expect in 1000 yd F class since that's where I would expect significant market demand for the 7 SAUM to be. Just speculation on my part.

I could have sent in fired brass for them to ream the chamber to. Of course I couldn't as I didn't have any. Catch 22. So they just did the default which I have no idea about. It is actually pretty tidy job they have done.

-TL

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[stagpanther]

It's possible your chamber and freebore/throat combination were optimized for the heavier (meaning longer) bullets up to the 180 +/- gr size (not uncommon for long-range 7mm). Just a thought.

[tangolima]

I did measure the bullet jump for Hornady 139gr spbt (hunting bullet). The throat is actually on the short side. Saami Max coal is 2.825". The bullet ogive contacts the riflings at 2.733". I'm seating the load to 2.7" to have 0.033" bullet jump. For eld bullets, I think I can seat it longer. The ogive is much slimmer and pointier.

-TL

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[stagpanther]

I took a look at hornady manual.. out of a 24" barrel they say you can get 3000 fps with a 154 gr bullet and 2900 with a 162--within 2.770 COL specs. That's very respectable; ballistically comparable to 280 AI but short-action capable, though the 280 AI might have the advantage when going with bigger bullets.

[tangolima]

That sounds right. I'm actually quite impressed by the speed, even I chickened out at 3020fps with 139gr bullet. As per calculator, it remains supersonic out 1.2k yd. SPBT bullet is not really built for long range, mind you.

-TL

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