Brass life is dependent on powder charge. Too much powder and primer pockets expand. I don't change body dimensions when I design a reamer. Off the shelf dies have to work. For varmint/target cartridges I'll spec out the neck forward. That's so a proven method for tuning a rifle can be followed.
SAAMI vs Custom Reamers
- Thread starter Mike in Oregon
- Start date
AlNyhus
Silver $$ Contributor
Mike, the 20VT is a pretty known quantity cartridge. Rather than struggling through this, I'd suggest asking the reamer mfg you're working with to send you the prints they already have for it. I'd be very surprised if there wasn't one already spec'd out that will fill the bill for you.
JGS gives exceptional customer service in this area...give Jasmine a call.
My 2 cents worth over a cup of joe...
Good shootin'
-Al
Mike in Oregon
Gold $$ Contributor
Already on it and done sir! Good looking out!Mike, the 20VT is a pretty known quantity cartridge. Rather than struggling through this, I'd suggest asking the reamer mfg you're working with to send you the prints they already have for it. I'd be very surprised if there wasn't one already spec'd out that will fill the bill for you.
JGS gives exceptional customer service in this area...give Jasmine a call.
My 2 cents worth over a cup of joe...
Good shootin'
gmr4
Silver $$ Contributor
Who makes the reamer for your brass manufacturer? That one question to get answered. Then what is recommended for the bullet you shoot? This is where many opinions come in….
I called JGS and they helped alot… i know owning my own reamer hasmade barrel to barrel transitions a non issue
I called JGS and they helped alot… i know owning my own reamer hasmade barrel to barrel transitions a non issue
Brass manufacturer? Brass is made on large multi stage transfer presses with custom tooling. No chamber reamer any where near it.
petersoncartridge.com
Drawing Brass | How Cartridge Cases Are Made | Peterson Cartridge
See the brass rifle casing manufacturing process at Peterson Cartridge from raw brass coils to the finished casings we deliver to you.
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gmr4
Silver $$ Contributor
I never thought of it until JGS mentioned ADG as brass to match my reamer. Maybe its something else??? Also ADG directs you to JGS. So maybe its a spec thing… i know this i dont get the clickers everyone talks about in my 7 PRCW. My assumption was it was the reamer itself.
Fast14riot
Gold $$ Contributor
Owning my own reamer, I rarely need to adjust my dies more than a thou between barrels, and I fire form brass for the new barrel before I retire the old one. I also know how many chambers were done on my reamer.
In addition to freebore and neck diameter, some SAAMI prints have some screwy dimensions. Like the 260 Rem with its 3° lead angle, or 6.8spc with a weird cone angle and short freebore.
In addition to freebore and neck diameter, some SAAMI prints have some screwy dimensions. Like the 260 Rem with its 3° lead angle, or 6.8spc with a weird cone angle and short freebore.
Problems arise when tolerances are tightened up on the body and when a no turn neck is too tight. Occasionally the brass can be the culprit requiring some careful polishing of the chamber to open it up.
swd
Silver $$ Contributor
Some SAAMI reamers are great the way they are. You need to compare specs to what you need. I have a SAAMI 6.5 Creedmoor reamer that has 2 F open midrange start championships on it. Is it best to have your own reamer? If you plan on having multiple barrels over the years, yes. Custom dimensions, maybe. It depends on SAAMI specs. Some have pretty large neck diameters that can over work the brass and some are fine. Free bore specs are a maybe depending on the bullet you plan to use and if need it fit in a mag or not or if you want the base of the bullet seated above the neck shoulder junction. Hopefully your gunsmith is well versed on reamers, have a talk with him.
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I've had several reamers done by JGS. I ask for a reamer print and then compare to the brass I will be using then ask for necessary adjustments to that print. In the case of the 20 Vartarg I found that I needed a bit larger head diameter to accomodate my Lapua 221 Lapua fireball brass. Jasmine at JGS is most helpful in sending print copies of reamers they have made. Note that a custom sizing die suited to your chamber dimensions may be necessary. Some important dimensions to compare are neck diameter, case length, head diameter, and .200" line measurement.
Mike in Oregon
Gold $$ Contributor
Just received an email from my smith and he said the same. Perhaps were on to something..??
Mike in Oregon
Gold $$ Contributor
The moral of the story is, it's not a bad idea to supply your own quality (JGS) reamer, even if it's a basic SAAMI spec's cartridge. And as for the wildcats, yes, definitely do your specs homework and supply the reamer!
Thank you so much guys!!!
Thank you so much guys!!!
ballistic64
Silver $$ Contributor
Neck turning sucks. I did it with two guns and was never good enough behind the rifle to see the difference between a tight no turn neck reamer and a required neck turn reamer with good brass. Run away.
AlNyhus
Silver $$ Contributor
Mike, make sure and look at the necks on the SAAMI reamer prints...most will have tapered necks on the order of .001-ish (larger at the neck shoulder junction than at the mouth). This aids extraction but may not be what you want if you're going to use bushing dies, etc. You don't want to chase your tail looking for the cause of tapered necks later.
Just a heads up....-Al
Edd
Gold $$ Contributor
Why would using bushing dies make this undesirable?
Just to throw a monkey wrench into the works, a brand new reamer isn't always a superior choice. That said, there are advantages to buying your own reamer if you plan to have more then one barrel made. Assuming the rifle builder knows how to dial in a barrel and sets similar headspace each time, your brass is reusable with subsequent barrels. I do this all the time with my own stuff I chamber at home, as do many others.
In terms of SAAMI vs Wildcat, it depends. Many Wildcats are a pain and require a learning curve. If a customer wants a wildcat--normally because of the mistaken idea that they need the absolute top velocity for a hunting rifle--I spend time explaining to them all the steps needed to make it work. I talk about necking up, necking down, fire forming, etc. I explain about how sometimes it takes several steps to neck down a cartridge to avoid crushing the shoulder, to get rid of the bell mouth at the case mouth, and to get the case neck straight.
If a customer doesn't understand this well enough I push them away from cartridges that need a lot of work. Not all wildcats need a lot of work. Our 6 UM-40 needs fireforming where our 6 UM-30 has head stamped ADG brass available. There is maybe 50-100 fps between the two.
Also, wildcats--even when based on a standard cartridge, can vary slightly in dimensions that can create problems. Our 6 UM-30 and 6 UM-40 are based on a 6.5 SAUM case, and that case can be used to make these cartridges. However, brass fired in these 6 UM cartridges will not likely fit into a 6 SAUM IMP chamber. After developing these cartridges we wound up with a bit larger size at the .200 line than the SAUM. This slight variation can create issues from cases being hard to size to clickers. Because of that we support both of these cartridges with reamers, dies, and brass.
I suppose that technically, when we throat a chamber longer that the SAAMI or CIP spec, it is no longer to spec, but that really isn't an issue. Now some guys think that when we throat a chamber for a certain bullet that it means the barrel will shoot that bullet well. That isn't true at all. It only means that the bullet seats optimally in the case with no bullet bearing surface taking away powder capacity.
In terms of SAAMI vs Wildcat, it depends. Many Wildcats are a pain and require a learning curve. If a customer wants a wildcat--normally because of the mistaken idea that they need the absolute top velocity for a hunting rifle--I spend time explaining to them all the steps needed to make it work. I talk about necking up, necking down, fire forming, etc. I explain about how sometimes it takes several steps to neck down a cartridge to avoid crushing the shoulder, to get rid of the bell mouth at the case mouth, and to get the case neck straight.
If a customer doesn't understand this well enough I push them away from cartridges that need a lot of work. Not all wildcats need a lot of work. Our 6 UM-40 needs fireforming where our 6 UM-30 has head stamped ADG brass available. There is maybe 50-100 fps between the two.
Also, wildcats--even when based on a standard cartridge, can vary slightly in dimensions that can create problems. Our 6 UM-30 and 6 UM-40 are based on a 6.5 SAUM case, and that case can be used to make these cartridges. However, brass fired in these 6 UM cartridges will not likely fit into a 6 SAUM IMP chamber. After developing these cartridges we wound up with a bit larger size at the .200 line than the SAUM. This slight variation can create issues from cases being hard to size to clickers. Because of that we support both of these cartridges with reamers, dies, and brass.
I suppose that technically, when we throat a chamber longer that the SAAMI or CIP spec, it is no longer to spec, but that really isn't an issue. Now some guys think that when we throat a chamber for a certain bullet that it means the barrel will shoot that bullet well. That isn't true at all. It only means that the bullet seats optimally in the case with no bullet bearing surface taking away powder capacity.
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