Matching your chamber to your sizing die vs buying a “better” press?

[Lucky6547]

Hello,
I wonder if the people who report getting amazingly consistent sizing with super expensive presses are actually just able to afford to have their chambers and sizing dies match more often than most people who have to use off the shelf dies and chambers?

What made me think of this is I recently just got a reamer made that matches my sizing die for my FTR gun. I talked to my gunsmith and he recommended a JGS with certain dimensions reference the sized cases I was getting out of my die that was not matched to the previous barrels’ chamber.

I was having trouble getting consistency in my sizing when the die was having to size too much with the old barrel. I tried multiple die brands in my rcbs press; whidden, Redding, rcbs, le wilson and a honed forster. I was getting most with +/-0.001”, but there were some 0.0025-0.003” out.

I was also getting super consistent results with a die in another rifle that I had gotten a Harrells die to match that chamber. This combination was always dead on or +0.0005”. I had been using a harrells combo press with that 6br. So I had assumed that the press was what was more consistent. The press is able to size 308 size cases, so I tried the die that ended up giving me the best accuracy even though it was sizing the brass a lot. It didn’t really improve the consistency even though it was marginally better. No more 0.003” outliers.

Once I got the new barrel with the new chamber reamer that matched my honed forster, the brass was consistent again. As an experiment, I put the die back in the rcbs and it was just as consistent (+/- 0.0005”) as the harrells suddenly.

I’m not saying don’t buy the nice presses, but if you aren’t matching your dies to your chamber, you might not see the difference…just my experience.

Take care,
Ken

 

[mgdietrich]

Agree, the dies are what makes straight ammo. Press is a smaller part of that whole system.

 

[DngBat7]

As ridiculous as this may sound. I have shot some great matches while still fireforming. Headspace as you are referring to is important. I put a lot of value in case to case consistency. I place more importance on the press. With my old hood and my new hood by arkco machine size consistent to .0005 case to case. To me when a lot of presses are giving a variance of .004 case to case, that I find not acceptable. But having a crooked die is unacceptable as well. Just my opinion. I’m sure somebody who knows way more than me will argu that.

 

[Fast14riot]

Aside from gross wear and defects in the press, the die matters more. My old 260AI barrel didn't match my die very well, I ended up needing ring dies. New reamer and barrels, everything is good again.

 

[Fast14riot]

As ridiculous as this may sound. I have shot some great matches while still fireforming. Headspace as you are referring to is important, But consistency more important. I place more value on the press. With my old hood and my new hood by arkco machine size consistent to .0005 case to case.

Some of my smallest groups have been shot fire forming my 260AI. I will shoot matches fire forming sometimes.

 

[DngBat7]

Some of my smallest groups have been shot fire forming my 260AI. I will shoot matches fire forming sometimes.

My point. My brass was nowhere even close to fitting my chamber perfect yet.

 

[Lucky6547]

My point. My brass was nowhere even close to fitting my chamber perfect yet.

No doubt that it shot well that way, but one of the biggest arguments for the really expensive presses are their consistency. But one thing I don’t know is: does the consistency come from the press? Would it still be consistent with the mismatch I talked about? Or is it more likely that the people who own such presses are also more likely to have custom dies and custom chambers already, and they just have the nicer presses because they like them?

 

[mikecr]

I think you have it backwards.
Your CHAMBER is your best die.
Use your chamber to form your CARTRIDGE the way you want it.
Then, have sizing dies made to suit your SIZING PLAN for your cartridge.

A press type/brand makes no difference to this.

 

[R.Morehouse]

When Mike Ezell designed his 30 Major reamer ( 6.5 Grendel necked up to 30cal. ) he did it having the Redding sizing die specs for the Grendel. So now the Redding sammi spec die sizes as a custom does with out the custom $ hit. Just have to open it up to 30cal. I thought that was a pretty cool idea & my 30 Major Redding dies work as my Goodling made 6ppc dies do.......I guess it's just a different way to approach it.

Regards
Rick

 

[SGK]

With my old hood and my new hood by arkco machine size consistent to .0005 case to case. To me when a lot of presses are giving a variance of .004 case to case, that I find not acceptable.

4 thou variance? And here's me wondering how I can size 98 cases and have 12 of them be 1/2 thou (only) shorter than the other 86 (which all measure the same). Lube consistency has a lot to do with that me thinks. (Forster Coax press and Whidden click-adjustable sizing die.)

 

[Alex Wheeler]

Its not so simple. You want the most consistent bump numbers ever, just make a fl die that hardly squeezes the case. All the force is applied to the shoulder. You'll get clickers in a few cycles though. The tougher the case and the larger it is the more you will have to squeeze it to make it work long term. The more you squeeze a case, the harder it is to get consistent bumps. So the more important your lube process and press becomes. A good press does help bump numbers, I have tested this. A good die does too. The correct way to design a die or chamber is to start with a virgin case number. Then through testing determine how much you have to squeeze it to make it last forever without clickers. Then you will know the chamber size. If you oversize a chamber to fit a die that brass will die sooner if you run it hard.

 

[DngBat7]

4 thou variance? And here's me wondering how I can size 98 cases and have 12 of them be 1/2 thou (only) shorter than the other 86 (which all measure the same). Lube consistency has a lot to do with that me thinks. (Forster Coax press and Whidden click-adjustable sizing die.)

You must an expert. I was just sharing my experience. My Forster would vary .002-.003. Then I had another mass produced press that was .004. The big bulky parts had a lot of springiness. But the fact you get so little is great.

 

[SGK]

I'm no expert at all. But I have found I have to be very consistent in applying lube. Any tension when extracting the case from the die will send them all over the place. As painful as it is, I lube each case individually. I have been using Hobo Oil. I tip the bottle up on my index finger and then twirl the case between thumb and forefinger. If I feel excess tension when extracting the case I twirl it in my fingers again and put it back through the press. (I can pretty much tell if a case will need this. And, again, it comes down to the lube application.)

PS: I'm bumping cases 2 thou (and I clean my dies with Napier Gun Cleaner and Lubricant before sizing).

 

[gunsandgunsmithing]

Its not so simple. You want the most consistent bump numbers ever, just make a fl die that hardly squeezes the case. All the force is applied to the shoulder. You'll get clickers in a few cycles though. The tougher the case and the larger it is the more you will have to squeeze it to make it work long term. The more you squeeze a case, the harder it is to get consistent bumps. So the more important your lube process and press becomes. A good press does help bump numbers, I have tested this. A good die does too. The correct way to design a die or chamber is to start with a virgin case number. Then through testing determine how much you have to squeeze it to make it last forever without clickers. Then you will know the chamber size. If you oversize a chamber to fit a die that brass will die sooner if you run it hard.

I've gone as far as 50 really, really hot loads with my method, hotter than most ever load. I don't anneal. Brass is only virgin once and then it's all about die to chamber relationship. I think I agree with your point if you take things to extremes but otherwise, it's worked too well, for too many years and too many guns to be broken. I've tested this a lot. I despise clickers and Lapua brass is the cheapest brass on the market unless you lose it. I haven't made it germinate at all, though! Lol!

 

[Shooter13]

PS: I'm bumping cases 2 thou (and I clean my dies with Napier Gun Cleaner and Lubricant before sizing).

THIS^^^^^ too, I have read so many people on this forum that say they don't clean dies and don't need a cleaning rod guide! Make sure you clean your neck bushing too.

 

[Alex Wheeler]

I've gone as far as 50 really, really hot loads with my method, hotter than most ever load. I don't anneal. Brass is only virgin once and then it's all about die to chamber relationship. I think I agree with your point if you take things to extremes but otherwise, it's worked too well, for too many years and too many guns to be broken. I've tested this a lot. I despise clickers and Lapua brass is the cheapest brass on the market unless you lose it. I haven't made it germinate at all, though! Lol!

My comments are not directed at you and your method. Just speaking in general terms, I have seen factory dies all over the place. And if you base a chamber on a big one your going to have a real fat chamber. Or maybe I am unlucky with dies. We get away with a lot more stuff with the smaller case heads too. The big stuff is so much harder to squeeze. On the Saum case I have a couple sized reamers. .002 bigger than the minimum it takes to work is all it takes to loosen up primer pockets on that case.

 

[BoydAllen]

If you have some fired cases of the caliber that you are planning on using for a new build, you can buy a factory die and size them (expander removed) , figure out what chearances you want to the chamber at various points, add those to the dimensions of the sized brass and order a reamer based on the totals. This is best done with fired brass that has been well used so that it is work hardened. If the die is of the one piece variety, you will have to have a tight neck chamber. We did that for a friend and with some figuring, ended up with a chamber neck diameter that allowed us to turn necks so that the loaded round clearance and neck tension were just what we wanted. The sized brass and loaded ammo were benchrest straight. Another thing worth knowing is that if you have a chamber that is too close of a fit at the .200 line to your unfired brass, you will have clicker problems and hard bolt lift at lower pressures than if you have a little more clearance. Bottom line there are multiple factors involved in chamber design. Some years back a friend was having bump consistency problems with a couple of magnums, using good equipment to size. We annealed the cases with a good two torch annealer and solved our problem without softening the necks excessively. If your only problem with sized cases is at the base, a ring die will solve that without messing up the rest of the case..

 

[gunsandgunsmithing]

My comments are not directed at you and your method. Just speaking in general terms, I have seen factory dies all over the place. And if you base a chamber on a big one your going to have a real fat chamber. Or maybe I am unlucky with dies. We get away with a lot more stuff with the smaller case heads too. The big stuff is so much harder to squeeze. On the Saum case I have a couple sized reamers. .002 bigger than the minimum it takes to work is all it takes to loosen up primer pockets on that case.

I also see that new brass varies a bit too.

 

[Dusty Stevens]

No doubt that it shot well that way, but one of the biggest arguments for the really expensive presses are their consistency. But one thing I don’t know is: does the consistency come from the press? Would it still be consistent with the mismatch I talked about? Or is it more likely that the people who own such presses are also more likely to have custom dies and custom chambers already, and they just have the nicer presses because they like them?

As long as the press that isnt precisely fit has some slack itll let the die do the work. Bad results because of a press is usually because its negatively influencing the case going into the die, so if the tolerances are tight it better be right

 

[CharlieNC]

Some of my smallest groups have been shot fire forming my 260AI. I will shoot matches fire forming sometimes.

Isn't it amazing how many reports you see like this, then a few posts later another is dwelling on .0005in sizing concerns. Shooting Fclass, barrel life would be reduced significantly if fire forming before competing with brass. My latest new barrel and virgin Lapua brass had .006 headspace but it shot fine. I understand BR shooting can highlight factors which matter, but of minor importance to others.