reamers/chambering

[VinceMule]

Ok, examples:

243, 243 AI SAAMI spec is .469 at the .200 line
Lapua & PMC (other European brands also) New brass is .470, brand new
Change reamer print to .4723 at a minimum, thicker necks wall thickness to be taken into account

Same thing on Lapua BR brass with a multitude of variants, web dimension at the .200 mark is too small, causing stiff bolt lift and "clickers" abound.

Alpha Brand of 6 BR and variants have their own reamer spec due to minor differences than Lapua

Same occurrence with Lapua 30/06 brass and SAAMI spec chambers,

Same thing with RWS 280 brass and SAAMI factory chambers

223 Lapua brass is thicker in the web and in the neck wall thickness and will not work well in SAAMI Match chambers.

and on and on

I am waiting for some new AGD 7 Mag brass with fingers crossed, hoping it is not too large. A pard was having some trouble, but I helped him out with an extra small base sizer, but he says the brass is super tough.

 

[elkaholic]

I learned about SAAMI tolerances and wildcats of the time in a reloading class. This was 1975, I was 12.
But I'm sure nothing in reloading has advanced beyond basic in over 100yrs.
Same kind of people, with their same kind of folklore, and their same bad choices.

Give me one technical basis for more clearance being in your answers.
Not a so & so says it, or had a problem or won with it, but your actual understanding of what goes on with clearances and gun design.

Here are some reasons:
clearance in the throat use to always be .0003 to .0005" over bore size for bench rest guys, but even when it worked, it only worked at 100 yards. Pressure goes up as well as es normally and groups fall apart at longer range. I don't make ANYTHING anymore under a full thou over bore size.Attainable velocity is also greater with a little more clearance. if your ..0003" reamer gets slightly worn, you get big pressure problems in a hurry.
Neck clearance was looked at the same way by many but .003" only on the neck means higher es which equates again to long range accuracy. .005 to .006 really settles things down and I've seen even .007 or .008 work just fine.
Chamber clearance at the web of the brass will cause problems if its even .0005" too small but .001"+ over what is enough doesn't hurt a thing.
Im sure there are other examples as well, and a novice reamer designer can't possibly just take a print and cover those things without some experienced help!

 

[L.Sherm]

Give me one technical basis for more clearance being in your answers.

I dont have to give anything to anybody, I test my stuff and have no problem getting .250 m.o.a or close to it with my hunting rifles at 600-700 yards.
Like I said there's alot smarter people than me on accurateshooter that will 100% disagree on it being " Basic" convince them. Ive seen it with my own eyes.
I recently had my 30-28 opened up bigger at the back end, what went from a .5 m.oa rifle to this after I did.
Same exact load.
Its not just by chance either, ive got a 6.5x300wsm, 6.5x06AI and 28 Nosler that all will do the same thing to 700.
That group is 1.75" the black dot is 1.5"

 

[L.Sherm]

But I'm sure nothing in reloading has advanced beyond basic in over 100yrs.

Ya dont think so ask Eric Cortina or Alex what was winning 5-6 years ago wont even get you close now

 

[VinceMule]

Life is a learning curve, hopefully. Elkaholic has a lot of wisdom in his post, not cheap to learn the hard way, either!

I wish we had a section on this board for reamer design as this would raise the knowledge base to another level for the average guy having a custom-built.

Much of the "secrets" of reamer design are spoken of when old gunsmiths have sold all of their equipment. Otherwise, the knowledge is kept close to the vest as trade secrets, and often, that knowledge is taken to the grave. JGS even locks the information per design and a guy has to tell them it is ok to make the design public.

 

[haisardao]

I dont have to give anything to anybody, I test my stuff and have no problem getting .250 m.o.a or close to it with my hunting rifles at 600-700 yards.
Like I said there's alot smarter people than me on accurateshooter that will 100% disagree on it being " Basic" convince them. Ive seen it with my own eyes.
I recently had my 30-28 opened up bigger at the back end, what went from a .5 m.oa rifle to this after I did.
Same exact load.
Its not just by chance either, ive got a 6.5x300wsm, 6.5x06AI and 28 Nosler that all will do the same thing to 700.
That group is 1.75" the black dot is 1.5"

How happy are you with your 30-28 Nosler, would you do it again, or go to a 300 PRC. I'm just curious as I'm always trying to build something new

 

[L.Sherm]

How happy are you with your 30-28 Nosler, would you do it again, or go to a 300 PRC. I'm just curious as I'm always trying to build something new

I'd do it again in a heart beat.
I can run it 100fps lower were it pressures out so its real easy on brass

 

[haisardao]

I'd do it again in a heart beat.
I can run it 100fps lower were it pressures out so its real easy on brass

Great. Who did your chambering? Or where did you find the reamer? also, do you just neck up grass and go? Thanks again,

 

[L.Sherm]

I'm gonna go out soon and test .2 on each side of the powder charge and .002 on each side of the seating depth and see if I'm in the middle of the nodes.

 

[L.Sherm]

Great. Who did your chambering? Or where did you find the reamer? also, do you just neck up grass and go? Thanks again,

I've got my own reamer, Dan Coffin in Victor MT fitted up my barrel and brake, i did the bedding and everything else.
I neck up 28 Nos ADG brass and just clean up the nks. My loaded round is .339 and chamber nk is .344. Freebore is .215.
You will get donuts but I ream them out with my K@M mandrel but I'm still above them with .215 freebore and .030 off

 

[MagnumManiac]

When I first saw this thread I tossed around my very first thought and told myself to see what answers came first…

I have done this, designing/ordering reamers, that I just don't understand the thinking behind basing a chamber off a piece of brass.

Firstly, basing a reamer print off of a piece of brass is foolhardy…the reason being most brass is .005" smaller in every dimension than SAAMI or CIP specs. Unless you know this and compensate, you are going to have issues with tight chambers, brass not sizing correctly, dies splitting and other issues. (I do not use neck turn chambers anymore!)
Secondly, having the dies made is very expensive, buying the die reamers is a problem, how many barrels are you planning on turning up and selling are you planning on doing? If this is for yourself, just get Whidden to make your dies, this is what I have done for my own wildcats, including hydro forming dies.

Thirdly, designing a chamber is thwart with compromise, get it wrong in one place, and it affects the overall result, just like tolerance stacking does. I have lived this more than once, the original dimensions for most Weatherby rounds prior to the 378 Bee were .500" long, .0005"clearance parallel sided throats, so that's what I stipulated using CIP dimensions for my reamers in 300, 340 & 375… US made die's do not like these dimensions, every case was not being sized on the shoulder, but the bodies were forcing the shoulders to elongate, the only solution was to turn down shell holders to allow the cases in further, it worked, but the area above the belt was sized too much…a compromise I didn't foresee.

Cheers.

 

[GRG]

Great information for somebody like me just beginning to work on custom chambering and wildcatting etc. The one thing I'm lost on is the term "Clickers". I'm sure it is very simple but could somebody explain what you mean?
Thank you

 

[VinceMule]

MagnumMania, this is not an attack on you or your thinking process, so please do not take it that way, as we are just having a discussion.

Quote, "
have done this, designing/ordering reamers, that I just don't understand the thinking behind basing a chamber off a piece of brass.

Firstly, basing a reamer print off of a piece of brass is foolhardy…the reason being most brass is .005" smaller in every dimension than SAAMI or CIP specs."

If I had found that brass was .005 under SAAMI or CIP spec, there would be no problem, but this is not the case with the exception of the Winchester brand of brass and Rem in some cases. Getting measurements off of the case is a system to double-check brass dimensions of that particular lot number vs the Reamer print, Winchester brass is smaller than Lapua, RWS, Norma, AGD in some cases, and Alpha with each cartridge having its particulars.

Cartridges I have worked with have been from the 17 Ackley Hornet to the 7 STW, larger cases, I have no experience with. I could go into the cartridges where I have seen problems with brass dimensions vs Reamer dimensions but it would be boring to most.

Magnum, you are correct that designing a reamer comes with compromises when it comes to dies, but often changing a dimension by .003-.0035 in the web(if necessary) can eliminate problems, again it gets boring to get into the specific cases. Specific cartridges with three different brands of brass from new brass companies may have their challenges. Dies from different makers are another issue as you are well aware of as production dies can certainly vary for a myriad of reasons.

 

[elkaholic]

Great information for somebody like me just beginning to work on custom chambering and wildcatting etc. The one thing I'm lost on is the term "Clickers". I'm sure it is very simple but could somebody explain what you mean?
Thank you

Clickers is a term which comes from the bolt resisting initial extraction on rotation which causes a click at the very top because you are applying extra pressure on the bolt handle. Its caused by the case swelling too far and gripping the chamber. It happens because you don't have enough initial sizing on the brass web (lack of clearance) or is also caused by an overload.
If an overload is involved, it will likely have an extractor mark on the case head by that time and have a flattened primer.