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cutting a chamber to match brass dimensions

SPAK

Stupid can be fixed
Full Member
Minuteman
Apr 3, 2009
2,257
112
Alaska
Hey guys,

has anyone ever had a chamber cut to match new lapua brass dimensions or at least set the headspace to match new lapua brass?

If I build a match rifle and only feed it lapua brass is there anything negative about doing this besides not being able to use factory ammo?
 
Re: cutting a chamber to match brass dimensions

Why wouldn't you have a die cut with your chamber reamer, rather than attempting to fit your rifle to the brass?
 
Re: cutting a chamber to match brass dimensions

longer brass life, possibly improved accuracy right out of the box?
 
Re: cutting a chamber to match brass dimensions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Frogman77</div><div class="ubbcode-body">longer brass life, possibly improved accuracy right out of the box? </div></div>
What makes you think this?
Give HateCa a call and run this past him.
Respectfully,
LG
 
Re: cutting a chamber to match brass dimensions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Downzero</div><div class="ubbcode-body">Why wouldn't you have a die cut with your chamber reamer, rather than attempting to fit your rifle to the brass? </div></div>

Because all that would produce is a useless die. You need a slight undersized reamer to cut a die. The die being the same dimension as the chamber will not size shit.
 
Re: cutting a chamber to match brass dimensions

There is no magic to holding the reamer .002" short of minimum while chambering nor machining .005" off the base of a die or the shell holder.
 
Re: cutting a chamber to match brass dimensions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: USMCj</div><div class="ubbcode-body">
Because all that would produce is a useless die. You need a slight undersized reamer to cut a die. The die being the same dimension as the chamber will not size shit. </div></div>

I was thinking the same thing, glad you said it.
 
Re: cutting a chamber to match brass dimensions

For headspace you'd just screw the die up or down....if on the other hand you are talking about headspace and neck and bell sizing then yes a custom die would be easier than a custom chamber.

Neck sizing and annealing will prolly yield the same result regarding brass longevity as well as not over pressuring the case.

~Mike
 
Re: cutting a chamber to match brass dimensions

my thought process is this...I've noticed a difference in accuracy from once fired brass to new brass. Once fired being more accurate...

I don't have any other factual evidence yet, but I was attribuiting this to the min headspace vs additional headspace of the new brass.

If I have the chamber to meet the headpace of the new lapua brass, I wouldn't have that difference between new and once fired.

does that make sense at all??
 
Re: cutting a chamber to match brass dimensions

This is correct...new brass WILL need to be fire formed to make it fit your chamber and there may be some accurancy issues as the brass does this.

You can do this by firing it as a plinking/fouling round and 'waste' a bullet or you can look into gas checks and work up a fire forming load.
 
Re: cutting a chamber to match brass dimensions

The idea of minimum chamber is not unique as the BR boys have been doing this for years with great success and I have been doing it since 1981.
I have a number of tight chamber reamers designed to give maximum case life. The killer of brass is expanding as much as .007" then being subjected to a FL die that reduces it back close to original dimensions.

With the right dimensions and the right brass you can easily load some cases well over a hundred times. In fact I started running a test several years back and I have one 30.06 LC 63 Match case I have loaded 157 times with no signs of insipient separation.

The rule of thumb I ascribe to is chamber with a reamer that does not allow the case to expand over .002" in any direction. Some cases this is impossible especially with the 308/7.62 case.
308 commercial cases I have seen measure .465 on the base measured .200" up from the rim where LC ball and match brass measure .468". SAAMI and Gov't chambers run .471-.473 if in spec though I have seen chambers that allow .475" expansion of base.

Thusly to cover the whole range you need a chamber slightly larger than .468" base dimension and I order mine .4685-.469".
This chamber will give fired cases slightly over .468 after they spring back after firing.

I have four sets of 308 reamers with base dims of various dimensions from .4685 to .471 which is a SAAMI dimension reamer.

I have four neck dimensions as well which run .337, .339, .341 and .344 (Saami). The 337 is only for commercial 308 Win cases. The .339 is for LC 7.62 Match which takes 99% of LC Match cases. Sometimes there is a slight burr on case mouths which cause it not to want to chamber.

The nice thing about a custom reamer is you can make a case gage with it when barrel is put on. You simply take a 1" long section of barrel, run the reamer in till the neck almost comes out the other end and you have the same neck as in your rifle thusly you can try 100% of your loaded rounds in the "gage" and not run it in rifle.

Finally I headspace to snug on a "GO" gage and my chambers normally don't gage the shoulder moving forward over .001" to .002".

Not all 308/7.62 brass is created equal as commercial brass has not hardness requirement while NATO STANAG ammo does so that it will take the violent feeding and extraction forces generated by belt fed guns primarily.

Thusly for long case life milspec LC/FA brass will hold the dimension of the primer pocket much longer than the softer commercial counterparts.

I have one extremely tight chambered 30.06. LC MATCH is .465 on base as it commercial 30.06. This one rifle generates fired LC MATCH with a .4652 fired condition. I had one set of brass I used on this rifle in matches for ten years and the cases do not show any signs of deterrioration.

I also have a 1905 Mannlicher-Schoenaurer Carbine in 9MM M-S and it has a very snug chamber.

The downside of a tight chamber is if you are a brass scrounger your dies may or may not size them down enough or bump the shoulder back enough for a tight chamber.

I have had to trim bottom of dies several times in order to get them to size back to where it will fit in a L E Wilson case gage.

There is another way to extend case life and that is to match the reloading die to the chamber. Dies give a variety of base resizing dimensions and I have some rifles with SAAMI chambers which are quite large thus I have multiple sets of dies for each caliber and they are marked as to the size they take a fired case back to on the base dimension, thusly for 30.06 I have a .465, .467, .469 and a .4705 die. I use the appropriate die that will work the brass the least.

My friend Ray Steele was Chief Armorer for the US Secret Service and built all their sniper rifles, match rifles etc and he ran tight chambers. He got me on tight chambers about 81 I guess it was. After he explained the logic of minimum brass movement I was hooked from then on. When Ray found a good reamer dimension (he ordered many to experiment with) and when he found the right reamer he ordered another under his name.

Ray is gone now but his reamer holds the 1000 yard any sight record held by a ex Secret Service type named Kovalchek and I also have a reamer to these dimensions. When Ray retired he had already sold his lathe and last I saw him he drove 700 miles here to rebarrel his law two rifles and he had started to deterriorate then. I bought most all his custom reamers a set at a time and I think of him every time I pull one out as the containers are marked with the Caliber and "Steele" on them.
In his day Ray was a top flight shooter having been a member of a Palma Team, Dewar Team and a Pershing Team. Only two people have ever done all three, the other was Larry Moore also gone. I have been on Palma and Dewar Team but not the Pershing. Interesting to note we all shoot southpaw.

Thusly there is plenty of background on tight chambers and if you get the right brass you are good to go. What is the right brass, well I will just say this if I ever hit the lottery I will buy 10,000 DWM cases of each caliber I use. Until then I will use LC Match and turn necks etc to get them uniform.


 
Re: cutting a chamber to match brass dimensions

so if I could set my chamber to headpace on the new virgin brass would this allow me to skip the "fireform" on the inital firing? Or at least minimize the difference in accuracy between new and fired brass?

I just didn't know if there was any drawback to having chamber smaller than saami spec. besides not being able to fire factory rounds.
 
Re: cutting a chamber to match brass dimensions

On my Palma rifle which has a Palma 95 match chamber, its real min dimensions. A good smith can give you what ever you want, but I don't think you are gaining any thing.

This is another way www.warner-tool.com/reloading.htm

Concepts - This is what WTC Dies will give you:
1.Minimal brass sizing for flawless chambering and maximum case life.
2.Concentricities of .0005" or better from top to bottom.
3.Head space adjustment within the die via hardened and ground tool steel retainer rings.
4.Standard die body will accept die inserts for any caliber from 6mm to 30-06.
5.Now introducing the Magnum die body that will accept larger cartridges up to 416 Rigby.
6.2 part die insert construction - one for the body, one for the neck and shoulder.
 
Re: cutting a chamber to match brass dimensions

I would just use a "GO" gage and headspace on lower end. For a gas gun you will need a little more but a bolt gun I run on min side.
Get a MO gage so you will know how to set your dies.
 
Re: cutting a chamber to match brass dimensions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Unsichtbar</div><div class="ubbcode-body">On my Palma rifle which has a Palma 95 match chamber, its real min dimensions. A good smith can give you what ever you want, but I don't think you are gaining any thing.

This is another way www.warner-tool.com/reloading.htm

Concepts - This is what WTC Dies will give you:
1.Minimal brass sizing for flawless chambering and maximum case life.
2.Concentricities of .0005" or better from top to bottom.
3.Head space adjustment within the die via hardened and ground tool steel retainer rings.
4.Standard die body will accept die inserts for any caliber from 6mm to 30-06.
5.Now introducing the Magnum die body that will accept larger cartridges up to 416 Rigby.
6.2 part die insert construction - one for the body, one for the neck and shoulder.

</div></div>

Any idea how much WTC charges for custom dies?
 
Re: cutting a chamber to match brass dimensions

http://www.6mmbr.com/warnerdie.html
The link above is excellent to see the whole system.

One of the big thing is you can use with more than one cal. You have ti remove the large nut on a RCBS press to accept the die.

"The complete WTC Die with one body insert and one neck-shoulder bushing is $325.00. This includes the headspace shims, allen wrench (for the shim holder) and a machined wrench for the lock ring. Additional caliber-specific body inserts are $100, while neck-shoulder bushings cost $50.00 each.

So, with a complete die and two (2) neck-shoulder bushings, you would have $375.00 invested in the die ($325 + $50). That sounds expensive, but consider this. You can use the die for more than one cartridge. All you need is another body-sizing insert ($100.00) and appropriate neck-shoulder bushings. If you load different cartridges that share the same shoulder angle and neck size (such as the 6mmBR and 6-6.5x47), you can use the same neck-shoulder bushings on both cases. The WTC Die body, made of 4140 steel, pre-heat treated and blued, will accept die inserts for any caliber from 6mm to 30-06.

Realistically, though, you'll probably want a new body insert and at least two neck-shoulder bushings for each cartridge you reload. That totals up to $200.00 ($100.00 for the lower "body" insert plus $100 for two neck-shoulder bushings, priced at $50 each)."
 
Re: cutting a chamber to match brass dimensions

Sure does look like a nice kit, bit it requires a RCBS press to use due to its thread pitch and size. I am not buying another press just to use that die.