How much variation in shoulder from chamber to chamber?

[Tiny Tim]

^^^^^ I've noticed similar things with new brass. Ive also measured all the major cartridge dimensions after firing in a factory chamber, then again after running through a standard RCBS sizing die. Eye opening to say the least.

 

[shortgrass]

RCBS makes a small base sizer, that will work. I use it on my 7 STW cases that are shot in a match chamber. Dies made will not size down far enough.

Even if you use a small base sizer and set it so it will reduce the diameter right above the belt, it will move the shoulder back. The sizing system I mentioned doesn't work the shoulder at all, just the diameter right above the belt. Seems to me, after the first firing of new brass the shoulder should be 'bumped' back just enough for reliable chambering. Otherwise, you are just over working the brass. And, my understanding is, you want the brass cartridge to fit the chamber without 'slop', or having to blow the shoulder forward again because it got pushed back too far during re-sizing. I'm a firm believer in "new chamber (rifle), new brass". Set the re-sizing die accordingly after that. If the diameter above the belt needs to be reduced for reliable chambering, I just resize that area with the collet die I mentioned in my previous posts.

 

[keithcandler]

Short grass, your thinking is right on the money, but out of 1000 reloaders, maybe one or two will get it. We use the same thinking on all of our bench and long range cartridges with Harrells and Whidden custom dies.

I had Larry's die for 10 years, never used it on 7 mags, 300 win mags, and 7 stw's.

I am a nit pickers nit picker on this kind of thing. I found on these mag cases, a full length sizing every firing gave me best accuracy, and this goes against what I do for my 6 PPC's, 6 BR's, 6 BRA's, 6x47's, 6 XC's, etc.

So, I take a case that has hard extraction, set the full length sizer(each rifle has it's own) to where the bolt closes easily ending up with a fitted case for that chamber. Dies are adjusted down slowly with very small adjustments so as to push the shoulder back as little as possible. Lock ring is locked, and only one brand of brass is used in that rifle. I start off with a case guard 100 with 100 new cases, by the 7-10th firing, the barrel is close to toast.

I shoot Rem brass in the 7 Mag, no particular good reason, just started off with it. I get about 7-10 firings on the brass, then start to see a ring form in front of the web. Time to throw that piece of brass away, and I am speaking of factory chambers.

Likewise, on my custom 7 STW's with a Match reamer that I have, no brass has ever been thrown away from case stretching, however the hot loads that I shoot open primer pockets after 4-6 firings.

Since 1978, I have never had any issue with a "Belt" of any kind using the method above.

My mags are hunting rifles, and groups at 550 yards are from 2.5-3.5" with tuned factory rifles and smaller with custom rifles.

I have talked to several die makers to try and get them to make sizing separate steps. A sizer for sizing only the web, then another for pushing back the shoulder only. Std Forster neck sizers will push back shoulders, but getting a die maker to make a series of web sizers is out of the question at this time. The web sizers could be made like straight wall pistol carbide sizers, but there is no demand at this point.
Truth is, not many people reload, and few are into advanced reloading like Short grass and I are...maybe 10% of the reloaders MAX.

 

[MNbogboy]

Is it possible to modify a second die (FL or Small base FL) to use prior to bumping?
Possibly completely removing a portion off the top portion...
Just a thought.

 

[keithcandler]

MNbogboy, your suggestion is what I have made to die makers that they could sell in graduated sets. Whidden made me a set, but said that they would make no more, no profit in it at at reasonable prices. The only way to do this kind of thing is in using carbide inserts in High speed steel dies like straight wall pistol carbide sizers.

I put a die in the lathe, and using a carbide part off tool, I cut the bottom of the die off. This ends up being a little short "Die Ring". Next, a standard Forster Neck sizer can be used to bump the shoulder to what dimension you like. This is a nit pickers nit picking way to size brass, if you have the patience and time for it, it is very rewarding...few have the patience for this kind of thing.

Hunting rifles get shot so little, after load development, chase the lands as needed, verify zero, it is just easier to full length size and throw the brass away as needed.
The system of starting off with 100 new cases in a case guard 100, go through all 100 then start over, gives an accurate barrel round count and brass life count.

I use the application of a "Die Ring" where a reamer does not match the brass where I am getting a click on my bolt lift, I could polish out the chamber but the "Die Ring" from the bottom of the die works like a charm. I use this on my 6BR, 6 BRX, 6 XC. Next Reamers will have a larger dimension by 0.0014 at the .200 mark from the bolt face to eliminate the bolt click.

A small base sizer, "Die Ring" works like a charm on belted cases, but I have seldom had to use them...only in custom barrels with "match" chambers where the dia at the web is .002+over brass dimension.

This reloading his a hobby, you can take it as far as you want to go. It is hard for us anal types to keep balanced in our approach in as far as time and money inivested giving how much improvement in our groups. We tend to dive into perfection with no end in sight....perfection for perfection sake....not to mention what ever the "talking heads" are saying at this time is proper.

 

[entoptics]

Thanks for the continued interest. I'll try to remember to update with results.

I've got a 39 Federal once fired, and about 180 Rem-Petes once fired. Gonna use the FC as recon. Salt bath annealed, shoulder bumped 0.006, trimmed to 2.490 ± 0.001. Neck turned to 0.0013 ± 0.0002. I'll mandrel size the necks before loading.

I'll use my findings from "break in" with the FC to inform my prep/sort/cull of the Rem-Petes. Perhaps I'll save $100 in brass, and 1/8th barrel life. Perhaps not.

Either way, I'll be a better reloader, $200 less poor.

Thanks again @lancetkenyon for giving me actual data to work with.

 

[Buckskinner]

Hopefully you are near or at SAMMI or it may be a frustrating start with that rifle. I have a Sendero 25-06 that basically has a near-crush fit at SAMMI specs.

 

[keithcandler]

Toss the Federal, it is soft.

 

[Philip J Theodhor]

You know that a cartridge Case Length Gage will tell you if you are within SAMMI Specs. If it fits in the Gage then it should chamber in any rifle that is held to Sammi Specification. This caliber specific Case Length Gage can be bought from companies like Lyman,Horandy, Wilson, Redding, RCBS and Dillon to name a few and will cost anywhere from $20.00 - about $35.00
IMHO this little tool is a worthwhile investment and will help you in determining in most cases if your brass will fit into a Sammi Spec chamber, however custom built firearms are another Story I would get the chamber tolerances from the Smith who actually did the build. Good Luck !

 

[entoptics]

Fired the new rifle today with the Federal brass I bumped 0.006" back. Everything chambered just fine. After firing, the shoulder is sitting 0.002" shorter than the R-P once fired brass I have on hand from the Rem 700 I used to have, so I'm good to go.

Except...The chamber is completely jacked. Huge burr near the breach is gouging the cases, and the chamber has more visible rings than a tree. Will be sending back to Savage ASAP. Never seen such a thing.

Seriously bummed. Nothing like having to box up your $900 rifle 6 hours after you signed the paperwork...

 

[Mram10us]

OP,
Glad it worked out with the ammo fitment. I have no issues with reloading once fired from other rifles. I do it with my rums. Use a comparator on a new piece of brass from a bag or pull the bullet from a new round. Saami pdf is a must for builders and reloaders imo. Sorry about the chamber. Hope it works out.