Finding max.brass size in chamber

[glider]

Some smiths want to keep there reamer specs a secret which I understand , My issue with this is how can I know maximum brass shoulder length. Base to where shoulder touches inside chamber (head space).
Using once fired brass is not a good idea if chamber is an improved version with bushing die to FLR.
Removing plunger on bolt and running brass in until bolt just closes seems like a good idea but how would I stretch brass to start?

 

[philip brousseau]

per BigEdp51 take a case and start a fired primer in it . put it in the rifle and close the bolt. measure primer to shoulder.

 

[Texas10]

The primer trick works pretty well, however I prefer to make and keep a fully fireformed case that fits the chamber snuggly. I will size without bumping back the shoulder for the first few cycles until the case chambers with just a slight effort to close the bolt. Cherry pick the best one and keep and label it.

 

[glider]

Primer trick!!
Slap my forehead easy peasy
I was thinking to split a case fill shoulder with epoxy and embed thread adapter for cleaning jags.
Using Sinclair's seating depth tool thread there rod to attach split case , insert measure. Then insert complete case and measure to base .
KISS works better in this case

Thanks again for Acc. Shooter forum

 

[rsmithsr50]

chamber cast is the way to go.
actual measurements

 

[bozo699]

chamber cast is the way to go.
actual measurements

And owning your own reamer is a big plus!
Wayne.

 

[Uncle Ed]

per BigEdp51 take a case and start a fired primer in it . put it in the rifle and close the bolt. measure primer to shoulder.

Primer trick!!
Slap my forehead easy peasy
I was thinking to split a case fill shoulder with epoxy and embed thread adapter for cleaning jags.
Using Sinclair's seating depth tool thread there rod to attach split case , insert measure. Then insert complete case and measure to base .
KISS works better in this case

Thanks again for Acc. Shooter forum

Using a new or resized case and a fired spent primer will tell you the amount of head clearance.

Simply start the primer into the primer pocket and then chamber and let the bolt face seat the primer.

Then use a Hornady cartridge case headspace gauge measuring from the primer to the shoulder. Or measure the case length from the case mouth to the base of the case with the primer removed. Then measure again after seating the primer from the base of the primer to the case mouth and the difference is your head clearance.

Your head clearance after sizing a case is also the amount of shoulder bump. And how far the case must stretch to contact the bolt face when fired.

Shooting a case and reloading it until you feel resistance closing the bolt does not give you a measurement and only tells you that you feel friction.

 

[Richard Jones]

Is there an advantage to this method vs. Wheeler method?

 

[glider]

Is there an advantage to this method vs. Wheeler method?

Wheeler is more accurate ,spent primers may not seat well or completely press against bolt . I think if some one wanted to invest time and $$ a tooling set up like I described will work good
Chamber casting becomes an art project
Otherwise use a new primer and proceed with caution

 

[BoydAllen]

A while back, I wanted to find the perfect bump setting for a particular rifle, actually for one of several barrels that I have for that rifle. The problem was that I did not want to go to the range with loading gear to produce a tight case. All that I had was a case was fired, but not tight when chambered, so this is what I did.

If you fold a piece of Scotch tape over on itself, sticky side to sticky side, and measure the doubled thickness, it will measure pretty close to .004, so I deprimed the case, and covered the head with a single layer of tape, carefully trimming to the edge of the flat all the way around the outside and the primer pocket.

When I tried the case in the rifle, making sure the lugs were freshly greased, it took a lot of effort to close the bolt, and afterwords the shoulder to head dimension was reduced.

I was doing the measurements with a Whidden gauge that is calibrated to read zero on a GO Gauge.

From that point, I carefully adjusted my FL die so that the shoulder to head dimension was reduced by a little at a time, removing the lube and trying the case in the rifle each time.

After the first sizing I had carefully measured the shoulder diameter, and the diameter .200 above the head to be sure that the die had reduced both dimensions, so that any change in bolt feel would be because of a change in the shoulder to head dimension.

When I was at .002 over minimum, the bolt would move with very light pressure, and stay wherever I put it without dropping. At .0015 over minimum it dropped straight to the bottom.

Of course all of this testing was done with the striker assembly removed from the bolt. There was no need to remove the ejector since the action is a custom, single shot, benchrest action that does not have one.

Making small adjustments of the die was made a lot easier because that particular die is fitted with a PMA Tool Micro Die Adjuster. For this barrel, my perfect die setting produces a shoulder to head dimension that is .0015 over minimum, .0005 more, has slight drag.

I had bought the Whidden gage out of curiosity, to try it out, and to change over to an absolute reference for setting dies. It is a very well made product that functions perfectly, BUT if I had thought for a bit, I could have paid about half the price (shopping around) for a GO gauge and used it, in conjunction with my Stoney Point (now made by Hornady) headspace gauge, to do the same measurements. Going forward, with other calibers, that is my plan.

 

[glider]

Without reamer print or custom go gauge for an improved chamber its off to the range ,

 

[Richard Jones]

Thanks, guys.

@BoydAllen can you further explain your use of a go gauge with a comparator? Thanks.

 

[dmoran]

@glider
I would be looking for a different gunsmith if there not willing to share the reamer spec's with you.
It is pertinent information for the end user to have/know, and in many ways a must !.!.!
Can't help but have doubt in there knowledge, and wonder if just a lame excuse.
A chamber cast is my advise.

 

[BoydAllen]

Thanks, guys.

@BoydAllen can you further explain your use of a go gauge with a comparator? Thanks.

It works the same as with the gauge only by comparing case measurements to what a GO gauge measures with the same tool. With the gauge that I used in my example (Whidden) I referenced from its zero. which was what a GO gauge would measure with that gauge. Using my Stoney point caliper attachment I would measure a GO gauge and that would be my reference number, my zero. In the example, my reference would still be .0015 over that number for my absolute correct fit case measurement.

 

[Longtrain]

Way, way back in early XTC days and shooting lots of rounds, trying to learn the game and loading many more rounds that the 20 or so I would load for deer season, I didn’t anneal and had a mixed bag of head stamps and number of firings on them. Shot’em, sized’em, loaded’em, repeat and repeat, until I had a number of jammed cases that failed to feed and locked my AR up and caused alibi after alibi. I wasn’t very popular when that happened.

Determined to find out what and why, I began to educate myself on loading. Getting good measuring tools, I found different brands and firings determined how much bump a case could take, they were all different, sure they were mostly NATO cases, but one die setting would not work for all the cases.

So, I trashed all my brass and obtained once fired LC, processed the lot and found that my bump was fairly consistent, I then took a sampling of about 8 cases and bumped and measured them all in .001 increments. At that point I found that my cases needed a specific bump measurement to chamber and the .001 less was a tight chambering, but .001 more was a comfortable fit. I took a piece of scrap wood and drilled 8 holes, one for each case, properly labeled it sat on my loading shelf a quick visual reminder what bump that chamber needed to feed alibi free.

Annealing and better case management made the job more predictable and acceptable. That was probably 25 years ago, a lot has changed since then, but it was a good lesson learned, even to today.

 

[338 dude]

per BigEdp51 take a case and start a fired primer in it . put it in the rifle and close the bolt. measure primer to shoulder.

Whooda thunked it

 

[Uncle Ed]

Whooda thunked it

With a rimmed case you just add the primer protrusion to your rim thickness and that gives you your actual headspace.

Cheap bastards use a primer rather than buying headspace gauges.

 

[BoydAllen]

chamber cast is the way to go.
actual measurements

While chamber casts have their place, I do not think they lend themselves to determining a rifle's maximum shoulder to bolt face dimension. In fact, I do not know how one would arrive at that dimension using a cast.

 

[glider]

Does anyone make a blank primer machined smooth for insert? If not It will not be hard to machine one