Headspace Gauge Accuracy & having too much time on your hands

[bigedp51]

It was Christmas a little early today and the little brown truck made a delivery. In an earlier posting a forum member was having problems chambering full length resized .243 cases which got my curiosity stimulated so I ordered a .243 go gauge to cross check my RCBS Precision Mic calibration with. (will have other uses down the road)

Checking the Precision Mic against the Forster headspace gauge the Precision Mic reads minus two thousandths or two thousandths below 1.630. (1.628 actual)

Question number one.

Have any of you found that the Precision Mic ain't too precision.


Using my Forster headspace gauge and cross checking with my Precision Mic I checked two of my FL .243 dies. The RCBS FL die when contacting the shoulder resizes to a case to zero or 1.630. My new Redding FL die will push the shoulder back to minus .003 or 1.627.

Question number two.

Have any of you forum members run into this much variation in resizing dies before.

Question number three.

Would you send the RCBS Precision Mic back to RCBS for calibration. Would you doubt the accuracy of the Forster headspace gauge.

Question number four.

What do you do when your retired, bored and its raining and you can't get to the range. :

 

[RonAKA]

I can't answer your first three questions, as I don't own a headspace gauge. On the fourth one, I like to find simple ways to do things that don't require expensive gadgets and tools. My method of setting the shoulder dimension on my 6BR is to use my Forster Bump/Bushing die. It does not size the body, so a fired case fits right up against the shoulder in the die. I just measure the OAL of the die and the brass in it with a vernier. Using this method I check a number of fired cases. I take the longest one, and subtract 0.001" from it. Then I set my die such that the longest cases have their shoulder bumped back to that number. I leave it there of course for all cases, and just assume the short guys will "grow up" eventually, become uniform, and all fit the chamber very well. Has worked well so far.

Of course I have no idea what the proper headspace is supposed to be or what the cases measure. But, I really could care less as long as they fit nice in my chamber. That is the second part of my answer to your fourth question. I like to break the "rules".

 

[fdshuster]

bigedp51: Like RonAKA I depend on the as fired case dimensions for my chamber(s) to adjust my various sizing dies, keeping them adjusted for "as fired", or .001" shorter, or as much as .003" shorter for the AR-15's. When switching barrels I do use go gauges to verify proper headspace, but because of tolerences built into the go, no-go and field gauges they provide only a basic starting point to know that the headspace length is within saami stds. Fine tuning headspace is left to adjustments on the sizing die. I have no experience with the RCBS Precision mic, but doubt there is anything wrong with it. Like you, I'm also retired, bored, it's snowing and we're settling in for the long Winter ahead. Nuts!

 

[shortgrass]

Any manufactured item, be it headspace gages or reloading dies, is made within a tolerance. Tolerances on gages are tighter (because they are 'gages') than tolerances on reloading dies (because reloading dies don't need to be made within .0001" or tighter tolerances). If everything was made to an exact size the price would be so high only a few would be able to afford them.

 

[bigedp51]

Any manufactured item, be it headspace gages or reloading dies, is made within a tolerance. Tolerances on gages are tighter (because they are 'gages') than tolerances on reloading dies (because reloading dies don't need to be made within .0001" or tighter tolerances). If everything was made to an exact size the price would be so high only a few would be able to afford them.

shortgrass

I fully understand what you are saying, I spent over 25 years in quality control at a military overhaul depot and have worked with and calibrated many types of meters and gauges.

I was trying to duplicate what happened to another forum member when he was unable to push is shoulder back far enough with a full length resizing die. What suprized me was I was able to duplicate the problem with my RCBS FL die and "thin" coating of resizing lube. This is to say the FL die went over center and the case was hard chambering and had rub marks on the base of the case from the bolt face.

My Redding die pushed the shoulder back .003 further and I was a little surprised at the shoulder movement between dies. Please note the RCBS die is dated 1973 and the bolt wasn't hard to close on a Remington 700 .243. Could the Stevens chamber be tighter than the Remington chamber. Meaning would Stevens be intentionally making the Stevens 200 chamber "snug" compared to other gun manufactures or is this tight chamber just a fluke.

Again I know the manufacturing world is made up of pluses and minuses but could computer controlled equipment of today be running "tighter" or closer to zero tolerances?

 

[jo191145]

Ed
Your results are not uncommon.
The specs are pretty loose in over the counter dies in comparison to what your used too
You probably would'nt be a very happy QC manager at most die manufacturers plants.
Custom dies are much better but still mistakes are made and some shooters are very touchy about + or -.0005" in the web area.
I've heard more than a few complaints of folks with FL dies not being able to size thier brass enough with thier chosen die in a factory chamber.
Only two answers to those types of problems. Send it back or fix it at home. JMO

 

[fdshuster]

bigedp51; "Could the Stevens chamber be tighter than the Remington chamber"? Absolutley, yes. Chamber dimensions all are dependant on the reamer used, they can all have small differences (and still be within SAAMI specs). Even at that, if Remington (for example) started with a new, never used chambering reamer, they would get one set of dimensions. Then over a period of more chambers being cut with that same reamer, the dimensions will become smaller, from the wearing away on the cutting surfaces of the reamer. When the reamer is approaching the point in which the chamber would be out of specs (SAAMI tolerences/ there's that word again), they will scrap the reamer & start out with another new one. This is one of the reasons that some of us spec out and buy our own chambering reamers: we know exactly what we are getting.

 

[bozo699]

Hey Ed,
answer #1, I personally don't think anything rcbs makes is very precise.
( Now thats JMO and I don't want or need 50 members jumping on me about it).
Answer #2, Yes I have noticed variations in resizing dies of the same make, and definitely variations between brands.
Answer #3, No I wouldn't unless it was way off, I don't think they would or could make a difference with it. and NO I don't think I would doubt the forster, do you have a redding to compare it with?
Answer #4, I only wished I could answer your last question but I am not quite there yet. LOL
Nice thread Ed
Wayne.

 

[dreever]

I use Redding dies and this slick little fixture to adjust shoulder bump.
http://www.larrywillis.com/

Danny

 

[bozo699]

I use Redding dies and this slick little fixture to adjust shoulder bump.
http://www.larrywillis.com/

Danny

Danny,
I tried to order one of these tools quite a while back, they were out and then it just slipped my mind. How well do you like it? is it better than other tools designed to do the same thing or just another way to do it? I think I will wait to see if you reply if not I may just reorder, they look like a quality tool for not much more than any other tool. I think I gave $89 for my Redding comparator tool that does 3 or 4 functions with one being headspace and I am not sure I like it all that well. I know I don't like its bullet comparator function, if you measured the same bullet 30 times you would get 30 different measurements.
Wayne.

 

[dreever]

Wayne,
I like it, it does what it claims to do. I can easily set up my dies with it, so changing from one mfg/lot of brass isn't a problem. A bonus is that i can take the digital dial indicator and use it on other fixtures to check runout etc..
$89.00 to use once in awhile at first seems a lot, but I've got a lot more than that in neck turning tools which I use once in awhile also so looking at it in that respect justifies it for me. It is a nicely made piece of kit also.

Danny

 

[bozo699]

Danny,
Thanks for the input, I am ordering one tonight
Wayne.

 

[teele1]

I can also say that the Innovative Technologies Digital Headspace Gage is the way to go to avoid oversizing brass. Its easy to setup and use. Thanks Larry. Thanks Snowman.

 

[BowGuy]

Heres another vote for Larry's H.S. guage. Very easy to setup and like his other tools, excellent quality.

 

[bozo699]

BowGuy,
I want to be the first to welcome you to the forum (Welcome)
I have to Laugh though as I have been here less than a year and I am welcoming you, I think it should be the other way around as I see your just shy of five years (with first post) better late than never.Please don't make it another five years between posts
Anyway I finally got my headspace guage ordered tonight should be here in a few days,thanks all.
Wayne.

 

[tenring]

I have several Redding Instant Indicators. They work similar to Larry's tool, but are caliber specific.

 

[CaptainMal]

It's best looked at as being relative rather than absolute in measurement. I use multiple RCBS Precision Mic's. Also have the Hornady (Stony Point) gauge. Both work great but I would never trust their absolute measurement readings. But, they both work to establish a benchmark you can compare other things to.

Your mike is showing you have the sizing die down too far. Just size down to maybe .001" below what is coming out of your chamber. All the tools are GREAT for that.

If you get a press, shell holder or die change that messes a setting up, the Precision Mic will find it and allow you to make corrections. Recently blew a head off a 270 case shooting a deer. Checked and trashed over 100 loaded rounds with .007 - .009 headspace issues. Darn RCBS press insert came loose and moved down without me catching it. The Precision Mic did.

Great little tool.

 

[BoydAllen]

Generally speaking, the RCBS Precision Mic. is a reloading tool that is designed to be used to compare fired case "headspace" to that of FL sized cases from the same rifle. Headspace is not a function of reamer dimensions, rather is determined by how far the reamer is run into the barrel during chambering relative to the barrel shoulder, and shoulder to bolt face measurements. (whether a reamer is SAAMI max, min. or custom dimensioned) A rifle's headspace is considered correct within a specified range. The GO gauge is the short end of that range. (The difference between GO and NO GO for a .308, the .243s parent case, is.004.) Rifles are not generally chambered at absolute minimum headspace. Doing so can cause problems with being able to set FL dies down far enough to bump shoulders. If RCBS was trying to make a tool that would be as nearly correct as it could for most rifles, setting the zero point at .002 over minimum would make some sense. Again these tools are not used for setting headspace when barrels are chambered. They would not work for that. They are for comparing fired and sized cases while setting FL dies for a particular rifle. Use the right tool for the right job. I doubt that there is anything wrong with either of yours.