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Old April 10, 2013, 09:39 AM   #26
Unclenick
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This is a bottleneck rifle case that headspaces on the shoulder, so all that matters with respect to jamming the neck in the throat is how long the neck is in the chamber as compared to how long the neck of the cartridge case is, and not the total length of the case. This causes confusion because the length of the case is what most people measure and what most trimmers use. Due to the error it introduces, there is some wiggle room built into the specs. Today you can buy trimmers that register off the shoulder that address the neck length directly (e.g., Possum Hollow, WFT, Gracey, and Giraud, in order of increasing cost), but they are not yet ubiquitous.

On that chamber graphic, the only chamber on that chart that gives me pause for concern is the PTC Match reamer with the very short 0.2034" neck. That is very close to the SAAMI 0.2027" maximum neck length. If I had that chamber, I would be watching trimming very closely, indeed, and checking neck length after sizing. The Wilson type gage is the quickest way to spot a long neck. The other chambers all have at least a hundredth in extra room that could be exploited.
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Old April 10, 2013, 10:09 AM   #27
BumbleBug
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Quote:
Originally Posted by jepp2
Or maybe rather than just expressing opinions, we offer data. For a minimal investment, you can buy a chamber length gage and determine the actual chamber length and what your maximum case length is. This would seem to be a better alternative to pulling bullets if that isn't necessary. You can buy it http://www.sinclairintl.com/reloadin...ku=749-000-811


jepp2 is right! Here is a .270 shell ready to measure for the length of my chamber. This is a must for people like me who don't trim every reload cycle or for someone worried about the safety of reloaded ammo in their own rifle. I order a plug for each new caliber I reload for.

BTW: Although I have not measured thousands of chambers & I've never measured an AR chamber, I've found most to be very generous in regards to SAAMI length.

FWIW...

...bug

Last edited by BumbleBug; April 10, 2013 at 10:34 AM.
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Old April 10, 2013, 10:17 AM   #28
Brian Pfleuger
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Interesting doo-dad but I can't see having a use for it, personally. Trimming is a simple, one time operation for me. I use the Lee case length gage and holder mounted in a cordless drill. All cases get trimmed to that length. I have never again had a case approach maximum length, over 8-10 reloads. I measure a few every time I load them. Even if the cases weren't too long for my chamber, I'd trim them once anyway, just for consistency.
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Old April 10, 2013, 05:00 PM   #29
schmellba99
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I use the plugs to measure my chambers as well (on bolt action rifles) and trim the brass to .003" short of an average reading.

Does it do anything good? Maybe, maybe not. Does it do anything bad? Maybe, maybe not.

What it does do is give me the ability to uniform my brass with the longest possible neck for my particular chamber. That means I have the most possible contact between the brass and projectile, and for my thought process that is a good thing.

BTW, the .223 ones are poorly manufactured in my opinion. The plug end is much too thick and needs to be turned down so that it can function properly.

I wouldn't waste my time measuring the chamber in an milspec AR though - they are mass produced barrels that are designed to tolerances that must accept ammo made from umpteen different manufacturers with umpteen different sets of quality control standards. Yes, theoretically they are all held to SAAMI specifications, but we all know and live in the world of reality and should understand that even with grandfather specs, each manufacturer produces ammo that has significant (in reloading terms anyway) dimensional differences.

AR chambers, outside of match or Wylde chambers, are very forgiving for ammo that is not exactly per spec. One of the reasons they are as good of battle rifle platforms as they are.
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Old April 10, 2013, 10:43 PM   #30
swcc22
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Re: So my buddy didnt trim

Trimming sucks (imo ) but it needs to be done
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Old April 11, 2013, 09:16 AM   #31
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Schmelba99,

Taking your last point first, all that matters in the chamber for trim purposes is the length of the chamber neck coming off the shoulder. That is determined by the reamer neck and shoulder profile. The neck length will be the same whether you use that same reamer to make a tight headspace chamber or run it in deeper to make a loose one. So unless the reamer is out of spec, even mass-produced, pre-chambered drop-in barrels will still have the SAAMI spec neck length pretty uniformly.

That length is the letter "M" spec on the reamer chart steve4102 linked to in post #25. I made an exaggerated drawing of the failure of headspace and total case length to control this once. I'll see if I can find it and stick it in here.

Found it. This is to show what you can measure with the Redding Instant Indicator tool. You can do this by relative readings using the difference between the case headspace and bullet ogive readings you get from the Hornady caliper adapter and inserts. The main thing is to notice the case lengths in both instances are the same, but how far the case mouth will go into the chamber neck is not, because the case stops on the shoulder.



Your 0.003" clearance reminds me Hatcher mentioned that rapid chambering (Enfield chambered at bolt-action rapid fire pace) could push the shoulder on the .30-06 back up to 0.006", meaning the neck would then stick into the chamber at least that much further. Given that the extra brass flows mostly into the neck during sizing, it should actually go in still further. This is probably why 0.010" to 0.020" of extra room is common in SAAMI spec chambers. The .223 rounds are lighter and won't have as much inertia for the slam forward to resize them with, but I'll bet this consideration is why the PTC Match chamber spec on that chart has 0.007" clearance from a SAAMI maximum case length. If you haven't done so already, you might want to try taking a few pickup cases you find at the range, making up dummies with them, then letting your AR chamber them or running them into your bolt gun chamber as fast as you can, then measuring them for neck growth.

Your comment about the Sinclair gage being tight reminds me that reamers wear out, narrowing with resharpening, and you can get some narrower necks that way. It is also another reason to look at that chart Steve linked to. Look at the range of chamber neck diameter differences ("E" and "F"). That, in turn, put me in mind of board member Hummer90's posts on case life at another board under the user name Humpy. He gets chambers cut with extra narrow necks so the case neck doesn't expand so much during firing and therefore isn't worked as much in resizing. He's got one .30-06 case that's been loaded and fired 158 times. Worth a read.
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Old April 11, 2013, 01:40 PM   #32
schmellba99
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My comment on the Sinclair gauge is that the shouldered portion of the gauge is too thick (not the radius - it measures what it should).

Without a drawing, basically I had to turn down so much of the neck on my .223 that the gauge would have almost no neck tension to hold it in place because the plug portion that bottoms out on the end of the chamber was too thick - I had to turn it down so that there was enough neck on the test cartridge to provide some tension to hold the plug in place, but still allow me to turn the brass neck down enough that the purpose of the plug could be utilized.

I hope that makes sense anyway.

Concerning the neck, we can nit pick everything here to death. There are a great many of you that get way more into minute details that I don't view as being really important concerning reloading rounds. I'm of the opinion that there is such a thing as diminishing returns and that spending countless hours on miniscule details on ammo for something like a milspec AR chamber or even a factory bolt action rifle chamber from any one of the production manufacturers just is not worth the time. Some folks derive great enjoyment out of that, and that is perfectly fine, but we can all agree that for the most part much of what we do as reloaders really goes well above and beyond what is necessary in the vast majority of firearms we own.

Case in point is this discussion about neck length when discussing a mass produced milspec chamber that is designed to be forgiving. A neck that is marginally out of spec is not going to cause problems any more than a chamber that has not been cleaned in 6 weeks and has had a few thousand rounds put through it during the course of battle in some God forsaken environment like Afghanistan or Iraq.

On the neck length discussion for bolt rifles, I can tell you (although I am at work and don't have my data with me) that on my Winchester Model 70 .243 run of the mill production rifle, the neck length is such that I don't have to trim brass very often because of the length from the bolt face to end of the chamber (in fact, I have some brass I purchased new that has 3 or 4 firings on that I still don't have to trim yet). On my Winchester Model 70 .223, I have to trim more frequently, but certainly not every firing. While that may not sit well with the anal retentive group, it suits my needs perfectly as it eliminates/reduces the frequency of an additional step in the reloading process (and one that I don't particularly enjoy doing), so whether or not it makes any difference at all in the overall results of the round's performance (highly doubtful), I like it. Both rifles shoot 1/2" groups at 100 yards and will hold MOA out to 400 (furthest I've shot either for measurement) with my handloaded rounds, which for my hunting purposes is far more than adequate.

Concerning my AR, I don't shoot it for precision. I FL resize every round with my factory run of the mill Hornady dies and load away, trimming every 3rd reload or so back to book spec. I will never spend the time measuring the chamber for a rifle that I never expect match performance out of. Additionally, I like the idea of slightly relaxed tolerances in that rifle so that it functions in less than stellar environments (great when you are hog hunting in the gumbo mud on the Texas gulf coast or are out in the desert in AZ and covered in sand).

In my bolt hunting rifles, I'm more interested in the brass lasting longer than my AR, but I'm not overly concerned about brass life either. In my AR, 4 or 5 reloadings on brass and odds are I'm not going to spend all that much time worrying about it as I don't have the time or desire to start annealing mass quantities of brass (were I to have a Giraud annealer and trimmer, that mentality would likely change).
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Old April 11, 2013, 04:39 PM   #33
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I sure understand all that. I often post in detail in part so strangers lurking in the forum won't try to copy something without understanding it.

I own lots of benchrest type loading tools even though I don't shoot benchrest. I found years ago that some guns would turn out to be picky about something unexpected, though. One year I was playing around with shooting Accurate 2520 in my M1A and was having trouble getting consistent groups. The gun would should about 0.7 moa with 168 grain Sierra MatchKings in any tuned stick powder load, but was about 1.25 moa with 2520. When I was working on the loads one day, I accidentally picked up some cases that I had carefully prepped for a Remington 600, and discovered the M1A groups shrank to the same 0.7 moa I could normally get from it with stick powders. By eliminating steps one at a time, it turned out to be flash hole deburring that was doing the trick. It never made any difference to my stick powder loads, but it did to my 2520 loads.

Ever since then, I've used every trick I could find to eliminate all variables except the one I'm controlling for the load development. That usually lets me find a load that doesn't need much done to it, but which would have been a lot harder to identify without having started out as perfect as possible. There's a mathematical reason this is true that has to do with the way standard deviations add.
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