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Just got the SAAMI drawings for the .300 Winchester Short Magnum case and chamber.<P>These are the maximum CASE dimensions. Chamber dimensions, of course, are altogether different.<P>rim diameter (�) � 0.535 inch<P>base � at 0.200 inch from breech reference line (BRL) � 0.5550 inch<P>shoulder � at 1.664 inches from BRL � 0.5381 inch (angle 35�)<P>neck � at 1.8021 inches from BRL � 0.3440 inch<P>mouth � at 2.100 inches from BRL � 0.3440 inch<P>cartridge over-all length 2.56 to 2.86 inches<p>[This message has been edited by Ken Howell (edited March 03, 2001).]

Could you post the drawing with the dimensions? For those of us not familiar with all the technical lingo, it's a little hard to "see".

Don't have the way to post drawings, so you takes what you gets! �o)<P>What's "technical" about what I posted?<P>"�" is shorthand for "diameter."<P>"BRL" is shorthand for "breech reference line," which represents where the face of the bolt is when the cartridge is in the chamber. It's the end of the cartridge, where (when you turn the cartridge or the case 90� in the right direction, you see the headstamp on the case.<P>In most case and cartridge drawings, the breech reference line is a vertical (up-and-down) line at the head end of the case, and the drawing of the case is to the right (this direction ��� > ) from the vertical line. All the lengths that I listed are from this vertical line, going in this direction ��� > from the vertical line.<P>At this end ��� > of each length that I listed is the diameter ("�") that I listed � for the base reference diameter, the shoulder diameter, the diameter at the base of the neck (front of the shoulder) and the mouth of the case.<P>I hope this makes it all less "technical." It's the best I can do with "jes' words" without "none o' them purty pitchers." Sorry 'bout that!

Dr. Howell, thank you for going to the trouble to share the numbers with us. <P>Thank your friend at Winchester for us too.<P>I'm not sure if I have any use for the WSM yet or not but its always better to know than not! Joe.

thanks for the explainations!(Now I SEE!) I did not know how or what that zero with a line sorta through it meant or BRL. guess i shoulda asked! (silly me!)

Mr. Howell do you have the pressure info on this round? People are asking about chambering this round in a Model 88 Win or a Model 99 Savage. It sounds like that might not be a good idea to me but I do not have your experience or knowledge. Sean<P>------------------<BR>Ask me about microwaving cats for fun and profit!

I don't have SAAMI's maximum pressure for this cartridge. My best GUESS is that it's probably rated at 60,000 lb/sq in. maximum � the pressure maximum of so many modern high-pressure cartridges.<P>I'm extremely leery, at this point, of rechambering any rifle other than a very strong modern bolt-action rifle for this cartridge, for two reasons:<P>� Enlarging the diameter of the chamber reduces the thickness of the steel around the chamber. The area of the greatest risk is where the steel is already thinnest � between the chamber and the minor diameter of the barrel thread (the diameter between the bottom of the thread "V" on one side to the bottom of the "V" directly opposite). The receiver at this point is an imperfect support for the barrel in terms of its ability to withstand extremely high pressure without distortion (bulging or bursting).<P>� Increasing the case diameter also increases the FORCE or thrust against the breech at any given peak pressure. The ratio of increase in force is the ratio of the increase in the net area of the case web (the area of the case web inside the walls of the case). Pressure is force per square inch. Increase the square-inch figure with the pressure the same, and simple arithmetic produces that much more force.<P>These are inescapable, irrefutable, real-world facts, not subject to wishful thinking or contrary opinion.<P>For these reasons, I would have no part in rechambering a Winchester Model 88, Browning BLR, Savage Model 99, or any similar nonbolt-action rifle for such a fat high-pressure cartridge.

Mr. Howell,<P> Thank You for your reply. In one of the reports on this cartridge the author mentioned 65,000 psi (not trying to contradict your answer to my question). I did not think such a conversion was a good idea and your reply strengthens my belief. Sean<p>[This message has been edited by LoneEagle (edited March 09, 2001).]

A friend of mine brought one of these cartridges back from S TEXAS two years ago where he had guided some WIN reps. They were saying then that it was from a GIBBS or JEFFRIES,I forget which.We had a 300 rum to compare it to,and it sure favored it.Sharper shoulder as I recall.<P>------------------<BR>Good judgement comes from experience,most of which comes from bad judgement

Mr. Howell: In your initial post on this, you stated that case dimensions were quite different than chamber dimensions. Would you be so kind as to go into a detailed explanation of this difference. <BR>When we see SAAMI chamber drawings, how do these differ from case dimensions? Generally, when designing or dreaming a "new" cartridge, I believe we are talking in chamber dimensions, and if carried through, these are what are provided to the reamer manufacturer and often the die maker as well. If we are starting these drawings (chamber) off of the measurements made from cases (parent), might not we be heading for a problem? Thank you.

Arts,<BR>Your max cartridge dimensions will be slightly smaller than your min chamber dimensions. This is to allow chambering of the cartridge into the chamber.<BR>Headache

Headache--I savvy that, but there is a lot more to my question that I would like to learn.

<BLOCKQUOTE><font size="1" face="Arial">quote:</font><HR><font face="Arial" size="2">Originally posted by Arts:<BR><B>Headache--I savvy that, but there is a lot more to my question that I would like to learn.</B></font><HR></BLOCKQUOTE><P>I'm with you on this one Art. The chamber guy at PAC_NOR told me yesterday that his friend had a no one in 300 RUM and was having trouble with sticking cases. Since I'm having one made in 7mm RUM, and given the rifle's weak extractor, I,m holding off on buying dies until I can find out more about this " case to chamber" difference.I bet Ken can enlighten us. He has a knack for explaining things.<P>------------------<BR>Good judgement comes from experience,most of which comes from bad judgement<p>[This message has been edited by gene williams (edited March 14, 2001).]

That's exactly the person I'm hoping will address this.

One interesting thing I've noted about the 404 case, and the supposed 404 based RUM cases. The 404 is specced as .540" diameter at the head and rim. The new ultra cases I've measured are .545" at the head, and .532" at the rim. A fired 300 ultra case I picked up was .550" at the base. Go figure huh? Another concern I'd have about using the Ultra case in a #1 is falling block extractors aren't the best for rimless rounds, and when you go rebated, it should only make matters worse.<P>I'm still concenred about how the ultra cases will function in my 416 howell, as the Howell is designed for 404 brass, not ultra brass.<P>As far as specs, SAAMI specs are designed so that the largest of factory cases will fit the smallest of factory chambers. To allow for manufacturing tollerances, there will be several thousands difference in case and chamber dimensions. This is where custom guns come into there own, the factory chamber that is likely .005" over brass dimensions can be brought down to .001-.002" over in a custom gun, brass life increases as well as accuracy. Most important is a throat just over bullet diameter, like .0001" over, that is where most accuracy is gained or lost.<P>I also look forward to learning more from Ken, and thanks again for selling me the 416 reamer, I know John is putting together several guns as we speak, and I can't wait to see what the Oehler 43 says. A great design, but 20 years to early. Sorry for the tangent.

458 Lott: Mr. Lott, I don't want to stick my nose in where it doesn't belong, but if you have a .416 Howell made on a .404 Jeff case, then the Ultra cases won't work because your extractor won't grab the rebated rim, or at least not fully. That's the only MAJOR problem (if the Ultra cases are long enough), because the case will fireform to your chamber, but I suggest you are going to be pretty bitter the first time you fire one. I hope you don't have too much trouble getting it out of the chamber!

Art,<P>Yes I've considered the rim issue as well. I don't know that it will really be an issue, the rim is only .004" less of a bite on the extractor. In theory the gun should be able to digest either case equally well. That said, I'll likely use the less exspensive ultra brass for practice, and 404 brass for hunting.

In preparation for making all those 930 case drawings in my first Custom Cartridges book, one of my first decisions was to NOT make the mistake so many others have made � using hearsay dimensions. Since most 'loaders mike cases, not chamber casts or reamers, clearly my best choice was to make case drawings, not chamber or reamer drawings.<P>Also, of the hundreds of official drawings that I have on file, from dozens if not hundreds of sources, the vast majority are case drawings, not chamber or reamer drawings. For most of them, I have only case dimensions, not chamber or reamer dimensions.<P>One problem was, and is, that for a good many cartridges, all I've been able to find are chamber and reamer drawings. Often, the only surviving paper trail for a wildcat cartridge is the reamer-grinder's dimensioned schematic drawing of the reamer � no detail at all on the dimensions of the case.<P>So I studied over a hundred old and recent SAAMI maximum-case and minimum-chamber drawings, comparing related dimensions to derive a rule of thumb for deriving case dimensions from chamber or reamer dimensions.<P>I got gibberish � a wide variety of clearance dimensions with no discernible rhyme or reason. I discussed this with a few reamer-grinders, who all confirmed my conclusion. There is no clearly establishable dimensional relationship between case dimensions and "corresponding" reamer dimensions (shoulder diameters, for example).<P>Apparently, each TYPE of case has its own unique set of loose "rules," with no firm standard or agreement for any of them. My impression is that for each type of case, every reamer-grinder has his own ideas about how much clearance is necessary at each key point on the case and chamber for the case to enter and be extracted from the chamber without binding or allowing excessive case expansion.<P>One reamer-grinder gave me a set of very general clearance dimensions � for my use ONLY in deriving very general case dimensions for my next Custom Cartridges book. I made a special generic "case in the chamber" sketch with just those general clearance dimensions on it. It's here somewhere � it kept turning up when I wasn't looking for it.<P>I've been looking for it ever since you posted your question, and haven't been able to find it. (I also want to make a CAD drawing of it on my hard drive, for reference when I'm making "case" drawings for the many cartridges that I have only reamer drawings for.)<P>My design approach has always been to make a carefully developed case drawing, then let the reamer-grinder use his judgment in adjusting the key dimensions for the reamers.<p>[This message has been edited by Ken Howell (edited April 08, 2001).]