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Question for the ballistic experts!
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<wildcat51>
posted
This question concerns the 356 Winchester cartridge. It is a fact that most custom barrel makers refuse to chamber contender barrels for 356 Winchester. (As a reminder 356 Winchester brass is available from many suppliers at the moment. It is in reality the 307 Winchester case with a .358 neck. Dies used are your standard 358 Winchester.) Now I understand the concern is pressure. Consider the following when comparing 356 Winchester, 358 Bellm, and 358 JDJ load data. I picked one of the most popular powders that is used in all three, H4895, and the 200 grain bullet for comparision.

-------------------------------------------
Hodgdon Manual No. 27 356 Winchester

Start - 43 grains Max - 46 grains
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358 Bellm load data

Start - 46.5 Max - 48.5
---------------------------------------------
Handloader Number 153 358 JDJ

52.5 compressed
---------------------------------------------

Compare the load data and it seems like the 356 Winchester is the baby of the bunch. I understand that the 358 Bellm and the 358 JDJ use 444 Marlin brass. Furthermore the 358 JDJ might have a diffrent taper that helps with pressures. But the 358 Bellm uses 358 dies as does the 356 Winchester. Just need some help understanding whats going here because I am confused. Is factory ammo really that hot compared to reloading data?
 
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<Headstamp>
posted
Well,

The JDJ and the Bellm round have more capacity than the 356. The Bellm and JDJ are about 1/4" longer in case length with the JDJ round having the shoulder furthest forward meaning the most capacity of the three.

The Bellm round uses a 358 Win sizer but the shoulder position is further forward than the 356 so the sizer really doesn't size all the way down the case. A Marlin die is used to size this remaining area. The resulting longer body gives it more capacity than the 356.

307 and 356 brass runs thicker also especially near the bottom third of the case. Remember, 307 and 356 data are not interchangable with 308 and 358 data. This is due to that thicker brass being taken into account.

In a stronger action like an Encore, one could goose up the pressure of the two wildcat rounds to 356 level and most likely have ballistics exceeding the 356 due to the increased powder space and being in a gun able to handle it.

The main reason for not chambering the 356 is the availability of factory ammo loaded to pressures/backthrust above what the Contender is designed to handle.

I'm no expert, but I play one on TV. [Wink]

Regards

[ 03-09-2003, 00:06: Message edited by: Headstamp ]
 
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<wildcat51>
posted
(correction made to agree with Headstamp) Pressure for the 356/358 win are the same. Yes the necks are longer on the 444 marlin based cartidges. What affect that would have on lowering pressure I am not educated enough to explain. The 356 win brass is thicker and 358 win dies properly sizes the web which should help contain pressures more if that is a concern. The fact that the wildcats have more internal capacity means that handloader maybe tempted to load them even hotter than the 356 win which seems to be the problem if it is one. What concerns me the most is that just because a cartridge is wildcat people think that the sky is the limit when working up load data.

A none related example of this is the 25-06 AI. Just spend a few minutes looking at some of the loads that some people are shooting vs the standard 25-06. Minor changes in the case does not give the excuse to load your case with enough Reloader 22 to exceed 257 Weatherby ballistics. But there are some out there that are doing just that.

[ 03-09-2003, 02:32: Message edited by: wildcat51 ]
 
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<Headstamp>
posted
Actually the 356 and 307 ARE loaded to the same pressures as the 308 and 358.(52,000 CUP) The only difference is it takes LESS of a particular powder to do it due to less powder space in the 307/356 due to the heavier walled case.

Longer necks are one thing but not the full story. Look at shoulder location compared to the the shorter 307/356 rounds. That's where the extra case capacity comes from for the 358 JDJ/Bellm rounds. Longer body length sans neck.

Anyone can overload any cartridge when handloading, that is really the handloader's responsibility. A gunsmith has no control over that or factory ammo pressures either. Hence, you won't find a 356 or 307 being chambered in a Contender.

Regards
 
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<wildcat51>
posted
I can except factory pressure limits for not chambering the 356 winchester. But the load data for the other two still puzzles me. Maybe some questions are better off left un-answered.
 
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<Headstamp>
posted
You lost me with your reply so I'll just defer to others to reply further on this subject.

Gave it my best shot. [Wink]

Regards
 
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<wildcat51>
posted
Let me explain myself more clearly. Putting posted 356 win pressures aside. The load data (grains of powder) same powder and bullet weight for the 358 Bellm and 358 JDJ equals or exceeds the 356 Winchester load data in the Hodgdon manual. Are the wildcats more forgiving of pressure or is the data in the Hodgdon manual ultra conservative?
 
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one of us
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wildcat51,

Case capacity is the key. The Bellm round and 356 have the same case taper while the JDJ round has less taper, decreasing backthrust. Backthrust is one of the keys with the contender.

Look at the 308/30-06 cases. Put 30 grains of powder in each and you'll get two different pressures because the '06 has a larger capacity. It may take 35 or 40 grains of the same powder in the '06 to reach the same pressure as the 30 grain charge in the 308.
 
Posts: 242 | Location: Beaumont, tx | Registered: 20 March 2002Reply With Quote
one of us
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Never say never......At one of the last gunshows here, Ed K. of Ed's Contenders had a rechambered contender barrel in.....yep.....356 Winchester!

I thought seriously about buying it......there is nothing unsafe about it IF the owner knows what he is doing and loads accordingly... it's not a problem if the loads are tailored for the pistol. I would simply treat it just like any wildcat and work up loads that were safe.

On a side note, I have corresponded with a guy who had a Contender barrel rechambered to 308 winchester and fired hundreds of full power loads through it without any problem......I wouldn't do it or recommend it, but it has been done.......
 
Posts: 1499 | Location: NE Okla | Registered: 22 May 2002Reply With Quote
one of us
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Wildcat51,

This is a really simple question you post.

Take two different cases that use the same bullet but one case has a 50 gr case capacity and the other has a 60 gr case capacity.

If you load 48.0 grains of a suitable powder in both under the same bullet. The smaller case will develope much more chamber pressure then the larger case.

Also even if we load 48.0 gr in the smaller case and say 52 gr in the larger case, the small case will still develope more chamber pressure even though it is using a smaller powder charge.

Just because two very different cases use similiar load data does not mean they are safe in the same firearms.

You can't just look at the load data and compare which round will be safe in different handguns. Life is not that simple, especailly here.

Good Shooting!!!

50
 
Posts: 701 | Location: Fort Shaw, MT | Registered: 09 April 2002Reply With Quote
<wildcat51>
posted
Fiftydriver,

Do you know of anyone that has pressure test data on the cartridges I am comparing?
 
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one of us
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Wildcat,

I have some "pressure-related" data on three Bellm cartridges which I derived from tests using the "Spring-Back" pressure determination method. That is a method Bellm suggested and I developed. It uses the "spring-back" of the brass case to determine a cut-off point for load level. The method centers on the fact that when brass stretches on firing it will spring-back toward it original dimension after the pressure has subsided. The amount of spring-back is inversely proportional to the pressure experienced during the burning of the powder. Since the spring-back is inversely proportional to the powder load, load work-ups will produce a linear curve up to the point the elasticity of the brass is exceeded. At that point the rate of growth of the brass case changes. The point where the growth rate changes indicates the maximum load that should be used in chamberings of reformed 444 Marlin brass in the Contender. It defines what I call the "Redline Load". This redline load does leave a safety margin, but to exceed it is certainly not recommended.

Three sets of loads I derived by this method are given on Bellm's page. http://www.bellmtcs.com Click on the Triad to see load data for the 7 mm Bellm, the 308 Bellm and the .358 Bellm.

Don Shearer
 
Posts: 223 | Location: Centennial, CO USA | Registered: 14 March 2002Reply With Quote
one of us
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Looks like most of the points have been covered pretty well here, but I would emphasize that the .307/.356 Win. brass is EXTREMELY thick back at the web area. It is much, much thicker than the .444 Marlin brass used in my .35 and the much greater capacity JDJ variety.

The thick brass is a two edged sword.... cuts both ways. One, it radically reduces case capacity, but, two, the thick brass takes much of the pressure load and keeps it from transferring to the breech face. Ie, the case acts more like a cork and less like a piston since the case 1) adheres to the chamber wall, and 2) its thickness resists stretching and allowing the case head to put full force back onto the breechface.

Given a choice of doing something extreme with a .308 Win or .307 Win. in a Contender, I would opt for using the .307 brass, hands down. Ditto, of course, for .356 Win v. ..358 Win. The .307/.356 brass is much thicker than both .308 Win and .358 Win. Bottom line is that with the same pressure, the thicker brass puts less strain on the frame.

BTW, regarding the discussions above concerning body tapers, they are all for all intents and purposes the same. Shoulder chamber diameters for .308 Win type cases is about .456-.457." Shoulder diameter for the .358 JDJ is about .455." Do the math if you like, but the JDJ with its longer body actually has a bit more taper than my round or the .307/.356 Win. Any difference is splitting hairs & mute point.

As for what the Contender will handle, I think there have been changes in heat treat/hardness of the Contender frames over the years. I recall some discussions about this back in the 80s but the details escape me.

Later vintages of frames appear to be pretty bullet proof, but still there are many examples of frames stretching.

I am still shaking my head in awe of the frame I saw withstand loads way too hot for even bolt actions...... and survive with no apparent loosening. But to push it like that is irresponsible.

Years of experience with all sorts of chambers suggests staying at about a 45,000 psi pressure level with rounds having the approx. .465" head diameter.

Gon Huntin is 100% right about handloading a .308 Win. to acceptable levels. I would suggest that if temptation prevails, he should have a rim counterbore machined into the end of the barrel to accept .307 Win. case rims. He could then use .307 Win. brass, and his frame would love him for it.

Mike
 
Posts: 791 | Location: Grants Pass, OR USA | Registered: 30 March 2002Reply With Quote
<wildcat51>
posted
Thanks Mike.

Like your explanation the best.
 
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one of us
Picture of LDHunter
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Classic Bellm!!!!

Added your message to my archives of your messages Mike.

Thanks for all the free advise you provide to us TC fanatics!!!!

$bob$
 
Posts: 2494 | Location: NW Florida Piney Woods | Registered: 28 December 2001Reply With Quote
one of us
posted Hide Post
You are most welcome fellas.

Thanks for the privilege of being part of the TC shooting fraternity.

Mike
 
Posts: 791 | Location: Grants Pass, OR USA | Registered: 30 March 2002Reply With Quote
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