.300/221 Rimmed?

[BitOfShush]

Thanks everyone... some very good points raised.

D-Mon
In my enthusiasm to post my results, I didn't acknowledge your help with the methodology

Regarding neck thickness, the .300/221R made from .357 Max brass measures 0.010" vs the .300/221 case made from old reformed 223 Win brass measures 0.0115".

.300/221 cases made from 221 Fireball brass measure from 0.085 to 0.0115" (they definitely need neck turning, I'm not surprised at the lack of concentricity given the extreme sizing from .224" to .308").

Stands to reason the .300/221 case has a thicker neck, as it is originally part of the shoulder.

These measurements are taken with a Mitutoyo digital vernier, not the best for measuring neck sizes... I'm getting a digital pipe micrometer soon, which will be far more accurate.

Jon
I sectioned both a .300/221R (discarded non-annealed case) and a standard .300/221 FB, and there is indeed a slight difference in case thickness at the head. Measured as best as I could just above the web, the .357 Max case wall thickness is 0.0395" vs 0.0400" for the .300/221 FB created from Winchester 223 brass.

Note the amount of burrs around the flash hole on on the Remington .359 Max case!

The biggest difference was in the case head thickness just below the primer pocket... the .357 Max brass is MUCH thinner than the 223 brass at 0.0480" vs 0.0780". The radius between the head and the case walls was also different... the .357 Max case was exactly R1.0mm vs R1.25mm on the 223 case.

Not sure how much difference R0.25mm and 0.005" wall thickness will make in overall case strength, but the much thinner case head below the primer pocket is a worry. It would be VERY wise not to exceed moderate .300 Whisper supersonic loads

Redtazdog
Thanks for the links... I'm sure I'm just reinventing the wheel with this .300/221R cartridge...

I'll see if BellM have a standard reamer print, but I'll also have some more fun designing my own

BoS

[JFettig]

quick results on sectioning those cases!

It looks like your .223 case has had its flash hole uniformed. I'm sure the .357 max cases could use that.

Its hard to say about the radius, its not that much of a difference but could make a difference. The one thing to notice is that the wall thickness increases before it gets to the radius. Did you measure both just above the radius?
That .0005" wall thickness wouldn't make any difference I'm sure, but the case head thickness might be a problem. I seem to recall that federal .223 brass had a case head thickness of around .050". You could section a few different common brands, RP, LC, Federal, and FC(yes, FC and Federal might be different, .223 vs 5.56).

One more thing to measure: the primer pocket depth. I seem to recall that pistol primers aren't as long as rifle primers. I'm not 100% sure this is true.

Regarding case length and reamers. I am pretty sure that the clymer 300/221 reamer is made for a 1.4" case length(from their old print anyway that they use to have up). Are all other outer dims the same?

Jon

[BitOfShush]

Flash hole uniforming is definitely on the list

Did a bit more measuring of primer pocket depth on both cases :

.300/221 FB 0.1165"
.300/221R 0.1180"
Difference 0.0015"

Yep, measured the wall thickness at the tangent of where the web radius joins the wall... did so a number of times to get a consistent reading... tricky!

One thing I didn't take into account is that this rimmed cartridge will be used in a Martini Cadet falling block action, and therefore the entire case will be supported by the relatively thick chamber walls... unlike the bolt and AR15 semi-auto actions where part of the rimless case head projects from the chamber and is enclosed by the bolt/extractor. Hoop strength of the relatively unsupported rimless case is crucial to maintaining primer integrity in high pressure loads.

Checking the 2006 Winchester Reloading Guide reloading catalog (which features CUP pressure readings on many cartridges) I discovered on that the .357 Maximum 180gr FMJ load develops 46,900 CUP vs the .223 Rem 55gr FMJ load's 41,000 CUP... so it would seem the case is plenty strong enough if well supported.

I'd say the weakest link is the primer... I had also heard that small pistol primers were slightly shorter than small rifle primers, but I can't find any confirmation on the web.

Indeed, while Sinclairs list both a large rifle and large pistol pocket/depth uniformer, they only list one small rifle/small pistol uniformer.. which suggests they are the same length.

There is an interesting article by James Calhoon at:
http://www.jamescalhoon.com/primers_and_pressure.php

He sums up:
"What does all this mean to the reloader?

- Cases that utilize small rifle primers and operate at moderate pressures(40,000 psi) should use CCI 400, Federal 200, Rem 6 1/2, or Win SR. Such cases include 22 CCM, 22 Hornet and the 218 Bee. These primers are also used in heavy handguns such as the 9mm., 357, etc. Other cases that use the small rifle primer can use the above primers only if moderate loads are used. Keep to the lower end of reloading recommendations.

- Cases that utilize Small Rifle primers and operate at higher pressures (55,000 psi) should use CCI 450, CCI BR4, Fed 205 and Rem 7 1/2."

I already have 1000 Federal SR Match primers, so will try them out first for cup thickness and consistency of ignition in sub-sonic loads... they seem to get a good rap from those picky benchresters!

Yes, aware of the issue with the case length of Clymer's reamer... PT&G are on the ball and specs are correct for their standard .300/221 reamer.
Interestingly, the 300 Whisper is also referred to as the 7.62x35mm in military sniping circles!

Some dimensions for the rimmed cartridge will change from the standard .300/221 FB (freebore, throat angle and case taper) to better suit cast lead bullets in a falling block action with less than stellar extraction.

I will complete the drawings over the next couple of weeks and send to PT&G for feedback... and then post here.

Thanks again for your help

BoS

[BitOfShush]

Spent a bit of time today making up some dummies to check freebore requirements etc and just thought I'd share them with the group:

[LouBoyd]

It looks to me like the 32-20 Winchester cartridge has just been re-invented. At least it's similar in shape and case capacity. TC used to offer the 32-20 as a standard Contender barrel for use with 308 diameter bullets, 10" twist.

It seems to me that these cartridges:
30 Luger (14.29 grain capacity)
30 carbine (21.0 grain capacity)
30-20 (21.7 grain capacity)
32-20 (22 grain capacity)
have been pretty much ignored for use as subsonics, arguably because of the lack of suitable strong actions to use with long heavy bullets. The 300 Whisper's capacity is more than necessary even for 240 SMKs.

[Thunderbolt]

G'day BoS, I have a Martini Cadet set up as a switch barrel with barrels in 17Mink and 20/357max. I'm watching this thread carefully as one of my future projects was hopefully to be a 300 Whisper Rimmed using 357max brass. My current project is a 310/357mag with the original barrel.
The thinking behind the 20/357max was to use standard reamers and dies, to eliminate the cost of custom dies and reamers which are quite substantial here in Aus. The chamber was cut by my local gun plumber with a standard 204R reamer run in short to 357max length and a rim recess cut in the face of the barrel. The reloading dies are cheap Lee ones. I trimmed the base off them to the right length. That was all easy and then came the usual problems you find with wildcats. as you discovered 357max brass is really hard and must be anealed before necking down. The next problem was the difference in diameter at the base of the case. The sized 357 brass would not fit in the chamber because of that few thou interference fit. I tried sizing down the solid head on a case but that was a wasted effort. So back to the Gunsmith and had him lap out a couple of thou from the rear of the chamber till the FLS max cases slipped in. Problem solved .I have the barrel stamped 204 short rimmed and its now up and running and slaying rabbits.
I believe from my experience that for a 300 whisper rimmed I would just have a chamber cut with the standard reamer and a rim recess cut to suit the max brass. Them I would use 300/221 dies and a 357mag shell holder. You already have the case forming sorted out- just give you G'smith a couple of your cases so he can lap out the first 0.200 of your chamber to suit your brass.
If you decide to go the custom reamer route then PTG are really good to deal with. There was no problem at all getting the 17Mink reamer from them.
I have assumed from the CBE bullet that you too are in Oz.
Keep us posted

Cheers

[Seddo]

How cool is this, someone else thinks the way i do. I have 2 x 22R martinis and a 357mag martini and have bene thinking about trying to get a whisper style round chamberded on a rimmed case. I was planning to use 222R cases instead of 357mag but either way who cares.

Let us know when you have it sorted, i would be happy to contribute to the cost of the reamer if i was allowed to get a barrel reamed with it. I looked at a thompson contender just so i could buy a whisper barrel but would prefer to use a martini.

[Thunderbolt]

G'day Seddo, BoS is probably still waiting on his reamer from PTG, takes at least 3months to get one. Hopefully he will keep us posted when he's got it going.
I have a Contender frame and MGM barrels are easy to import but like you I would prefer to do one on a Martini.
357 Max brass is cheaper and stronger than 222 rimmed brass, its downside is that its really hard and must be annealed before necking down

T'bolt

[amafrank]

You guys might try checking with Dave Manson at Manson reamers. He's been making some oddball stuff and I got my 300-221 reamer from him. His stuff is all top quality and the customer service is better than any of the others I've dealt with.

From all I've read the small rifle and small pistol primers are the same outside dimensions with the thickness of the cup and material hardness being the only difference. Its the large pistol primers that are shorter than the large rifle as they share diameter too. That means loading the 357 max cases with small rifle primers is a very doable thing and recommended if the pressures are up there. I know guys who load small rifle primers in a number of high pressure handgun rounds as a standard procedure.

Looks like an interesting round to fiddle with and I was at the bluing guys shop today looking at a few max's he had on the bench and thinking how well they would do for a whisper type round.

Frank

[BitOfShush]

At LAST, the .300-221 Rimmed reamer has arrived

Sent PTG three formed .300-221R cases to take measurements from using their optical comparitor, also measured the neck thickness of 20 357 Max cases as well as 20 formed cases to ensure the reamer neck diameter was correct.

The normal 2-3 month custom reamer timeframe was lengthened by a couple of communications stuff-ups and then the Go/No Go Gauges were found to have been made up to the wrong specs! Once notified, PTG acted very quickly to rectify the problem however, and new gauges were promptly sent out.
Very pleased with their customer service overall...



Because of the nature of headspace in a falling block action (and potential slack in the linkage pins) I elected to have the rim gauges made up at .060" Go and .065" No Go.

NOW... I want to use this project to determine whether my chosen .300-221R specs for case length, freebore, neck clearance and leade angle will work with cast projectiles yet still allow longer jacketed projectiles (SMK etc) to be chambered down a standard Martini Cadet action ramp... I don't want to be grinding down the ramp and weakening the action

Some interesting barrels being produced at Truflite in NZ:
http://www.truefliteriflebarrels.co.nz/13544/index.html

I have an old Omark 44 .308 win heavy target barrel with a shot-out throat but otherwise great bore ($20 at a Gunshow!) that would be just perfect as a 'test mule'... the heavy profile will easily turn down to the Cadet's 1" external profile and .750" x 14 tpi barrel tenon.

Twist is 1:9.5" so it may not stabilise the really heavy slow stuff but I can then determine whether I like the round enough to stump up for a nice match grade 1:8" barrel.

I will post again when I have something to share... but as Captain Oates once said "... I may take some time"