Wildcat chamber to cartridge clearances?

[lar45]

Hi everybody.
I am considering a new semi-wildcat 35 cal cartridge and AR15 build.
First my question, then the details.
How much clearance between the chamber and the cartridge is acceptable at the case head?

I want to build a 358 something mostly for hunting Hogs in southern Arkansas, but it could also double as a Deer gun.
My thoughts are to use existing chamber reamers and loading dies, to avoid the high cost and wait time of custom tooling...
So two options.
1: 358 Win- run it in 1.700" in a standard .358" AR barrel, then cut the base off of stock 358 Win dies for case forming and loading. RP 308 win case capacity is 47gn H2O. Should be able to load to 46Kpsi
2: 350 Rem Mag- run it in 1.700" in a standard .358" AR barrel, then cut the base off of stock 350 Rem dies for case forming and loading. 450 Bushmaster case capacity is 54gn H2O. Should be able to load to 38.5Kpsi.

The only problem I forsee is the base of a 450 Bushmaster case is .500". Measuring down 1.7" from a 350 Rem Mag case shows .505".
Is this going to be too much slop, and will it cause problems when loading to 38.5Kpsi?

The 358 Win option seems to be the simpleist to do. Case forming is basically, cut the case, run it into the die, trim to length and you are done. Any 308 based case should work and cases are fairly cheap and will always be availible.

The 350 Rem option needs a few more steps. I tried running a case directly into the 350 die, but the neck folded up on me. So I ran a case into a 416 Taylor die to start a neck, then ran it into the 350 die and it worked perfectly. The neck is too thick, so it'll need turned. I have the Hornady tool, just need the 35 cal mandrel. 450 Bushmaster cases are much more expensive and who knows if they will go out of production in the future?

I am thinking of limiting myself to 180-200 grain bullets and make the cases as long as possible to seat a 200gn bullet, cast or jacketed, and still be able to fit into an AR15 magazine.
I have some Hornady 200 Interlock and FTX. I found some Speer 180s at Midway, they had a limit of 2, so that's what I ordered. For cast, I'm looking at the Lee 35-200.

I found an AR barrel manufacturer that said they would make me a barrel if I supplied a formed case to set the headspace with.

I ran several powders through Quickload
The 358 case should do
180- 2310fps
200- 2140fps

The 350 case should do
180- 2330fps. If I can find AR Comp, it might go 2410fps
200- 2170fps If I can find AR Comp, it might go 2240fps

One thought I had was with the 6.5x55 Swede, the base is .480", but some US ammo companies make ammo for it from 06' based brass with a .470" base.

I downloaded some pics:




The bullets will be seated deeper, that's just as far as I could go without cutting down the dies.

Now go ahead and shoot holes in my plans...

[Mk42gunner]

Interesting question. I think 0.005" may be too much, but I'm not sure. Have you compared chamber to cartridge dimensions and tolerances on the SAAMI website?

I haven't messed around with anything other than 5.56 in an AR, so I bet you already know which bolt head and magazine you will need.

One way to try things out might be to rechamber a break open .357 to the smaller of your cartridges to try, then if it doesn't meet your needs/wants, go with the larger round.

As for case length, I would set it so the Lee 35-200 ended up at magazine length or very close to it.

Sounds like fun.

Robert

[Moleman-]

Have you looked at 358 Yeti? https://mdws.forumchitchat.com/post/...8-yeti-7416019

https://mdws.forumchitchat.com/post/...a-only-8206275

.002" is pretty tight if you're making your own cases .003"-.005" clearance is nicer as it give you more brass options. You might want to track down a 22-250 bolt and extension (800 series) so you can run hotter than 38K psi on a .473 bolt head like the Yeti does.

[lar45]

Yes, I have looked at the 358 Yeti, and it looks amazing if I could only find one of their high strength bolts.
The Yeti needs custom dies also I believe.
Will the 22-250 Bolt fit in an AR15 bolt carrier?

[Moleman-]

Olympic used to sell the bolts and the special extensions and yes they work fine in a standard ar15 carrier. You have to use the matching extension with them and there are at least two different styles that I'm aware of. Round lug in pic is the OLY 22-250, other is standard extension and 450BM bolt. I have several wildcat uppers that use them. Sadly they have dried up. There are die sets and barrel&bolt sets or uppers available for the Yeti. Don't know if they'd make you the wildcat you want using Yeti parts or not.

[357Mag]

[QUOTE=lar45;5656310]Hi everybody.
I am considering a new semi-wildcat 35 cal cartridge and AR15 build.
First my question, then the details.
How much clearance between the chamber and the cartridge is acceptable at the case head?

I want to build a 358 something mostly for hunting Hogs in southern Arkansas, but it could also double as a Deer gun.
My thoughts are to use existing chamber reamers and loading dies, to avoid the high cost and wait time of custom tooling...
So two options.
1: 358 Win- run it in 1.700" in a standard .358" AR barrel, then cut the base off of stock 358 Win dies for case forming and loading. RP 308 win case capacity is 47gn H2O. Should be able to load to 46Kpsi
2: 350 Rem Mag- run it in 1.700" in a standard .358" AR barrel, then cut the base off of stock 350 Rem dies for case forming and loading. 450 Bushmaster case capacity is 54gn H2O. Should be able to load to 38.5Kpsi.

The only problem I forsee is the base of a 450 Bushmaster case is .500". Measuring down 1.7" from a 350 Rem Mag case shows .505".
Is this going to be too much slop, and will it cause problems when loading to 38.5Kpsi?

The 358 Win option seems to be the simpleist to do. Case forming is basically, cut the case, run it into the die, trim to length and you are done. Any 308 based case should work and cases are fairly cheap and will always be availible.

The 350 Rem option needs a few more steps. I tried running a case directly into the 350 die, but the neck folded up on me. So I ran a case into a 416 Taylor die to start a neck, then ran it into the 350 die and it worked perfectly. The neck is too thick, so it'll need turned. I have the Hornady tool, just need the 35 cal mandrel. 450 Bushmaster cases are much more expensive and who knows if they will go out of production in the future?

I am thinking of limiting myself to 180-200 grain bullets and make the cases as long as possible to seat a 200gn bullet, cast or jacketed, and still be able to fit into an AR15 magazine.
I have some Hornady 200 Interlock and FTX. I found some Speer 180s at Midway, they had a limit of 2, so that's what I ordered. For cast, I'm looking at the Lee 35-200.

I found an AR barrel manufacturer that said they would make me a barrel if I supplied a formed case to set the headspace with.

I ran several powders through Quickload
The 358 case should do
180- 2310fps
200- 2140fps

The 350 case should do
180- 2330fps. If I can find AR Comp, it might go 2410fps
200- 2170fps If I can find AR Comp, it might go 2240fps

One thought I had was with the 6.5x55 Swede, the base is .480", but some US ammo companies make ammo for it from 06' based brass with a .470" base.

I downloaded some pics:




Lar-

Howdy


FWIW -

9.3 X 62 Mauser has a nominal .476" base diam, and slightly rebated .470" rim diam.

Shoulder diam is .451", which is just .003" less than a .308.

9.3 X 62 case lg is .426" longer than a .308 case

The Mauser case has a rim-to-shoulder dimension that is .479" longer than the R-t-S dimension of .308Win.
The 9.3 X 62 has a .306" long neck, vs .300" neck lg on the .308Win.

The faster case taper rate of the .308 die body should accept the longer case side walls and slower taper rate of the 9.3X62 case.

Dependent on how long a wildcat case you wanted to run, it might be possible to use an unmodified .308 FL die for wildcat case forming..... before the ( nominal ) .476" base diam of the 9.3 X 62 makes contact inside the bottom area of the die ? If not, perhaps a .308 seater die body manufactured w/ appropriate machining ....could be impressed into wildcat case forming; instead ? Seater die dimensions would be not as tight as those of an FL size die. The idea being.... to use existing dies; and avoid die mods if possible.

I'm not convinced that the parent brass would even require a pre-case forming annealing. Just sensible lube.

Notionally, the .366" cal parent case would neck-down to .358" final cal in one step. Calibre redux from .366" neck ID to .308" neck ID would likely result in the starting .0125" neck wall thickness of the Mauser case becoming thicker towards that of the .308Win ( which appears to run around .0143" ) as the parent brass is necked-down by the die. Exactly HOW thick the neck walls might be on the necked-down 9.3x62 case would remain to be seen. I have some of that brass and a .308 die, so some checks could perhaps be made; if desired.

*** Additionally, let's remember that the more and more you might shove the shoulder down on the 9.3 x 62 case to the new wildcat's shoulder location.... the thicker and thicker these case necks will become.***
The implications of the above are important ! It might be that final-formed necks of this 9.3 X 62-based wildcat would require very little outside neck turn, and / or inside neck ream...to reach final spec' desired.


Just thinkin.....



With regards,
357Mag

[Fitz]

I run a yeti in both a AR-15 and a savage 110 bolt gun , both are deadly accurate but with the C.O.A.L the AR-15 is limited to a 250 gr. rn ,where the savage is capable of handling a 310 gr boolit . don't think you can fit a 358 win. in a AR-15 magazine limit of 2.265 max. now in the AR-10 the 358 win. is a great performer with up to 280 gr bullets.

[357Mag]

Lar- -


Ooops !

In my previous message... I'm mentioned .308Win case specs....when I meant to quote those for .358Win.

None-the-less... Comment is that a 358Win FL die cast taper rate would still be faster than that of the longer
9.3 x 62 case, and the latter still features a longer rim-to-shoulder dimension than the .358Win...so previous comments about 9.3 x 62 case fit would still apply.

The .065" longer neck of the .358Win form die would help guide the .206" lon neck of the 9.3 X 62 parent brass up into the .358Win form die.

From the prints I reviewed, it appears .358Win neck walls are .015" thick, so should accommodate the 9.3 X 62
parent case just fine.


A thousand apologies for the errors !!!


With regards,
357Mag

[357Mag]

Correction, again !


.306" long case neck on 9.3 X 62 Mauser. Bad typing



Regards,
357Mag

[lar45]

The 308/358 cases will form perfectly.
My problem is with the 450bushmaster case being slightly smaller than the anticipated 350 Rem Mag reamer.

[lar45]

Fitz- I'm trying to do a 358win short X 1.700" ish. This would be a Yeti-ish round but with standard reamers and dies.
I'm going to limit myself to 200gn bullets, so my case length will probably be slightly longer than the Yeti.

[ulav8r]

I ran several powders through Quickload
The 358 case should do
180- 2310fps
200- 2140fps

The 350 case should do
180- 2330fps. If I can find AR Comp, it might go 2410fps
200- 2170fps If I can find AR Comp, it might go 2240fps

...

308 cases should be available as long as guns are available, why risk availability/dimension problems to gain 20-30 feet per second? The larger case might have a 5 yard advantage.

[MarkP]

Keep in mind SAAMI lists min chamber and Max cartridge. Min chamber usually has a +0.002" tolerance and Max cartridge will have a -0.008" tolerance. Most cartridges are mfg'd closer to the minus side of the tolerance. Fired 450 brass will be larger just ahead of the bridge. I think you will be fine with 0.005" diametral clearance.
I love the 350 Rem Mag, all of mine shoot cast pretty similar to jacketed both velocity and accuracy wise. All are 1:16" bbl's. Xp-100R, SEVEN KS, 673, 700 Classic.