8mm XCB

[338RemUltraMag]

Ok lets discuss the 8mm XCB, I am going to start with the 8mm-06 as a start, I would love some geniuses input here.

Joshua

[felix]

Actually, I like the idea myself. My preference would be the stock 8 Mauser case but with the neck length of the 30-30 for deep seating purposes. Why, because my barrel would have zero freebore with 3 degree total throat, and twist commensurate with the primary boolit shot. My primary boolit would be the RCBS 180, so my twist would be 16 with 3 to 7 lands, each 0.005 in height with a rounded junction to the groove at normal angle. ... felix

I don't know what you are really asking because your case selection is already designed very well. ... felix

[Love Life]

I just don't see what the 8mm XCB gives you that the 8X57 in a purpose built rifle wouldn't.

[btroj]

It gives a longer neck and a different throat. A customer reamer could do the same on an otherwise stock 8 x 57 case by moving the shoulder a touch.

Biggest trouble with a custom reamer is getting a sizer that works.

[tomme boy]

Don't you use the same reamer on a blank die set that you use to do the chamber. I thought that was how you did it.

[338RemUltraMag]

I would be happy with a 8mm-06 standard made, if it were to be changed I would like the shoulder set back .075 to make a longer neck. But that is if we HAVE to play with the cartridge.

[felix]

Bonanza-Forster loves that kind of work. Send them the reamers. ... felix

[338RemUltraMag]

Ok, I just looked in my loading manual, the 8mm-06 will push a 220 gr bullet to 2500 fps. That is exactly the performance I am looking for.

Do we need to change the design or should we just call this good? I know an easy way to make a *slightly* longer neck is to use 270 brass.

[felix]

You got the case size you want in the standard 06. Why not use it without "qualming" about it? Remember, a lead boolit will shoot faster than a condom, suggesting the 06 size is slightly large. Hence, the stock German case size, or the XCB size. Do your own extrapolations. ... felix

[338RemUltraMag]

You got the case size you want in the standard 06. Why not use it without "qualming" about it? Remember, a lead boolit will shoot faster than a condom, suggesting the 06 size is slightly large. Hence, the stock German case size, or the XCB size. Do your own extrapolations. ... felix

I ask for the ideas of other people smarter than I because I do not know everything, ya know I dont see a need for smart **** remarks.

[btroj]

I don't think it was a smart **** comment, I think Felix was saying to think about it and the realities become rather obvious.

If an 8 mm 06 does 2500 with a 220 jacketed and lead would go faster then Felix is telling you it is too much case. Go with a 8 x 57 or the XCB case to reduce powder capacity.

8 x 57 eliminates all troubles in case forming, dies, etc. the XCB gives a better neck design and throat but requires some case forming. It would allow a tighter neck, use a neck turner, and get more preside bullet alignment.

So, what do you want and what are you willing to do?

[Love Life]

It would allow a tighter neck, use a neck turner, and get more preside bullet alignment.



Neck turning gets old. Just get a match chamber cut correctly and you will be fine unless you are competing in legit benchrest.

[cbrick]

I ask for the ideas of other people smarter than I because I do not know everything, ya know I dont see a need for smart **** remarks.

Hhmmm . . . Read through this post and thought I missed something. Went back and read it again so at least I now know that I did miss something, dunno what but I must have.

I just didn't see anything even close to a smart **** remark.

Rick

[btroj]

Neck turning gets old. Just get a match chamber cut correctly and you will be fine unless you are competing in legit benchrest.

Agreed. Just that some enjoy turning. Weird.

[338RemUltraMag]

I am sorry for being nippy, and I openly apologize to Felix, as fas as case forming I enjoy that kind of thing, so I will go with a 30 XCB necked up with no further changes. That will allow all the speed necessary and will be a proven design.

Now Tim, is the reamer a removable pilot or fixed reamer? If removable is it possible to use it to make the 8 XCB?

[Love Life]

Agreed. Just that some enjoy turning. Weird.

That is weird...unless you CBRick's awesome and amazing case prep contraption. I don't want to get off topic though.

I can see the benefits of the longer neck in the cartridge, and I hope it shoots really well.

[btroj]

I am sorry for being nippy, and I openly apologize to Felix, as fas as case forming I enjoy that kind of thing, so I will go with a 30 XCB necked up with no further changes. That will allow all the speed necessary and will be a proven design.

Now Tim, is the reamer a removable pilot or fixed reamer? If removable is it possible to use it to make the 8 XCB?


The 06 reamer used for the 30 XCB won't cut an 8 mm neck. Pilot size doesn't matter for neck size.

For 8 mm XCB you need an 8 mm 06 reamer.

[btroj]

That is weird...unless you CBRick's awesome and amazing case prep contraption. I don't want to get off topic though.

I can see the benefits of the longer neck in the cartridge, and I hope it shoots really well.

I forgot about that prep center. Now I'm drooling again.

[HARRYMPOPE]

Jesse Dresler in Oregon has done a short 8mm on a BR or 308 x 1.65 case ( can't remember the details) it was not any adbantage over a short 30 and was.abandoned.Roy Smith's 338 Manx on a 1.5"(or so) .473 head diameter case was a success and should be revived.

[tomme boy]

I think a 8mm-08 case with a 3006 length neck would be perfect for this. It should be way more efficient than a 8-06 Plus it would work on a short action. You could use 7x57, 8x57 brass if you have it. Or 3006 if you really want to do a lot of case work.

[Newtire]

I think a 8mm-08 case with a 3006 length neck would be perfect for this. It should be way more efficient than a 8-06 Plus it would work on a short action. You could use 7x57, 8x57 brass if you have it. Or 3006 if you really want to do a lot of case work.Not really that much work tomme boy. If I'm hearing this right, a .30-06 case with the shoulder shoved back to make a longer neck. I've done this before to form a whole batch of 8mm brass. I turned off the excess in my case trimmer using my Makita to run it and then knocked off the huge burr by running it up into my sizing die just enough to break off the burr and then finishing it off with the chamfering tool. Works real slick. You could drive over to Lanark to Forsters from Clinton and pick up your dies in person even.

[runfiverun]

it's more involved than a simple re-form to 8 mauser.
the neck/shoulder/throat relationship is much, much different.

you turn the necks simply to get everything exact with the minimum of trouble keeping everything in that relationship as perfect as possible.
an inside neck reamer for the cases would definitely be a quick way of getting what you wanted if you could control the wobble of the cutting motor/tool.
but a concentric turn is definitely the way to go.
it also allows you to manipulate the centerline of the barrel/boolit relationship with the brass thickness.

[geargnasher]

+1 Lamar.

There is definitely a call for a ".30 Mauser" or the slightly less tapered body of the .30 XCB because no other cartridge in that niche exists, but in 8mm or even .35 caliber I can see no advantage that a similarly-sized wildcat case might have over the already proven 8X57 JM Mauser or (if needed) the '06 family (8mm, .338, .35 Whelen, etc).

What we get into is efficiency with preferred powder burn rate and preferred boolit weight per caliber and expansion ratio. At 24-2600 fps in a .30-'06 there is always about 5-10 grains of extra room in the case which requires buffer or filler to optimize. The .308 Winchester is too small and the neck shorter than we'd like to gain similar velocities with cast-friendly burn-rate powders. The .30 XCB is just perfect for 150-180-grain boolits at 24-2700 fps at 100% loading density and upper-40K PSI peak pressure. The 8mm Mauser is close to perfect in all respects for maximizing typical 8mm boolit weight performance. Fixating on having a longer neck than the 8mm Mauser is looking for a solution to a problem that really doesn't exist in my opinion.

As for the 8mm '06, it may not be ideal, but a removable-pilot '06 reamer could be fitted with an 8mm pilot and the neck cut with a neck/throat reamer.

Gear

[Newtire]

it's more involved than a simple re-form to 8 mauser.
the neck/shoulder/throat relationship is much, much different.

you turn the necks simply to get everything exact with the minimum of trouble keeping everything in that relationship as perfect as possible.
an inside neck reamer for the cases would definitely be a quick way of getting what you wanted if you could control the wobble of the cutting motor/tool.
but a concentric turn is definitely the way to go.
it also allows you to manipulate the centerline of the barrel/boolit relationship with the brass thickness.

I thought you were wanting a longer neck on an 8mm case. You would have to cut the chamber for a longer throat of course the way I see it. Neck turning is a whole nother area to discuss.

[runfiverun]

the longer neck would be a benefit.
if the sides of the neck were/are cut parallel in the chamber.
it helps with the whole centerline thing again.
the 8m [32] XCB if designed similarly to the 30 XCB would gain the same benefits of the case volume over an 0-6 sized case.
it would basically duplicate the 8 mauser's case capacity but would change the neck/shoulder angle slightly and give a slightly [to much] longer neck [if the reamer was made that way]
a fairly parallel case wall [like Ackley cases have] and neck is a huge help when shooting lead.
you'd have to of course design the case with the action length in mind, as you could stretch the neck out another 4mm if you wanted to use the larger X61 case.

the waay longer neck is something that was discussed in the original planning stages of this XCB thing.
one of the first rounds discussed had a case volume of the 300 savage with a 30-30 length neck giving the round a 2.015 case length.