A new rifle. ......

[Harter66]

In the spirit of conversation rather than why can't I make this work .

I have been working on a 264 WM 1st there was misinformed brass conversion. it seems that a 300WM is not only longer but has a fatter flatter shoulder also,and the 275 H&H dies really didn't help much as a transition die...
More good stuff this 50 yo rifle has been apart and together a lot but doesn't seem to have been fired . So among other things there is no throat wear which makes getting the patch into the throat and still covering any of the nose/bore ride and not have half the 258-120 sp down inside the case requires the patch to be back off the nose/ogive about .2 inches to get even close to a book OAL . The bore ride is of sufficient diameter to make full contact for that distance. This and helping another member, Over Max ,I have been back to read the guidelines for success .....several times. I have 4 rifles that have delivered the goods,1 that amounts to slap some paper on it and shoot little groups with whatever powder was laying around. I have 2 to work with now that just don't have the throat space to get the patch in the bbl. There was a thread that PDawg,I think,did working "the half patch" with little to no joy and mediocre at best results. For me getting into the high 2000s and minute of Mulie to 300 yd would just tickle me silly.
Anyway the 264 remains unfired today but there are 20 rounds that will chamber and eject in 1 piece and the lube dents should come out of the 8 survivors in the 300WM RP an 12 brand new Hornady 7mm RM simply chamber necked and loaded with a cast start load to get the cases out to the right shape. On that note 12 gr of Unique is a lot of powder (to me anyway) but holy cow the LCHB lists 23.? as a max load . That struck me as a 25k load . I only loaded 27gr in 1 1/4 oz duck loads back in 80s when it was still ok to kill geese dead with 4s at 60 yd.... oh well.

Yes I'm well aware that this plinker load isn't the fast track nor does even tip toe into the "cartridge potential", but then my current concern is to get it on paper and polish the bore and form a few pieces of brass in preparation for the real loads and a full case of something slow. With just a little luck it might even let me get enough slicked up to get a little more patch in the bbl.

[Nobade]

Well, you have got your work cut out for you. I can't think of much else that would present a bigger challenge for getting to work with PP boolits. Have fun on the journey, once you get it to work you will certainly have achieved something. Everything else will seem really easy!

-Nobade

[Harter66]

It suppose the easy way would be to relieve both this 264 and the 03A3 to accommodate the patched nose...... it just seems such a waste to "hack all that bbl" wear out ,especially when there is an old 7mm that will take a .299 slip fit that's fixable though with a little off the end .....like the treads . I may lap the lead a in the 264 just to slick it up. Then give it a case reduction to a volume more like a 260 for now just to work out the bugs . I know how much time some have invested in hitting 3k but by the books that's the window of this beast. Yes I think I'm trying to talk myself up to tearing the wrapper off.

[flounderman]

7 mag makes 264 but the neck is a little short. You might need to ream the necks, depending on the chamber. I would think trying to make 264 from 300 you would end up with thick necks. I did have to anneal some 7 mag brass I made 264 out of.

[Harter66]

Well , I may yet have to ream but I think the .268 ID of the fired brass will do.
The 10 gr of Unique gave me almost 1800 fps and the accuracy was good enough for 200yd gongs and even a good hit on a 400 12x 12 swinger . There was just a whisp of lead color on the lands that cleaned up with just a couple passes with a brush and a patch. The start load of 4831 was either dismal or completely over shot the target backer at 100. Not improbable based on book nubers that suggest over 1000 fps difference. I also wondered about bullet failure with the fast twist .
The Lee data is pretty hot along side Speer,Lyman & Hornady.

[Harter66]

I have dabbled a little bit more with this one. The new 7mm mag Hornady brass needed to be run through the sizer die to secure the 260-120 fp NOE production. I only sized about 1/4 of the neck and then flared it to finger start the boolits. I will mention that with the plain base boolit it may take some of the wiggle out of the case tension being all in the bottom lube groove.

The rifle has had about 12 rounds of jacketed down the bore with w857 and the leade area is much happier now. (Shhhhh don't tell) .

With some real target time and the Unique load I tried both green bar and some lesser receipt paper. With both run through a 265 Buckshot push thru sizer to "iron on the patch " and "crimp the base wading" sort of both delivered easy chambering and ejecting as long as they weren't fed exclusively from the magazine. This tends to mangle the boolits and sometimes even pull them out of the case . With half of the case in the chamber area the base can be down far enough for the Mauser controlled feed to pass over the head and not tweek the boolit. Groups were identical save for human error. I think the bbl is touching as the group it tall and skinny suggesting that the bbl is pushing up as it heats.

As soon as I get the rest of the 40 Unique loads empty I will try some with 4350 4831 and w857 (I bought the 857 for this rifle) .

I suspect that the jackets may have stripped a bur or something as the boolits will chamber freely now with the nose fully patched to the ogive . A custom expander is in order for better neck support and possibly even a custom mould. With 25 cal 140-160 gr moulds being so common and all.