275 Rigby / 7×57/7mm Mauser

[RBHarter]

275 Rigby / 7×57 Mauser
The Rifle was an 06' and extremely touchy about case capacity, Donna , short for Prima Donna...... 1965 Savage 110LH marked 275 Rigby on prefit Adams and Bennett 24" barrel . Currently unfired , cleaned, amateur lapped at to pick off major burrs and find tight/loose places .
New 1971 Winchester 7mm Mauser cases unfired and untouched by human hands .
3@20 total of 60 one lot .
Weigh lotted ,169.0-170.6 gr electronic scale resolves to .2 gr . Length @ 2.230 +- .002 w/Starett 2.0-3.0 micrometer .
169.0 @3
169.2 @16
169.4 @8
169.6 @8
169.8 @7
170.0 @5
170.2 @7
170.4 @7
170.6 @1
I've decided to use the largest .5 gr lot of brass and blame fliers on case variations. So cases will be 169.2 through 169.8 lots and add the 169.0 to make out 40 cases.

Cast bullets used RCBS 7mm-168 @ 178.6-179.0 gr bare , and NOE 287-150 Hunter @ 151.2-151.4 gr naked . Both gained about 2.2 gr with checks and lube applied . Sized .285 . The alloy ......well roof jacks a probably WW . I don't know really it's about a 16 bhn 2 weeks old and water dropped from the mould .

Bore groove dia .278×.284 . The 7-168 touches full contact about .15 on the nose the 287-150 is set off the lands about .1 as it needs to cover the lube groove .

I'm out of practice I guess .......
The 287-150 was loaded with 6.0 Unique, I didn't get a chronograph reading them . 8 rounds in FC 59 Match formed brass . I chose these to ensure the scope and barrel were pointed in the same general area. As luck would have it it was on the vertically . About 8" high . It strung a little but since it was an unfired barrel , fresh install , rearranged optics etc . They landed in about 3" strung vertically and left . Fired at 25 yd .

Next up was the virgin Win brass loaded with the 7mm-168 SP . The first 10 were loaded with 9.0 Unique and the first 5 hit kind of wild just above the first load but fired at 50 yd . An adjustment was made and the over was lowered to only about 4" high and left . But they pulled into more like 1.5" .

The next load was was 10.5 Unique . About 2" I take responsibility for at least a 1/2" of that . These loads had a dark smudge in the leade suggesting a little more size might be in order . Heating mat have been working against me too .

Last up 38 gr of IMR 4831 . Dad had several lbs so I may as well put them to work . 2040 fps . The Strelok app says at 2000 fps MV the 50 yd velocity is 1874 fps and 1145 ftlb holding 971 ftlb at 100 yards . That's within my target goal for the load .
The first 4 presented about a 2" triangle 4" high and right .
The 5th I put in to a wasted 48qt cube cooler full of water . The hope of catching the bullet was wasted . The splash was pretty impressive about a 6 gallon spray the exit in the foam looked to be closer to a dime than .284 .

I'm not disappointed by the bullets or the rifle . Actually if I'm that close to a load the first go then Im pretty happy .

 

[Bret4207]

Good post!

 

[Ian]

287-154-FN-E5 is the new name for the Hunter; it's a Barlow design like the RCBS. I'd much rather see you trying the 290-137-FN.

Not bad for bullets that don't fit. Weighing cases and bullets is good for trimming down the last inch, not the first one.

The modern 7x57 has a throat real close to the '06 in shape, and a disproportionately large chamber neck and loaded neck clearance....a recipe for frustration with two-diameter bullets. Lemme do some measuring, I may have something for you to try...

 

[Ian]

Ok I think I have something that will work. .277-8" x .286-8" powder coated but with a nice tapered transition. Shoots under 2 MOA at 100 with my 93 Chileno using open sights and no gas check with 9 grains of Unique and absolutely no special prep. The mould had problems and I need to work the mould over a titch more to get rest of the twist out of the block alignment (or maybe just lap it round). I might cast some more this weekend and can send you some if you want.

Tim gave me a shot-out 7-08 barrel (lands worn down to .002" high) and it had about the same problems the modern 7x57 has with cast. I made some cases out of .308 blank brass which had necks I could turn to over 20 thousandths thickness. Once I got the chamber neck clearance down to under 1 thousandth, even the Lee 130 would get 9/10 under 1 MOA at 100 at 200,000 RPM. I found IMR canister 4831 worked pretty well at the top end. I messed with it for a few months and never did completely figure out the occasional flyers that kept me over my MOA goal. Fun to try, though.

 

[RBHarter]

Composite overlay .......closer to 4" . I never measured the NRA slow fire black .
Virgin new barrel fit on a rifle that for 1.5 grains in an 06' case would cast a bullet over there a ft . I'm sure the barrel needs to settle some yet .



I know I'm off my game .

I wish there were some "soft" SP .400 BC 175s but there aren't even when it's good . Everything is made for the 7mags .
I don't really know what to expect from an unfired barrel on a Savage. Maybe I should have lapped it , or run a bunch of jackets through it . I should probably check the twist but I'm now pretty sure it's a 90-9.25 , as soft as the bullets are at 2000 fps I'm almost certain they would have come all undone . In a true 8.5

 

[Ian]

Wet-paper patch 50 of your 6.8 bullets with copier paper and run those through DRY, best lapping for cast procedure I know of for a fresh barrel.

 

[RBHarter]

I'm open to suggestions. I have several bags of assorted cast up on my shelf .

I ran MM design program out to see where the 7mm standard twists ran out. I don't what formula was plugged in but bullets out to 1.78" were still good to go in an 8.5 at something bizarre like 265 gr . Needed 2k with the 168@179 gr .

 

[RBHarter]

I might do that too. I have a 270-150 also .

3-400 Sierra 120s also and some other odds and ends from Hornady and some outfit nobody's heard of that dealt in local precision.

 

[Ian]

This is what you're fighting, except it's even worse because your rifle likely has no parallel freebore section.



Something like this is what I had in mind:

 

[fiver]

maybe seat out further too.
i run my 145's clear out to the top of the lube groove.

i gotta laugh about the penetration you seen.
i've tried warning everyone about the 7mm and how much it will penetrate just about anything if the nose has any sort of slope to it.
i'd be pretty happy if Tom would cut the 165-A as a 7mm, or his version of the XCB down to 286 or so.
both of them would fit most of the throats out there, and make a decent enough hunting bullet.

 

[Dimner]

maybe seat out further too.
i run my 145's clear out to the top of the lube groove.

i gotta laugh about the penetration you seen.
i've tried warning everyone about the 7mm and how much it will penetrate just about anything if the nose has any sort of slope to it.
i'd be pretty happy if Tom would cut the 165-A as a 7mm, or his version of the XCB down to 286 or so.
both of them would fit most of the throats out there, and make a decent enough hunting bullet.

Please please please...someone convince him to do that. I know it's a tooling issue, but man oh man, I really need to find a custom 7mm bullet mold maker.

 

[Ian]

I really don't know why Tom couldn't. He catalogs a "heeled" design with a .255" heel and another with a .257" heel, but they're both under 100 grains. He also catalogs a couple of ~170 grain plain based, lube-groove bullets and a couple of 7mm slicks for powder coat.

I don't know why he couldn't make a 150-grainer with .180" meplat, .255" check shank, and shallow lube grooves. Maybe anything longer than 100 grains stresses the Micro Mark boring bars too much if he has to use one that will poke in a .255" hole.

I'd be looking at a 31-200F with a check shank scaled down to 7mm.

 

[Ian]

I worked on that mould for a couple hours and cast about ten pounds of bullets. I must not have moved enough metal because shortly the blocks were twisting again and casting .003" out of round on the base. I managed to manually align the blocks close enough to make a pile of so-so round bullets, the rest will get powder coated and shot through the Chileno without gas checks. If you want some of the good ones, I'll check, powder coat, and send them your way. They're too small to shoot as-cast, .2755-6 x .284-ish.

 

[RBHarter]

I can move the 168 out . The 150 has the whole lube groove out of the case to kiss the lands . The 168 is actually set back a little I can get lands on 1/3 of.the nose and still have the top groove in the case . Im going to ruin a 270 RP case if I have time this weekend. 2/12s make it rough to spare much time .

I may have to let the barrel out a 1/16 of a turn . You know how you can see something but you can't feel it or really even measure it? There's something like that at the case mouth and even FL hard jam sized virgin brass takes a firm bolt to close it. I may have a neck lip that's aggrevating things as a result of zero nothing headspace, a situation unique to a prefit jam nut barrel or a short chamber that just ain't long enough.

 

[Bret4207]

This is what you're fighting, except it's even worse because your rifle likely has no parallel freebore section.

View attachment 30602

Something like this is what I had in mind:

View attachment 30603

And yet, many people report Barlow designs shooting rather well. Sometimes the stars align?

Take pity on me and please tell me, which mould maker is "Tom"? I cant keep track of which company is which just going by the guys name.

 

[Brad]

Tom Is Accurate Molds

 

[RicinYakima]

And yet, many people report Barlow designs shooting rather well. Sometimes the stars align?

Barlow designs shoot very well if the bullet fits, and you don't push them over about 1600 f/s. Ideal 311284 is especially good with Springfield or Krag barrels with a couple of thousand FMJ rounds through them. You can get "fair" (2 MOA) accuracy at 2000 f/s but it takes a hard alloy and very slow powder (H4381). FWIW

 

[Ian]

The design can do a lot better than that in certain situations, but you have to get a lot more stuff right. Ever build up a case neck to minimal clearance with copper plate? Ever shoot an ENTIRE 8-pounder of 4831 working on alloy composition? Ever have a custom chamber reamer made just to reduce one dimension? Have you made an array of bullet nose sizing dies in half-thousandth increments? These are the sort of things people have done to make up the shortcomings of the two-diameter bullet when they want to exceed the BHNx1400 or 140,000 RPM.

They could have just ordered a mould for a bullet that fit their rifle in the first place, select an alloy that optimizes the dynamic fit of the design, and worked a load for it to match the desired performance range while making the rifle sing in tune.

 

[Bret4207]

Tom Is Accurate Molds

Thank you.

 

[fiver]

you forgot the tape... LOL
and the reduced capacity cases whittled down then polished by hand with steel wool.
and the ruined size dies.
and,,, probably should have worked a little smarter on some of them.