Alf,
Most factory rifle have short magazines, and some have long throats, they dont' match so you load accordingly.. it's called freebored..Weatherby for instance freebores..Brnos have a long throat to match the 06 magazine, Win. doesn't, Remington does't, and neither does Ruger, they have std or short throats...

Ray, are you referring to the ZKK series or the BRNO's made before that? Thanks

Just for reference, the W-W 175 Silvertip ammo shot 2,351 fps in my 25" barrel.

My most challenging rifle to date was a Mod 70 featherweight (push feed) in a 7X57. I tried every handload and factory load imaginable to get that gun to shoot. Then started working on the gun (pillar bedded, FF barrel, recrowned the muzzle, tuned the trigger, changed scopes. Spent a lot of time and effort and it still sprayed bullets (best was 3-4" CC @ 100 yards).
It sat in the safe for +10 years. I read on this forum a few years ago to use a heavier bullet and seat it way out. The rifle appears to have avery long throat.
Well I bought some 160 accubonds seated them way out (OAL 3.150"; funky looking cartridge) and ran them to 2630 FPS ahead of some IMR 4350 and that gun will shoot 5 shots into a quarter or less @100 yards.
I hunted with it this weekend. I think this is a excellent 250 yard load.
Best info I ever received off this forum

Ray:

I am having difficulty understanding what you have just posted?

Most factory rifle have short magazines, and some have long throats, they dont' match so you load accordingly.. it's called freebored..Weatherby for instance freebores..Brnos have a long throat to match the 06 magazine, Win. doesn't, Remington does't, and neither does Ruger, they have std or short throats..

Just to be clear as to what my position is on the term "freebore"

It is literally that part of the bore that is free of engraving ie " free of bore" the distance between the end of the chamber and the onset of the barrel groove or engraving it is defined in the CIP manual by Dimension G which is physically measured from point H which is the end of the cut chamber and point F which is the onset of the cut groove in the bore. The bore defined as the dimension of the predrilled barrel before the grooves are cut.

In original terms it meant that the dimension of that part of the barrel was the same as the predrilled bore and in fact which is of larger diameter would have to be squeezed into that dimension. So to "freebore it means that the unrifled area has to be overcut so that the bullet runs without being forced untill it engages the rifling.

For the 7x57 with it's original 7.25mm bullet this dimension was cut to 7.3 mm minimum. So for a distance 19.2mm the bullet lies in a 7.3mm chamber before engaging what is seen as engraved barrel. The bore of the 7mm is 6.98mm minimum with a groove dimension of 7.24mm minimum. The factory allowed for a groove of 7.25mm +/- 0.004mm and a bore of 7.0mm + 0.003 , - .02mm this was for Normalized 7x57.

Mauser cut and then lapped their chambers and bores to the same spec as the modern CIP spec. The original Mauser spec can be found in factory drawing 140358D B2 of 1932

CIP accepted the 7x57 in 1984 and they define the minimum freebore for this cartridge as defined by Measurement G as 19.2mm and the freebore bore diameter as 7.3mm

Mausers original 7x57 had only a 79mm max box to take the max COL of 3.07 inches or +/- 78mm long 7mm cartridge. This is the max box dimension found in the Spanish model 93, the models 95 and 96. I have two Boer war 93's I have a Boer war Ludwig Loewe 95 Plezier Mauser and then Oberndorf 96's ( two of them made for the Swedes in 7x57).

I have a original early WJ Jeffery 275 built on a 95 barreled action also with this dimension.

Then there is the two Rigby 275's that are built on pre 98 or transitiion 98 actions. They are Mauser Built and the max boxes measure 79mm.

All of these rifles have the same barrel dimensions all will feed original Eley ammo as well as original Boer war DMK ammo which I have in my collection.

That was the set factory spec of the 7mm Mauser and it remained so throughout Mausers history. It also preceeds the 30-06 by 10 years. The throat of the 7mm as defined as the distance from the end of the cut chamber to the onset of the cut grooves in the barrel has remained constant throughout Mausers history and it was the dimension accepted by CIP as shown

My Brno rifles in 7x57 of which I currently have 14 have the same chamber specs as the originals, their max boxes measure 88mm's, My ZKK 600 in 7x57 also measures 88mm. All of these BRNO's and they have variations in action fitments, they are not all identical will feed a max COL 7x57 round loaded with the original 173 gr mil hardball.

So I do not understand what you mean by a standard chamber and throat dimension.

I do not know what Winchester did nor Remington. I consider them to be Americanized 7x57's

I do have Ruger No1 RSI fullstock in 7x57 and that will feed the same loads loaded to the same spec as all my other 7x57's My standard load if the old Round nosed 175GR Hornady bullet loaded to exactly the same COL as the original factory ammo. I have a big stash of these because I dont think Hornady still offers that bullet.

quote:

the old Round nosed 175GR Hornady bullet loaded to exactly the same COL as the original factory ammo. I have a big stash of these because I dont think Hornady still offers that bullet.

I just checked their website. Apparently they still make them at almost $42.00 per 100. I know damn well I can't find any locally.
Paul B.

Alf,
Without going into all the technical stuff, and perhaps my termanolgy is wrong..Allow me to clear up my meaning.

In my Brno mod. 21 or 22, I can seat a 175 gr. bullet .284 deep into the case, actually I can seat it less than that, but .284 is the reccomended least, and it still works thru the mod. 21s 06 length or mauser length magazine..You have Brnos in those models so you can try this if you don't allready know it, and I'm surprised if you do not. All my custom rifles are set up the same way..

The Factory rifles I have had in that caliber had a magazine that would not allow that, some had short throats and you had to seat to the cannalure or close. some had longer throats or leads and short magazines..the rifling starts further forward than some in simple terms whereas I believe the term "freebore" applies to bullets making a long jump before contacting the lands wereas with a "long throat" the bullet can actually touch the rifling when the bullets are so set in the case..The 130 gr. Speer however must make a jump but for whatever reason that has not effected the accuracy in any of the guns that I have shot..

It has been my main pain that factory rifle bullet seating depth is determined my the magazine and not the chamber in many cases, and if the throuat is long then the bullet must jump.

Call it what you will, I won't argue termonowledgy..

lal,
I dont' know how the these later CZs are chambered..you can just barely start a 175 gr. Hornady or Nosler, or whatever in a fired case and close the bolt easy on it, then measure the OAL of the loaded round.

I bought one of the early Ruger 7x75 tangs...WAY BACK. The distance from the end of the chamber to the beginning of the lands/grooves was so long I couldn't seat rounds that would feed through the mag and touch the lands with th older 175? gr RN's.

It shot factory rounds into "normal" 2-3" groups, but drop into the 150gr bullet range and all I got were what I considered patterns.

I rechambered it to 7x57 Imp but didn't cut the threads back to eliminate that...whatever you want to call it...freebore, jump, excessively long throat...WHATEVER.

I never got that rifle to shoot unless I seated 175 gr RN's out where they just barely hung in the case and single loaded. That action has carried several different calibers since and is now my 510 Makatak, the 7x57 barrel is long gone and the 7x57 IMP dies are rolling around in the junk drawer.

You can call it what you want...Weatherby called it "freebore" and from what I understand, anything beyond about half inch or so of "jump" to the lands is/was called by that name..."FREEBORE".

You can get a freebore condition by many methods, one being what Ruger did...chamber for a specific bullet/SAAMI/CIP spec and maybe added a little...or pick a specific bullet and seating length then add a bit of jump CUSTOM BUILT rifle...to reduce pressures, just for kicks or anything inbetween.

The good and bad part of factory rifle makers is they follow SAAMI/CIP specs...many times without seeming to think of what they end up with. Bean counters don't know squat about 'smithing and won't listen...I think.

Sometimes there are ways around, sometimes not...you just have to deal with the maker's concepts if you buy factory rifles.

The 7x57 was originally designed to kill PEOPLE in military weapons with completely different design parameters...not animals...the fact that it does both very well hasn't been lost on humans.

The easiest way to come up with a more accurate weapon to shoot the lighter bullets is to have one built/build it yourself and have the reamer cut for parameters that fit YOUR RECEIVER and bullet preference.

Luck