I have a m98 with a lothar walther barrel on it. It is having to be re-chambered and the gun smith asked me if I want the throat length extended out to utilize more of the case for powder.

So what would be the ideal chamber length? I plan on shooting 140 and 150 grain bullets.

Perry

You should ask that one in the gunsmithing forum. But for 140-150 grainers you shouldnt need any extra throating. That is typically for those who like 160-175 grainers and such. A standard 7x57 reamer should suffice for what you want.

I have a standard length '98 to which a 7x57 FN military barrel was attached. It is accurate with 130-175 grain bullets and by being able to seat the bullets out, powder space is not encroached upon. So, saying all that, I would get a standard CIP chamber in the event you want to go retro with 175 grain bullets or pass the rifle along to someone else.

I know that lots of folks like a shorter throat when using light to mid weight bullets but I have built all mine, and my customer's, with a standard reamer and they shoot lights out.

In the 7x57 I have been using the most, I am loading 120 gr BT's and it is easily a 1/2 MOA rifle.

Perry, I had the same concern when I built my last 7X57. What I ended up doing has worked well and I would probably proceed the same way if and when I do the next. First I choose a couple bullets that I hoped to use or to select between. Then I made up dummy rounds so the base of the bullets weren't intruding below the neck of the case. Finally I checked clearance in the box to be sure it wasn't either too close or excessive. This turned out very well for me because a 160 Nosler partition when seated to the base of the neck had about .080" clearance to the front of the box. With this dummy round, I had the rifle throated so there was about .020" clearance to the lands. I've found my best accuracy came when the bullet "jump" is minimal but just can't bring myself to have contact on a rifle made for hunting. This might work as well for you using whatever bullets, magazine length and throating clearance you personally like. Best of luck...

pretty good advice above.

I had mine cut for 140gr bullets and that's what I use.
I can squeeze some heavier ones in there without fear of losing any velocity because I made the case volume bigger by simply having the chamber cut as an Ackley.

that's a win-win.
I didn't have to worry about magazine length.
I have all kinds of throat to erode.
I have all sorts of room for load work ups.
factory ammo still works.
the only negative was the cost of the reloading dies.

quote:

Originally posted by eddiel4:
Perry, I had the same concern when I built my last 7X57. What I ended up doing has worked well and I would probably proceed the same way if and when I do the next. First I choose a couple bullets that I hoped to use or to select between. Then I made up dummy rounds so the base of the bullets weren't intruding below the neck of the case. Finally I checked clearance in the box to be sure it wasn't either too close or excessive. This turned out very well for me because a 160 Nosler partition when seated to the base of the neck had about .080" clearance to the front of the box. With this dummy round, I had the rifle throated so there was about .020" clearance to the lands. I've found my best accuracy came when the bullet "jump" is minimal but just can't bring myself to have contact on a rifle made for hunting. This might work as well for you using whatever bullets, magazine length and throating clearance you personally like. Best of luck...

This exactly what I did at the reloading bench but was waiting to take the dummy round to the gunsmith, wanted to ya'lls opinions first.

Thank you all for the info!!!

Perry

I think that the hoo-haw about getting extra velo by seating out is WAY over blown and something that, in reality, is just plain hooey...the gain(in your mind AND in actuality) is very small to begin with and can be offset by just being careful HOW you reload.

I've done it MANY TIMES in many calibers and cartridges, but the plain truth is you DON'T have a before/after scenario to use as a comparison UNLESS you first use a "STANDARD" seat length...THEN...throat for the longer length.

The standard calculation is you will increase your velo/volume by 1/4 the DIFFERENCE in case volumes...i.e., the volume of the case with the original seated volume minus the volume of the case with the extended bullet seating.

Say you get a difference of 5 gr after seating out (which is VERY doubtful)...your net gain will be ~1.25 gr...1/4 of 5...and your velo will be the same, 1/4 the difference between the original velo and the afterwards velo.

Yes...you WILL get a velo increase but you won't really know the amount until AFTER the dust settles...it may or may not be significant. In actuality the amount of gain is very small because the area gained can be calculated with QL y simply changing the seated length for whatever bullet you want to use.

Example from QL and my own 7 x 57

7 x 57 M, Fed cases at ~60 gr H2O, usable case volume ~52.8 H2O, 140 gr Nosler BT, 50 g/760, 3.08", ~2865 fs, 2550 ftlb, 22" bbl... a load I used pretty much constantly...or 50 g RL-17 (when it came out) was slightly faster, ~2915...BOTH produced under 1/2" 3 shot groups.

Seat that bullet out to 3.15" and optimize the other parameters and you gain ~30-40 fs and 40-50 ftlb energy...usable case volume increased to ~54.8 or 2 g H2O.

You can mix and match parameters and gain a bit more H2O volume, velo and energy...and it is fun to do the cogitating, but the only way to REALLY GAIN is to MAXIMIZE ALL PARAMETERS by wildcatting the he** outta everything.

I would go along with Lamar...the 140 gr 7 mm bullet in ANY brand will take care of ANY animal in earth is placed right. I shoot much heavier bullets but only in my 7RM and 28 Nosler and most of the other 7mm, large case calibers I've had over time, but for my small case 7's I shoot the 120 and 140 gr Nosler BT or V-max at pretty much standard COAL's.

GOOD HUNTING

good points.
I took my 10% [about 5-6grs more] and moved on.
I still keep my loads under 2900 fps the bullets I use just work better there.

Another thing I've done is to make a chamber cast to see how long the actual chamber neck is...then use a longer reformed case to utilize the full capacity of the ACTUAL CHAMBER length and seat the bullet WAY out. Works great in the x57 cases by going to '06 or x62 mm cases and rethroating if needed.

Depending on the bullet dia. you can gain quite a bit more volume when added to a blown-out case.

LOTSA mucking around when doing this sort of wildcatting in the past...today all you have to do is go to a larger case and rechamber...if you do your homework and research you can go up in 10 gr H2O increments using all the bolt face sizes relatively cheaply and easily.


Good Hunting

That depends on the bullets used..Copy a Brno mod 21 or 22 chamber and magazine...or just ream it to fit a 30-06 magazine is the simple solution..That's usually pretty close to seating a 284 Barnes X .284 or one caliber deep in the case..All mine are done so and that's what I came up with over the years and saves using mics over and over again...This will allow using 130 to 175 gr. bullets..Don't concern yourself with bullet jump on the light bullets, in a good barrel that's hogwash..

The fact is most bolt actions are set by the length of the magazine that allows the case to feed and function and most chambers are cut shorter than magazine length and you will need to recut the chamber a tad..Mostly you seat a reloaded bullet ( I use a 160 Barnes X) in 7x57 seat it to feed in the magazine, the see if it feeds in the chamber properly, if not cut a bit more throat..