Hi all
My 7x57 has a fairly tight chamber.
I’ve got a load developed with the following components:
145gr Barnes LRX
47gr H414
CCI mag primer.
This load is incredibly accurate.

Now I’ve always used 7mm-08 load data for the 7x57 to load it to its full potential.
The Barnes data says 46.5gr of 414 in a 7mm-08 should give you 2800fps.
Given that the 7x57 case is 6mm longer than the 7mm-08
I figured that half grain that I’m loading extra should be just fine.
(46.5gr vs my 47gr)

I shot this load over the chrony the other day and I’m surprised that it’s running 2850fps! 50fps over book.

I could back off a bit powder wise but wonder if 50fps over book is that big of a deal given the larger case capacity?

Am I overthinking this?

If your bolt lift is "normal", no shinny spots on the case head, and reloaded brass from this load still has tight primer pockets, I`d count myself lucky and go with it.
Besides, I find H4350 more difficult to find than H414.

Most of the time the bolt lift was normal but on two occasions I thought; “mmm was that bolt a bit sticky just now or am I imagining it?”
Case head looks fine, to me.
Maybe I’m just being a sissy about it? But then I’d hate to have my rifle explode in my face too

Not exactly comparable, but 50.5 grains H4350 gives me 2864 FPS at a measured 56.6 KPSI with a 150 grain Nosler BT.

The 7x57 should out perform 7mm-08 - you have a greater capacity - that's why proper loaded 6mm Rem will provide higher velocities than a 243. My 7x57 mauser can approach 280 factory loads.

I think you guys are probably right and that I’m making a fuss over nothing.
I’m going to load some mild rounds up, and see what the primers look like compared to the hot load.
I’ll start there I guess thanks for the advice gents

How do you measure the pressure in your rifle?

How does 46.5 gr shoot?

PressureTrace

I think you load should be just fine. I do basically the same but use RL17.
Paul B.

I feel a lot better about it now.
I’m going to fire a few light loads in it anyway and compare the primer strikes anything else I should compare?

I believe you should be fine.

I somehow missed your question, sorry.
It shoots ok, but groups open up a bit, think It shot 1.25" groups

You don't specify anything about your action strength, barrel length, CIP chamber/leade, SAAMI chamber?
With a long euro style freebore, my BRNO 23 5/8 7x57 gets only 2700 fps with 49 gr of 414, WLR, WW brass and the Speer 145...good brass life, so I suspect pressures are not too high.
It's all about internal volume in your rifle only...brass...freebore...seating depth.

I probably should have added that my loads are fine in two rifles, a Winchester M70 XTR FWT and Ruger #1A. However, a third rifle with extremely tight chamber gives pressure signs much sooner and my RL17 loads are not suitable with that rifle. You didn't sat what rifle/barrel combo you were using.
Paul B.

This! Most manuals suggest loadings for this round at minimized CUP/PSI pressures because of the older guns one can still fire. So if their loads are running 55K PSI 1/2 more grain might take it to 58? so what?

In round numbers, a grain of powder is about 2500 PSI in the 7x57. So Fotis' estimate is conservative.

It's a Brno 21 action, so a small ring mauser, the barrel was replaced so it's not the original cavernous Brno chamber.
This chamber is quite short/has very little freebore.

The chamber on this one is quite tight, not 7mm-08 tight but tighter than any of my 7x57's have ever been.
It's a Brno 21 action and a douglas barrel I can't remember what reamer was used now but think it was a Pacific Tool and guage reamer?

That sure puts it in perspective, thanks for that

I never knew that, you learn something every day!
Am I doing my math wrong or missing something though? if I'm using 47gr of powder and 1grain = 2500PSI.
I'm looking at 47x2500=117500?

Doesn't work that way. What he's said was that if you are at 55,000 PSI and add 1 more grain of powder it will increase pressure by 2500 PSI

Yup. The change in pressure is pretty linear at near normal loads, but not over the full range of zero to full loads.

Oh I see, thanks for clearing that up.
It's useful info

If i am loading an unknown or poorly documented cartridge / load combination, I find a load that achieves the desired velocity and appears safe ( bolt lift and primer condition, admittedly not very scientific) and shoots well, then I choose 5 cartridges to do a stress test with.
Load and shoot the same five cases at least five times. If the primer pockets are still tight, the load is producing safe pressures in that rifle.

I did that with a Brno 21h in 7x64. Worked up a load that was 3-4 grains of powder over the load data I had on hand, which was from USA sources. European data showed more promise, but with different powders. I chose a comparable burn rate powder, same weight bullet of similar construction. Things were looking OK. But to verify, I shot and loaded the same 5 cases 6 times. Primer pockets remained tight, accuracy and speed exceptional, and performance was better than I hoped. All good. Went on to shoot those same cases 10 times and they were still OK. So despite being "over book" I have full confidence that the load was certainly OK in my rifle.

Makes sense, I’m going to try that!

Incredible accuracy...great velocity...quit while you are ahead!

I never intended to hot rod it, or try and get more velocity out of it.
Just concerned that it was too hot of a load and that someday I may get a big surprise.

I'd be just fine with your load. Seems well within the norms for the cartridge and as long as your cases hold up along with accuracy on repeated firings I wouldn't worry about it a bit myself. 2850 with that LRX should be a great critter getter.

Yes

First I've heard of using 7mm08 data. I'm loading for a cousin now and was having trouble grouping wise but got it worked out by loading a bit long for his push feed featherweight win 70. I used 7x57 data 140gr core lok, rem 9.5 and 40gr imr 4064. oal 3.074

Yup, i shoot 48gr IMR-4350 under old school 175gr Speer Grand Slams and Partitions for 2700 fps, have shot that GS load since day one, no issues with 24" barreled '09 DWM 98 Mauser, even had 'Smith check for lug setback after 2-300 rounds, all GTG, RP brass is reloaded it's fourth time, i'll anneal, trim and load again when these are gone.

H414 is easier to find, because many are deleting from the inventory, I know I have. It's too temperature sensitive for this part of the country.

Doesn't sound fine to me....most likely wont explode in you face but it could eventially wreck your rifle.

Myself I would stick with the loading manuals for the 7x57.

Thought I had it worked out but it wouldn't repeat the 1 group I got so switched to 50gr h4350 & nosler 140bt and they repeat great.

I loaded 139 gr Interlocks and 140 gr Partitions to 3000 FPS in a 22 in Ruger Tang safety M77 for years. 53 yrs of IMR4350 goes all the way into the neck of Winchester brass.

I think your load is a little weak.

Maybe you should check the latest Speer manual on the 7x57. The latest Nosler has a few good loads as well.

The problem with 7x57 data in most manuals and factory loads as well is there are too many old 93/95 Mausers and rolling block rifles still in use. SAAMI was cautious regarding pressure for the cartridge. Look at it this way. My Winchester M70 Featherweight also comes chambered in cartridges like the .270 and in 7-08 in the short action rifles. The 7x57 cartridge can hold more powder than the 7-08. So, it stands to reason that using 7-08 data in my 7x57 M70 is perfectly feasible. Due to the larger case pressure and velocity should/would be slightly less. I have three rifles chambered to the 7x57. Two, the M70 and Ruger #1 have no problem with 7-08 data. The custom Mauser does have problems even with the weak factory ammo at times which is puzzling as the rifle was originally a .270 Win. The only thing I can figure is the chamber is extremely tight. I'll probably take it back to the gunsmith who built the rifle and see if he can figure it out.
Paul B.

I dont need to check the loading manuals I sold all my 7x57 guns years ago...no way I'm using 7mm 08 loading data in a 7x57.

Why such apprehension?