7x57mm - Searching for Seat Depth

[Rookie21]

I'm loading for a Winchester Model 70 Featherweight XTR in 7x57mm Mauser and I feel I might have a powder charge figured out but want to fine tune the seat depth. I've been shooting/testing at 100 yards distance but perhaps to see the change in group sizes easier I should try moving on out to 150 or even 200 yards. What do you more experienced load developer guys here think?

Also I have planned to shoot batches of ammunition with four different seat depths. 0.015'', 0.020'', 0.025'', and 0.030'' off the lands.

Current components are: 42 grains of IMR 4064, 140 grain Boat Tail Spire Point Sierra Game King (#1905), CCI Large Rifle Primers, and R-P stamped brass (started life as Hornady factory ammunition).

Any suggestions would be appreciated. I kind of feel like I'm headed in the right direction but not sure.

[std7mag]

I'd say several things.

I've found cup & core bullets seem to like about 0.020" jump from the lands. Has been my best results.

I'd also say your over max charge according to Hodgdon.

I'd also try a different powder. IMR 4064 is showing maxing out around 2,600 fps.
IMR4831 & RL19 will give you better velocities.

I do most of my load testing at 100 yards, then shoot 600-800 yards to true my velocities.

[Rookie21]

My chrono says that my load of 42 grains of IMR 4064 is pushing nearly 2800 FPS. Where did you read 2600 FPS was the max? And according to several reloading books I have, 42 grains of IMR 4064 is about at the max but not quite. Pretty close though. Enough that I’m not going to push it any further.

I also have some H4350 powder I’ve been wanting to try but I wanted to exhaust my efforts with one powder first before moving on. Plus I have a crap ton of IMR 4064 so I figured why not figure a way to use it.

Now what do you mean by “cup and core” Bullets? I’m unfamiliar with bullet terminology.

Thanks for the input on the jump.

EDIT: I just checked the Hodgon website to check out some reloading data and I see where they say 40.5 grains of IMR 4064 is the max load.. I have Lyman, Sierra, Hornady, Speer, Richard Lee and Nosler books and where it varies some (42-43) 42 grains is pushing max load but is still safe according to these books. Perhaps there is a new recipe for manufacturing? Is it hotter than it used to be?

[Scorch]

I have loaded for 7X57 for over 40 years. I never used 4064, I used IMR4320, IMR4350, Reloader 15, and WW760. I used 4320 for years as my go-to because of accuracy, but about 10 years ago switched to WW760 and can't complain. Good velocity and good accuracy. But in response to your original question, .020" off the lands always gave me good accuracy.

Most of the variation in max loads for 7X57 comes from loads intended for new rifles versus older rifles like 1893 and 1895 Mausers, Remington Rolling Blocks, and other older military rifles. Modern bolt actions can handle the extra pressure, but there's no need to push it to 60,000 psi, the 7X57 will do fine at 54,000 psi and give you better accuracy.

[std7mag]

Yes, Hodgdon was where i got that information.
And do yourself a favor. Don't go too solidly by Noslers load data. Tends to be engineered fiction.

In your case, i'd probably use Sierra's data. Just keep in mind when looking at their velocities they tend to use a 26" barrel.

Also remember that you should start low when changing lot numbers of same powder. IE 2 different 1lb bottles of the same powder. Lot numbers can be found on the outside of the bottle.

Essentially anything NOT a monolithic (pure copper or brass), or VLD (Berger, Lapua) is a standard cup & core bullet.
Mono bullets are generally said to like 0.050" from the lands.
VLD are a beast unto their own. They generally do well one of two ways. Jammed upto or into the lands, or a really long jump to the lands.

By all means, try the 4350. For the case volume, the slower burning powder will help with velocities, and help keep pressures below threshold.

[Paul B.]

I checked the OP's load in my Sierra manual and he's OK there. BTW, Sierra used a 26" Barrel. I too shot an M70 Featherweight and have worked up loads past max for several powders. I got to 2880 FPS with the 140 gr. Sierra Pro-Hunter using W760. I felt it was a bit too warm for the day I was shooting (102 in the shade.) so dropped back to 2800 and called it good. A gentleman on another site stated that using RE17 in his M70 Featherweight he attained a bit over 2900FPS. I contacted him and he passed his data on with the warning to start low and work up. Hell, I knew that. Anyway, I do my load work ups in Tucson's very hot summers believing pressure will show up quicker, thus warning me to quit while I'm ahead. I did he work up starting 4.0 gr. below where he quit and worked up a half grain at a time. Temperature during these trials ranged from 98* to 105* on a couple days. I did reach his 2900 FPS level with very good accuracy. Pressure symptoms appear perfectly normal. I've run a few more tests in the 2700/2800 FP level and probably will settle on the 2800 FPS level.
I've since started working with the 150 gr. Nosler Accubond Long Range (ABLR) and have reached the 2900 FPS level but no pressure signs again but lousy accuracy. I have a test series made up at the 2700 FPS level using various seating depths with the hope I'll find something that works. I have three rifles in 7x57 and so far not a one likes that bullet. My .280 Rem. absolutely hates it.
I'm quite sure people will state how dangerous my loads are etc. ect. ect. Normally I follow the manuals unless I find otherwise. The 7x57 however normally come with a throat long enough to be considered a freebore when using bullet of 150 gr. or lighter. You get some leeway there. Cases in point. The Nosler load works in a Ruger #1A and the M70 Featherweight. It's accurate in both rifles. When working up a load for my custom FN Mauser however, pressure signs show up almost immediately after reaching what commercial ammo is supposed to be putting out. I was always curious about the original 1892 load with 173/175 gr. bullets so loaded up a batch with the 175 gr. Hornady to 2300 FPS and ran them over a chronograph. The Ruger and M70 ran 2300 and small change and the Mauser was almost 150 FPS faster. Getting what I consider a viable hunting load that is also accurate is the challenge I have with that rifle. I want to take it on my elk hunt this year and want at least a 2700 FPS velocity 1.5" groups or smaller; preferably smaller.
Paul B.

[std7mag]

Paul does have a good point on the longer throat. Think Weatherby.

Something else that hadn't occurred to me was the handycapping pressure limits SAAMI put on the Mauser cartridge. (51,000 psi).
I'm loading my 257 Roberts to +P rating. (58,000 psi)

I'm sure in a modern bolt rifle, such as your Model 70, +P performance should be comfortably obtained.

Just remember, and i have said this to many a 280 Rem loader, it's NOT a 7mm Rem Mag!
Safety, then accuracy, then velocity.

[T. O'Heir]

"...42 grains of IMR4064..." That's 1.5 over current Max. It's just the differences in manuals though. Hodgdon shows 42.5 is Max for a 140 and they got 2615 FPS out of a 24", 1 in 8.75", barrel. Isn't likely that 1.5 grains more powder gives that much more velocity.
"...moving on out to 150 or even 200..." Easier to walk the standard 100 yards when testing loads.
"...four different seat depths..." Off the lands is not a seating depth. It's an optional OAL thing that is not done until you have a load. There is no set distance off the lands either. Nor is there a formula.
Every chamber is different. Finding the distance off the lands your rifle likes is a 100% trial and error thing. The whole process is more trouble than it's worth. There isn't enough improvement in accuracy to justify the time it takes to do.
And it has absolutely nothing whatever to do with the bullet.

[Rookie21]

Well, I tried 15, 20, 25 and 30 thousandths away from the lands. Seems I had some potential around 20 and 25 so I may try an in between measurement and see how it shoots. This is probably my last try before moving on to working with H4350. Thanks all.

[Bart B.]

Consider this situation......

You've picked load data that produces the fastest velocity for a bullet. Then adjusted charge weight and bullet jump for best accuracy.

If a faster powder ended up shooting the same bullet 100 fps slower with the same safe peak pressure and groups half the size as the slower powder, would you use it?

A compromise is at hand. Do you want the bullets to win the race to the target? Or arrive on target in the smallest area?

[Rookie21]

Well heck yeah lol the only reason I’m using IMR 4064 is because my grandfather used it in this gun and some other people mentioned it a good powder for this cartridge and I also happen to have a lot of it right now. But I will be visiting some other powder options soon. I’ve already tinkered with some H4350 and the recoil is much more comfortable than what I’m shooting right now.

[hooligan1]

I'm still wondering how Brass is Rem-Peters but started life as Hornady.
Also I read post #8 and as usually he doesn't add any useful info. If it was up to him we'd throw rocks at our intended targets, must be in the water....
I like the bullet pick, also Sierra has a manual if you are gonna use this particular bullet, I'd call or email Rich MacHoltz, he's a Sierra tech, with many years of experience, and he's a great conversationist.

[Rookie21]

What info would you like? And I know about the Sierra manual - I have one. As for the brass, I don’t know what to tell you. It’s brass from ammunition I bought in 2010 maybe 2011. It’s stamped R-P and the caliber/cartridge designation of 7x57mm. I was looking for helpful advice and maybe spit ball some ideas around but if you’re looking for certain details to talk about just ask.

“As usually he doesn’t add any useful information...” was that all directed at me?

[hooligan1]

No that wasn't directed at you,.
Headstamped Rem Peterson is Remington ammo, nothing Hornady has to do with.
I wouldn't throw a spitball unless I had you striking out on previous pitches.
The Hornady LnL comparator tool will help you get the measurements you're looking for.
My standard rule of jump is first .005 then .010 to then .020, .030, .060, .090. I usually start with a median powder charge, and test 3 rnds at these jump measurements, it usually gets me heading in right direction quickly.

[std7mag]

Rookie,

We are not saying that 4064 isn't a good powder, it is. Just perhaps not the best powder for your application.

Test powder charge first. Then seating depths for optimal group sizes.
As Hooligan said, if you have questions, don't be afraid to call the manufacturers. Sierra is very helpful with their customer service!

[Rookie21]

Been doing some testing. So far 42 grains of IMR 4064 and a 140 grain Sierra Game King is still a good shooting load but I'm tinkering with bullet seat depth. I think I'm close though.

I did try some loads with H4350. Less recoil. Slower velocity. Shoots nice but I haven't gotten a load yet that shoots as tight as the IMR 4064 load. I haven't exhausted that powder yet. I think theres a good one in it somewhere.

With my better shooting loads that I've tested I'm getting groups of about two to three inches at 200 yards with a power scope. I was hoping to see tighter groups but for a factory sporter barrel and low power optic perhaps I as a shooter may not be capable of shooting tighter.. not sure. I'm gonna try some more loads but right now.. the hot load of 42 grains of IMR 4064 is still a good one.

[Dufus]

I developed my 7x57 loads in the mid 70s. I settled on a 145 gr Speer Hot Cor with H4831. It shot very accurately. I have never chronographed the load as it was so accurate I just used it as is.

[Rookie21]

What distance did you test your loads at?

[Dufus]

I was using iron sights, so I developed at 100 yds. After I settled on the load, I shot it at 200 and 300 yds just to get the trajectories. I never shot any game farther than approximately 175 yds with it. I did hit a jack rabbit at about that distance as well. The rifle is still tuned with iron sights as I never wanted a scope on it. It was a military action with a Douglas barrel with almost as much freebore as the original military barrel had.

Note that the freebore didn't allow me to chase the lands.

[Bart B.]

What's your criteria for best accuracy?

Smallest 3-shot group? Smallest 25-shot group? Which is statistically the best?

[std7mag]

Chasing the lands may be difficullt.
I think the "standardized" 7mm Mauser chamber was done for a 175gr round nosed bullet.

I know i've had issues with the long leade on the standard 284 Win, as it was originally chambered in a semi auto.

[Dufus]

Posted by Bart B.

What's your criteria for best accuracy?

Smallest 3-shot group? Smallest 25-shot group? Which is statistically the best?

If you are talking to me, I shoot nothing less than 10 shots with ample barrel cooling time, since almost all my rifles are for hunting. I do not shoot competition any longer, but did shoot a lot of silhouette in the 70s. That was my efforts at competition.

If you are talking to the OP, my answer is "I don't know" and apologize for buttin' in.

[Unclenick]

Land chasing is difficult. There used to be a page up by a fellow who spoke with a Somchem guy from way back when they had a load development program people could sign up for and bring in their rifle. They developed the charge with the bullet contacting the lands because that makes pressure about 20% higher than when it is 0.030" off the lands. You never want to take a max load developed well off the lands and just move the bullet out into land contact. It takes about 10% less powder to hit the same pressure when in contact with the lands. Anyway, the story related was that a fellow brought an old 8 mm Mauser to the load development service. Inspection showed the throat was badly worn, but the owner said it was his grandfather's hunting rifle and he wanted to be able to hunt with it again for sentimental reasons. So, they proceeded to try. The furthest forward load wasn't promising, so they set the bullet deeper in and it shot better. And they kept backing it in deeper and it kept getting better. In the end, it shot a group of about 1/4", IIRC, and was the most precise shooting hunting rifle and load the program had ever produced.

The late Dan Hacket told of a 40X chambered in 220 Swift he had for benchrest shooting that only grouped 5 shots into about 1/2 moa no matter what bullet and load he used. He always seated 0.020" off the lands because everyone said it tended to be best and he'd had good luck with it in the past. Then one day in changing to a bullet that was 0.015 shorter than the one he had been loading, he turned his seating die micrometer the wrong way, so instead of letting it come forward 0.015 he wound up adding another 0.015" to its jump instead, putting the bullet a total of 0.050" off the lands. He had 20 rounds loaded before he discovered the error. He considered pulling and reseating the bullets, but decided to shoot them in practice. To his amazement, the "too much jump" bullets gave him two 1/4" groups and two true bugholes "in the ones".

So, regardless of what is mostly the case, you have to try more and further bullet jump than you might suppose to be truly sure you are where you need to be. Many shooters report that once they establish the best jump for a barrel, the same gun tends to like the same jump with other bullets, though you want to confirm that when you've found a good one in a particular gun. Many also report finding two sweet spots if they go back far enough, though one will be better than the other. So there is more experimenting you could do.

You may want to read this other example from Berger.

[Bart B.]

Originally Posted by Dufus

If you are talking to me, I shoot nothing less than 10 shots with ample barrel cooling time, since almost all my rifles are for hunting. I do not shoot competition any longer, but did shoot a lot of silhouette in the 70s. That was my efforts at competition.

10-shot test groups are twice as good as 3-shot groups. You'll do well with them.

[Unclenick]

Actually, almost 8 times better.

The spread: