Second opinion please, am I over pressure?

[NorthIdahoDude]

Backstory: Loading for my 7x57, 22 inch Shilen barrel, Tikka receiver, 1:8 twist, historically kind of slow and tends to pressure out before I hit the velocity I want. Accuracy with 175 ELD-Xs and slow powder (4831 and friends) and lowish pressure has been excellent (3/4 MOA or so), but ES/SD has been very "meh". 4350 and friends has not yielded good accuracy with the 175s, so I figured I'd see if something middling between 4350s and 4831s might work. Which brings me to:

N555
Norma brass
CCI BR2
3.237 OAL (.050 off the lands - yes, deep throat)

QuickLoad seems to think I can go to like 50 grains before I push a Tikka action, but that seemed way hot based on VV data for 280 and 284, so I loaded a 45.5, 46, 46.5, 47, and 47.5 and starts sending them over the Magnetospeed, and WHOLE-E this thing is cooking fast - start load was 2535 (hotter than my 4831SC load already), but primer corners nice and round, so I continued, and 47.5 was 2625!!!!

Now, QuickLoad thinks that 2625 is about 58kpsi. Primers don't look bad, nothing but the velocity being wildly off the QL estimates seems amiss... But VV says 2600 FPS is about what I'd expect out of a 280, not a 7x57 ...

So what thinks y'all - am I likely pushing the pressure envelope?

Pic of the primers, left is H4831SC loads that are around 51kpsi (says QL), middle row is the test I just ran, 45.5 at the top, 47.5 at the bottom (dots from a sharpie on the primers so I didn't confuse them mid test), and right row is unfired BR2s for reference.

 

[NorthIdahoDude]

Primers are pretty flat and you're getting some cratering so yeah, gettin hot. You could keep running it there but that Norma brass will likely have a limited lifespan at that pressure.

The N555 primers dont seem any flatter or otherwise different than the H4831 primers, do they? (Stares harder).

 

[Shortschaf]

Honestly I load everything to heavy bolt lift then back off.
Probably unsafe. Idk. Done it a couple dozen times.

If you are worried then back it off. Probably prudent to not run ammo wildly faster than any factory or book or internet stranger has published

edit to add: remember you don't win prizes for having the extra 100 fps

 

[NorthIdahoDude]

Side angle so we can see how much round is left on the edges.

 

[NorthIdahoDude]

Honestly I load everything to heavy bolt lift then back off.
Probably unsafe. Idk. Done it a couple dozen times.

If you are worried then back it off. Probably prudent to not run ammo wildly faster than any factory or book or internet stranger has published

edit to add: remember you don't win prizes for having the extra 100 fps

I'm honestly not so much trying to get extra velocity, 2500 ft per second makes this lethal to well beyond what I would reasonably huck lead at a critter from. I am interested in getting more reasonable SD/ES, which seems to be easier to do in a somewhat higher pressure range. And hey, if it's not dangerous velocity, I'd take some extra, sure.

 

[NorthIdahoDude]

I do get about 0.001 to 0.002 more case stretch from the N555 loads (but identical case stretch across the 45.5 to 47.5 test rounds).

I don't have a precision micrometer, but as far as I can tell the set of calipers and guesstimating by seeing where the needle is between marks, the case heads of all the low end N555 loads are maybe .0002 or so expanded from once fired Norma factory brass. The H4831SC heads look about .00015 over once fired Norma.

But the top 3 N555 loads look like about .0005 over, with the top one maybe .0006 ish.

So, there's my sign, I think - around 46.5 is probably starting to push it. 45.5 is still a hair faster than my 4831 loads anyway, so, I'ma start there and see what my easy load development gets me.

 

[S-3 ranch]

Honestly I load everything to heavy bolt lift then back off.
Probably unsafe. Idk. Done it a couple dozen times.

If you are worried then back it off. Probably prudent to not run ammo wildly faster than any factory or book or internet stranger has published

edit to add: remember you don't win prizes for having the extra 100 fps

Honestly this seems like the best choice is ladder stack a few till it gets tight bolt, then use the next one down
Your probably not going to find much information because it’s a old military round and everyone is just gonna keep it low pressure
Highest load I could find was 46gr 4350 @ 2500+/- with a 175

 

[NorthIdahoDude]

Nosler has some load data on the hot side (2575 with a 175 ABLR IIRC, in a 22 in barrel like mine, using N165), but no N555. So I am def spit balling a lot here, LOL. And unlike common cartridges like 308 and such, quick load does not seem to be all that accurate for my 7x57.

John Barnsness/Mule Deer would tell me to just keep feeding it 4350 until it makes a 7-08 look slow, but that theory has not worked out very well for me, LOL

 

[wind gypsy]

Primers don’t look bad to me. If you get a few firings on a peice of brass and aren’t getting any sticky bolt lift in a tikka action.. I’d feel pretty dang good about it personally. Those velocity #s are in line with published 7 SAW velocities and you have more case capacity and it sounds like a longer throat on your side.

 

[DiabeticKripple]

Might just be the pic, but the top primer on the N555 looks like it has a sliiiight crater on it.

I’d say you are right there on max pressure.

 

[NorthIdahoDude]

So, here's some only vaguely related insanity (and I mean, pure insanity)

QuickLoad and my 7x57 have never been on the same page, and I don't really understand why. With my 308's and 30-06s and such, it'll get me within about 75 FPS out of the box, and if I weigh the actual H20 capacity of my cases and use that, it'll usually get me within about 25 FPS. However, no amount of tweaking has ever got it to estimate within 100 FPS of correct on the 7x57. That's not the insane part.

On a lark, I asked Grok (X's AI tool) to estimate where 60,000 PSI would be with N555, 175 ELD-X's, in a 7x57, at 3.237 OAL, with 60 grain capacity Norma brass, 0.050 off the lands, in a 22 inch 1:8 twist barrel... And it said:

N555: ~46.5 grains, ~2570 fps, ~60,000 PSI, ~98.2% burn.

The Magnetospeed says 46.5 grains was 2573 FPS.... only off by 3 FPS.... and that is exactly the piece of brass as I work up the ladder where I see slightly more case head expansion (in so far as I can tell with calipers that only read 3 decimals and I'm trying to guesstimate to 4), which is about what I'd expect to start seeing around 60kpsi...

My QuickLoad says that load would be mid 2400 FPS and low 50kpsi range...

To be clear, I 100% I am NOT recommending anyone use Grok (or any AI) for a reloading tool, but damn if I'm not impressed with that...

 

[Sinistram]

Generally, I'd say you're over pressure. The primers may look fine, but that is only one indicator of pressure, and a specious one at that. The increased velocity should be your first sign. If you're getting dramatically higher speed than the manual says, you're too fast. There's no free lunch here.

 

[S.Clancy]

Generally, I'd say you're over pressure. The primers may look fine, but that is only one indicator of pressure, and a specious one at that. The increased velocity should be your first sign. If you're getting dramatically higher speed than the manual says, you're too fast. There's no free lunch here.

Yea, I basically stop if I am getting around book max. All my guns are a little below book max and show nothing for pressure signs in the brass.

 

[NorthIdahoDude]

100% agree, exceeding the manual is near 100% a sign of excess pressure (excepting a few corner-case situations like the +P throating or similar). Except there is no manual data here - I'm using quickload and information gleaned from vaguely similar loads (not even the same powder) that are in manuals that by and large limit themselves to around 52,000 PSI or less, when I'd like to be around 59,000PSI or so.

Generally, I'd say you're over pressure. The primers may look fine, but that is only one indicator of pressure, and a specious one at that. The increased velocity should be your first sign. If you're getting dramatically higher speed than the manual says, you're too fast. There's no free lunch here.