No signs of over pressure?????

[500plus]

Recently brought a new second-hand Blaser R93 in 300 win mag 25.5" barrel and have been building up a load for it using 178 gr Hornady Amax with H4831sc federal 215 primers and new Winchester brass annealed trimmmed etc.
Started off at 70 grains and ended up with 73.5 on the first outing going up in 1/2 grain lots 73 being stated in my Lee manual as max for 180gn. Bullets were seated as far out as possible to still fit in the mag at 3.325 total length.

Rifle shot exceptionally well with the worst 3 shot group being 1.1" and the best .43" .
Chrono clocked the starting loads at around 2840 and max load at av of 2935.
Accuracy was great but I thought I might be able to get the magic 3000 as there no signs of excessive pressure at 73.5.
I loaded some more bombs from 73.5-74.5 Thinking surely ill reach 3000 or flatten a primer what ever comes first.

Not so, no signs of pressure and still no significant rise in MV at 2976 av.
Back home to load more hotter rounds 74.5- 75.5 surely this time!
Back to the range finally broke 3000 barely but STILL no signs of excessive pressure!
Cases ejected easily primer looked the same as at 70gn even under my magnifying glass!??

I have settled on a very accurate load of 74 grains that averages around 2948 but am still intrigued as to how much powder this bad boy will take before it flattens a primer or at least shows some signs.
As I'm relatively new to reloading (2years .270&.243 ) and belted magnums, is this normal and would it be safe to keep going? My 270 Tikka sticks pretty hard to the book and quickly shows signs around stated max loads. Is this normal for 300 win mags?

Any help would be much appreciated. Thanks

 

[Red hunter]

I don't have a Hornady book to look up your combo. But with the lack of reloading supplies right now I would be happy to have found a good combo that will not trash my brass after a couple relaodings. I would also dare say that if you seated your bullets deeper into the case you will start seeing the pressure signs. If it shoots good, as is ,who cares? Start shooting it at longer ranges and see how it does. I like shooting more than reloading. My .02

 

[Shane1]

You don't always see signs of pressure with a 300 win mag ecpecially if brass in new or even once fired. If you watch the chrono you'll notice the velocity increase drops off when you get to pressure. example- if 1/2 grain from 73 to 73.5 to 74 gives you 50 fps each then 74-74.5 only gives you 20 your at max pressure, chambers are generous on 300wm and brass is usually undersized alot. I've seen 20 thousandths stretch at the shoulder before, sometimes has to be shot 2 or 3 times in my gun before shoulder is pushed far enough forward to touch, I believe this obscures the pressure to an extend. I can shoot 78 grains h1000 in win brass thats new or once fired (hot load) with no pressure, when the case gets to where I need to bump the shoulder (fully fire-formed) that same load will cause extractor marks and sticky bolt lift. Be careful you may be over 70,000 psi before you realize it.
Be safe, Shane.

 

[lever-hed]

Those are fair comments. Typically that cal is headspaced off the belt, but many headspace it off the shoulders.. Typically, where you begin to see head separations is just ahead of the belt. Keep an eye on that portion for any signs of thinning case walls. Also, primer condition is not always the only indicator (if any) of over-pressure signs. You have to take into consideration that cartridge has several bearing points, from case wall, to the belt, to bolt face, and if the cartridge has room to move around, that movement will 'absorb' a lot of the pressures.. when you have all of or most of the pressures bearing in the shoulder -bolt face combination, you may begin to see over-pressure signs and these can occur, and do occur rapidly when they do , just when you have the least attention on it. Take into consideration the batch of brass you use for load development.. not all cases are loaded the same charge, some have much higher charges, and repetative higher charges with lower charges do funny things to brass.. In a new 25-06 bbl I had started out development, I had low pressures that actually regressed the headspace from -.002 to -.009 .. I used that same batch of brass for my regular loads once I settled on a charge, and sure enough, case head separation occurred after the 5th reloads.. that is more of an extreme example, but relevant still.. have fun.

 

[500plus]

Thanks guys that's really helpful yes I suspected I wasn't seeing the whole picture just by looking at the primer and ejection. Might actually back it off a bit to 72.5 which was the next most accurate load to increase case and barrel life. Cheers

 

[JeffP40]

If the primer pockets get loose after 4 or 5 loads, you are pushing it a bit too hard. Stay tight, good to go.

 

[jasent]

If your velocity has flattened out and does not increase with charge increase it may just be that your gun with that combo is unable to burn more powder. Could be that the bullet is leaving the gun before all the powder is burned. So it can't get the higher speed or pressure you where watching out for. I'm surprised you did not break 3000 fps with it, I shoot 185gr Berger's at 3050 with no pressure signs. I see pressure at around 3100. my barrel is only half inch longer than yours

 

[500plus]

If your velocity has flattened out and does not increase with charge increase it may just be that your gun with that combo is unable to burn more powder. Could be that the bullet is leaving the gun before all the powder is burned. So it can't get the higher speed or pressure you where watching out for. I'm surprised you did not break 3000 fps with it, I shoot 185gr Berger's at 3050 with no pressure signs. I see pressure at around 3100. my barrel is only half inch longer than yours

Hi there thanks for your replies. Yeah I thought I'd get to 3000 a fair bit easier.
Have noticed some of my cases that took the higher charges in load development 75.5gr are loose in the primer pocket.
What powder are you using and how many grains just out of curiosity?
Think maybe the baring surface of the Bergers is possibly a bit shorter than that of the Amax making the Amax slower??
Am happy loading at 74 now get really steady MV at 2947 average. Shot 3 three shot groups the other day at 510 yards the furtherest I've ever shot and the worst was 5 1/2"and the best 2" was just about 6" low so think my drop data might be a little out.

Thanks again guysgun)

 

[Bart B]

You have to take into consideration that cartridge has several bearing points, from case wall, to the belt, to bolt face, and if the cartridge has room to move around, that movement will 'absorb' a lot of the pressures. when you have all of or most of the pressures bearing in the shoulder-bolt face combination, you may begin to see over-pressure signs and these can occur, and do occur rapidly when they do , just when you have the least attention on it.

This is really strange. Especially when every round fits the chamber pretty much the same way when fired. And the pressure builds up in all directions the same amount; same pressure's everywhere inside that case. So it's all pressing against the chamber wall and bolt face the same all over.

If the uneven case surface was able to "absorb" pressures, then all those pressure reading's from strain gauges put at one point on the barrel would not be reliable. One would have to add what pressure was "absorbed" by the case under the strain gauge to the pressure reading it had to be correct. What method would be used to measure how much pressure was absorbed by the cartridge case?

 

[jasent]

I'm burning 74.5 gr of reloader 22 with cci 250's. I tried imr7828 but didn't get the accuracy I was wanting. with this load im getting 1/2 moa out to 500 sofar.