280 AI Initial Load Dev - Help

[TxhunterPRC]

Doing load development for my Weatherby Model 307 Range XP chambered in 280 AI. Did the initial barrel break in with 100 rounds of 160 grain Nosler AB's and 140 BT's. Gun was plenty accurate with the factory loads. Probably averaged right at or just above 1'' groups with them.
Did a lot of research for the bullet I'm wanting to shoot which is the 168 ABLR. I reached out to Capstone group and they sent me their load data for N560 and N565. N560 shows to be able to get slightly more velocity so I started with it.
Bumped shoulders .002'' and running a .310'' bushing for .002'' neck tension in hornady dies with the micrometer seating die.
Before going out to the range, I used GRT to get a baseline for the initial 6 loads to try out. Started at 60g and worked to 62.5g in .5g increments. GRT said I would exceed max pressure (68k) at the 62g charge. Bullets were seated .02'' off jam. GRT showed that everything other than the 60g charge should have a 100% burnt powder.
Went to the range this morning and shot these loads. Expecting to find pressure before the 62g charge. I ended up not seeing a single sign of pressure. Not one primer was cratered, no ejector swipe, and no hard bolt lift on any round fired. VV's load data for this bullet and barrel length has the max load at 60.7g and a velocity of 2920 fps. The 62.5g charge averaged 3,060 fps, much faster than anything I've seen with this combo.
Once I got back to the house, I calibrated GRT with the real world velocities I saw and it has the chamber pressure at 73k psi.

My question is, has anyone seen an instance like this where you can go that high above book and still see no pressure? On my 6.5 CM I can go about a grain above book max before seeing ejector swipe so I back them down. It has me thrown off that GRT has that high of a pressure but I'm not seeing any signs. I know it is theoretical but it's the best tool I have to estimate pressures. I inputted all real world data into GRT as well. Such as, actual case capacity, COAL, bullet length, powder temp, jump and what not. Any insight would be helpful because I'm stumped on if I should keep going and try to find actual pressure signs or back down? For what its worth, the 62.5g charge (the highest charge I shot) was by far the most accurate. All others averaged about 1.5'' and the 62.5g group was .6''.

Components:
168 ABLR
Nosler once fired brass
VV N560
CCI 200's

 

[Leibhart1]

I just started using GRT and input some of my phenomenal shooting loads in my 300WSM and 2 loads in my 6.5PRC and calibrated. All are using ADG brass and none of them are showing any signs of pressure. If I remember correctly my 300 load was at like 73k and the PRC loads were 68k and 71k. I did just see an episode of Hornadys podcast that said just because you aren’t seeing pressure signs on brass doesn’t mean you aren’t already at SAAMI pressure. They said, more than like once you actually see signs you are very well over pressure. GRT is a great tool to work up to pressure in my opinion and I just shot 3 different powders loads today that are under max pressure and they shot lights out. It was by far the easiest load development I have done and I attribute it to not being over book pressure. I I have learned recently that a cartridge will most likely shoot better under max pressure and that definitely seems to be the case from my experience today.

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[TxhunterPRC]

I just started using GRT and input some of my phenomenal shooting loads in my 300WSM and 2 loads in my 6.5PRC and calibrated. All are using ADG brass and none of them are showing any signs of pressure. If I remember correctly my 300 load was at like 73k and the PRC loads were 68k and 71k. I did just see an episode of Hornadys podcast that said just because you aren’t seeing pressure signs on brass doesn’t mean you aren’t already at SAAMI pressure. They said, more than like once you actually see signs you are very well over pressure. GRT is a great tool to work up to pressure in my opinion and I just shot 3 different powders loads today that are under max pressure and they shot lights out. It was by far the easiest load development I have done and I attribute it to not being over book pressure. I I have learned recently that a cartridge will most likely shoot better under max pressure and that definitely seems to be the case from my experience today.

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I completely agree on just because you aren't seeing signs, doesn't mean you aren't already over pressure. Also agreed about the accuracy relative to pressures. My 6.5 CM and 300 PRC both start getting finicky once I get above max pressure by about a grain. I'm kind of surprised I didn't see any pressure signs since you almost always hear about how soft nosler brass is. I've loaded my 300 PRC in ADG brass 5g above book max and never saw any pressure signs, albeit the load was the least accurate.

 

[pods8 (Rugged Stitching)]

You’re over pressure imho, your primer pockets may be short lived. Tack on a hot day or snow/rain on ammo (doesn’t grip the chamber wall well) and you might have an unpleasant pressure spike.

 

[cbuck516]

I have often found max load well beyond what VV lists as their max charge weight, but do find their max velocity usually lines up pretty closely to what I find in my rifles (when I am using lead core bullets). When I am using a bullet with very low engraving pressure I have definitely worked up to charge weights that were over 70k in simulation.

 

[112Savage]

I have not used VV powders before but I’ve used a lot of nosler and Peterson 280AI brass. 280AI is a long and straight cartridge with a standard bolt face this means lots of surface area to resist bolt thrust. I’ve had loads in nosler brass that I thought were safe that after 3 loads wouldn’t extract. The case hides pressure very well. I suspect that is why the 7BC is very similar in design.

My 160AB and 162ELDX loads run about 2880-2910 in a 22” weatherby and 2950-3000 in a 24” C6 barrel using RL23 and RL26

 

[ZWA]

168vld, Peterson brass, 565 and 215M have been a really accurate combo for me.

 

[PanhandlePilgrim]

I always look for the upper node and don't really care if my brass doesn't last 10 firings. It doesn't sound like you're at a dangerous level of pressure and personally i would run it. That being said, N560 is one of the more temp sensitive VV powders so I would proceed with caution when shooting in warm temps.

 

[35WhelenAI]

Velocity equals pressure. You calculated pressure based on a program and it showed you are well over pressure. What else do you need besides that and the velocity showing you are over pressure? Pushing velocity well past the factory data and rejoicing versus showing concern is, well, the sign that you need a bigger case and another cartridge entirely if that has now set the bar for velocity you want. Your post has the right tone, that you are taking note and an 11% over pressure is nothing that I would want to have in a rifle that is next to my face or listen to folks say it's no big deal.

 

[aachey]

As stated above, the velocity you are seeing, is indeed a sign of pressure.

 

[35WhelenAI]

Better than VV data would be Nosler data with that same powder for that same bullet. You are 100 FPS over a Nosler max load. You start 10% low and work up. When you reach published velocity call it a day. It's that simple. That was a great first post with all of the minutia and information, but none of that is pertinent other than the powder charge and the velocity with the components you are using. Ultimately you wanted to know if you are over pressure or not, and you are.

 

[112Savage]

I said it before and I’ll say it again. Ackley improved cases especially the narrower diameter and longer ones hide pressure signs extremely well. If you’re over 3000fps with a 160-168gr bullet in a 22-24” barrel 280AI, then you’re flirting with overpressure. There is no magical powder or action that will overcome that fact.

 

[35WhelenAI]

I have a 35 Whelen AI, I get about 80-100 FPS over the standard 35 Whelen. I'm doing case head measurement which is a step 99.9% of the guys that reload will never do. Those are based on 65,000 psi, standard 35 Whelen is loaded to lower pressure. Traditional pressure signs are useful, however if you've read P.O Ackley's books, read between the lines and it will tell you that his design doesn't show pressure, but doesn't mean it's not higher pressure than the parent cartridge. As long as it's within the design parameters of maximum pressure for a lever gun or a bolt rifle, then it's fine. It's unfortunate some good cartridges were downloaded back in the day.

When it's all said and done, the 280 AI (65,000 psi) is loaded to a higher pressure by SAMMI specs compared to the standard 280 Rem (60,000 psi) and that's most of the gain.

 

[SloppyJ]

AI cases hide pressure until they suddenly appear in spades. My only experience with a 280ai was with 59gr of 4831sc behind 160gr Partitions. It was a great load and way more than what I needed for deer. I've since sold it to pursue lighter recoiling cartridges. 4831sc and 280ai is like peanut butter and jelly.

You're over pressure, how much, I'm not sure. I also wouldn't be loading them 2thou off the lands. Thats playing with fire if you're already running that hot of a load.

If you want to run it that hot, I understand. I think we all do. But back off the seating depth. Don't be surprised when you start blowing primers because there's no tension on them after a few reloads.

 

[sanpedroranch]

Chamber dimensions play a role. The saami 280 ai chamber is not the same chamber design as PO Ackleys. Also, freebore has an impact. My 280 ai (non-saami) and my (4) 260s all have custom throats. I’ll use my 260’s for explanation. My manuals have 40 or there about as max for H4350. Since I have more freebore I am safely able to go above max by nearly 10%. My 20” 260 shoots lights out with 140 gr bthp and 43.2gr and zero pressure. I was able to take it to 44.1gr with a slight extractor mark and no bolt lift issues. I put a can I have to back down significantly. It’s what Roy Weatherby learned on and the radial shoulder to safely get the results he was wanting speed wise. I had a 6.5x257wby built about 20 years ago and was adamant that I didn’t want the longer weatherby freebore because I was using Berger VLD’s that are known to be jump sensitive. My smith told me it was a bad idea because I wouldn’t get nearly the speed the cartridge was known for. After about 8-10 powders I realized he was right and had the barrel setback and redone. Ever since then I’ve always factored chamber design into the build.

 

[SloppyJ]

Chamber dimensions play a role. The saami 280 ai chamber is not the same chamber design as PO Ackleys. Also, freebore has an impact. My 280 ai (non-saami) and my (4) 260s all have custom throats. I’ll use my 260’s for explanation. My manuals have 40 or there about as max for H4350. Since I have more freebore I am safely able to go above max by nearly 10%. My 20” 260 shoots lights out with 140 gr bthp and 43.2gr and zero pressure. I was able to take it to 44.1gr with a slight extractor mark and no bolt lift issues. I put a can I have to back down significantly. It’s what Roy Weatherby learned on and the radial shoulder to safely get the results he was wanting speed wise. I had a 6.5x257wby built about 20 years ago and was adamant that I didn’t want the longer weatherby freebore because I was using Berger VLD’s that are known to be jump sensitive. My smith told me it was a bad idea because I wouldn’t get nearly the speed the cartridge was known for. After about 8-10 powders I realized he was right and had the barrel setback and redone. Ever since then I’ve always factored chamber design into the build.

So you shrunk the freebore to match the distance to the lands you wanted and lost velocity? Or are you saying you shrunk it so much that it pushed the bullet back into the case? The first example doesn't make sense to me, the latter does.

I've always wondered how the weatherby cartridges would shoot if they had a smaller freebore but didn't adjust the bullet seating depth or even maximized it keeping 10thou off the ogive of the bullet.

 

[35WhelenAI]

I'm not saying that's diminishing returns, but way more work than I'd put into designing a rifle. Weatherby free bore was for velocity and nothing more. The cartridges don't act any different if you put a standard free bore in them. I don't have experience with that but it makes sense.

 

[sanpedroranch]

AI cases hide pressure until they suddenly appear in spades. My only experience with a 280ai was with 59gr of 4831sc behind 160gr Partitions. It was a great load and way more than what I needed for deer. I've since sold it to pursue lighter recoiling cartridges. 4831sc and 280ai is like peanut butter and jelly.

You're over pressure, how much, I'm not sure. I also wouldn't be loading them 2thou off the lands. Thats playing with fire if you're already running that hot of a load.

If you want to run it that hot, I understand. I think we all do. But back off the seating depth. Don't be surprised when you start blowing primers because there's no tension on them after a few reloads.

Very true and certain powders are that way like H4350. It’ll sneak up on you without warning.

 

[35WhelenAI]

The quicker the powder the quicker the pressure sneaks up on you.

 

[sanpedroranch]

So you shrunk the freebore to match the distance to the lands you wanted and lost velocity? Or are you lsaying you shrunk it so much that it pushed the bullet back into the case? The first example doesn't make sense to me, the latter does.

I've always wondered how the weatherby cartridges would shoot if they had a smaller freebore but didn't adjust the bullet seating depth or even maximized it keeping 10thou off the ogive of the bullet.

It’s a but of both a tad of the latter but more of the first. my first load work up I ran the 142 SMK . It did eat into case capacity, but where the loss was more noticeable is where pressure was seen in relation to charge weight. The barrel with the normal weatherby freebore and the first version without the weatherby freebore. Without the freebore I saw over pressure significantly sooner than with the freebore. I’d have to find the original reamer print that I had made to give exact dimensional differences. From memory I recall I was able to gain several hundred fps without pressure indicators with the freebore. There is a direct correlation between higher pressure and higher velocity. Also depending on burn rate some of what I’m saying can be mitigated. That freebore is what made speeds possible and allowed the weatherby cartridge line to handle the higher pressures. Hence why his initial rifles were built off the proven K98 known to handle the highest pressures only second to the arisaka action. It’s also why the mark v from 257wby up has a 9 lug action and if I recall the most contact surface are of the locking lugs of just about any action in production.