When Wildcats get too wild with pressure Dr Mike!?!

[longrangehunter]

I was going to PM Dr Mike to ask him what I’m going to spell out here, but instead why not share it!?!

Over twenty years ago I had a Jarrett 280AI built, along with two loads that came with the rifle. A 150 Nosler BT behind a stiff load of IMR4831, alongside a 175 Partition with just as stout load of IMR7828.

Not withstanding that those loads were developed at 203’ above sea level, and I was living in Montana above my town of 5550’. Those loads blew the primers out on me when I went to test fire the gun. They also came with three targets for each load and a data card for them. It was 3150 for the 150 BT, and 2950 for the 175 PT.

A quick phone call to fix the issue was obviously reduce the charges on both loads. Which wasn’t a problem since he also sent me 200 pieces of FF 280 Remington brass to 280 AI.

The 150 BT came down one or two grains to 58.5, and for the 175 PT to 59.0. Which cleared up the blown primmer issues.

The question is why is Hodgdon so low in the velocity department vs what Nosler is listing?

Sure, I’ve seen plenty of slow barrels and some really fast ones in my life time. So there’s that, barrel and chamber dimensions, different components, bullet seating depths and lot to lot variations in smokeless gun powders, etc.

I want to avoid that portion of the equation, only to focus on how let’s begin with PO Ackley vs Art Alphin of A Square Ammunition Co. who I knew used testing equipment for pressure during his load development work.

At the time I had this rifle there was no reloading manuals for the 280 AI, so people incorrectly or correctly assumed the improved ballistics of the cartridge design….. And while some might have gone one way, others may have gone to the extreme… Way over pressure.

At the time I just took what was shown for a Remington 280 and increased the powder charge weight by 5% in all the different reloading manuals for a given bullet weight and took the average of them combined for the same powder.

I still have my notes, and when I looked at a few months ago the Hodgdon manual for a given powder it was the same as what I had for the same powder from a 5% increase over a 280 Rem.

Ok, so I have 50 rounds left over from my Jarrett Rifle and wanted to ask Dr Mike if I should just dismantle them, or test fire them in my new rifle? I know that they will be way faster than even listed in the Nosler book I have.

It’s definitely a better action, but that’s not how I’d look at it now that I’m older and wiser to the situation.

Hodgdon used a Swift AFrame 175 SP for their data, and a pathetically slow velocity of only 2686 ft./s with 56.5 of IMR7828ssc in a 24” bbl.

Nosler lists 2772 with 58.0 grains of IMR7828ssc in their 24” H-S Precision rifle with the 175 PT/ABLR bullet(s).

I used to get around 2900 with the 175 PT in my 24” barreled Jarrett using 59.0 grains.

It should be rather clear by now that I’m getting too. The hard data that is published today vs what people used previously to determine whether or not they were within the context of safely being prudent or extremely overzealous with speed!!

What do you say Dr Mike?

 

[TackDriver284]

If your barrel is new, I would work up slowly and safely,,,wise choice if you were blowing primers with these reloads on another rifle, then the charges are too high. I would pull those bullets carefully and save both the powder and bullets. Resize the brass, if you have an annealing machine, then anneal before you size. Work up a ladder to max book charges to see what your velocity is and check your pressures. I don't rely on the manuals for exact speed and charges, I use them as a guide. I follow what the paper tells me, what my chronograph shows, how the rifle reacts at the range, and what the brass shows me. I also check measurements on brass thickness, loaded round neck diameter and check clearance in your chamber to ensure there is enough clearance between the loaded round necks to the chamber. I had similar high pressures in my 300 Win Mag where the new Lapua brass necks were too thick that clearance was very minimum at around .001" -.0015", that the necks had to be turned to have more clearance. I was shooting faster than normal with book charges, but after neck turning the brass down, it started shooting normally again. Some things we overlook at the end, its part of reloading and common sense.

The question is why is Hodgdon so low in the velocity department vs what Nosler is listing?
I also have the same question in mind. Different companies use their own bullets, powders, barrel types, twists, etc for their tests and they differ from each other and results may be higher or lower in their results. I looked this up, and pasted it here.

• Component Variations:
  Each reloading manual uses different components for their load data, and these components can vary across manufacturers.
  • Bullet Construction: Bullet weight, diameter, and design (e.g., jacket type, core material) all affect pressure and velocity, leading to different optimal charge weights.
  • Powder Lot and Type: Powder lot variations and different powder types (even within the same name) can have different burn rates, impacting charge weights.
  • Primer Type: Primer type can also affect the load's performance and pressure, leading to different recommended charge weights.
  • Case Brand: Case dimensions (internal and external) can affect how much powder a case can hold and how the pressure is generated, leading to different charge weights.
• Testing Methodologies:
  Different manuals may use different testing methods and equipment, which can lead to variations in the data.
  • SAAMI Standards: While all manuals should adhere to SAAMI standards, there can be subtle differences in how these standards are interpreted and implemented, leading to slight variations in the data.
  • Chronograph and Pressure Measurement: The type of chronograph and pressure measurement equipment used can also affect the data.
• "Work Up" Philosophy:
  Reloading manuals always recommend starting with lower loads and working up to a maximum load, as different firearms and components can react differently to the same load data.

 

[SJB358]

I think the 280 Ackley is about the most overloaded cartridge out there. It’s also one of the coolest ones he created but I think folks in the old days ran them up till they hit pressure signs and backed off a grain and called it good. With the straight side walls it grips the chamber better than a case with more slope so by the time you see pressure you’re way over anything considered normal max and backing off a grain usually puts you on the cusp of probably still high but useable since it’s a very forgiving case design.

Only the 280 Ackley can whoop 7 Rem Mag loads with less capacity and usually barrel length due to its “more efficient cases”. Well, we all know capacity is capacity.

Seems like your way of figuring out the difference in case space from the 280 Rem and loading accordingly more in charges is about the safest bet while taking it to 65k vs the 58k of 280 Rem data.

Cool post, grabbing some popcorn and seeing where it goes.

 

[JD338]

I've been messing around with the 280AI for almost 20 years now. Great cartridge design for sure. I agree with Scotty that it's probably the most over loaded cartridge out there. Some of the speeds I got were insane. I knew they were way over pressure. Discussed this with my gunsmith a couple of times. He always said that I could back off on the charge weight. That's what I did and tweaked the load for best accuracy.
I've settled on the 150 gr ABLR at 3100 fps. An extremely accurate load that shoots fast, flat and hits hard. Case life is great too. One thing in my favor is that the chamber has a long throat which allows me to seat the bullet way out there. This allows for more case capacity. Also, the 150 ABLR doesn't have a lot of bearing surface so my speeds are a bit higher.

JD338

 

[longrangehunter]

@TackDriver284
@SJB358
@JD338

I agree with your assessment of what I believe most people were doing wrong with the 280AI and why I decided to post this!

I just could not bring myself to telling Kenny Jarrett that a few years later when I went to help him out in November of 2004 after firing the two people that he had been using for developing his loads for the rifles he made.

He felt the ammo really wants to be pushed to produce the smallest possible group, and I’ve ran across one other person that felt that way too years later at the Kettle Falls Steel Challenge this gentleman was using in his Accuracy International 260 Remington.

That individuals load was a one and done in new Lapua brass. I know that because he ended up giving me all his brass that day. It was toast, way too hot and he said it was junk.

@TackDriver284, The new rifle I’m using now has roughly 125-140 rounds through it, so it’s broken in by now and should have settled in to produce consistent velocity.

On a side note, the Reamer I used is not the SAAMI Version, but a tweaked version between Nathan Foster of NZ. and Dave Manson of Manson Precision Reamers that I’ve copied and pasted below that Nathan Foster wrote:

A series of enhanced performance reamers designed by David Manson and Nathan Foster, tested with the help and support of Grant Lovelock, co-owner of True-Flite NZ.

• .280 Remington FMR
• .280 Remington Ackley Improved FMR
• 7mm Remington Magnum FMR
• 7mm Practical
• .30-06 Springfield FMR
• .30-06 Ackley Improved FMR
• .300 Winchester Magnum FMR
• And re-introducing the M-852 Match

With that info above I’ll add what I personally know about the reamer design. The length of the body dimension to where the shoulder begins was shortened which prevents FireForming a std. 280 Remington in the chamber! Which I wasn’t aware of, and unfortunately it Can’t be Done. It’s very slight….. As in factory brass and ammunition is roughly .001-.002 shorter than the chamber length. They’ll fall out on their own no problem, but you might feel a slight resistance when closing the bolt.

Which also changed the end of where the shoulder ended vs the SAAMI 280AI. They both add up to the same OAL of the case, but unlike the SAAMI version the neck diameter is straight vs a tapered neck dimension that Nosler used.

It also has a longer throat than the SAAMI version too. My personal loads are 3.400+ and .025”-030” off the lands with the 160 BT, and the Partition.

Maybe I’ll post the chamber drawings of the two, but that’s the differences as well as the throats are different too.

It was designed to shoot everything well. IMO it shoots the older bullets better than before, but I was just not seeing the newer high BC bullets being easy to tune which it was supposed to aid in.

For me personally, I don’t like to waste my time and energy trying to get something to shoot. That and not having to eat up barrel life testing everything under the sun.

@JD338, The 150 Ballistic Tip load that I reduced was almost as fast as your load, I only had a 24” bbl vs yours?

That said Nosler does list IMR4831 with the 140 BT, which is just slightly higher than the 58.5 grains I had used in the old reduced load but with a 150 Ballistic Tip. I think it was around 3075 f/s in that Jarrett rifle, but I know longer have that gun.

I however do have 40 rounds of that ammo that I produced myself in new FF RP brass that I may either dismantle, or test fire it? And why I wanted to see what Dr Mike thought?

 

[longrangehunter]

The pfd files I have for the two can't be copied since they're locked. But I'll do my best to explain it in written form.

Cartridge base to shoulder FMR is 1.8914" vs SAAMI Spec 280 AI 1.8923".
Shoulder to neck FMR .0828" vs SAAMI 280 AI .0819".
Neck length is the same for both @ .3858"
Only the FMR Neck dia. remains the same across the neck length @ .3175 back to front .3175".
Whereas the SAAMI Spec 280 AI is : .3176 back to front .3156".

There is a slight change at the cross section of the beginning of the shoulder FMR: .4565" vs .4550" for the SAAMI version. At that has to do with the relationship at which (their) individual shoulders begin vs each other. The FMR is slightly larger in diameter at the body/shoulder section, and slightly smaller at the shoulder/neck junction.

I could Photo copy them, but since I don't own or have the Copy Rights to the FMR I'm not going to.

 

[JD338]

@TackDriver284
@SJB358
@JD338

I agree with your assessment of what I believe most people were doing wrong with the 280AI and why I decided to post this!

I just could not bring myself to telling Kenny Jarrett that a few years later when I went to help him out in November of 2004 after firing the two people that he had been using for developing his loads for the rifles he made.

He felt the ammo really wants to be pushed to produce the smallest possible group, and I’ve ran across one other person that felt that way too years later at the Kettle Falls Steel Challenge this gentleman was using in his Accuracy International 260 Remington.

That individuals load was a one and done in new Lapua brass. I know that because he ended up giving me all his brass that day. It was toast, way too hot and he said it was junk.

@TackDriver284, The new rifle I’m using now has roughly 125-140 rounds through it, so it’s broken in by now and should have settled in to produce consistent velocity.

On a side note, the Reamer I used is not the SAAMI Version, but a tweaked version between Nathan Foster of NZ. and Dave Manson of Manson Precision Reamers that I’ve copied and pasted below that Nathan Foster wrote:

A series of enhanced performance reamers designed by David Manson and Nathan Foster, tested with the help and support of Grant Lovelock, co-owner of True-Flite NZ.

• .280 Remington FMR
• .280 Remington Ackley Improved FMR
• 7mm Remington Magnum FMR
• 7mm Practical
• .30-06 Springfield FMR
• .30-06 Ackley Improved FMR
• .300 Winchester Magnum FMR
• And re-introducing the M-852 Match

With that info above I’ll add what I personally know about the reamer design. The length of the body dimension to where the shoulder begins was shortened which prevents FireForming a std. 280 Remington in the chamber! Which I wasn’t aware of, and unfortunately it Can’t be Done. It’s very slight….. As in factory brass and ammunition is roughly .001-.002 shorter than the chamber length. They’ll fall out on their own no problem, but you might feel a slight resistance when closing the bolt.

Which also changed the end of where the shoulder ended vs the SAAMI 280AI. They both add up to the same OAL of the case, but unlike the SAAMI version the neck diameter is straight vs a tapered neck dimension that Nosler used.

It also has a longer throat than the SAAMI version too. My personal loads are 3.400+ and .025”-030” off the lands with the 160 BT, and the Partition.

Maybe I’ll post the chamber drawings of the two, but that’s the differences as well as the throats are different too.

It was designed to shoot everything well. IMO it shoots the older bullets better than before, but I was just not seeing the newer high BC bullets being easy to tune which it was supposed to aid in.

For me personally, I don’t like to waste my time and energy trying to get something to shoot. That and not having to eat up barrel life testing everything under the sun.

@JD338, The 150 Ballistic Tip load that I reduced was almost as fast as your load, I only had a 24” bbl vs yours?

That said Nosler does list IMR4831 with the 140 BT, which is just slightly higher than the 58.5 grains I had used in the old reduced load but with a 150 Ballistic Tip. I think it was around 3075 f/s in that Jarrett rifle, but I know longer have that gun.

I however do have 40 rounds of that ammo that I produced myself in new FF RP brass that I may either dismantle, or test fire it? And why I wanted to see what Dr Mike thought?

lrh,
My rifle is a M700 blueprinted, tubb recoil lug and a Hart 24" #5 contour, 1:9 twist barrel with 6 flutes.
Shoots 120 BT, 140 BT/AB/PT, 150 ABLR/PT/E-Tip, 160 BT/AB, 168 ABLR in the.3s or less.

 

[Johnly]

I've been guilty of this in the past before the 280 AI had SAAMI specs and QL were available.
I have a couple 280 AI rifles built on blueprinted 700 actions for long range work that have 1/8 twist 28-30" barrels.
One day I decided to see how fast I could push a 140 gr. Nosler BT seated long using Hodgdon H100V powder.
I went as high as 61.0 grains when plunger marks appeared and the velocity was 3342 fps.
Pressure was likely over 70k psi and the experiment was a worthless exercise of excess.

 

[JD338]

I've been guilty of this in the past before the 280 AI had SAAMI specs and QL were available.
I have a couple 280 AI rifles built on blueprinted 700 actions for long range work that have 1/8 twist 28-30" barrels.
One day I decided to see how fast I could push a 140 gr. Nosler BT seated long using Hodgdon H100V powder.
I went as high as 61.0 grains when plunger marks appeared and the velocity was 3342 fps.
Pressure was likely over 70k psi and the experiment was a worthless exercise of excess.

When I mentioned insane speeds, that is exactly where I went with the 140 gr BT. My experiment was done with RL22 and the guidance of my gunsmith. He had told me that 3300+ fps was likely 70,000 psi. I backed it down to 3200 fps and it shot lights out.
The 140 gr AB at 3200 fps is a flat shooting, hard hitting load for most anything in NA.

JD338

 

[truck driver]

Not a 280AI but a 338WW, I had picked up some Swift A Frames to load in my 338WW. The 210gr bullet would show pressure signs faster than a standard cup and core bullet like a Nosler or Sieara. The Jacket material of the Swift grabs the lands and groves of the barrel causing more breach pressure, so you need to back them off more than other brands at top velocity loads.
At least that is what I was told by someone on here and have not tried to load them since and still have a partial box somewhere on a shelf. Not that they are not a good bullet because they are, I just couldn't figure out the right powder charge I needed, and the Ruger M77 Hawkeye stainless steel barrel was a little rough and not broken in yet to smooth it out.

EDIT! OOPS made a mistake the bullet wasn't an A frame but a Sirocco.

 

[longrangehunter]

Not a 280AI but a 338WW, I had picked up some Swift A Frames to load in my 338WW. The 210gr bullet would show pressure signs faster than a standard cup and core bullet like a Nosler or Sieara. The Jacket material of the Swift grabs the lands and groves of the barrel causing more breach pressure, so you need to back them off more than other brands at top velocity loads.
At least that is what I was told by someone on here and have not tried to load them since and still have a partial box somewhere on a shelf. Not that they are not a good bullet because they are, I just couldn't figure out the right powder charge I needed, and the Ruger M77 Hawkeye stainless steel barrel was a little rough and not broken in yet to smooth it out.

EDIT! OOPS made a mistake the bullet wasn't an A frame but a Sirocco.

You’re absolutely right, the pure copper jacket seems to be very grippy!

I tested the 7mm 160 AFrames in my 280AI and wondered the same thing! I still have that box with most of them still there.

 

[Aussie Wanderer]

Great read, thanks guys. Always learn something new on here.