Question about starting/minimum load

[wesc]

I have a 325 WSM (the knowledge necessary to answer isn’t specific to the cartridge) browning a-bolt and I’m interested in creating a light deer/black bear load with Barnes 160 ttsx bullets. I’d like velocity no higher than 2800fps for both improved barrel life and recoil reduction.

I’m still fairly new to reloading but I’ve loaded > 750 bottleneck rifle cartridges in calibers 6 and 6.5mm creedmoor, 30-30, and some heavier 200gr 325 WSM loads. That being said, I’ve completely followed available data and it’s fairly consistent from reference to reference on those loads. As such, the following confuses me (all w760 with a 160gr ttsx unless otherwise stated):

Hornady has data for 150gr and 170gr interlocks both starting at about 60gr of w760 as their minimum loads with velocities of 2800 and 2600 FPS respectively.

Barnes sent me data with a minimum load of 67gr and 3100fps.

Lyman states 65.7 of w760 for 2985 FPS.

Now, I’ll admit that 325wsm is a less common round so I’m sure the various companies haven’t spent nearly as much time developing data as they do on 6.5 creedmoor or .308 but why the tremendous variation on minimum load data?

Given the Hornady data stating 59-60 grain w760 starting loads for their 150 and 170gr interlocks, a load ladder for a 160gr ttsx of 61-64 grains w760 seems reasonable to me. Thoughts?

Lastly, I know other rifles can fill this role better (to include the cartridges I listed above) I’m interested in answers to the above question.

Thanks very much.

 

[wesc]

Bueller...Bueller....

 

[spife7980]

Why is it different? Because of literally everything. Case, primer, powder, bullet, chamber, barrel, equipment, hell even their parameters themselves for what’s a safe minimum.

And most they time they don’t test every single combo, especially not the esoteric stuff, it’s quickload-esque derived.

 

[itwillis]

You will have much better results in my opinion if you want that weight of bullet to use the Hornady ones near the minimum load.

Those copper solid Barnes’s require a lot of pressure to get them moving in the barrel, but once they are going they move easy, and the starting loads are a little higher to overcome this. Running light loads with those can lead to some wild pressure spikes if the bullet can’t accelerate fast enough.

 

[wesc]

You will have much better results in my opinion if you want that weight of bullet to use the Hornady ones near the minimum load.

Those copper solid Barnes’s require a lot of pressure to get them moving in the barrel, but once they are going they move easy, and the starting loads are a little higher to overcome this. Running light loads with those can lead to some wild pressure spikes if the bullet can’t accelerate fast enough.

No kidding. I hadn’t heard that about the coppers. Any idea why? I mean, the hornady bullets of the same grain are bound by a copper jacket. Definitely interesting

 

[Rust]

No kidding. I hadn’t heard that about the coppers. Any idea why? I mean, the hornady bullets of the same grain are bound by a copper jacket. Definitely interesting

Thin copper over soft lead, compressible and easier to force into the rifling. Solid copper, much less compressible and harder to force into the rifling.

As far as different manuals go, different primers or different batch of primers, different powders or different batches of powder, different brass or different batch of powder, different bullets different batch different bearing length etc, different barrel and/or different barrel length. Just switching primers alone for otherwise identical loads in the same rifle can produce different results. Brass can have different internal volumes between differing brands or even different batches of the same brand.

Weird and potentially dangerous things happen with overly light loads which can be hang fires or pressure spikes. If the case isn't full enough the powder doesn't ignite properly which could result in either of the above conditions. Might not happen very often as in once in a blue moon but you don't want to be the blue moon boy.

 

[Lynn Jr]

Wesc
When a manufacturer gives you a load they use data obtained with specific components a specific reamer and there barrel length.
The difference between a jacketed lead core bullet and a monolithic solid is bearing surface length and friction.
Jacketed lead core bullets engrave easily but they also expand easily so they fill the bore the entire length of the barrel.
On a monolithic solid they require more initial engraving force but after that they don't fit the bore as snugly (obturate) and have less friction.
In general the easiest way to overcome the increased engraving is to use more bullet jump when seating solids.
Due to the lower friction solids also tend to have more velocity and require more powder all else equal.

In your case I would start with 0.050 bullet jump and run the ladder in the reverse direction until you reach a accuracy node at a lower velocity.

 

[wesc]

Wesc
When a manufacturer gives you a load they use data obtained with specific components a specific reamer and there barrel length.
The difference between a jacketed lead core bullet and a monolithic solid is bearing surface length and friction.
Jacketed lead core bullets engrave easily but they also expand easily so they fill the bore the entire length of the barrel.
On a monolithic solid they require more initial engraving force but after that they don't fit the bore as snugly (obturate) and have less friction.
In general the easiest way to overcome the increased engraving is to use more bullet jump when seating solids.
Due to the lower friction solids also tend to have more velocity and require more powder all else equal.

In your case I would start with 0.050 bullet jump and run the ladder in the reverse direction until you reach a accuracy node at a lower velocity.

Thank you all for the insight and wisdom. I did seat out for such a jump (not intentionally for this purpose but loaded to factory depth) so I’ll give a try from 64gr and work down slowly and cautiously. If I find a node early I’ll stop and if I’m seeing very high standard deviations consistent with wild variations in pressure generated I’ll stop. I’ll let y’all know how it goes. If anyone has other thoughts please feel free to air them

 

[Vettepilot]

The low or reduced load danger is not fully understood according to my studies, and it is NOT consistent. They have been unable to reliably reproduce it. It is believed that under certain (unknown) circumstances, some low/reduced loads can actually detonate, instead of burn, causing of course a sudden insane pressure spike.

This might never happen...... or it might happen on the next shot. In some calibers, reduced loads, usually called reduced recoil loads are specifically published. I have often read that when "playing" with reduced loads without data, it is best to use a much faster burning powder. Apparently these do not exhibit the little understood possible detonation tendency of many standard rifle powders at low load charges.

For what it's worth....

Vettepilot