Thread: My 260AI Load Development Begins

Originally Posted by Tikka7mm08

Thanks @R93 - so will necksize this latest brass and see if it the bolt closes nicely. If not sign there is too much pressure, ie headcase expansion?

I would measure the case head with a mic. Anything over .0005 over from a new case I would keep an eye on.

In saying that I could get away with 46grns of RL17 in my rifle.
I stopped using it because it was a prick to get when you needed it.
Do you have a body die?



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Ok. I just went through all brass. TBH I hadn't kept them in batches for refiring - lesson learnt. 11 tight bolt after neck sizing, 16 AOK. I then FL sized the tight ones but it made no difference, still tight bolt, so they are in the bin.

I don't have body die? I have kilos of RE17.

I might drop back to 44gn and see how I go...? Or when firing a fireformed case with 260AI for first time check case head with mic...? I measured a new Lapua case and it is 11.91mm - the NS case are all 11.91mm and 11.92 with 1 case at 11.94mm. My Mitutoyo only goes 2 DP in metric and 3 DP in imperial...do I need something much flasher to measure 0.0005 (mm?)??

Check that those tight cases don't have ejector marks on the base by primer, these will be proud and make your brass longer to the shoulder and may cause a tight fit. If so then that's a sign of over pressure.

Originally Posted by Tikka7mm08

Ok. I just went through all brass. TBH I hadn't kept them in batches for refiring - lesson learnt. 11 tight bolt after neck sizing, 16 AOK. I then FL sized the tight ones but it made no difference, still tight bolt, so they are in the bin.

I don't have body die? I have kilos of RE17.

I might drop back to 44gn and see how I go...? Or when firing a fireformed case with 260AI for first time check case head with mic...? I measured a new Lapua case and it is 11.91mm - the NS case are all 11.91mm and 11.92 with 1 case at 11.94mm. My Mitutoyo only goes 2 DP in metric and 3 DP in imperial...do I need something much flasher to measure 0.0005 (mm?)??

No sorry to confuse.
I am a dinosaur and still use imperial when it comes to reloading.😆
Also case head expansion is the best way to indicate max pressure in an Ackley Imo.

You don't want to see much case head expansion at all. .0127 mm is .0005 inches.
Best done with a blade mic or an accurate vernier but I use a normal mic and mark my case for a 12 o'clock and measure the same place each time.
.260 Ackley will be around max pressure at around .0005 inches or .0127mm in my experience.


A body die would likely have given you a few more goes out of the brass you binned until it wouldnt hold a primer.

Drop the load back as you said and see how you go.
I get 2930ish with 140 class projectiles but have not tried the bergers.
I get around 8 goes out of a case before I have to bin so I am still on the slightly hot side for my barrel.

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OK gotch...thanks @R93

Just bought a body die...hadn't needed one before.

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So the body die didn't seem to bring the tight brass back in the spec. I set it so it was firm bump of shell holder and die. I got Quickload and it suggests my 45gn RE17 is too hot...which is what my brass is telling me. I am looking at getting a Whidden hydraulic die too just to avoid fireforming brass, as I find that a waste of time and money (I only want to shoot FF loads now).

My body die will still bring them to chamber after 8 or so firings but they won't hold a primer well enough.

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I had to shave 20 thou off my shell holder to get my body die to work for my 7mm08AI.

Originally Posted by wsm junkie

I had to shave 20 thou off my shell holder to get my body die to work for my 7mm08AI.

Pretty sure Redding state something about using the correct shell holder for their body too, for this very reason.

That would make sense...my shell holder is pretty slim compared to LNL case center one but obviously not enough.

@Mathias yes...just ordered this set of shell holders.

#1 Competition Shellholder Set : COMPETITION SHELLHOLDER SETS | Brownells

Originally Posted by Tikka7mm08

@Mathias yes...just ordered this set of shell holders.

#1 Competition Shellholder Set : COMPETITION SHELLHOLDER SETS | Brownells

I see these are + on thickness, wouldn't you want to go - on thickness so it allows you to engage the case further into the die? Or have I got this completely wrong?

aw fark...I thought they were - and +

I need -.

Originally Posted by Tikka7mm08

aw fark...I thought they were - and +

I need -.

While it may read + on the shell holder, I think it really means -

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