Early Pressure Signs - 260AI Nosler Brass

[APGE]

First off- .9 gr is not starting low.

0.9gr lower than a quickload prediction of 56k psi (based on measurements, not QL defaults), not 0.9gr lower than a published max.

 

[Dusty Stevens]

Man i wouldnt use ql for starting loads. Get one out of the book, start low then input your actual data in ql to qualify your actual components. One missed variable can spell disaster or a stiff load like you encountered.

 

[APGE]

To get accurate results with QL:

All weights and measures inputted to the program as accurately as possible, this means

-Case volume in grains of water
-Bullet measured length, diameter, small diameter (BT), length of taper, and weight
-Powder charge weighed to 0.02 grains
-Cartridge overall length
-Distance to the lands (or jammed)
-Set start pressure (there is a factor for coated bullets in the drop down)
- Model several powders in the burn rate appropriate for application (H4350 is vg for 260ai)
-The OBT must be known for your barrel length
-The OCW (really great if it overlays the Pmax) must be very close to the Pmax. This is the Z1 line.
- The OBT will dictate the amount of powder to use. Sometimes you will not get to the next higher node as psi is over max.

Now load 5 rounds and chronograph them, optical chrono's can give erroneous velocities. The Labradar is the most accurate and user friendly. Magnetospeed is accurate but not user friendly to the degree the radar is.

Compare predicted velocity to actual.

If it does not jive (should be within 30 or so ft/s of predicted) adjust the Ba of the powder, only up to 5% though.

The powder adjustment, it may require adding or reducing powder charge to get back to the OBT.

Bullet weights can be tweaked up to 4%, this moderates the effect of a fast or slow rifle bore.

Weighting Factor, can be tweaked up to 10%, for a 260Rem it is 47, for the AI I would try 45 or 46. This does not jive with the QL default but is arrived at through calculation.

Also, input the temperature you will be testing in as this effects the Ba.

A load that is on or very close to the barrel time and the Pmax and Z1 lines overlayed will be a good load, a very good load.

QL works well for me. The user has to have knowledge of internal ballistics to fully realize what the program is capable of.

With out velocity been known , the QL program does not work!

This is basically my procedure, except I omit the chronograph and find the node for the particular combination by exploring small increments either side of the QL prediction using default burn rates. I'm really starting to wonder if I I've had slow 4350 to date and the batch used in recent testing is a hot one.

I know one only has to look at h4350 and ADI 2209 in QL to see how much different batches of the same powder can vary, but it is curious that people on both sides of the pacific ocean find nodes around the same charges of 4350 (USA) and 2209 (Australia, where it's made).

 

[savagedasher]

I shot 260 So for years
The best power I found was
Norma MRP
And I found as much a 3 gr of case capacity in cases

 

[Geno C]

I’ll share my load since you asked.

44.6gr H4350
Lapua LRP brass
Rem LR primer
140 Berger vld
2.890” ish oal
2936 FPS from a 27” barrel

It’s on the high side but that where it shoots best. There is no way at my loaded length that I could get to 46gr! It would lock up the action, no doubt.

 

[Edwin Gideons]

I use Lapua "Palma" S/R brass for all my .260A.I.s.. This brass is about as strong as you will find anywhere. Now I don't want to get into bitch session, however, 46 grs of H4350 is a bit over the top for any "naked" 130 class bullet. With a Berger 140LRBT, which has a short bearing surface, 44.0grs is about tops and that MAY very well produce a sticky bolt lift! I know you are using a "MOLY" coated bullet, but 46+grs, especially for a "Non-Palma" brass, in my opinion, is asking for pressure signs.. My last .260A.I. using the 140LRBT load was 43.4grs of H4350! That produced 2930 and on a L-O-N-G shot string in the Arizona sun, caused a very stiff bolt lift! Remember, that is with necked down Palma brass. What would have happened with L/R primer brass?

That is wild that you were getting pressure signs from 43.4grs in an AI. My match load for two different rifles was 43.5grs of H4350 under a 140 ELD-M in .260 Lapua brass with a 210M at 2.855". That was in a straight .260 and I am still using all of that brass. I never had any pressure signs and most of those cases are going on their 9th and 10th loading. My velocity was 2850 any day of the week. Would the extra .023" of length on the LRBTs jack up the pressure that much?

 

[Edwin Gideons]

What do the other two makes of brass have for volume ?

My Lapua .260 brass fire formed averages 56.7 of H2O volume.

 

[Bart B.]

There are too many variables in component lots and cartridge assembly, plus bore dimensions, that Quickload doesn't allow inputs for to let their data be reliable and what your stuff does. It shows trends as some variables change.

That's what their rep told me when I asked them about how precise the calculations would be.

At 46.1gr I got a light ejector swipe

Most cartridge case heads start extruding into bolt face cutouts at about 75,000 psi. I've shot proof loads with about 80,000 psi that didn't have ejector wipes on case heads.

 

[JimSC]

In a regular .260 with a 30 inch Shilen barrel with H4350 and 142 SMK's I had pressure issues at 42.5. I backed down to 42.1 and am getting 2850 with single digit SD's and no pressure signs at all. A powder puff load compared to what you guys are using but it works

 

[Bart B.]

Into the lands is 10,825 psi, subtract 29psi for every 0.001" off the lands, this will be your start pressure.

where does this come from?

Never heard of such stuff.

 

[BCBRAD]

where does this come from?

Never heard of such stuff.

Quick load

 

[Jeff A]

Just basic stuff here but be very sure your cases are devoid of any sizing lubricant and your chamber is clean and dry.