Lil gun mystery.

[almar]

Typically, I get close to load data results when starting out and fine tune from there but I'm using this powder in a 22 k hornet where the load data suggests 12.5 to 13.5 grains but I'm getting way too much pressure and velocity at 12.5gr. Loose primer pockets too. I have to load in the 10 to 11 gr range to get normal results. Any ideas why? Just brainstorming here.

Seating depth is just off the lands and much less than suggested.

2 different calibrated scales.

Chrony is giving normal results with other cartridges and loads.

Cz527 with 26 inch pacnor barrel. 12.8 grains yields 3400+ fps. With a 40gr vmax. 11.2gr yields 3100 fps and normal looking primers but on the high pressure side.

Cci spp

Note: the same batch of lil gun seems to produce expected results with 300bo subsonic but I may test a little more to be sure.

[TurnipEaterDown]

"Seating depth is just off the lands and much less than suggested."

If your loading is "just off lands", and your COL is "much less than suggested", it tells me your gun is short throated.

Obviously a wildcat. I would start with loading to expected velocity in reliable source. I see the 5th edition Sierra manual has the K-Hornet, 14" barrel, and they get max 2950 on 40 gr.
Think I would expect ~10% velocity improvement w/ your additional 12" barrel, so, if it were me, I'd expect no more than 3200-ish max on a 40 gr.

The pressures are also possibly higher than you might want to see on a SPP. I know lots of resources say to use SPP in Hornet, but I used Rem 7 1/2 in my 17 Ackley hornet and they did fine for me, and allowed me 3800 fps on 18 gr (which likely really produces excessive pressure, so I bring it us as a 'primers are tough' comment).

[almar]

But the amount of powder I need to get there is lower...why? I tried 2 different batches. One new and another I bought in 2016.

[TurnipEaterDown]

It's an economy chamber... Saves you powder...

Seriously though, burn rates vary and chamber & bore dimensioning has effects on pressure curves. Do other powders come up to velocity unexpectedly quick as well?

If everything comes up fast, then you just have a chamber/bore/etc. that gets pressure (& velocity) quicker than you might expect.

My 17 Ackley Hornet really never let me get near some old data, and I exceeded others. Just showed me that I didn't know what I didn't know about the actual pressure in the case. Just used what worked well, as it was all non-standard anyway.

[DDriller]

I use a lot of Lilgun and find I hardly ever use as much as called for. QuickLoad almost always calls for too much.

[dale2242]

Normal loads using Lil Gun setting in the hot sun have wanted to over pressure for me.
Try to keep your rounds cool.

[brokeasajoke]

I experienced this exact same thing. Got flamed on a Facebook reloading page for pistol primers and using less than min loads. You are not the only one that has had this problem. I know this is another site but read through my journey with Lilgun. I wish it would have worked as it is plentiful around here.
https://forum.accurateshooter.com/th...ssure.4050687/

[rbuck351]

I have experienced wide velocity/pressure variations using lilgun in my K Hornet so I don't use it.

[almar]

I'm getting some pretty good accuracy with it but I was wondering what caused this. It seems to be common though. I like to treat my hornet brass mildly. I may start using 2400 for a bit. I have 4 lbs and I never even tested it in the hornet yet...

[DougGuy]

What COA does the published load data call for, and what is your COA?

If you have to seat deeper in the case than the published COA calls for, and you don't modify powder charge to suit the shorter COA, there is where your over pressure is coming from.

[almar]

I actually extend it out more because I single feed but the bullet is not pushed into the lands. I also use 22 hornet data not 22 hornet so you would expect less pressure.

[CWME]

Minimum spec chamber perhaps? Necks too thick to release the bullet? I cut a 22BR chamber on a Shilen barrel last fall. Headspace was perfect, necks were a bit too thick for the chamber. Pressures were way high with a starting charge. After turning necks down a couple .001 pressures dropped. I was able to work up to a decent node from there.

[earlmck]

Interesting, almar. I had exactly the same experience with my k-hornet, or even more so. First shot with the starting load expanded the primer pocket so far I didn't even find the primer. Old low-wall, but must have been stout enough to handle 70k plus pressures I would guess. I happily use Lil'gun for other stuff but haven't returned to try on k-hornet again.

[Bent Ramrod]

Have you checked your case lengths? My “normal” Hornet cases will lengthen a few thou and need trimming after a couple reloads. If this isn’t done, loads that previously showed no excess pressures will start to loosen primer pockets. There isn’t a lot of web down there to resist this, so it doesn’t take much pinching of the bullet at the chamber end to make it happen.

Of course, one of the advantages claimed for the K and other sharper-shouldered Hornets (and wildcats in general) was a reduction or elimination of this lengthening tendency. As well as blistering velocity increases, vastly improved accuracy, enormously increased barrel life and more essential Coolness for the shooter. Trust, but verify.