Thread: .25 Creedmoor 40⁰ Improved rifle build

I've been having a bit of a play with the quarter bore Creedmoor after picking up that nice little Rem mod 7 action here. It made some dies and put a barrel on it this morning and chambered it for some testing.





The rifle will eventually be a very short and light bush rifle
in a carbon stock with a suppressed 14" barrel.
The barrel is a 1:10" twist so I'll be keeping under the 120gr in projectiles.

For now I have chosen the 115gr Nosler balistic tip projectiles but will probably have a crack with some of the 110gr Hornady ELDXs.

I necked down a few Lapua SRP 6.5 crd cases and fireformed them to get the nice sharp 40⁰ shoulder and a small bump in case volume.



Onto a ladder test with some RL16 and the Nosler 115gr BT. The Barrel is still at 20" until I sort the stock inlet.
I had a look at some loads on hodgdons app and the max load for a std 25 creed with a 115gr and 2209 is 43.8gr giving 3036fps in a 24" barrel @ 60900psi.

RL16 is a little faster burning than 2209 but I also have an extra grain or so of volume in the 40⁰ improved case.
I started the ladder test at 42gr and went to 46 gr where I was at full capacity with a slight crunch but still had a rattle.

42gr- 2737fps
43gr- 2824fps
44gr- 2880fps
44.5gr- 2886fps
45gr- 2917fps
45.5gr- 2930fps
46gr- 2989fps

While there was no signs if excessive pressure such as a heavy bolt lift or smeared ejector stamping the primers were starting to crater and flow into the firing pin hole.
I think it had more to give but stopped there as I'm not a fan of compressed loads and 46gr seems like too much even I the larger volume case. My gut feeling tells me 44 to 44.5gr is closer to where I should be.





The same full case 46gr load with a 75gr vmax gave 3050fps





I've seen this Lapua small rifle primed brass hide a lot of pressure before but I'm really not sure with this one.
Does anyone have quickly they can do a quick model of this load to see what pressure I'm running at?


Water capacity of 53.5gr to the top of the case mouth.
115gr Nosler Balistic tip
RL16 powder
Small magnum primer
COAL 68.80mm
20" long 1:10" twist barrel