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

Very cool project. Following

Originally Posted by Wingman

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.

Attachment 275464

Attachment 275465

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.

Attachment 275466

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.

Attachment 275469

Attachment 275470

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

Attachment 275471

Attachment 275472

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

Very cool I had a 25-08 imp many years ago and would love one of these again.
I used 115bt and 110AB at around 2900 in a 22" barrel, back then I used N160.
Keep us posted on the progress

Sent from my CPH2531 using Tapatalk

I toyed with the idea of .25-08 40⁰ improved too,
initially I was going to run my .250 wildcat that is a shortened .284win case but thi action didn't feed it well and the slower powder required would likely just run inefficiently in a short barrel and just fireball.
I also considdered the 2mm shorter .25x47 Lapua 40⁰ improved..
I went back and forward with the decision for a week before I went with the Creedmoor case. I figured it would be the most efficient way to get speed in the short barrel and I already had plenty of lapua srp brass

The 115bt is a stunning harvester on big red stags, - that primer flow into a non bushed Remington firing pin hole is normal as the pressure gets up there

A short 7mm08 pokes the 120g BT out at 3000fps, I wouldn’t go too short or you risk only reinventing a smaller wheel

Yeah the 115gr BT stood out to me too as I've used the BT in other cartridges and it kills great.. not a high BC low drag bullet but it fits the roll I'm building this for. I have plenty of other long range hot rods for other hunting but this will be a short bush basher that carries a nice compromise of velocity and stopping power with this bullet choice. The 115gr Berger VLD hunter and Hornady 110gr ELDX might also be worth a look.
I know I won't be retaining the 3000fps but a respectable 2700-2800fps will do just fine in a shorty.

Yes I've seen the primer flow a lot in open tolerance firing pin holes but I'd feel a bit better about it if I knew approximately what pressure this powder is generating in these loads. Anyone got quick load?

Short barrels are easy to load for, choose the fastest powder the cartrige can safely be loaded with load until max velocity stops climbing due to barrel length then back it of a touch to get the best efficency and no fireball.

https://www.p-max.uk/index.htm

From my mentor

Originally Posted by Friwi

https://www.p-max.uk/index.htm

From my mentor

Thanks mate, that's what I needed.
Looks like my intuition was correct.. 44gr puts me in the 62000psi Saami pressure max range.. 46gr has me up around the 75000psi lapua SRP cartrigde max range.

Shame they don't list Hodgdon Superperformance powder

Sent from my CPH2531 using Tapatalk