Ok so I spent another few hours at the range today doing some load development with the 225gn FTX and testing the no crimp= more velocity theory.
Well I am very impressed indeed with the results!
Using Rem 7½ primers, Hornady cases,Hornady 225gn projectiles and Win296 powder I got the following results.
53gns w296 2745fps
54gns w296 2806fps
55gns w296 2809fps
I tried 55.5gn which again showed next to no velocity increase.
These results are with zero crimp applied.
The case is nearly full with 54gns of 296 so all I did was seat to a length that had mild compression of the power and didn't have the projectile pushing itself back out after seating. In other words a depth that gave consistent length with out getting longer after seating the pill each time. It is quite long with most of the projectile protruding from the case but there is plenty of room in the magazine and the projectile is still far enough from the lands to not be an issue.
I am very pleased with the results. Accuracy is still very very good. The last scope zeroing group I shot for the day went 0.6 inch at 100yds with out too much concentrating at all.
Pressure signs were moderate compared to all my other rifles of different calibres and also reassuring to see due to fact that I did not see any at all till way the other side of any published data.
I didn't quite make the 4000ft/lbs I was chasing but 3900 odd is just fine with me. In answer to a previous question about why I wanted to reach 4000ft/lbs.......... there's no real reason other than why not...... and maybe a touch of ocd that makes 4000 seem a lot better than 3934ft/lbs..... though 3939 might have been alright too
Trajectory should be substantially improved with the increase in velocity over factory ammo as well I hope.
If someone has any ideas about why I gained 200fps by not adding crimp I'm all ears. To be true though the gain is not from the lack of crimp but the ability for more powder to make more velocity with the lack of crimp.
My theory is the primer shunts and jams the pill into the lands so acting like a crimp but with even more of a delaying effect to allow a more complete powder burn?
Would love to hear some other theories.
Cheers
Brett