Interesting day of load development

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Re: Interesting day of load development

Postby 450whisper » Fri Sep 22, 2017 5:28 am

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

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Re: Interesting day of load development

Postby mcb » Fri Sep 22, 2017 8:27 am

Those are spectacular if a bit scary numbers you have. I wouldn't shoot those in my AR using someone else hands but in a bolt gun that is impressive work.

My guess on the higher velocity without crimp is that crimps can actually loosen the cases grip on a bullet. Especially if you do not have a groove/cannelure in the bullet into which you are crimping. The brass case is "springier" than the bullet so if you're just crimping into the smooth side of a bullet the brass case may actually springs back more than the bullet that is a just a thin jacket of copper or brass on top or relatively soft "un-springy" lead.

Found this with working up 45 ACP loads for USPSA competition. Tried to crimp the 230 FMJ more to get more consistent velocity and I lost a little velocity and started have bullets walk out (shooting in a revolver). Went back to very little bell initially and just enough tapper crimp to remove the bell without leaving a noticeable ring in the bullet if I pulled it and the walking out problem went away.
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Re: Interesting day of load development

Postby 450whisper » Fri Sep 22, 2017 9:07 am

mcb wrote:Those are spectacular if a bit scary numbers you have. I wouldn't shoot those in my AR using someone else hands but in a bolt gun that is impressive work.

My guess on the higher velocity without crimp is that crimps can actually loosen the cases grip on a bullet. Especially if you do not have a groove/cannelure in the bullet into which you are crimping. The brass case is "springier" than the bullet so if you're just crimping into the smooth side of a bullet the brass case may actually springs back more than the bullet that is a just a thin jacket of copper or brass on top or relatively soft "un-springy" lead.

Found this with working up 45 ACP loads for USPSA competition. Tried to crimp the 230 FMJ more to get more consistent velocity and I lost a little velocity and started have bullets walk out (shooting in a revolver). Went back to very little bell initially and just enough tapper crimp to remove the bell without leaving a noticeable ring in the bullet if I pulled it and the walking out problem went away.


You could be very well dead right in what you say. Thanks you for that. Though I must admit when I was testing with the lee factory crimp die and trying to achieve greater velocity I reckon some of the bullets may have looked like an hour glass they had so much crimp. But what you say seems more valid when I think of some the other calibres (nearly all pistols) that I have had experience taper crimping.
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Re: Interesting day of load development

Postby plant_one » Fri Sep 22, 2017 9:56 am

if you're getting an hour glass shape out of them - you're crimping WAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAY too much.

its especially dangerous on straight walled rebated rim cartridges that headspace off the case mouth. bad juju right there and a good way for someone to end up injured, most likely you and possibly those around you.

i had a buddy screwed up like that loading up his first batch of beowulf... pulled the case clean in half, and thankfully left enough brass in the chamber to prevent a second round from chambering. when the front part finally fell out (they never did find the back half) he gave the remaining reloads for me to pull down.

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the three on the left were 3 of about maybe a dozen (out of >300) that i found that were correctly crimped when i pulled them. the three on the right... well ya... no bueno territory. some of the rounds i pulled down were crimped so hard i actually broke a petal off my collet puller taking these rounds apart!



while i appreciate the value of a proper crimp, you need to apply them with caution and in a very controlled fashion. i'm saying this as a very general statement, not so much to pick on you. i keep sharing this image so that hopefully some beginner will see it and will respect the process and possibly save themselves a nasty injury
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