For plinking in my 400PDK I had loaded some pistol bullets in front of 4320. I know not the best but Loadtech said around 2400fps and I had several lbs I would have never used. The darn pistol bullets was only .713" and set in the cannelure the OAL was 2.96". So I had set some crimped in the cannelure and some I left at 3.13" seeing if they would feed any different.
A total of 6 bullets in the cannelure ranged from 2247 to 2265FPS. I call that REAL darn close. However the ones with no crimp (a .410 pistol bullet in a neck set for .411) ranged from 1800 to 2180 with most being under 2000. I gather that there wasn't enough pressure generated by the small bullet and no crimp to get a consistant burn. Probably lucky I didn't have other issues.

Anyone seen this much difference? Or have any other thoughts what caused the large difference in velocity? From point forward all of my bullets for this rifle will be crimped that is for sure.

saeed did an experiement on crimp vs no crimp, and foudn velocities both higher and more consistent with!

Crimping can have a dramatic effect on a load. I used to load my 357 Colt Python with a stout load and no crimp and was not impressed. The recoil was more like a 38 and the cylinder flash was huge. I started crimping and the flash was gone and the shock on my wrist was triple. Crimping has a place. I crimp my 375 H&H to keep the bullet tips where they are supposed to be while in the magazine. I haven't tested the effect of the 375 loads crimped vs uncrimped as I knew going in that they would be crimped and did not work up loads uncrimped.

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crimp vs no crimp, and foudn velocities both higher and more consistent with

I've seen some benefit in magnum pistols. I have never seen anything like the 10+% as well as the consitancy gain.

here's his write up
http://www.accuratereloading.com/crimping.html

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here's his write up
http://www.accuratereloading.com/crimping.html

Jeffe I had seen his test. In two of the test his velocity actually went down. Like I said I have seen a small velocity increase in magnum pistols. More like a 1-2%. In my case in this rifle I got a 10-20% velocity increase with a crimp. My only guess is with the light pistol bullet in a 411 without the crimp I wasn't building enough pressure to burn the powder correctly.

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My only guess is with the light pistol bullet in a 411 without the crimp I wasn't building enough pressure to burn the powder correctly.

I can relate to that. Using Lil'Gun in a hornet with not even neck tension does not burn the powder well at all. I overcame this by using heavy bullets and a stiff powder charge. The end result was a higher than normal velocity with a heavier than normal bullet. Other folks crimp their horne loads with lighter bullets to get consistant burn.

Hey Paul, How was the "Accuracy" between the Crimped and Non-Crimped?

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Hey Paul, How was the "Accuracy" between the Crimped and Non-Crimped?

I have no clue. I was shooting over my Chrony to test some max velocities. So I had about 40rds all total in the same 4" group(yes there were some flyers). The pistol bullets were to try and square up the shoulder on some new brass. The crimped ones did the uncrimped didn't build enough pressure to square the shoulder.