Crimps, OAL, Pressure Issues

[davem]

I've read that on revolver ammunition you want a good crimp so the powder burns correctly but that's it. There is a 38 special wad cutter load that used a tiny charge of Bulls eye and yet the loads were blowing off the revolver top straps. No one knew why. I thought that maybe pressure was increased because the 148 gr. wad cutter was pushed all the way into the case but apparently tests were done by a gun writer who used double charges. The issue seemed to be the crimp. A lot of reloaders were just seating the wad cutter whereas you were supposed to put a crimp over the end of the wad cutter. When the powder first started burning those cartridges without a crimp had the bullet move forward until hitting the forcing cone/lands of the bore and at that point the top strap blew off. I don't have the details, it may have been that the wad cutters were out of the case and all the force of the charge went straight up.
When I heard of this explanation I transitioned over to a bolt action rifle. I remember the Lee Factory Crimp dye. A lot of competitor companies had ads that such a crimp wasn't necessary and a lot of target shooters didn't crimp their rifle reloads. So, I'm wondering on a crimp or no crimp on a rifle reload for a bolt action.
I think it was a book by Bob Hagel that spoke about working up a reload and test seating the bullet until it was just contacting the lands and then back off .003" for easy chambering of the round. Some one told me if a rifle cartridge is loaded such that the bullet is touching the lands upon chambering that pressures sky rocket.
Maybe I need better reloading books that cover some of these issues. In any event, any comments on any of these issues appreciated.

 

[F. Guffey]

There is a 38 special wad cutter load that used a tiny charge of Bulls eye and yet the loads were blowing off the revolver top straps

How many straps did it have? I do not know what a tiny bit is.

Like trains, I am going to sit back and watch this one go by.

F. Guffey

 

[Longshot4]

First of all I beleave you need to not be caught up in hear sayers. Here is a old saying from Hollywood that will fit you'r Thread.

Just the facts mam just the facts.

You had the right idea when you mentioned to get more manuals.

Note: Get 3 of the latest loading manuals and read them until you know them well. You will see how they don't say it the same way but they cover a lot of FACTS.

Loading takes a certain mind set. Safty

I wish you well

 

[Hammerhead]

There is a 38 special wad cutter load that used a tiny charge of Bulls eye and yet the loads were blowing off the revolver top straps. No one knew why. I thought that maybe pressure was increased because the 148 gr. wad cutter was pushed all the way into the case but apparently tests were done by a gun writer who used double charges.

I'm guessing it was the double charges.
The deep seated wadcutter load is a well established load, millions have been shot. Normally they use fast powders and get little to no crimp, just remove the flare, maybe a little more. Even a heavy crimp is unlikely to cause a problem.

Heavy crimps are for slower powders. It helps hold the bullet back for a fraction of a second so the powder gets going. If pressure is higher, it's because the powder burned more efficiently.
It's hard to believe, but some powders are hard to ignite. My friend loaded up some .38s with HS-7 (a slow powder, now discontinued) with a light crimp and had a primer fail to ignite the charge. A heavier crimp combined with a magnum primer would have fixed the problem.

The short OAL of the wadcutter load requires much less powder than a normal bullet of the same weight.

 

[davem]

I guess nobody has any worthwhile information. Thanks any how.

 

[F. Guffey]

I guess nobody has any worthwhile information. Thanks any how.

http://thefiringline.com/forums/showthread.php?t=341348

It is not easy to talk over the choir.

No one knew why.

They still don't.

Some believe it is related to something that happens in a combustion engine with spark plugs and timing and fuel that burns slow or fast. some foreigners explained it many years ago, problem, the phenomena did not happen every time, the foreigners moved on and we are still talking about it.

F. Guffey

 

[mikld]

I'm no ballistic expert, but, I think you have some false information. I have, and often read of seating wadcutters from flush to 5/16" or so out of the case. I have used a dusting (2.5 gr.) of Bullseye up to max. loads of W231 under 150 gr. DEWC without pressure indications. No crimp, light taper crimp, heavy roll/profile crimp made no noticeable difference in indications of overly high pressure. I have loaded, once or twice 150 gr .38 cal. wadcutters to Magnum pressures/velocities with no overpressure signs. "Blowing off a top strap" would take a double or even triple charge of Bullseye (unless it followed many, many very "hot", overloaded rounds in a weak design/construction gun and even then it's doubtful).

I've read theories about primers pushing bullets slightly before good powder ignition, but that is in micro seconds and mostly in rifle cartridges and doesn't increase pressures dangerously.

I would suggest one pay very little attention to unsubstantiated/undocumented stories heard around the gun shop or range...

Fishermen's lengths grow as they are related, and shooter's groups shrink as they are told. Perhaps this story is one of those where 6 or eight grains of Bullseye shrunk to "a tiny charge"...