does case crimping affect bullet size?

[GL49]

I've read threads and posts that will tell you to be sure your case tension on the boolit isn't sizing down the boolits when you seat them, especially with a softer alloy, but what about when you load them and then apply a heavy crimp, either for a magnum handgun or a tubular magazine lever action? Won't the crimp on the case tend to size down the projectile when it leaves the case? Or does the first little bit of the boolit open up the crimp and then you don't have to worry about it?

[runfiverun]

it can with a low pressure load.
neck tension will insure good powder burn crimp is there to keep the bolit from moving under recoil or being shoved back in a tube magazine.

balance.
crimp,alloy,load,lube,diameter.

[44man]

Yes, I have brought this up many times. The boolit is what opens the crimp and if too soft it will leave a little crimp that you can see on fired brass.
That can scrape or size soft lead.
Gas pressure after boolit exit will not iron the case mouth.

[Bret4207]

It can be an issue. It' becomes more of an issue with work hardened brass and crimps applied by a gorilla. If you have a problem then check your brass for signs the crimp isn't ironing out. Anneal if needed. Try a lighter crimp.

IMO, if you crimp is so heavy and your brass so resistant to ironing out, the hardest boolit you can produce won't help.

[williamwaco]

Bullet crimping, if done properly has virtually NO effect on the actual bullet.
Especially if the bullet has a dedicated crimping groove.

If overdone, crimping can heavily damage the bullet.


To see what I mean, navigate to

http://reloadingtips.com/how_to/crimping_revolvers.htm

and scroll down to the last bullet picture.
.

[44man]

Bullet crimping, if done properly has virtually NO effect on the actual bullet.
Especially if the bullet has a dedicated crimping groove.

If overdone, crimpig can heavily damage the bullet.


To see what I mean, navigate to

http://reloadingtips.com/how_to/crimping_revolvers.htm

and scroll down to the last bullet picture.
.
True but over crimping can bulge brass below the crimp and break tension or you will not chamber either.
It is crimp left after firing that should not be there.

[Shiloh]

Bullet crimping, if done properly has virtually NO effect on the actual bullet.
Especially if the bullet has a dedicated crimping groove.

If overdone, crimpig can heavily damage the bullet.


To see what I mean, navigate to

http://reloadingtips.com/how_to/crimping_revolvers.htm

and scroll down to the last bullet picture.
.


Good pis and explanation at the posted link. Thanks.

SHiloh

[williamwaco]

True but over crimping can bulge brass below the crimp and break tension or you will not chamber either.
It is crimp left after firing that should not be there.


No argument here but the question was how did affect the bullet diameter.

[GL49]

44man,
If I see the crimp is not fully gone from a fired case, it makes sense it must be sizing down the boolit as it leaves the case. A person could seat a boolit, no crimp, pull it and find out if case tension is sizing it down, I can see that. Now if I crimp the same boolit in the case and pull it, and then take my measurements, I wonder if I would see the crimp gone and the projectile not sized down if everything is working properly. My gut feeling tells me this may not be an accurate representation of what goes on when the cartridge is fired. I'm going to have to try that during my next loading session.

[44man]

44man,
If I see the crimp is not fully gone from a fired case, it makes sense it must be sizing down the boolit as it leaves the case. A person could seat a boolit, no crimp, pull it and find out if case tension is sizing it down, I can see that. Now if I crimp the same boolit in the case and pull it, and then take my measurements, I wonder if I would see the crimp gone and the projectile not sized down if everything is working properly. My gut feeling tells me this may not be an accurate representation of what goes on when the cartridge is fired. I'm going to have to try that during my next loading session.
Those are good thoughts. Pulling a boolit is different then the tons of force when shot.
Some want expansion after the boolit leaves the brass to "obturate." Not the best in any case, it only improves so much because soft boolits "slump or skid."
Just toughen boolits to resist sizing and open the crimp fully. Just plain water dropped WW metal can turn things around.

[williamwaco]

I don't know the answers but I have made lots of observations over many years.

I am talking here about .38 special and .357 magnum.

I have pulled bullets before and after crimping. In my experience, pulling a bullet through a crimped mouth will scrape ( make visible scratches in ) the bullet but it will not reduce the diameter of the bullet. The only way I can explain that observation is that the crimped case mouth expands to let the bullet out then contracts back to its original diameter after the bullet is gone. ( I am talking about pulling bullets here, not firing them.)

I find that in the overwhelming majority of cases, after firing, the crimp is entirely gone regardless of pressure. In my experience it is VERY rare for any visible crimp to remain after firing even a 3.0 grain Bulls Eye load.

I can not visualize any method by which the gas pressure can "iron out" the crimp. When the bullet leaves the mouth of the case, pressure should equalize (almost) immediately so that the pressure ironing out the crimp is matched by the pressure outside the case resisting it. We know that gas leaks back around the mouth of the case in low pressure loads - but what about Maximum loads in which there is no indication of powder residue on the outside of the case ? They both iron out the crimp.

I would buy a ticket to see a high speed video of a cutaway chamber with a low pressure .38 special load ironing out that crimp.


.

[Char-Gar]

If everything is done right, a crimp won't have an effect on the bullet size. If not, then it will.

Bottom line: If your crimp is changing the diameter of your bullet, you are doing one or more things wrong. I will leave it to others to give the lectures on all of the ends and out of cast bullets and crimping.

[Bret4207]

44man,
If I see the crimp is not fully gone from a fired case, it makes sense it must be sizing down the boolit as it leaves the case. A person could seat a boolit, no crimp, pull it and find out if case tension is sizing it down, I can see that. Now if I crimp the same boolit in the case and pull it, and then take my measurements, I wonder if I would see the crimp gone and the projectile not sized down if everything is working properly. My gut feeling tells me this may not be an accurate representation of what goes on when the cartridge is fired. I'm going to have to try that during my next loading session.

Maybe. It makes sense. Thing is brass, especially work hardened brass, will spring back to an extent. So, you have to wonder if the crimp you find after firing is the same crimp that was there as the boolit was passing through the crimp area or if what you see is the spring back that was left after the boolit passed by. I dunno, I bet it varies from case to case though.

[btroj]

Try different amounts/styles of crimps and see what the target shows. Find what your gun/load combo likes best then run with it.
All that matters is what the target shows. What works, works.

[44man]

Maybe. It makes sense. Thing is brass, especially work hardened brass, will spring back to an extent. So, you have to wonder if the crimp you find after firing is the same crimp that was there as the boolit was passing through the crimp area or if what you see is the spring back that was left after the boolit passed by. I dunno, I bet it varies from case to case though.
That could happen and maybe it would show more when it is fired in a large chamber.
I have never been able to measure fired boolits because of damage in the trap.
The most crimp left on was from a friends brass from a .38 with swaged boolits. I have found other brass on the range with crimp left.
I don't know if it always happens and wonder about a real soft boolit that expands a lot while in the brass with fast powders. Maybe it will iron off the crimp but then again, the boolit will suffer slump damage. I don't like to replace one problem with another! [smilie=l:

[largom]

In my RIFLE loads I usually crimp just enough to remove any flare on the case, however, sometimes I apply a heavier crimp to improve powder ignition. I also go with Bret on the work hardened brass resisting expansion. My boolits are soft but are all gas checked and I make my own neck expanders so I can control neck tension. I have never experienced boolit damage due to the crimp.

Larry

[felix]

Breach seating outshoots any other type of seating, bar none. That process must be mimicked by any other method of holding a projectile as is practical in the type of gun being contemplated. ... felix

[44man]

Breach seating outshoots any other type of seating, bar none. That process must be mimicked by any other method of holding a projectile as is practical in the type of gun being contemplated. ... felix
That is correct.
I have spent years trying to convince others that brass, what you do to it and what it does to a boolit is the starting point.
BRASS IS EVIL!

[GP100man]

Here`s a batch of 357 brass that did exactly what ya`ll talkin about .It did not straighten out or some of the crimp was left after firing .

I`m kinda anal `bout brass prep, I even uniform flash holes in my hunting rounds & always check & trimm for a consistent roll crimp .

I would call my crimp a medium on plinkin & medium/close to heavy on the heavier hunting boolits & loads 357 & 44.

I annealed the said brass above ever so lightly ,you can barely see any discoloring & a few loaded & tested , they opened straight , a few more were tested for heavy boolits jumpin the crimp ,the last 1 held tite on a 360-180 NOE travelin 1150 fps & the group was smaller than average (good day) for me.
The brass went back into the hunting rounds rotation, I`m confident I did`nt hurt the brass as extending it`s useable life was what I was after , but in the back of my mind I was thinkin "this has to be better for the boolit also !!"

http://i746.photobucket.com/albums/xx110/GP100man/102_0510.jpg

[44man]

GP100man, I also annealed some revolver brass and could not stop boolit pull. Everything I shoot is hunting loads with recoil.
Boolits that move from recoil will increase air space with slow powders. Not good.
I have learned to live with brass work hardening and find it more accurate with the right alloy.
Light recoiling loads might gain some accuracy. Gun weight alone and how it recoils can also affect pull.

[GP100man]

44man , I annealed some of this brass first as like always ,spinning it in flame ,in low light until a low glow appeared , that was way too much annealin ,it would not hold a boolit for 1 shot.

To relieve tension on straight walled brass very little heat is needed, also quenchin does nothing for the brass other than stoppin the heat from reachin the case head. Besides what actually needs annealing is probably only the front 1/3 of the case .

This has been my exp. with 357 180 gr. boolits , I have`nt done anything with the 44 yet ,but I suspect the heavier boolits /larger caliber boolits will undoubtably be harder to hold still.

Just for the record I annealled the above brass by spinning it with a CD in a propane flame as low as I could get it for `bout 2-2.5 seconds ,no quench.

Don`t try this with nickeled brass.

[44man]

44man , I annealed some of this brass first as like always ,spinning it in flame ,in low light until a low glow appeared , that was way too much annealin ,it would not hold a boolit for 1 shot.

To relieve tension on straight walled brass very little heat is needed, also quenchin does nothing for the brass other than stoppin the heat from reachin the case head. Besides what actually needs annealing is probably only the front 1/3 of the case .

This has been my exp. with 357 180 gr. boolits , I have`nt done anything with the 44 yet ,but I suspect the heavier boolits /larger caliber boolits will undoubtably be harder to hold still.

Just for the record I annealled the above brass by spinning it with a CD in a propane flame as low as I could get it for `bout 2-2.5 seconds ,no quench.

Don`t try this with nickeled brass.
Anneal is tough to get the same with just the right amount but I use it more with rifle calibers. I made a turn table where the case is centered in a pan and gets tipped in water.
Revolver loads can really go to pot in a hurry. I will not do it again.