I was wondering how much is to much to crimp a casing. The reload books say to work in small incriments untill you get the desired crimp. what is a desired crimp and how do you tell.

Crimp is perfect when you have no more than you need to keep the bullet from moving in the case. In all bolt action rifles I use no crimp at all. In magnum handguns (revolers and single shots) I use a moderate to heavy crimp due to the powder that I use. In semiautos I use a moderate crimp because the action works so fast it can jam the bullets back into the case. In my 30-30 (single shot) I use no crimp. It depends on powder, weapon, and magazine type.

PaulS

Swamp-man,

I agree with Paul, it depends on what you're shootin' in !

When reloading for any of my Contender barrels, (or any single-shot weapon for that matter) there is no need to be concered with how tight it is due to feeding through a magazine or how it will be effected by recoil. When loading for a revolver or semi-auto magazine, you do need to consider those. I make sure my .45 ACP crimps are tight for both these reasons. The Contender loads - they're just tight enough to prevent the bullet from spinning or moving back and forth. I regularly crimp my 7mm TCU Contender loads below the cannelure on a jacketed SP bullet and it works fine without even putting an indentation in the bullet. Same with some .32 H&R mag loads where the bullets have cannelures. The key is properly sizing the neck to hold the bullet well if you do not need to crimp tightly due to shock, vibration and feeding issues.

Took me a bit to figure out "how much" and how it affected accuracy, but once I got there, it worked !

Happy trails -

If you give more details of what you're loading it would help too.

For bullets with a cannelure I like to have the case end just touching the bottom of the cannelure grove.

With the Lee Factory crimp die it's a little harder, but usually a just barely visible crimp is fine. You can put calipers on the case end wise and see if the end dives down a little or is parallel all the way to the end.

I am loading for a 240 wby using 70 grain matchkings,using hornady dies.

I was under the impression that you need some sort of crimp to build up the pressure in the case to reach the velocities this gun is capable of.Maybe I have received some bad info in the past on this subject.

I would just ask what's more important to you, accuracy or velocity? You're using a Match King, so I presumed you weren't hunting, so velocity shouldn't matter much. Unless, of course, you're one of those people who hunts game animals with Match Kings.

[ 11-01-2002, 02:45: Message edited by: Russell E. Taylor ]

Crimping is one of those semi-controversial subjects as it pertains to accuracy. There have been more than a few experiments with products like Lee's Factory Crimp dies and how they can improve accuracy. Saeed did one and posted it here as I recall.
I don't go to Bench Rest matches but I think you'd be hard pressed to find a BRer who crimps his ammo...I may be wrong.
Lee's argument for their product is that a factory crimp will compensate for poorly sized or unevenly trimmed cartidge cases. I believe that you can achieve the same result if you use proper dies, or even better, one of the premium resizing dies like the Forster. and lube properly and pay attention to trim length. Saeed's limited experiment proves me wrong.
I use the Lee Factory Crimp die on hard recoiling cartridges in my bolt actions like my .375 H&H and my 416 Rigby. All my tube magazine cartridges get it...45-70, 348, 30-30. And all my handgun cartridges get it...revolver and semi-auto.
I tend not to use it on things like my -06, or 7mm-08, or .222/.223.
That's just my druthers...

I don't crimp rifle ammo at all, unless it's for a tubular magazine. But, a heavy crimp is necessary in revolver ammo that uses slow powders like H110 or WW 296. If loading revolver ammo with jacketed bullets, crimp as much as the bullet groove will permit without swelling or deforming the case. With lead bullets, you can crimp as much as the crimping die will permit! You CAN definitely SEE a proper crimp on revolver ammo. Use a TAPER crimp die for auto pistol ammo, if the reloaded cartridge will not drop FREELY into the chamber. If it drops in with no problem, don't crimp auto pistol ammo. It needs as much case mouth as possible to headspace it correctly!

Besides crimp, bullet tension has alot to do with uniform velocity. A good tight bullet fit is what allows us not to crimp. Seyfried had an article years ago that talked about this. It was intresting that if you don't have bullet fit a crimp would never hold a bullet in with out the bullet fit. He even measures his expander to make sure that the are under bullet size. I don't crimp single shots or bolt rifles. I crimp all revolver cartridges heavy. It doesn't matter what charge. Why? Beacuse I am lazy. I set the crimp heavy for max loads and leave it. I have been impressed with the crimping die that Hornady had with the 480 dies and Dillon's .

This give me an idea to chrono some loads with and without crimp and check groups etc. Something to do after hunting season.

Hcliff

With time for just a short trip to the range yesterday, I decided to do a very limited test of the crimping issue.

I've worked up a reduced load for my .338 Win. Mag. -- 200-gr. Hornady flat point, 38.0 gr. XMP-5744. 2100 fps and about 1" groups. This is equivalent to the old .33 Win. and should do fine for deer at the close ranges where I might (if I live a clean, upstanding life) see them in Maine this fall. I thought maybe with the reduced load, a slight crimp would help ensure complete and consistent ignition.

I took 6 rds. as-is and crimped 6 with the Lee Factory Crimp die, 1/2 turn down from touching the shellholder. I fired one fouling shot then 3-shot groups, alternating between the two loads, and always letting the barrel cool.

Results:

Uncrimped #1--MV 2094, ES 38.32, SD 19.41, 1.03"
Uncrimped #2--MV 2082, ES 21.02, SD 10.58, 0.94"

Crimped #1--MV 2071, ES 20.68, SD 11.35, 2.02"
Crimped #2--MV 2078, ES 4.63, SD 2.44, 1.59"

So this suggests that with this particular load, the crimp may improve consistency a tad (at the expense of velocity), but may harm accuracy. I would have to shoot more groups to have a truly valid test, but based on these results I'm not going to bother for this load. I will continue to try it for future loads, especially in hard-kicking rifles and for reduced loads.

John

[ 11-04-2002, 17:17: Message edited by: John Frazer ]

This also shows that the load with the least velocity variation is not necessarily the most accurate load.......

Thank you gentlemen fo all the info.It appears that I have some experimenting to do.

P.S. yes I do use matchkings for hunting game animals.Have been doing so for years with varios calibers and have never been disapointed.But I do not want to get one of those heated discussions going on about the matchking.

I believe crimping can help accuracy, it did with my .223 Savage. From what I have read and a little experimenting is that the smaller diameter bullets with higher velocities will benefit more from a crimp especially when trying to reach the lands, the amount of bullet seated in the case is usually minimal so light crimp will help it achieve even pressure when entering the throat. The deeper you can seat a bullet the less a crimp is needed. IMHO