To crimp or not to crimp?

[hughd]

As it relates to TC's, what are the pros and cons of crimp vs. no crimp? Also is the shape of the brass a factor? ( straight wall or not) 

[shot1]

It depends on which caliber you are talking about. With bottle neck cases I don't crimp. But for straight wall pistol calibers like the 357 mag, 45 Colt, 44 mag etc. I always crimp because the powders that I use, mostly H-110/296, needs good bullet pull for the pressure to build good and make them shoot good.

[P.A. Myers]

Straight wall cases without a consistent firm crimp wil cause variations in velocity and accuracy will suffer. This is true for single-shots too. How to get that consistant crimp is another subject.

[hughd]

What are the advantages of no crimp on bottle neck cartridges?

[skarke]

Many load single shots to just touch the lands.  This allows for consistent pressure patterns like crimping, but might be even more precise.  I don't crimp for the contender or encore, but all loads are either just off, or just on the lands, depending on what I see at the range.

[shot1]

In a single shot where you can load the bullet close to the lands there is really no advantage in using a crimp on a bottle neck cartridge. The main usage of a crimp on a bottle neck round is to keep the bullet from pulling forward out of the case while in the magazine under recoil impulse or being driven back into the case through the function of a semi-auto. I have used the Lee Factory Crimp Die on round that are to be fired in some of the old military bolt rifles that I shoot. Most have really long throats and you can't load the bullet close to the lands and still have the round short enough to work through the magazine. The Lee Factory Crimp DOES make these loads more accurate most of the time. One note from the school of been there and done that and have the T-shirt. For hunting ammo DO NOT LOAD THE BULLET INTO OR REALLY CLOSE TO THE LANDS. If you do not fire the round and go to unload the weapon it can stick the bullet in the bore and dump all the powder out into your action and it takes a cleaning rod to poke the bullet loose. Out in the woods you usually don't have a cleaning rod. This will ruin a days hunt. I like to load my bullets no closer than 10 thousands to the lands for hunting ammo. Which happens to shoot really well with most hunting bullets in most calibers I have found over the years.

[buckeye509]

What tool or method do you use to measure the distance from bullet to lands? I'd like to reload with more precision and would appreciate any advice. I'll be reloading .308 and .223 in bottleneck cartridges.

[flipajig]

What I do is take a case and set up a dummy rd. with no powder or primer seat the bullet with the press
and insert it into the barrel and close the gun. if it wont close then seat the bullet a little bit more. continue with this process
until it will close easly. when the bullet is touching the lands your there. ajust your seating die to where its touching the bullet
and then seat it 010,000 more away from the lands. lock your seatinig die in place check to see if your gun will close with out any problems and your there. im loading for my 7-30waters 30-30 and 223 with this method and its working great.

[P.A. Myers]

Be sure to full length resize the dummy case so the only resistance are the lands. Some of the loading manuals will list a total overall length that you can use if it lists a bullet you are using. While I totally agree that you dont want to jam your bullets into the lands, a bit of clearance is not a problem. Precise and close bullet to land clearance is important to paper shooters. Revolver bullets travel a long way before the rifleing and can be quite accurate.

[shot1]

Take a case and full length size it. Take a cutting tool and cut a line from the case mouth down to the start of the shoulder on one side of the neck. Clean up the burrs. Before every use pinch the case neck a little tighter with your fingers. You will be able to see it get tighter by looking at how close the distance is between the sides where the cut line is. Place the bullet that you want to use into the case mouth by hand enough for it to hold on it's own. Then for a single shot like the contender etc. place the case into the chamber and with your thumb press it into the chamber until the extractor engages the rim. Now close the action and open it. The bullet will be pushed back into the case easily when it comes in contact with the lands. Ease the round out of the chamber and measure your over all length. It is better if you have a comparator set up on your caliper so you can measure from the O-give of the bullet because not all the bullets in the box will have the same nose length exactly. This will be your to the lands measurement. Now you can seat the bullet deeper and know how far you are away from the lands by comparing the difference in the over all lengths. You can then pull this bullet out with your fingers and use it to load up a round.  

[Grumulkin]

In loading for probably 3 dozen rounds the ONLY time I ever found an accuracy advantage to crimping was with low pressure 45 Colt loads shot in a revolver.  Sometimes Barnes bullets tend to be loose in the cases so I crimp those.  I also crimp for heavy recoiling rounds to be shot in guns with a cylinder or magazine.  My no crimping policy applies to all powders and all cases whether or not straight walled.

A lot of guns do shoot better with bullets seated close to the lands but I think it matters less if the chamber, throat and barrel are cut with good alignment.  I shot several cartridges with accuracy many would drool over where because of magazine considerations the bullet is far off the lands.

[buckeye509]

Interesting stuff. Thanks.