CRIMPING

[GuitarmanNick]

I crimp every pistol load and anything for semi-auto fed rifles. Using Lee dies, a light taper crimp can be done on any bullet. Not sure it is needed, but I know they are all going to be the same length as they are chambered.

 

[INTJ]

I'm intrigued that some have reported an improvement in accuracy by crimping. I don't debate this but rather find it intriguing.

If there is an improvement in accuracy it's likely due to more consistent ignition. When we consider most non-match chambers, and handloads, there are generous tolerances and significant inconsistencies in brass thickness, brass hardness, seating depth, shoulder length, etc. Those tolerances and inconsistencies can lead to a lot of variation as to when and how the bullet leaves the case upon firing. A Lee Crimp die can help mitigate that.

When we load match ammo, especially for high accuracy applications, we make everything as perfect as possible. Primer pockets are uniform, primers are weighed and seated consistently, brass is sorted, neck diameter is consistent. When sizing, every case is measured and sized again if needed to make sure shoulders are pushed back the same, every bullet is measured and sorted, each bullet is measured after seating and sorted by seating pressure and seating depth, etc. Whenever a measurement falls out of our tolerance and can't be fixed, that round is relegated to duty as a fouler or slighter. Crimping this ammo would likely hurt accuracy by deforming the bullet.

Contrast that with typical hunting handloads. Cases will vary more in weight, primer seating will vary significantly as well as the amount of primer compound, necks can vary in thickness by .002" or more, shoulder lengths can vary easily by .002" (if they are even measured after sizing), and there is a lot of variation in seating depth as bullets typically aren't sorted nor checked after seating other than spot checks. A Lee crimp seems to help this kind of ammo. Not to mention if it is a magazine rifle that is heavier recoiling.

At least that is the theory...................

 

[antelopedundee]

If there is an improvement in accuracy it's likely due to more consistent ignition. When we consider most non-match chambers, and handloads, there are generous tolerances and significant inconsistencies in brass thickness, brass hardness, seating depth, shoulder length, etc. Those tolerances and inconsistencies can lead to a lot of variation as to when and how the bullet leaves the case upon firing. A Lee Crimp die can help mitigate that.

When we load match ammo, especially for high accuracy applications, we make everything as perfect as possible. Primer pockets are uniform, primers are weighed and seated consistently, brass is sorted, neck diameter is consistent. When sizing, every case is measured and sized again if needed to make sure shoulders are pushed back the same, every bullet is measured and sorted, each bullet is measured after seating and sorted by seating pressure and seating depth, etc. Whenever a measurement falls out of our tolerance and can't be fixed, that round is relegated to duty as a fouler or slighter. Crimping this ammo would likely hurt accuracy by deforming the bullet.

Contrast that with typical hunting handloads. Cases will vary more in weight, primer seating will vary significantly as well as the amount of primer compound, necks can vary in thickness by .002" or more, shoulder lengths can vary easily by .002" (if they are even measured after sizing), and there is a lot of variation in seating depth as bullets typically aren't sorted nor checked after seating other than spot checks. A Lee crimp seems to help this kind of ammo. Not to mention if it is a magazine rifle that is heavier recoiling.

At least that is the theory...................

Does it tend to cause ANY bulging of the neck? If you mike it is the neck diameter uniform all the way down?

 

[K22]

If there is an improvement in accuracy it's likely due to more consistent ignition. When we consider most non-match chambers, and handloads, there are generous tolerances and significant inconsistencies in brass thickness, brass hardness, seating depth, shoulder length, etc. Those tolerances and inconsistencies can lead to a lot of variation as to when and how the bullet leaves the case upon firing. A Lee Crimp die can help mitigate that.

When we load match ammo, especially for high accuracy applications, we make everything as perfect as possible. Primer pockets are uniform, primers are weighed and seated consistently, brass is sorted, neck diameter is consistent. When sizing, every case is measured and sized again if needed to make sure shoulders are pushed back the same, every bullet is measured and sorted, each bullet is measured after seating and sorted by seating pressure and seating depth, etc. Whenever a measurement falls out of our tolerance and can't be fixed, that round is relegated to duty as a fouler or slighter. Crimping this ammo would likely hurt accuracy by deforming the bullet.

Contrast that with typical hunting handloads. Cases will vary more in weight, primer seating will vary significantly as well as the amount of primer compound, necks can vary in thickness by .002" or more, shoulder lengths can vary easily by .002" (if they are even measured after sizing), and there is a lot of variation in seating depth as bullets typically aren't sorted nor checked after seating other than spot checks. A Lee crimp seems to help this kind of ammo. Not to mention if it is a magazine rifle that is heavier recoiling.

At least that is the theory...................

Thanks for the explanation - very interesting. Also appreciate the painstaking steps match shooters take to assure uniformity. That probably part of the reason they hit that tiny bull in a bench rest target on a regular basis which I've seen some of them do at the range.

Makes me happy I'm just satisfied varmint level accuracy (in the 1/2 moa range) but I agree, even with carefully crafted precision reloads for precision varmint hunting there is variation, probably a lot. Even though I deburr flash holes, uniform primer pockets, and full size case with a .001 to .002" measured shoulder bump, the variation in bullet ogives / weight even in quality hunting bullets like the Nosler BT's and differences in weight / dimensions of standard Rem / Win / Hornady cases is probably a lot.

 

[searcher]

On rifles, I do a light crimp on my .375 H& H Magnum hunting rifle and on .223 ammo used for plinking and/or home defense with bullets which have a cannelure. On any ammo requiring utmost accuracy, I utilize bushing dies on brass with turned necks to give me the needed uniform neck tension without the ill-effects of a crimp on the bullet and without overworking the necks. I have ALWAYS been able to get better accuracy not using a crimp. Regarding pistol ammo - I do crimp with good accuracy results.

 

[INTJ]

Does it tend to cause ANY bulging of the neck? If you mike it is the neck diameter uniform all the way down?

I have not noticed any bulging. I also haven't miced the neck diameter.

 

[MikeRu]

When I compare accuracy/group size with vs without a slight crimp (really a squeeze of just 0.5/1000 or so), I wind up crimping the next time I load.

 

[MGYSGT]

I never crimp my .223 ammo.

 

[Coonman300]

. Most of these rifles have very long throats and I believe using the crimp does about what loading bullets closer to the lands does for other rifles. It retards bullet movement out of the case for that split second until pressure and burn gets going good much like the bullet hitting the lands and is slowed a split second and accomplishes the same thing.

Interesting thought. I have a Ruger 22-250 that shoots Sierra and Hornady Bullets very well 25 thou off the lands. I got some Berger Bullets and I have to jump them a lot further so they will fit in the magazine and they don’t shoot well at all. This may be worth a try to improve groups with that bullet. Thanks!

 

[Coyotefurharvester]

No crimping for bolts or AR. I do size(inside diameter) the necks 0.003-.004 under bullet diameter for AR regardless of bullet type.

 

[danny]

How many here crimp their rifle handloads with something like a Lee FCD aka Factory Crimp Die? If so do you do all loads, just hunting ammo, other?

I don't know anyone that crimps any rifle ammunition, and that includes ammunition to be used in a semiauto.

Danny

 

[PhilC]

I don't crimp any rifle ammo unless it's a tube fed lever action.