Crimping centrefire bullets?

[CROWMAN]

This query does not refer to tube underlever rifles but to centrefire rifles.

Do you crimp as standard when reloading? if yes? have you found increased accuracy?

[Thegreg]

Nope. Never had the need to. Some people swear by it for improving accuracy/consistency but in truth the main practical purpose for crimping rifle ammo is [in a magazine], it stops the bullets receding into the cases under recoil.

Another downside is it drastically reduces the life of your brass.

Depends what you’re doing I suppose.

Cheers
Greg

[CROWMAN]

[QUOTE=Thegreg;8218532]Nope. Never had the need to. Some people swear by it for improving accuracy/consistency but in truth the main practical purpose for crimping rifle ammo is [in a magazine], it stops the bullets receding into the cases under recoil.

Another downside is it drastically reduces the life of your brass.

Depends what you’re doing I suppose.

Cheers
Greg[/QUOTE

I've asked as a shooter in The U.S. who seems to be vastly experienced swears by it in relation to a 6.5 Grendel which we message about.
However another vastly experienced re-loader at my club never does, saying better to concentrate on the same weight, measurements etc.
I'm tending to go with the latter.

[aris]

Consistent neck tension is certainly a thing. Never heard of any competitive shooter crimping. Annealing, neck turning, expander mandrels - yes.

[223AI]

[QUOTE=CROWMAN;8218587]

Nope. Never had the need to. Some people swear by it for improving accuracy/consistency but in truth the main practical purpose for crimping rifle ammo is [in a magazine], it stops the bullets receding into the cases under recoil.

Another downside is it drastically reduces the life of your brass.

Depends what you’re doing I suppose.

Cheers
Greg[/QUOTE

I've asked as a shooter in The U.S. who seems to be vastly experienced swears by it in relation to a 6.5 Grendel which we message about.
However another vastly experienced re-loader at my club never does, saying better to concentrate on the same weight, measurements etc.
I'm tending to go with the latter.

Andy Muir by any chance?

I crimp some loads, don’t crimp others, not so sure about it drastically reducing case life as the case mouth gets trimmed anyway.

If you concentrate on everything else anyway, as you should, then experiment with crimping and see what results it gives you!

[DedIdick]

I do but 3 out of 4 f my centre-fire rifles are straight pulls.

[CROWMAN]

[QUOTE=223AI;8219945][QUOTE=CROWMAN;8218587]

Andy Muir by any chance?

I crimp some loads, don’t crimp others, not so sure about it drastically reducing case life as the case mouth gets trimmed anyway.

If you concentrate on everything else anyway, as you should, then experiment with crimping and see what results it gives you!

You've got him in one!
He has been very informative especially re Grendels.

Another very experienced member of my shooting club never has and doesn't see any point in crimping, so as you say get your reloads as good as you can without crimping and the try crimping to see if any difference.

[223AI]

Yeah, he’s very knowledgable and a big proponent of crimping generally. As I say, I don’t crimp a whole lot other than ammunition for my tube fed .357, will do the same for the 45-70 when it arrives. A lot of people swear by it in .22 hornet including Muir and he knows a lot about Grendel. I also crimp my latest load for .223 but that’s because I got a load of (really) cheap .223 Winchester bullets which I am running for a cheap <150 yard vermin load as it helps the neck tension appreciably.

[CROWMAN]

Yeah, he’s very knowledgable and a big proponent of crimping generally. As I say, I don’t crimp a whole lot other than ammunition for my tube fed .357, will do the same for the 45-70 when it arrives. A lot of people swear by it in .22 hornet including Muir and he knows a lot about Grendel. I also crimp my latest load for .223 but that’s because I got a load of (really) cheap .223 Winchester bullets which I am running for a cheap <150 yard vermin load as it helps the neck tension appreciably.

An interesting comment from a US forum site:-

'Increasing crimp increases the start pressure of the round by making the bullet take a little longer to free up and start moving. However, this all happens when the pressure is low on the rising portion of the curve. It does result in a little bit higher peak pressure and a little bit more velocity results, but it's not huge. Board member Hummer70, who used to work at Aberdeen Proving Grounds said he'd tested bullet pull on old 7.62 ammo which had been 60 lb when new, but by oxidation cold welding had got as high as 600 lb, way more than a crimp can introduce, but that still fired fine. So the pressures and velocity changes are not very significant. What is significant is the velocity consistency can improve and that indicates improved ignition consistency. With some powders, particularly the slower spherical powders, this can improve performance. For stick rifle powders it does not seem to be necessary if you clean and size your cases consistently and prime correctly.

The way to tell if crimping is helping ignition consistency for you is with a chronograph. See if the velocity SD and ES decrease as a percentage of the mean velocity. But even if they do, also check group size on paper. Getting that added consistency of velocity is no good if you are distorting a bullet to the point it no longer flies straight.'

I believe that this what Andy Muir is referring to?

[Thegreg]

[QUOTE=223AI;8219945]

Andy Muir by any chance?

I crimp some loads, don’t crimp others, not so sure about it drastically reducing case life as the case mouth gets trimmed anyway.

If you concentrate on everything else anyway, as you should, then experiment with crimping and see what results it gives you!

I’ll explain my comment on reducing case life. I suppose this depends on the type of crimp, but the type you often see on factory ammunition, where there are 4 deep compressions around the case mouth, this is the type I wouldn’t even bother trying to reload.

It’s probably 0.5mm-0.75mm or so down the neck, so I’ve never managed to trim it all away, and they can be so deep that they cause fractures in the brass if you press a new bullet in.

It’s possibly what Lee recreate with their “Factory Crimp Die”, and I know plenty of people wax lyrical about those.

I 100% agree that consistent neck tension is important for accuracy, but it can be achieved without relying on crimping.

Cheers
Greg

[223AI]

[QUOTE=Thegreg;8220149]

I’ll explain my comment on reducing case life. I suppose this depends on the type of crimp, but the type you often see on factory ammunition, where there are 4 deep compressions around the case mouth, this is the type I wouldn’t even bother trying to reload.

It’s probably 0.5mm-0.75mm or so down the neck, so I’ve never managed to trim it all away, and they can be so deep that they cause fractures in the brass if you press a new bullet in.

It’s possibly what Lee recreate with their “Factory Crimp Die”, and I know plenty of people wax lyrical about those.

I 100% agree that consistent neck tension is important for accuracy, but it can be achieved without relying on crimping.

Cheers
Greg

Ah so you’ve never actually crimped a bullet?

Crimp type depends on how you crimp, the most common for bottle neck rifle cartridges is with the Lee FCD, this crimps a much smaller portion of the case mouth than the heavy factory crimps you mention above. So is generally removed when you next trim the brass.

If the rounds I do crimp, I’ve never noticed a detrimental effect on case life .

[223AI]

An interesting comment from a US forum site:-

'Increasing crimp increases the start pressure of the round by making the bullet take a little longer to free up and start moving. However, this all happens when the pressure is low on the rising portion of the curve. It does result in a little bit higher peak pressure and a little bit more velocity results, but it's not huge. Board member Hummer70, who used to work at Aberdeen Proving Grounds said he'd tested bullet pull on old 7.62 ammo which had been 60 lb when new, but by oxidation cold welding had got as high as 600 lb, way more than a crimp can introduce, but that still fired fine. So the pressures and velocity changes are not very significant. What is significant is the velocity consistency can improve and that indicates improved ignition consistency. With some powders, particularly the slower spherical powders, this can improve performance. For stick rifle powders it does not seem to be necessary if you clean and size your cases consistently and prime correctly.

The way to tell if crimping is helping ignition consistency for you is with a chronograph. See if the velocity SD and ES decrease as a percentage of the mean velocity. But even if they do, also check group size on paper. Getting that added consistency of velocity is no good if you are distorting a bullet to the point it no longer flies straight.'

I believe that this what Andy Muir is referring to?

Quite possibly, I wouldn’t be too worried about chronograph, find a load that works, load a batch and don’t crimp and a batch with crimp, shoot at a target and see if either groups better. The size of the group needed is a while other conversation!