Bottleneck Cartridges....To Crimp or Not to Crimp

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Bottleneck Cartridges....To Crimp or Not to Crimp

Post by THE LONE STRANGER » 24 Apr 2019, 1:15 pm

Greetings All,
Questioning the process of crimping or not crimping a bottleneck cartridge.

To be used in a non tubular magazine (internal/detachable box magazine etc).
To be fired from rifles (min. 16" barrel).

Have read where some will lubricate the inside neck with graphite to allow an easy release of projectile.
Then one will be advised to crimp to ensure adequate ignition of powder before projectile leaves the case.
Lee Precision also advises this hence their Factory Crimp Dies.
I have a couple of revolvers that are chambered for bottleneck rifle cases with barrels of 8 & 10 inches in length. I have found that I must crimp these cases otherwise I have a lot of unburnt powder left and poor accuracy etc.

What are the pros and cons of the question I am asking in relation to rifle use?
All feedback appreciated.
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Re: Bottleneck Cartridges....To Crimp or Not to Crimp

Post by No1_49er » 24 Apr 2019, 3:56 pm

I think you've answered your own question.
Crimping does assist with better/complete powder burn because of an increased pressure prior to release of the projectile. 30-30WCF would be a classic case (sorry about the pun) for this.
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Re: Bottleneck Cartridges....To Crimp or Not to Crimp

Post by marksman » 24 Apr 2019, 4:47 pm

IMHO if you are jumping the bullet a slight crimp does have benefit on any round no matter the mag config because you will get a more even start pressure
but as I said a slight crimp so you can just see it
military rounds were glued for a similar effect

about the graphite for a smoother release I believe a smooth release is very important for consistency
if I pull one of my reloads the bullet has no marks eg.. scratching and has enough neck tension so you cannot pull the bullet with your fingers
I polish the inside of the neck for an even seating pressure that should give an even consistent release
I dont use graphite for bullet release but I do for sizing so there may be some inside the neck when seating
this is what I think and the way I do it anyway :drinks:
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Re: Bottleneck Cartridges....To Crimp or Not to Crimp

Post by grandadbushy » 24 Apr 2019, 5:37 pm

I have found with my 7mm mag that a slight crimp gives better accuracy not much but a bit and a better burn on the powder my 22-250 I don't crimp I've found the brass lasts longer and there is no benefit to accuracy or powder burn by crimping :thumbsup:
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Re: Bottleneck Cartridges....To Crimp or Not to Crimp

Post by SCJ429 » 24 Apr 2019, 6:21 pm

I would think that a crimp is detrimental to accuracy and would not assist a complete powder burn. You may want to crimp for other reasons, personally I would not.
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Re: Bottleneck Cartridges....To Crimp or Not to Crimp

Post by bladeracer » 24 Apr 2019, 7:11 pm

Generally not but it comes down to bullet weight, neck tension, feed system, and recoil. Load the mag, shoot some rounds, then inspect the ones in the mag. If the bullets have moved then crimp them.

It can sometimes be beneficial to accuracy so may be worth experimenting with to see if your firearm prefers a particular bullet to be crimped.
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Re: Bottleneck Cartridges....To Crimp or Not to Crimp

Post by Stix » 25 Apr 2019, 9:53 am

marksman wrote:IMHO if you are jumping the bullet a slight crimp does have benefit on any round no matter the mag config because you will get a more even start pressure
but as I said a slight crimp so you can just see it
military rounds were glued for a similar effect

about the graphite for a smoother release I believe a smooth release is very important for consistency
if I pull one of my reloads the bullet has no marks eg.. scratching and has enough neck tension so you cannot pull the bullet with your fingers
I polish the inside of the neck for an even seating pressure that should give an even consistent release
I dont use graphite for bullet release but I do for sizing so there may be some inside the neck when seating
this is what I think and the way I do it anyway :drinks:


What do you polish the inside of the neck with & how far do you go with it Marksman...or better asked, what is the process you use...?
I get some pretty bad (noticeable) marks in the direction of expander ball/bullet release direction that id imagine are pretty deep & take a lot of polishing to remove...i do brush out necks before sizing but dont tumble them...

And also, how often do you do it...? (every loading/firing...every anneal...? :unknown: )

SCJ429 wrote:I would think that a crimp is detrimental to accuracy and would not assist a complete powder burn. You may want to crimp for other reasons, personally I would not.

What are the reasons you think it would be detrimental to accauracy SCJ...?
And are the reasons based on experience...?

Cheers guys
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Re: Bottleneck Cartridges....To Crimp or Not to Crimp

Post by in2anity » 25 Apr 2019, 10:17 am

I’ll play devil’s advocate - imo crimp doesn’t do much for improving accuracy - it’s not a science, thus can’t be treated as such. On the other hand neck tension from sizing is inherently more precise.
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Re: Bottleneck Cartridges....To Crimp or Not to Crimp

Post by No1_49er » 25 Apr 2019, 10:25 am

SCJ429 wrote:I would think that a crimp is detrimental to accuracy and would not assist a complete powder burn. You may want to crimp for other reasons, personally I would not.

There are a lot of people who reload the 310 Cadet with 2205. An un-crimped load will generally leave a trail of unburned powder in the barrel.
A crimped load will usually show no evidence of unburned powder, and an observed improvement in accuracy.
It is surmised that the crimp delays the projectile release until a greater pressure is generated, which also improves powder combustion.
Those observations seem to be fairly consistent among my colleagues.
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Re: Bottleneck Cartridges....To Crimp or Not to Crimp

Post by SCJ429 » 25 Apr 2019, 11:06 am

I polish the inside of the neck with Autosol on a felt tip attached to my Dremmel. Then use some graphite powder when seating the pill

Consistant neck tension is the most critical aspect of loading. It would be difficult to do this with a crimp. The OP would be better off with a Lee Collet die and try low neck tension than using a crimping die.

Not sure about 2205 and a Cadet, if you wanted more pressure could you jam the pill into the lands? Do you get the same speeds out of loads where you burn all of the powder? Could you use a faster powder and a magnum primer?
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Re: Bottleneck Cartridges....To Crimp or Not to Crimp

Post by in2anity » 25 Apr 2019, 11:14 am

SCJ429 wrote:The OP would be better off with a Lee Collet die and try low neck tension than using a crimping die.

Yes this - particularly with respect to bottlenecks.
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Re: Bottleneck Cartridges....To Crimp or Not to Crimp

Post by in2anity » 25 Apr 2019, 11:24 am

No1_49er wrote:
SCJ429 wrote:I would think that a crimp is detrimental to accuracy and would not assist a complete powder burn. You may want to crimp for other reasons, personally I would not.

There are a lot of people who reload the 310 Cadet with 2205. An un-crimped load will generally leave a trail of unburned powder in the barrel.
A crimped load will usually show no evidence of unburned powder, and an observed improvement in accuracy.
It is surmised that the crimp delays the projectile release until a greater pressure is generated, which also improves powder combustion.
Those observations seem to be fairly consistent among my colleagues.


IMO

I mean I'm sure there is truth to this 49r, but I'm assuming you guys are slinging lead pills through your cadets? If so, I take it you flare the mouth before seating to prevent shaving? And arbitrarily flaring the mouth can't be good for neck tension, and I think crimping back the arbitrarily flared mouth is indeed probably a step in the right direction. Unchecked lead pills over a fast powder is a whole different ball game...

But say (hypothetically) you replaced your lead pills with jacketed ones in the cadet; my recommendation would be to use a collet die with an (under)sized mandrel to get some good tension (and bypass the flare ofc), then use magnum primers to help lower that std dev - if you followed those steps, I bet a crimp would do absolutely zero in terms of accuracy....
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Re: Bottleneck Cartridges....To Crimp or Not to Crimp

Post by marksman » 27 Apr 2019, 8:14 pm

Stix wrote:
marksman wrote:IMHO if you are jumping the bullet a slight crimp does have benefit on any round no matter the mag config because you will get a more even start pressure
but as I said a slight crimp so you can just see it
military rounds were glued for a similar effect

about the graphite for a smoother release I believe a smooth release is very important for consistency
if I pull one of my reloads the bullet has no marks eg.. scratching and has enough neck tension so you cannot pull the bullet with your fingers
I polish the inside of the neck for an even seating pressure that should give an even consistent release
I dont use graphite for bullet release but I do for sizing so there may be some inside the neck when seating
this is what I think and the way I do it anyway :drinks:


What do you polish the inside of the neck with & how far do you go with it Marksman...or better asked, what is the process you use...?
I get some pretty bad (noticeable) marks in the direction of expander ball/bullet release direction that id imagine are pretty deep & take a lot of polishing to remove...i do brush out necks before sizing but dont tumble them...

And also, how often do you do it...? (every loading/firing...every anneal...? :unknown: )

SCJ429 wrote:I would think that a crimp is detrimental to accuracy and would not assist a complete powder burn. You may want to crimp for other reasons, personally I would not.

What are the reasons you think it would be detrimental to accauracy SCJ...?
And are the reasons based on experience...?

Cheers guys


sorry to have not replied sooner Stix

I use an old cleaning brush, nylon or bronze wrapped up with steel wool and saturated with autosol
put this into a drill and spin in the neck for around 3-5 seconds

this works for me but is only done when first prepping the brass :drinks:
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