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View Full Version : Taper or roll crimp semi auto rifle ammo?



LittleLebowski
01-20-2017, 10:21 PM
I'm trying to make up my mind on .223 AR ammo, I use a Lee FCD on my .300blk stuff.

5pins
01-21-2017, 12:58 AM
Makes no difference with rifle ammo since it head spaces off of the shoulder and not the mouth. I don’t even crimp my .223 ammo.

SecondsCount
01-21-2017, 01:45 AM
I taper crimp my 223 rounds with a Dillon die.

The lines are blurred for me as to what an FCD does that a taper crimp die doesn't do. The only difference that I can see is that some taper and definitely all roll crimp dies can be affected by case OAL. You definitely have to make sure that the cases are very close in length when using a roll crimp die or it will buckle the case.

SecondsCount
01-21-2017, 01:48 AM
Makes no difference with rifle ammo since it head spaces off of the shoulder and not the mouth. I don’t even crimp my .223 ammo.

I don't crimp ammo that will be soley used in my bolt guns but I do put a slight crimp on anything going through a semi auto to prevent setback.

Win94ae
01-21-2017, 09:08 AM
I roll crimp with my AK. I haven't found any issues in about 4 years.

GuanoLoco
01-21-2017, 11:26 AM
I ever so slightly slightly kiss .223 with a Dillon Taper crimp die. Process is size/trim with an RT1200 and expand case mouth with a M-die for seating flat base bullets in a case neck that is very tight post-RT1200.

LittleLebowski
01-21-2017, 11:33 AM
I ever so slightly slightly kiss .223 with a Dillon Taper crimp die. Process is size/trim with an RT1200 and expand case mouth with a M-die for seating flat base bullets in a case neck that is very tight post-RT1200.

Jeez, I wish you lived closer so that I could pick your brain.

GuanoLoco
01-21-2017, 11:48 AM
Jeez, I wish you lived closer so that I could pick your brain.

I've reconfigured the Mark 7/1050 for 40S&W (friend bought the conversion hit - about $600 as he is changing divisions to USPSA Limited/Major).

After that it will be a cycle of 223 brass processing (another friend, a 3-gun pro, is bringing over his RT1500), then 223 loading, then back to 9mm brass processing and loading.

You learn with each cycle.

5pins
01-21-2017, 01:33 PM
I should probably revise my answer. If I’m loading cheap 55gr blasting ammo, I will use a slight crimp. I use the Lee factory crimp die for that. Otherwise I don’t crimp even for an auto. Good case neck tension is very important however.

walker2713
01-21-2017, 02:32 PM
I don't crimp ammo that will be soley used in my bolt guns but I do put a slight crimp on anything going through a semi auto to prevent setback.

^^^^^^^^

Ditto This

GuanoLoco
01-21-2017, 09:09 PM
Unless you are roll crimping in to a cannelure I seriously doubt that crimping is doing anything to reduce the likelyhood of bullet setback. 5pins has it right - it's all about neck tension. The Dillon size/TRIM (not crimp) die makes this a non-issue as the neck tension is crazy high.

Here's a test. Measure cartridge OAL. Using both thumbs, press bullet against a piece of wood as hard as you can. Re-measure OAL. If it hasn't changed you should be good.

SecondsCount
01-21-2017, 09:29 PM
Unless you are roll crimping in to a cannelure I seriously doubt that crimping is doing anything to reduce the likelyhood of bullet setback. 5pins has it right - it's all about neck tension. The Dillon size/crimp die makes this a non-issue as the neck tension is crazy high.

Here's a test. Measure cartridge OAL. Using both thumbs, press bullet against a piece of wood as hard as you can. Re-measure OAL. If it hasn't changed you should be good.

I agree that neck tension is key but years ago I started putting a slight crimp on my AR loads that were loaded with a 55 V-max. It ended the setback issues I was having.

GuanoLoco
01-21-2017, 09:36 PM
What crimp die?

SecondsCount
01-21-2017, 11:26 PM
What crimp die?

Dillon.

GuanoLoco
01-22-2017, 10:28 AM
I am guessing this works because the jacketing on a small diameter 223 bullet is relatively hard and/or the end of the case mouth is digging in to the bullet jacket. Given the relative springiness of a brass case I find it hard to believe that crimping is giving much compression benefit unless the case mouth is really loose to begin with.

What size die, trim process and expander bit, if any, are you using?

LittleLebowski
01-22-2017, 10:28 AM
I had malfunctions with a suppressed 5.55 SBR (like a fool, I forgot to bring different weighted buffers to fix this), and experienced bullet setback all of the way into the case with powder spilling, hence the OP.

Clusterfrack
01-22-2017, 11:43 AM
I'm trying to make up my mind on .223 AR ammo, I use a Lee FCD on my .300blk stuff.

I don't crimp most of my rifle rounds, but the FCD does a good job.

SecondsCount
01-22-2017, 10:39 PM
I am guessing this works because the jacketing on a small diameter 223 bullet is relatively hard and/or the end of the case mouth is digging in to the bullet jacket. Given the relative springiness of a brass case I find it hard to believe that crimping is giving much compression benefit unless the case mouth is really loose to begin with.

What size die, trim process and expander bit, if any, are you using?

I assume you are asking me as you didn't quote my post.

These days I use all Dillon dies but back when I was having an issue, about 25 years ago, I was using RCBS dies. Currently using the Possum Hollow trimmer but looking at an EZ trim or Giraud Triway.