why roll crimp for semi auto 30/06

[m715]

I reload for my rem700 30/06 bolt action.I also have a 742bdl semi auto.I would like to run reloads through the semi as well.Seems I remember reading somewere that to reload for semi auto The bullet must be roll crimped.I taper crimp for the bolt action and have no problems.My question is why do you need to taper crimp for the semi but not for the bolt action.

 

[243winxb]

Neck Tension

Sierra on Crimp- http://www.exteriorballistics.com/reloadbasics/gasgunreload.cfm

 

[rcmodel]

I taper crimp for the bolt

How do you do that?

No 30-06 seating die I am aware of has taper crimp capability.

The fact is, if your case neck tension is as it should be, there is no need at all to crimp for anything less then an elephant rifle or a tubular magazine like a 30-30 lever-action.

In those instances, recoil can pound the bullets back in the cases.

You have no such issues in your 30-06 bolt-action, and if the semi-auto feeds right, there should be no such issues with it either.

rc

 

[Ifishsum]

If he's taper crimping I assume the OP is using a Lee set with a FCD.

This is my take - loading manuals recommend crimping loads for semi-auto actions because it's the safest way, and it's the same reason all factory ammo is crimped. The casual reloader may not pay a lot of attention to neck tension, or even know whether it's good enough on the cases they're loading. Crimping adds insurance against a bullet getting pushed back into the case and possibly raising pressure to a dangerous level. When making a recommendation to a relatively new reloader or to someone who's proficiency I don't know, I'd also recommend the safest method. Personally, I don't crimp every round I load for a semi-auto rifle but when I'm using a bullet with a cannelure I usually do - because I haven't found a reason not to.

Pretty much all rifle seating dies make a roll crimp rather than a taper crimp. The extra Lee FCD is the only exception I'm aware of, but the standard for rifle dies is a roll crimp. That's likely why you saw that recommendation. If the bullet has a cannelure - and if you're going to crimp it - I believe a properly applied roll crimp is probably more secure than a taper crimp.

 

[rcmodel]

The Lee rifle FCD does not taper crimp either.

It collet-crimps a depressed ring around the case mouth.

rc

 

[cfullgraf]

I have a Lee 30-06 taper crimp die. It is not an FCD. It is not a seater die.

But, I have not crimped any reloads for my Garands in 8 to 10 years.

 

[m715]

Ihave an rcbs fl sizer and rcbs seat die.

 

[USSR]

As previously stated, no need to crimp for either of your rifles, it's all about neck tension.

Don

 

[Captaingyro]

The fact is, if your case neck tension is as it should be, there is no need at all to crimp for anything less then an elephant rifle or a tubular magazine like a 30-30 lever-action.

In those instances, recoil can pound the bullets back in the cases.

Just to clarify, pounding the bullet back deeper in the case would indeed be the danger in a rifle with a tubular magazine, but in an elephant rifle (usually a side-by-side double) or the OP's 742 with it's box magazine, the bullets being jerked forward in the case under recoil would be the concern.

One technique for determining if your neck tension is adequate in that case: Measure the OAL of a finished round, then load it into your kinetic bullet puller. Give it a whack quite a bit harder than any recoil you anticipate, and measure it again. If it hasn't grown, you're GTG.

 

[rcmodel]

A double-rifle pulls bullets because the rifle recoils, and the bullet in the 2nd. barrel tries to stay where it was, while the case is jerked away from it.

A box-magazine rifle pounds them deeper in the case because the whole round is trying to stay where it was, while the magazine they are in is accelerated rapidly to the rear.
(Witness flattened lead bullet tips on the ones you don't shoot.)

Nothing in a box magazine has a hold of the round to yank it off the bullet, or squirt the bullet out of it.

rc

 

[Captaingyro]

Take a look at one of your AR mags. There is indeed something that will hold the case back, while the bullet is free to move forward.

See that vertical rib that's stamped (or molded) into the side of the mag? It engages the case at the shoulder, and prevents it from moving forward more than a slight amount. There's a little slop built in, of course, so rounds that are loaded right to max mag length could contact the front of the mag and be set back. Normal length rounds, however will be stopped by the shoulder and the possibility of bullet pullout exists.

 

[rcmodel]

I thought we were talking about Remington 30-06's.

You can hardly pull a .223 bullet with a bullet puller and 40 whacks anyway.


rc

 

[Captaingyro]

I assumed you'd be able to put your hands on an AR mag easier than a Rem 742 mag. Here's the 742 mag in .30-06:

 

[m715]

guess i will take my 742bdl and garand out with some of the reloads.I thank I will run all but the last one of a full clip through the gun,I will remove the last round from the chamber and measure it.If the last round does not grow I would have to be ok.

 

[m715]

Got out to shoot the loads.I measured the col of first bullet in the clip.fired three of the four rounds through the bdl,then unchambered the last round and measured again.The bullet was .003 shorter than when I loaded it.Did the same thing for the garand.fired seven of the eight measured the last round it was .007 shorter than when I loaded it.I read the link that 243winxb posted.The neck tension makes since.Would the lee factory cimp die do the same thing.From what I read it sounds like that die squezes the neck of the case instead of roll crimping it.Did I read the description of the die correctly?

 

[rcmodel]

Yes you did.

The Lee FCD collet crimp die squeezes a ring on the case mouth into the bullet cannulure.

rc

 

[Walkalong]

C&H makes a .308 taper crimp die, and perhaps a .30-06, I don't know, and it would work to taper crimp .30-06 if one desired.

 

[m715]

o.k. so I should reduce the resizer ball on my die by .001 to .002 under bullet dia to get the neck tension I need to fire the non canalure bullet that I use in my 06 bolt action to prevent the bullet from moving if I want to fire it in the bdl or garand.Now I wander if the bullets in the bolt action that are in the clip when firing are also getting shorter?

 

[USSR]

o.k. so I should reduce the resizer ball on my die by .001 to .002 under bullet dia to get the neck tension I need to fire the non canalure bullet that I use in my 06 bolt action to prevent the bullet from moving if I want to fire it in the bdl or garand.

If you are able to grasp a loaded round by the case and press down on a table with the bullet and have the bullet slip further into the case, then yes.

Don

 

[soloban]

I FL size my .30-06 with a Redding Die and seat with a competition seater using 150gr SMKs. No crimp, never had an issue in my M1 at all.

 

[tahoe2]

Rem 7400/280 Rem

I have been reloading for this one for over ten years, from 130grns to 160grns and everything in between without a bobble.
My secret is not a secret--LEE--"factory crimp die"