Been discussing my decision to buy a 458 win mag rifle with someone, and was told that I should be crimping the rounds because the heavy recoil can cause bullet setback for the rounds in the magazine. Is this a realistic issue? Can a bullet be setback in the case only as a result of recoil?

Thanks

quote:

Can a bullet be setback in the case only as a result of recoil?

Yes

Bullet weight, power of the load, weight of the rifle, how you hold the rifle, neck tension sharpness of the recoil etc all can impact it.

Doesn't have to be something like a 458wmag. I've had bullets move in a light weight 338 wmag. Had to reduce the expander to give more tension and it stopped.

The solution for setback, given by ramrod340, is right on the money. Increasing neck tension by reducing the sizer button is far more consistent than increasing neck tension by crimping. Any time one can increase consistency in the loading process, accuracy will increase.

In the handgun game the old rules have been -holding the cartridge in your hand you shouldn't be able to push the bullet down with your thumb. With something like a 44mag revolver too much crimp will cause poor accuracy. Get proper tension then put a bit of crimp for best results.

Yes, proper neck tension and a wee bit of crimp also, is the way I like to do it too.

Ammo colliding with the front of the box is what drives the bullet deeper into the cartridge case.

Recoil pushes the rifle backward, the inertia of the ammo in the box makes it hit the front inside wall of the magazine box that is moving rearward.
This collision with the front of the box drives the bullet deeper into the cartridge case.

Recoil actually makes the bullet move forward in the case, like in a revolver where it ties up the revolver by making the bullet protrude beyond the front face of the cylinder.

Bullet nose hammering the front wall of the box:







Dimpled front wall of box may cause failure to feed.
There are all kinds of ways to re-inforce the front wall of a sheetmetal box.

RIP:

Just like an Inertia bullet puller!

There is no crimp or a "Tight neck tension" that could not be broken by simply wacking the bullet puller real hard on a solid surface.

The heavier the bullet the easier it is to dislodge it from the mouth of the case.

Care should be taken when crimping as neck tension can actually be released if too much crimp is applied especially if using the bullet seating die to do the crimping.

The amount of neck tension release when crimping will also depend on the softness or hardness of the case neck, hence annealing cases will maintain good neck tension by making sure the neck brass is not springy and at the same time the softer brass will allow a crimp to be applied without releasing neck tension.

Crimping bullets with a cannelure type 'groove' requires brass soft enough to actually mould to the cannelure surface as there is not an actual crimping groove where the case mouth is folded into to prevent bullets being pushed back into the case under recoil in the magazine.

Good crimping using the bullet seating die is also aided by having a well dimensioned die that supports the case neck. The RCBS dies I have for my .404 were custom made and the bullet seating die is dimension so well that it actually folds down the very slight case mouth flare I apply when loading cast bullets, I back the die off a little and do not apply a crimp for cast. When loading RWS cannelured solids I set up to apply a good tight crimp as the case neck is well supported and maintains a very good neck tension, possibly not needing a crimp in my Mauser as there is no play in the magazine box but just a little insurance to make sure the bullets do not move under the stout recoil in the light rifle.

My .458 loads are usually so compressed that setback isn't the issue, the compressed load trying to push the bullet back out is. The crimp helps with that.

In any case, I increase neck tension (case mouth tension?)by not using the expander die at all. The straight wall sizing die doesn't have an expander ball. Crimping is a bonus, and will stop the case mouth from snagging on everything in sight.

Save the expander die for rounding out dented cases and cast bullet loads.

Absolutely frightening pictures! I learned something that I wouldn't have ever thought about myself. Who would have thought about the effects of inertia on the rounds!

Thank you all for the great information

Heym makes their magazines caliber specific now just to fight this problem. It is an awesome design but very expensive I'm sure.

I have read that setback can cause huge pressure spikes and that is not good. Peter Capstick wrote about a 458 Win Mag that kept being pushed to the bottom as he was topping off the magazine during elephant culling. When he finally fired that round it made an errant explosion and almost got him killed when it failed to perform on a frontal brain shot. Made for interesting reading anyway.

Back in my early days when you could get soft tips or soft tips. I had 3 rounds that I always loaded first. So their tip got beat to death. Hard to believe but nice tip or flat or no tip for normal hunting accuracy was close enough.

I use a Lee Factory Crimp die for my 500 Jeffery. I highly recommend it. Also as has been mentioned with a powder that requires a bit of compression with your bullet of choice will also alleviate the concern to a great extent.

I generally turn the expander ball down a couple of thousands, sometimes three thousands, whatever works without crushing the shoulder when seating the bullet, then I also use a powder that compacts just a tad and then add a light crimp. Not sure what Alf is saying about a crimp with a tight bullet fit, I have had no trouble getting a very light crimp with above practice. I really like this with double rifles but the cases are very malable so care has to be used and it takes some try and change to get it right sometimes.

I use the LEE crimp plus neck Tension, better result than crimp function in seating dies where I have had reduced neck tension due to crimping - process of crimping actually expands case neck.

Make sure you chamfer the case mouths too, have had them collapse when seating bullets after sizing fired factory cases (Hornady).

Cheers,
Chris

Here's another one-
In 2006, I was hunting in Mozambique with a 375 RUM. I had chambered each round before traveling.
After taking several animals, all with one shot kills, my PH and I undertook a croc hunt. The first shot pegged him in the cervical spine, but he was thrashing and I attempted to reload for a follow up shot. The next round in the box had apparently swelled at the shoulder from hammering in the magazine, rather than the bullet being set back. (Lee factory crimp die)
The round stuck in the chamber, and I had the devil's own time getting it out. Thank God it was not a charge situation, that could have gotten ugly.

I have had the mag box in my 416 Rigby modified with internal rails to stop the case slaming into the front of the mag. This was only partialy successful so I use a Lee Factory crimp as well. Minimum crimp to do the job and I make a habit of first round in today is last round in tomorrow.