Home Forums Hunting & Shooting AR and Tactical Rifles Crimping

brand new in the box from the factory...I shall continue to crimp!

Maybe rost and mule deer should give lessons to Winchester.

Proof that neck tension might be more important than faulty crimping....

I think they forgot to crimp that one, don't see any marks anyway.

bullet set back explosion?? You decide...

http://forums.1911forum.com/showthread.php?t=412136

It proves that nothing is idiot proof after reading what the OP went through to get his 9mm to shoot what he thinks was a .38 Super.

That was a 38 super mag as in magazine not a 38 super round in a 9mm chamber.

he just chambered a 9mm several times and pushed the bullet back.

I miss-read it. He does say he had multiple FTF's before he dropped it in the chamber. He should have noticed setback of the bullet.

Most definately but in this case stupid shows how high pressures can run when a bullet is set back far enough.

I've seen crimped ammo get set back, usually due to magazine problems.

For semi-auto handloads, I crimp. I use the Lee Factory Crimp die. It helps secure the bullet and improves accuracy.

Here is what Sierra has to say about Neck Tension on a service rifle.

Neck Tension

When we stop to consider the vigorous (read, downright violent) chambering cycle a loaded round endures in a Service Rifle, it becomes pretty clear it suffers abuse that would never happen in a bolt-action. This is simply the nature of the beast. It needs to be dealt with since there is no way around it.

There are two distinctly different forces that need to be considered: those that force the bullet deeper into the case, and those that pull it out of the case. When the round is stripped from the magazine and launched up the feed ramp, any resistance encountered by the bullet risks having it set back deeper into the case. Due to the abrupt stop the cartridge makes when the shoulder slams to a halt against the chamber, inertia dictates that the bullet will continue to move forward. This is exactly the same principle a kinetic bullet puller operates on, and it works within a chamber as well. Some years ago, we decided to examine this phenomenon more closely. During tests here at Sierra�s range, we chambered a variety of factory Match ammunition in an AR-15 rifle. This ammunition was from one of the most popular brands in use today, loaded with Sierra�s 69 grain MatchKing bullet. To conduct the test, we chambered individual rounds by inserting them into the magazines and manually releasing the bolt. We then repeated the tests by loading two rounds into the magazine, chambering and firing the first, and then extracting and measuring the second round. This eliminated any potential variation caused by the difference between a bolt that had been released from an open position (first round in the magazine) and those subsequent rounds that were chambered by the normal semi-automatic operation of the rifle. Measuring the rounds before chambering and then re-measuring after they were carefully extracted resulted in an average increase of three thousandths (0.003") of forward bullet movement. Some individual rounds showed up to seven thousandths (0.007") movement. Please bear in mind that these results were with factory ammunition, normally having a higher bullet pull than handloaded ammunition.

To counteract this tendency, the semi-auto shooter is left with basically two options: applying a crimp or increasing neck tension.

Here is a little test done using the Lee Factory Crimp die. Three different rifles, three different cartridges, same results, Improved Accuracy.

http://www.accuratereloading.com/crimping.html

Here is just one of Many accuracy tests I have done with the Lee Factory Crimp die. Stock Colt AR-15, Cheap Midsouth Varmint Nightmare bullets, 10 rounds each target, 100 yards.



It is inevitable in these crimp-vs-no crimp discussions that someone will bring up the Benchrest shooters and how they do not crimp. This is of course Apples to Oranges at best. The BR guys don't shoot cheap Midsouth bullets and they don't shoot off the shelf $900 rifles either, so what they do or don't do with their high $$$ equipment has Nothing to do with the average Joe with his average equipment.

this average Joe will crimp his bullets, anyone else can do what they want. I also have found what I believe to be better consistency with crimped 65 grain SGK bullets and 75 grain Swift S2 bullets, so far!

Still interesting that of the couple ( well maybe its a few more) folks that I know that have shot service rifle AR even before we started and continue to this day, almost all do not crimp.

And if you think that BR shooters have high dollar guns, don't discount CMP guns.... they are not run of the mill ARs for sure. I've had some that would scare the hell out of .25 moa at 600 yards....

Never mind that what sierra did, was a one of test, vs at least a couple of us firing more rounds in a year than they do in their tests.

But as I've noted for folks that want insurance and don't pay attention to neck tension( I also use it for accuracy tweaks) or powder choices, then crimping may well be the same bandaid that weighted carriers have been.

But then again how many folks FL size/ with neck bushings for tension and actually test how primers, powder charges, seating depth and neck tension affect accuracy, off a bench at 600 yards and in 600 yard prone only matches? I'm lucky in a tiny way, that I have a 600 yard bench on my property and out my back door.

It's also interesting how those that preach the evils of crimping and use the BR comparison have actually never tried the Lee Factory Crimp die. No first hand experience with the die, just talk about how bad it is.

I should add to, in sierras defense, that the average joe doesn't understand reloading nearly enough and really should crimp.

There is a reason that factory ammo normally is crimped too, just to cover all the bases.

In fairness I've never actually said it was evil. I've simply said if everything that you do in reloading was understood, and done correctly for the situation, then crimping as not going to be needed.

While I have never used a lee factory crimp, that is true, I do have a few of the friends mentioned above that have to try every last new thing that comes out, even if their ammo is good as is, and they didn't use crimped ammo for long.

Regardless, anything, neck tension included, for it to be as repeatable as it can be, the cases have to remain the same length for the tension to be repeatable and not many folks i know that shoot AR trim every time they reload.

Even though I cannot figure out how a LFC die can supposedly crimp the same amount on a short trimmed or a long case, its really a moot point because most folks crimp for reliability and not accuracy.

Since I no longer compete, I'll give you this much, IF I ever can find time I"ll buy a crimp die and play wiht my match guns once just to see.

My negative reason on top of all this is its one more thing that work hardens the neck of the brass more than you would by simply sizing, and that may be too anal of an opinion. Especially since I anneal every 4-5 loadings.

Good info. What expander plug size do folks recommend for .308's?

I would think that a competition shooter would be more concerned with accuracy then case life, but that's just me.

Did you read through this accuracy test?
http://www.accuratereloading.com/crimping.html

Hands down crimping is more accurate. You should see the difference in my 41 mag. You do know it is a big factor of burn rate in powder.