is it better

[Jerome Cooper]

Crimping is sometimes a necessary evil to prevent bullet movement under recoil or if here is a possibility of the bullet telescoping when feeding. It should be kept to a minimum...just enough to get the job done, for it cold works the mouth of the case and shortens case life. In cartridges that seat on the case mouth a taper crimp is usually applied, but not enough to interfere with the seating. Cases should be kept to uniform lengths so that dies apply the best and the desired amount of crimp. J.Cooper

Information

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[Gun Surfer]

Been shooting M1A, AR15 and M1 for a quite a while, using match and military style BT bullets without crimping. I have also periodically checked reloads cycled into the chamber with a calipers for all three, never noted any change in OAL. All brass used was properly sized and in good condition. I'll keep testing but do not anticipate any problems.

[Bruce_in_Oz]

One of the "cute" features of the Garand is that the cartridge is almost exclusively guided into the chamber by "control" surfaces that bear on the case, not the bullet.

Back in the "good-old-days", I would test for component wear / distortion in the feed mech. by feeding sized, empty cases from a clip.

M-14s are pretty good, too.

In the AR-15, the bullet DOES play a part, hence all the fooling around over the years, with the "bullet guides" in the barrel extension. The M4 Carbine introduced deeper bullet guides that actually extend into the alloy structure of the lower receiver. M-4s, have a shorter barrel AND a gas port MUCH closer to the breech. Not only that, but the buffer tube (and hence bolt travel) is shorter and the buffer is (was??) lighter. Thus the entire cycle runs a different set of pressures AND timings from a "full-sized" A2 or A3.

That said, pretty much all of the feed failures I have ever seen on the AR platform involved faulty ammo, a fouled weapon, a faulty mag, or a combination thereof. This includes a LOT of shooting with soft and hollow-point "sporting" projectiles.