Case Crimping

No.

If your .45 ACP loads are taper-crimped .469" - .471", they are exactly right.
If they feed and chamber they are exactly right for your gun.

If his loads were more accurate then your loads??

I'd say you were expecting more from his loads, and tried to concentrate on your front sight harder with is loads!

Or you shot his loads before you shot yours, and your brain was simply tired the explosions going off in front of your face before you got around to your loads.

rc

Do you use the same machines? Some progressives fling some powders worse than others.. and then there's the set-up/operation of the machines to minimize this.

I guess I would try more more crimp.
Perhaps his powder measure is more accurate ?

I find a crimp of 0.473-0.472" to be best. 0.473" is what SAAMI shows for a loaded round.
Same seating die? Same care putting the bullet as straight up-and-down as possible? Any tilt to the bullet will mess up accuracy. Did you chamfer your cases at least once?

You said "same bullet type" in your post. Does that also mean the same manufacturer? There has to be something different unless it was just a
lack of concentration.

0.473" is what SAAMI shows for a loaded round.

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No, .473" is what SAAMI shows for a maximum ID loaded round case diameter for the .45 ACP.

The actual case crimp on GI mil-spec .45 ACP ammo is .469" to .471".

.473" is the largest case neck diameter that will fit in a SAAMI standard chamber.

It has nothing at all to do with the actual proper case mouth taper-crimp diameter.
Or what it should be.

It should be .469" - .471".

rc

I see the SAAMI drawing as indicating the outside of the case at the mouth is to be 0.4730 +0.000/-0.006, where 0.4730" is the target or nominal dimension.
Any way, I found for me that a 0.472-0.473" crimp is good for me.

Lots o folks have experimented with crimping and accuracy. Lots o folks have found a difference in accuracy.

Esp if your ammo is loaded on the light side for the powder/bullet you're using, some little bit of extra crimp could improve accuracy.

I've seen some data showing decreased standard deviation of velocity at specific taper crimp levels. The deviation increased with more or less crimp.

The common knowledge is that neck tension comes from sizing/expanding. And that taper crimp just removes the excess flare. That's most of the story, but there might be a little more to it.

Who knows? For your specific ammo and gun, crimp might make a difference.

Bullseye in light loads is very sensitive to the crimp. You can also screw them up with too much bell before you seat. The neck tension is also important. You may also notice that too light a crimp will give you a dirtier load with bullseye. I load with just enough bell to keep from shaving lead and taper crimp a little tight at .471. Good shooting.

noylj said:

rcmodel said:

The actual case crimp on GI mil-spec .45 ACP ammo is .469" to .471".

Click to expand...

I found for me that a 0.472-0.473" crimp is good for me.

Click to expand...

Most factory jacketed ammunition is taper crimped at .469" - .471". IMO, this amount of taper crimp helps with feeding/chambering of the finished round and easily done with separate seat/taper crimp operation.

For my lead target loads, I use the thickness of case wall added to the bullet diameter as my taper crimp (.452" + .021") which comes out to .473" and the rounds will still drop down even in the tight chambered Sig 1911 barrel. Since I seat and taper crimp in the same step, using .469"-.471" taper crimp will shave the lead off the side of the bullet. The .473" taper crimp rounds reliably feed/chamber from the magazine in the Sig 1911 and of course in the looser chambers of M&P45 and RIA 1911.

I have done comparison range tests of different taper crimps .469" - .473" (done in two separate operations) and IMO, I think OAL has greater effect on accuracy than the amount of tamper crimp for lead loads. My thought is closer the bearing surface of the bullet is to the start of rifling, less high pressure gas leakage and faster the chamber pressure build.

You said "same bullet type" in your post. Does that also mean the same manufacturer?

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Well ?

neck tension comes from sizing/expanding.

Click to expand...

Yes.
It could be more or less case tension is making the difference. It could the brand of brass or the primer used. There are any number of variables or combinations of variables that can effect accuracy.