Crimp effect...

[2ac]

I've been using the magical H322/77 GR CC load with good results. I'm considering adding a light crimp to help with consistency and pick up a Lee die. Is this going to effect my load, zero, etc? I want to load up a few hundred for my last hoorah in the PNW, before I relocate to WI.

[boombotz401]

Won't know until you test.

Case trim will have a big factor on this...a 1.760 will crimp differently than a 1.750 case.

Trim all your cases to the same length before loading


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[Kansaswoodguy]

I crimp nothing. I do have the Lee die and have played around with it in two different calibers im not saying it will not help you in your quest for better ammo. It's just another step in reloading that I'm uninterested in the time commitment for accuracy gains that I couldn't quantify in the group's down range. Now just trimming your brass if it's all over the place in lengths will gain about 1/4 -1/2 moa in accuracy in my opinion.

[noylj]

>Now just trimming your brass if it's all over the place in lengths will gain about 1/4 -1/2 moa in accuracy in my opinion.

This, to me, is one problem: too much "in my opinion" and not enough testing. Too much of the Greek method, where thinking about things was sufficient and testing was beneath the dignity of a philosopher.
I can say that with a 0.75-1.25MOA rifle, I have seen no improvement in trimming cases all to the same length, matching head stamps, or crimping vs not crimping out to 200 yards. Those were tests I ran and any one can run tests to determine what variables REALLY have any effect on their shooting.
I don't speak for 0.2-0.5MOA guns or long range shooting; however, I haven't read of any one's actual test results yet, just "in my opinion," "it couldn't hurt," and "consistency is always best."
One article in a magazine actually started off with, and I'm paraphrasing: "The first step to accuracy is to uniform the primer pocket and deburr the flash hole."
That is the FIRST step?
It is amazing how often in history those same thoughts were destroyed by someone finally TESTING and REPORTING.

[markm]

The Lee factory crimp die is huge for my accuracy. My groups open up well over moa with 77s not crimped. I ran a test a few years ago. I couldn't believe it.

There should be no difference in load. At least I found nothing significant other than accuracy suffering.

[Kansaswoodguy]

My poor humble opinion is based off of my person testing also shooting 223 at 100yds when my brass was left untrimmed with some desent variances in case length my groups open up from around .75 moa to around 1.25 moa. Now if I'm running all the same brand of brass normally LC and there is little difference in length from case to case I don't bother trimming them but I shoot a great deal of 223 ammo so it becomes a time issue. I tried the Lee crimp die in two different calibers and never could get my groups to shrink that I could measure so I gave up on them. I have no doubt that markm is seeing a difference in accuracy and I've read enough of his posts to know he is an accomplished shooter and I respect his opinion but I can assure you that his reloading regiment and mine are different. In fact the only reason I ever tried the 77gr SMK was do to markm stating that he was able to get them to 1000 yards he was absolute right, I shot them Saturday to 1000 yards out of one of my AR's. Everyone that reloads has to find what works for them personally trying lots of different methods and keeping the ones that work for you is what it all about.

[2ac]

The Lee factory crimp die is huge for my accuracy. My groups open up well over moa with 77s not crimped. I ran a test a few years ago. I couldn't believe it.

There should be no difference in load. At least I found nothing significant other than accuracy suffering.

I'm guessing case length must be consistent to get the desired result?

[308sako]

FWIW; The good fortune I am having with the 62 grain Hornady BTHP is also my first foray into Lee's crimping die. Coincidence, perhaps, but very pleased with the consistency I am getting. It is my plan to run some fairly long strings through the Oehler and see if the standard deviations are more or less when crimped as well. Later in August for that however.

[markm]

It's definitely going to vary in the context of your process and dies. I think sinister uses no crimp, but annuals... and gets the same level of accuracy.

[bigedp51]

Bullet grip/neck tension on a standard full length die can be controlled by expander diameter.

At the Whidden custom die website they sell expander kits with five expanders. These five expanders are from bullet diameter to .004 under bullet diameter.

Many reloaders use the Lyman type "M" expander die and bump the case neck mouth onto the second step of the expander. This creates a step inside the case mouth and aids seating and reduces neck runout. And as you can see the lower part of the expander is .003 smaller than bullet diameter and no crimp is required. If using the "M" die makes you nervous you can apply a "light" taper crimp for case mouth streamlining. My main point here is the expander diameter can be used for more bullet grip and not crimp.



Below a brand new RCBS .223 expander and why you should polish your expanders. And my .223 expanders are polished .0025 to .003 smaller than bullet diameter.