Crimp question

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Crimp question

Postby Cutright » Thu Nov 10, 2016 4:49 pm

I have a new question about crimping. I have been loading the .450 for a little over a year and have not noticed this before (it was probably happening, I just haven't noticed). I am loading 200gr Barnes for deer into new brass. When I put the taper
crimp on it the bullet can actually be spun by hand. It will not pull out, but it will spin. After the side crimp it no longer spins. I'm sure that I just have the taper crimp too low, but I haven't had any problems with the die at this depth in the past. The case is even a little rippled (I thought it was from the grooves in the bullet). It feeds and shoots fine. Should I be worried? Do I just need to back the taper crimp die out some?
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Re: Crimp question

Postby Bmt85 » Fri Nov 11, 2016 3:30 pm

Sounds like you don't have enough neck tension. Try .002-.003". As to the taper crimp try running .473-475".

Edit - long day when I posted, thought you said the bullet was spinning before taper crimp. My bad.
Last edited by Bmt85 on Sun Nov 13, 2016 3:47 pm, edited 1 time in total.
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Re: Crimp question

Postby Hoot » Fri Nov 11, 2016 6:59 pm

If you have any of the 200gr bullets from the same box as the ones that spin that haven't been loaded, mic one of them. Read not caliper, micrometer. You may have a lot that snuck out of the factory undersized.

Do you anneal your cases? Cases improperly annealed will stretch as the bullet seats and not spring back.

If you're using the expander die, stop. You don't need it with jacketed bullets.

I wrote about this before, but it bears repeating. The cases will reliably headspace off of the mouth down at .465, so don't be bashful with the taper crimp when you have a driving band groove at your disposal. Take an old case and try it yourself as no two chambers are identical. Keep sizing it smaller and measuring to see where the "thunk" gets soft. It'll surprise you. Do not do this with smooth walled bullets. There's no where to push the brass down into.

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Re: Crimp question

Postby Cutright » Fri Nov 11, 2016 7:43 pm

I used all of the bullets, so I can't mic them. I have read your posts in the past so I do not use the expander die. The bullets do not spin before the taper crimp is applied. Also after backing off the crimp die they did not spin. I did not anneal the cases, but they were new Horady brass. I didn't think you could put too much crimp on them and did not want them jumping with the recoil or bolt closing on them.
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Re: Crimp question

Postby pitted bore » Sat Nov 12, 2016 10:33 am

Cutright-
Here's a guess about the cause of your spin-able bullets:

When the seater die shoves the bullets into a new or resized case, the case mouth started with a smaller diameter than the bullet and so it grips the bullet more or less tightly.

Next, when you shove the case with the seated bullet into the taper crimp die, the case and the bullet together are both forced (swaged?) to a smaller diameter. Then, when withdrawn from the die, the case springs back a bit from that smaller diameter. The copper bullet does also spring back, but not as much as the case. The alloy from which cases are made is intended to be capable of springing back. Otherwise, they would take lots of force to remove them from a chamber after being fired. Copper is less springy and more malleable than cartridge brass.

The result is that the bullet now fits less tightly in the case mouth, and can even be spun.

The effect is not so noticeable with the cup-and-core type of jacketed bullet. The cupro-nickel alloy jacket has more spring-back than the solid copper bullet.

My guess may be incorrect, or I may have expressed it unclearly. Helpful comments are invited.

--Bob
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Re: Crimp question

Postby Hoot » Sat Nov 12, 2016 11:29 am

Given that when you backed off and they were more snug, I'll guess too much downward taper crimp pressure. As to why, I can only guess that too much downward force on the mouth causes the case to "squat" down and widen the area just below it. Never had that happen, so I can only visualize it in my head. The taper crimp die has a fairly linear taper inside. Once it has driven the mouth down into the groove as far as the pitch of the taper will allow, continuing to push the case deeper into the die will grab the portion of the case below the groove and try to drive it into the band or body. Trying to drive relatively hard brass into relatively solid copper is going to in all likelihood, seize up the case against the die wall. Further pushing will as I said, drive the entire case downward.

Imparting the taper into either a groove or to a lesser degree, a cannelure, should present minimal resistance to the handle stroke, so a good indicator of too great a travel would be when the handle resistance goes up noticeably in a short period of time. In the case of smooth walled bullets, the taper crimping cycle is immediately harder to impart. Jacketed lead core bullet walls yield easier than solid copper, so you can impart a taper crimp even on the smooth walled bullets without needing so much force as to thin the case mouth walls. Experience has taught me that the benefit of the taper crimp is still hard to appreciate on smooth sided bullets. They have always for me, been more challenging to crimp. I sure wish the Hornady 250gr FTX and 300gr SST-ML bullets had a cannelure right at the optimum seating depth for the AR magazine. It would make the results more consistent from session to session. Luckily, white tails don't need such heavy bullets in this caliber, to reliably drop them in their tracks.

I do not run my taper die squeaky clean inside. While it is not dripping lube, I do like to keep the inside wall somewhat lubed with a little and I mean little bit of gun oil applied with a long, double ended q-tip. If upon applying the light layer of oil, the q-tip comes out dirty, I flip it to the clean end and wipe it out, then repeat with new ones until they come out clean. However many passes that takes, once the applied lube end of the q-tip comes out clean, I flip and wipe one last time with the dry end. I'll still leave a fine coating on the inside, but not enough to worry about it contaminating the case or bullet. That having been said, I still wipe down my finished loads with a clean rag ever so lightly moistened with denatured alcohol. Emphasis on ever so lightly. I lay the clean, moistened rag on the upturned palm of my hand, lay three finished round on it, flip the side of the rag up on top of them and roll them a pass or two between my hands. Easier seen than written.

One last mention. When I say q-tip, I don't mean the ones for your ears. Technically, what I use are double ended, cotton tipped applicators. They have a wood shaft and are about 6 inches long. You can get them from countless sources for around $12.50 per box of 500.
Example
A box lasts me about a year. "It's a clean machine..." Image

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Re: Crimp question

Postby Cutright » Thu Nov 17, 2016 3:45 pm

Thanks guys for all the input. Since I have your attention, I have noticed another issue. I wanted to make sure that the bullets were not jumping with the bolt be slammed shut, so I measured one after it had been loaded a few times after hunting. A very small indent is noticeable on the PRIMER from the firing pin. I cannot imagine that being normal. What should I do about this FullSizeRender.jpg
FullSizeRender.jpg. I guess I have to figure out how to post a pic
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Re: Crimp question

Postby Hoot » Thu Nov 17, 2016 7:31 pm

Cutright wrote:Thanks guys for all the input. Since I have your attention, I have noticed another issue. I wanted to make sure that the bullets were not jumping with the bolt be slammed shut, so I measured one after it had been loaded a few times after hunting. A very small indent is noticeable on the PRIMER from the firing pin. I cannot imagine that being normal. What should I do about this FullSizeRender.jpg
FullSizeRender.jpg. I guess I have to figure out how to post a pic


That's not unheard of, especially chambering a round over and over. The firing pin is free floating and you must have it and the raceway pretty clean if that's happening since it doesn't have much mass. I've seen micro-tics on my primers when I remove an unfired case. Doesn't happen with my CCWS BCA but I have more than one AR.
It takes a hard hit to get reliable ignition, even with the brass Rem 7 1/2 primers I use. I don't worry about it but some folks do and often cite some slamfire they heard or read about. The odds of it happening to you are probably 1 in a million. so, after you have passed 500k rounds, really start worrying! ;)
Seriously though, consider how popular the AR is and how many rounds are fired nationwide each week an yet you read of an event every 2-3 years. Even then, the damage to the upper is such that its hard to definitively say that maybe the hammer caught the sear or maybe it didn't and rode the pin as it chambered anyway. If it keeps you up at night, you can always go to the SS thick-walled primers.

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Re: Crimp question

Postby Cutright » Fri Nov 18, 2016 8:10 am

Thanks. That makes me feel a lot better. I was thinking that the CCWS was contributing to the problem, but I will just make sure that I'm outside when I close the bolt on the 500k time. My wife will kill me if I put a hole in her wall!
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Re: Crimp question

Postby Chris P Bacon » Fri Nov 18, 2016 8:23 pm

Sometimes we may feel the need to load indoors, for what ever reason. There is a well known method of doing this, that adds a layer of safety against slam fires (for handguns and rifles). I suggest locating the following in the garage in case it gets tipped over.

Get yourself a five gallon bucket, fill it with a bag of dry play sand. Aim down into the center of this bucket anytime you need to load indoors.

Once a bullet leaves the barrel you cannot take it back. So always, safe direction!

However, using this bucket method, if a slam fire ever occurs, count your blessings, and be thankful no one was injured!

Do it, it's cheap insurance.

If bored, and want to see how well it works;

http://www.youtube.com/watch?v=Eo-YMjuyNA8
and
http://www.youtube.com/watch?v=2OpHjldbO5s
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