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Thread: Frontier ammo 223
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24-05-2017, 16:29 #11
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24-05-2017, 17:31 #12
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Re: Frontier ammo 223
The bullet needs to be strong enough to withstand the centrifugal forces generated by the spin imparted by the twist.The bullet can also not be shot at velocities that exceed its ability to engrave the rifling. A heavier bullet would have a lesser velocity and therefore not be as strained by the twist - forward motion retarded by resistance offered by twist.
Some one commented that your load seemed low ?, I do not know your bullet weight or velocities, but if you are shooting at lower velocities perhaps those CMJ's are not electro plated to spec and becoming basically cast lead when leaving barrel - a very soft lead at that.
You mentioned AR - I would assume thats one of those fancy looking assault like rifles, their twist is often as low as 1:7 suited for up to about 90 gr bullets I have read. Putting a 50 grainer down that barrel at 3200 fps could cause your symptoms.
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24-05-2017, 17:34 #13
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Re: Frontier ammo 223
Copper coating coming off. Buy better bullets or reduce your load.
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24-05-2017, 18:15 #14
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Re: Frontier ammo 223
Erm, being frontier it is safe to assume 55gr and with 23gr of s321 he more than likely is running 2600 to 2800 fps
@Gomsaag do you know the following?
What AR is it? barrel length, twist rate?
LOA?
How are you measuring your 23gr of S321?
What is your muzzle velocity? have you tested it over a chrony?
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24-05-2017, 19:48 #15
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Re: Frontier ammo 223
It could be that you are over crimping the rounds and its damaging the jacket, or not chamfering your case mouths after trimming.
I only get this at 2800fps + with Frontiers.
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24-05-2017, 21:56 #16
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Re: Frontier ammo 223
I have to agree that over crimping or a rough (un-chamfered) case mouth is probably the culprit. I'm guessing DM4's have a 1 in 9 inch twist. The a bullet of 55 grains cannot possibly be spinning too fast to self destruct at that twist rate.
Very light (as in 43 to 35 grain) varmint bullets of fragile construction have that issue in 1-7 twist barrels when driven fast.
Over crimping Frontier CMJ's can cause jacket separation, even in 9mm and .45 handguns at relatively sedate velocities. I have shot hundreds on 55gr CMJ's through my 1-9 twist AR with no issues. But I make sure I have no sharp edges on case mouths and I crimp just enough. I have heard of 55 gr CMJ's losing jackets out of 1-12 twist LM's. But from speaking to the owners I realised that their idea of case prep was to crank shitty brass through a press as quick as possible with no trimming or chamfering and trying to duplicate NATO spec velocities. Twist rate has nothing to do with it in all likelihood
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24-05-2017, 23:01 #17
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Re: Frontier ammo 223
A CMJ bullet does not have a jacket so to speak, it is a electro plating process and the coating is bonded by " become one " means - like galvanizing. It is not a copper jacket on a lead core that can be peeled off like a interlok bullet, it is a bonding process that has no real layering, more a becoming one thing effect. I do not know how to explain it. You could dent a CMJ bullet but you would be hard pressed to deduct from its structural integrity.
These bullets were either too thinly plated or pushed past their limits. - A last long shot ---- if rifle was brought to me for problem solving that I would look at, would be a very oversize bore and a hard pressed low quality bullet .............CMJ .
We know that bullet is loosing coating and throwing lead - surface material by looking at picture.
The exact reason is blurry, but what is happening has been answered.
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25-05-2017, 07:54 #18
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Re: Frontier ammo 223
In theory: yes. In practice: no...CMJ's lose jackets regularly. I recently replaced my chrono because a large piece of plated on "jacket" hit the screen. The bullet still made a perfect hole in the cardboard. But the plated jacket even though it is thin (like the side of a beer can) stayed one piece and peeled from the lead core. And that piece of jacket came from a 147 gr CMJ at about 900 fps.
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25-05-2017, 08:09 #19
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Re: Frontier ammo 223
CMJ plating definitely peels off.
Also beware of rapid erosion of muzzle breaks due to this...
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25-05-2017, 08:23 #20
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Re: Frontier ammo 223
As can been seen in this photo there is no excessive crimp and no scuff marks on the bullets, loading with a dillon XL650 23grain of S321 witch is a low to medium charge i am using a dillon precision case trimmer and i believe it is a 1-9 twist 14.5 inch stainless steel barrel, I do not know the speed for i do not have a chronie but i reckon its around 2800fps.20170525_080652.jpg
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