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Posted: 10/15/2008 6:34:18 AM EDT
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I have been reloading for the 450 Bushmaster for 3 Months now and have had great success but I recently ran into a problem. The problem is the mass of the bullet is great enough to be pulled from the case due to the bolt velocity during cambering. Much like a bullet puller would do. This has only started when using Barnes solid bullets. Because the 450bm seats off of the case mouth a role crimp can not be used, rather a taper crimp is used. When taper crimp too much the bullet is dented and is loose in the case. When I use too little taper crimp the bullet has pull problems. When I think I have it right and I can tap a loaded case vigorously on my butcher block it does not move but the bolt will still move it. It jumps from 2.60 to 2.80 COL or it will jump from 2.60 to 2.70 COL What does the military use to seal there bullets, and will it help with bullet pull? Please help this is getting frustrating. |
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Does the military use these bullets? I have found it very frustrating to beta test new cartridges. I have found that bullets that have a heavy crimp can still be accurate even if "dented." My only advice is keep playing with it. I would go with a heavy crimp, or you have to be prepared to shoot every bullet you chamber. If not, you will be collet pulling them with your barrel as the collet. Expect chamber pressures to be very high with the rounds in the lans. |
No the military does not use this bullets, but they do use some type of sealant on 5.56. I can not use a heavy crimp on the Barnes, because when I do a heavy crimp it dents the bullet and the brass has some bounce back. The solid Barnes has no bounce back, so I'm left with a loose slug in the cartridge. It feels like a rim fire bullet, Its not coming out of the case but it is loose. |
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Insufficient neck tension. Take a sized case and measure the width of the neck at least 3 palces, average. Then seat a bullet and measure the neca at at least 3 places, average. Seated average - sized average = neck tension You want 0.003 in neck tension in Semi-Auto Actions. |
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Metal on metal contact improves bullet retention. Clean the neck area with a bronze brush spun in a drill to get all the carbon off the neck. Get a Lee Universal Expander:  This expander has a conical insert that does not expand the neck. It only flares the case mouth. This will give you maximum tension on the bullet. |
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The 450bm has no expander ball. I have a neck tension of .003 I have found if I set the Barnes bullet deeper to the crimp groove it only moves .008 every time I cycle it through magazine. I have tried all advice above with the exception of the bushing type seizer die, and it has not cured the problem. I have tested peeing the case in 3 locations around the case with a small nail set and then the bullet only moves .003 every time I chamber it. I believe this would work if I had a way to make it consistent. I got the idea from the same peen marks on the case neck of 7.62x25 rounds. I assume it was to make the sub machine gun the round was made for more reliable. Does some one make a die to make these peen marks? Edit: I am not using the expander die |
Actually, the brown goo they use to seal the neck increases bullet pull substantially. Just try to pull one of those bullets. You'll be smacking that hammer for hours or your collet will mangle the bullet in the process. Unsealed bullets come out with ease. |
Powdered rosin works just as well and is less messy. That stuff used in military ammo is asphalt. Rosin is well known as a friction enhancer for things like barrel vises. |
As noted, the stuff is a form of liquid asphalt. With age, it does stiffen up and increase difficulty of pulling the bullet. However, that is more-or-less an unintended consequence. If the sealer alone was sufficient, the mil would not go to the expense of crimping. If you have an asphalt-sealed, uncrimped bullet that you want to remove, just set up your press so the bullet-seating die just nudges the bullet inwards a little bit. This will break the seal of the asphalt, and allow the bullet to be removed MUCH more easily. If you're using a collet-type puller, this trick will reduce the collet-induced marks on the bullet. If using an impact (inertia)-type, this procedure makes smacking the bullet out possible, period. Side note on inertia-type pullers--the hammer style: always smack them on the END grain of a piece of 4+4 lumber. Doing so greatly lessens the chance of the thing shattering and possibly injuring the user. Also, but a little bit of foam in the receptacle where the bullet will impact once it comes loose. This lessens the chance of the bullet being damaged, expecially soft lead and hollow-point types. As for crimped, sealed bullets, it is probably best to just use a good collet-type puller, and adjust for minimal bullet damage. |
What kind and brand of rosin and how do I apply it. |
If you have a rosin bag, 5 minutes in clean tumbler with the bag an bullets is plenty. As an alternative, dissolve about 50 grains of musical instrument rosin in 2 ounces of denatured alcohol and dip the bullet bases in it. Let dry before seating bullets. Use this only on once-fired cases as very clean brass is already "sticky" enough. Once fired cases have enough oxidation to prevent cold welding. It will also work with moly coated bullets to increase neck tension. Don't overdo it as it will be invisible to the naked eye. |
Get a LEE Facory Crimp Die. They will make you one as explained in an earlier post. Also, if you're determined to "seal" the bullets, you can use fingernail polish on them. Dip the bullet in the polish, let the excess run off and seat as usual. |
If you have carbon fouling inbetween the case neck and the bullet shank, you will never arrest bullet movement. Squeezing the neck against the bullet will only damage the bullet. The last guy who did a neck tension test using the FCD used new brass with soft necks. Realistically, brass fired several times with work-hardened necks does not submit to severe crimping. |
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