re-chambering same round

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re-chambering same round

Postby randazzo87 » Wed Dec 27, 2017 10:47 pm

hello all
I recently purchased a 450 bushmaster in a ar15 platform rifle for deer hunting. I have noticed even with factory loads while loading and unloading the same bullet the case over all length would grow each time. I purchased the lee 4 die set and tried to adjust using the lee factory crimp die with same result. Im new to reloading the 450bm and looking to get some input. I have read that some use light amount liquid cement un case mouth but im nervous of raising pressures. Any help would be appreciated
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Re: re-chambering same round

Postby Texas Sheepdawg » Thu Dec 28, 2017 8:03 am

Welcome to the forum.
Yeah, there tends to be bullet jump on the ARs when chambering. Not sure if Hornady has changed their crimp or what, but I honestly don’t remember having this many reports of it up until this last year.
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Re: re-chambering same round

Postby Hoot » Thu Dec 28, 2017 8:26 am

Welcome Aboard OM!
If you're cycling your action to work it in, you're better off using proofing dummies than live ammo. That having been said, to my knowledge, no one makes 450b proofing dummies. For reloaders, that's easily overcome at the expense of a few cases and bullets. The heavier the bullet you're using, the worse the tendency to pull from a full bolt drop, so if you're making some proofing dummies, use the 200gr FTX and crimp them into the cannelure pretty firmly. Otherwise, super glue them in. Its not like you're going to shoot them with dead or no primers. The use of sealing adhesives, to enhance neck tension has come up around here before. Getting every round to adhere to the same consistency with adhesive is no less unpredictable than relying on a crimp. That and no one wants to be the guinea pig. ;)

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Re: re-chambering same round

Postby earlwb » Thu Dec 28, 2017 8:59 am

yeah I noticed that problem when I made up some dummy rounds to test my magazines with. The big heavy bullets will work their way out of the case if you slam them home a few times. At least up until the bullet reaches the rifling in the barrel though. The basic simple solution is don't load the same round too many times in the gun. Rotate them to help prevent the bullet creep. Use dummy rounds for testing. Also having a reloading setup is good as you can reseat the bullet back to its COL in the case if you get too much bullet creep. There is a point where the cartridge length grows too much and the round won't fit in the magazine too.

There are some topics in the forum on making and using a side crimper tool. That should help alleviate the problem, but it still doesn't cure it. as it will still happen anyway.

If you aren't into reloading, you don't have to buy a full expensive reloading setup unless you want to though. You can get a Lee Handloader press for $29. The Lee reloading dies go for around $30 too. Then you can reseat the cartridges back to the proper overall length as needed. But if you are careful you could use a table vice to carefully push the bullet back into the case slightly too.
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Re: re-chambering same round

Postby plant_one » Thu Dec 28, 2017 10:32 am

repeated chambering is a valid concern in several firearm types, often for different reasons, but still valid none the less.

in an ar you dont want to load any round too many times under full bolt drop - even in calibers where bullet movement isnt an issue - due to the floating firing pin dimpling the primer over an over. its not usually an issue for a few strikes (4-6) but eventually you will get a slam fire if you do it enough.


for those of us with uppers that have a forward assist, you can mitigate this issue by riding the bolt down with the charging handle slowly and then bumping the last couple clicks to cam the bolt into the lugs with the forward assist. as an added bonus, if you do this right, you can do it very quietly when you sneak into your stand in the morning.


for those with semi-auto pistols, the opposite can happen as we see with our big fat bulelts in the 450 bushmaster, that being bullet setback. as the bullet nose rides up the feed ramp, over time the crimp will fail and the bullet will start to move back into the case. This can lead to a pressure spike if it gets enough setback.

Like with my AR - i rarely will chamber a round more than 4 or 5 times in any of my semi auto's before i cycle it to the bottom of the mag, or put it in the training ammo bin.
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Re: re-chambering same round

Postby randazzo87 » Thu Dec 28, 2017 11:33 am

Thank you to everyone, a lot of info learned. I previously loaded 5 dummy rounds and was cycling through firearm. I was just shocked on how the bullet was being pushed from full bolt drop. I have never ran into this situation before. My upper does have forward assist and it makes a lot of sense to soft slam the bolt and use the assist. I'm going to give that a try and see how much the bullet pulls. Now as far as the lee factory crimp die goes. How much crimp do I need? I'm loading hornady 250gr ftx bullets once my pick up some lil gun powder. Also so I'm guessing that lightly applying glue to case mouth probably wouldnt be a go idea then?
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Re: re-chambering same round

Postby plant_one » Thu Dec 28, 2017 11:55 am

most of us are crimping so that the case mouth is 0.474" - 0.475"

get as close to the case mouth as you can without falling off the edge for the measurement.


and yes, applying glue is probably not the best idea LOL




if you need a good sealer for waterproofing concerns, you can lightly apply some sally hansons hard as nails (clear nailpolish top coat) around the mouth of the case after you're done loading it up. you can also seal primers this way too. my uncle tipped me off to this as he's been doing it to hunting ammo for decades.

dont get carried away, you're not trying to paint the round with it. a little dab will do ya and all that.

cutting half (or more) of the bristles off the brush will help keep the application amount to the bare minimum needed. take a few bristles off at a time until you get the brush size right.

i also use the stuff for head cement to keep thread from coming unwound when tying flies, so i can confirm that it is in fact very water resistant. several commercial tiers i've spoke with about it, its all they use as their customers (fly shops) ask for it by name - and several insist on it because of its durability.
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Re: re-chambering same round

Postby Hoot » Thu Dec 28, 2017 1:41 pm

randazzo87 wrote:...snip... Also so I'm guessing that lightly applying glue to case mouth probably wouldnt be a go idea then?


2nd world NATO manufacturers for many years used a bituminous product to seal the bullets and primers. Essentially some kind of tar dissolved in a solvent. Surprisingly, it didn't build up in the leade. When I was restoring Cold War era semi-autos, I burned through my share of Indian and Argentinian 7.62x51 sealed with the stuff. Must have burned off. The bullets sealed with the it were a mofo to pull!

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Re: re-chambering same round

Postby earlwb » Thu Dec 28, 2017 8:43 pm

You would be amazed at how easy most of the large caliber ammunition is to pull the bullets using an inertial bullet puller. Other big bore calibers have the same problem too. It does tend to be unique to the semi-autos in this respect when the cartridge is slammed home fast and then has that sudden stop. Just like using an inertial bullet puller on it. Revolvers have the unique characteristic of having the bullets get pulled out from the inertial forces involved in shooting. People have had their revolvers jam up as adjacent bullets get pulled out and stop up the cylinder when firing. That is why you see them using rather robust crimping on the bullets too. The semi-auto pistols have been known to push the bullet deeper into a case when being rammed into the chamber in some cases too. Semi-auto rifles and some lever action and pump action rifles in certain calibers can have it happen to them too.
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Re: re-chambering same round

Postby Jim in Houston » Sun Dec 31, 2017 11:38 am

plant_one wrote: . . . you can lightly apply some sally hansons hard as nails (clear nailpolish top coat) around the mouth of the case "


You can get Sally Hanson's Hard as Nails at Wallgreens, CVS, or your local grocery store in the cosmetics section.
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