How many reloads do you get before you have to trim your cases of 300 blkout? What do you trim down to?

Discussion about rifles in 300 AAC BLACKOUT (7.62x35mm), hosted by the creator of the cartridge.

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Biglou62
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How many reloads do you get before you have to trim your cases of 300 blkout? What do you trim down to?

Post by Biglou62 » Fri Mar 29, 2019 4:26 am

I'm new to reloading 300blkout. I would like to know how many firings are everyone getting before they have to trim their cases. I just ran through my first 4,000 cases and now this is going to be my first time reloading them. I just formed them and trim them all down to 1.358. So I'm just wondering what to expect on how many reloads I can get without having to trim them again. I'm assuming that I will most likely have to measure a handful after each shooting and reloading session to make an accurate judgement of my own. But I would still like to know what others out there are getting. Thanks for your replies.

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strobro32
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Re: How many reloads do you get before you have to trim your cases of 300 blkout? What do you trim down to?

Post by strobro32 » Fri Mar 29, 2019 6:48 am

Are you loading subs ar HV?
I have never needed to trim the cases. The primer pockets wear out first. HV can ware the primer pockets faster.
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plant.one
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Re: How many reloads do you get before you have to trim your cases of 300 blkout? What do you trim down to?

Post by plant.one » Sat Mar 30, 2019 11:11 am

usually after one firing you shouldnt need to trim... however... you'll have to check them.

case neck growth can vary based on a number of things, including but not limited to your specific load - ie: were they hot or fairly mild? etc




id say if you randomly sample 50 or so after you resize them you should be able to get a rough idea of where you're at as far as case length at this point


hth
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Re: How many reloads do you get before you have to trim your cases of 300 blkout? What do you trim down to?

Post by Sig220 » Sat Mar 30, 2019 11:48 am

I would agree with Plant's post, but my experiences are different... :P I always check brass after each firing by measuring random cases.

I don't trim to 1.358 anymore on newly formed brass. I use 1.362-1.365 now......because I never had brass grow long enough to trim before the primer pockets got loose. If I do have a piece of brass that survives the primer pocket woes I would trim it back to 1.365 I think. As I dont think it will last long enough to grow very long before the pocket is too loose. Once I run across a piece of brass where the primer seems too easy to insert, it gets marked with a black marker and left at the range or wherever it is fired. (I don't recover it!)

Leaving a little extra brass in the neck does not cause any problems for me, but it does allow a little bit more brass to hold the projectile! I only load high velocity loads if that matters to anyone. Not barn burners, but faster then 1500fps :roll: I only shoot my 300BO from a AR as well.

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Re: How many reloads do you get before you have to trim your cases of 300 blkout? What do you trim down to?

Post by Triggerthumb » Sat Mar 30, 2019 7:00 pm

I just joined the forum. I really enjoy shooting and the 300 Blackout is a great round. I have been reloading for about 40 years. I have a Model Seven Remington that is a real tackdriver. I check my cases after each firing, I like to keep them in the1.363 -1.365 range. I don't go through the rounds like a AR platform gun so I'm kind of finicky about each one. 1.363 is the magic number for me.

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Re: How many reloads do you get before you have to trim your cases of 300 blkout? What do you trim down to?

Post by RKB731 » Sun Mar 31, 2019 12:14 pm

I do an initial trim to 1.355”-1.360” and that’s it. I have some 300 Whisper brass that I’ve been shooting for over 13 years that’s never needed trimming.
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