Does 300AAC require a heavy crimp?

[MFInc]

I recently loaded 50 rounds of 300AAC. These is the first attempt to load this round. Been doing handgun charges for about 2 years now. Anyways went to the range a few weeks ago to test them. Loaded one, ejected it and checked OAL. it went form 2.005 to 2..013, so I tried another and another, and they all moved. Ovisousley they weren't crimped enough. I re crimped themafter restting OAL today and took to the range. The same thing was happening to all but 2 of the rounds. I measured each one and there is about .007-009' difference between crimp and neck. According to the spec in my rcbs die instructions it's saying that number should be smaller. I'll get some pics of the rounds up here shortly. I hate to be quttier, but i just may abandon 300 blk all together as this is a PITA for me.

 

[W.E.G.]

Who cares if the bullet moved 0.007"?

 

[Walkalong]

.007 isn't enough to worry about unless you chamber them over and over.

That said, neck tension, neck tension, neck tension, with a good crimp into a good cannelure.

 

[EricBu]

I recently loaded 50 rounds of 300AAC. These is the first attempt to load this round. Been doing handgun charges for about 2 years now. Anyways went to the range a few weeks ago to test them. Loaded one, ejected it and checked OAL. it went form 2.005 to 2..013, so I tried another and another, and they all moved. Ovisousley they weren't crimped enough. I re crimped themafter restting OAL today and took to the range. The same thing was happening to all but 2 of the rounds. I measured each one and there is about .007-009' difference between crimp and neck. According to the spec in my rcbs die instructions it's saying that number should be smaller. I'll get some pics of the rounds up here shortly. I hate to be quttier, but i just may abandon 300 blk all together as this is a PITA for me.

New brass? Converted 223 brass? Once fired head stamped 300 BLK brass? One of the biggest issues with 300 BLK is converting 223 brass, and not annealing it. The cut for the conversion is made on the unannealed portion of the brass, and annealing is the key to neck tension. Annealing softens the brass and reduces spring back. Unannealed 300 blk, if you have any neck tension guages, you will see that even when you size it, it springs back to very nearly the unsized point immediately. I've seen some that was so bad, a proper guage literally fell out. That means the only support for that bullet is your crimp. Some will make up for that with a heavy crimp, but that's just covering up the problem (crimping is NOT a replacement for poor neck tension). If you are using actual head stamped 300 BLK, then you could have other issues going on. In the great scheme of things, unless you are using big bullets that are close to the OAL for 300 BLK (basically AR mag length), the issue is if it jumps out enough to hang in the mag......OR it sets back enough to cause higher than anticipated pressure. The other issue with poor neck tension is that if you have a round that does not go all the way into battery (for whatever reason), and you attempt to clear it...depending on the bullet type and weight, it **could** leave the bullet in the chamber, which will require you to rod it out.

One of the worst offenders is folks selling converted brass, who've simply done the trimming and sizing, but did not anneal it (bulk annealing equipment is expensive). Folks buy this converted brass, and then have all kinds of problems and never figure it out. There are soooo many brass peddlers out there selling converted brass like this, it's amazing.

You can bust out a torch, socket, and cordless drill and anneal a couple yourself to test this, super easy to do, and lots of youtube tutorials on "poor man annealing" out there.

 

[Soonerpesek]

They aren’t getting ever so slightly into the lands and moving when you eject them…??
I don’t load that cartridge, so I don’t know what the COAL should be…

 

[MFInc]

New brass? Converted 223 brass? Once fired head stamped 300 BLK brass? One of the biggest issues with 300 BLK is converting 223 brass, and not annealing it. The cut for the conversion is made on the unannealed portion of the brass, and annealing is the key to neck tension. Annealing softens the brass and reduces spring back. Unannealed 300 blk, if you have any neck tension guages, you will see that even when you size it, it springs back to very nearly the unsized point immediately. I've seen some that was so bad, a proper guage literally fell out. That means the only support for that bullet is your crimp. Some will make up for that with a heavy crimp, but that's just covering up the problem (crimping is NOT a replacement for poor neck tension). If you are using actual head stamped 300 BLK, then you could have other issues going on. In the great scheme of things, unless you are using big bullets that are close to the OAL for 300 BLK (basically AR mag length), the issue is if it jumps out enough to hang in the mag......OR it sets back enough to cause higher than anticipated pressure. The other issue with poor neck tension is that if you have a round that does not go all the way into battery (for whatever reason), and you attempt to clear it...depending on the bullet type and weight, it **could** leave the bullet in the chamber, which will require you to rod it out.

One of the worst offenders is folks selling converted brass, who've simply done the trimming and sizing, but did not anneal it (bulk annealing equipment is expensive). Folks buy this converted brass, and then have all kinds of problems and never figure it out. There are soooo many brass peddlers out there selling converted brass like this, it's amazing.

You can bust out a torch, socket, and cordless drill and anneal a couple yourself to test this, super easy to do, and lots of youtube tutorials on "poor man annealing" out there.

Some of it is Converted LC brass, that I got from Ammo depot I think. It was not anealed from what I could tell. Some of the brass is factory 300BLK HS. Ammo inc and Aguilar I believe. both non anealed as well. the two rounds that held and shot were LC converted brass. A few of the bullets have a line on them as inthe pics. Sound sliek i need to aneal the cases. Ididnt think I would have to on factory brass that i am not converting . I'm not really trying to aneal any brass though as these rounds took forver to get done. and they were still wrong.....ugh. ty

 

[MFInc]

Who cares if the bullet moved 0.007"?

Not trying to have one get stuck in the barrel? that's not good....

 

[EricBu]

The ammo inc is jageman, good brass, I'm sure they anneal it ( you can't always tell by looking), aguilar I know nothing about. What are you using as a sizing die? Are you flaring? If using jacketed bullets, especially bt, no need to flare...too much flare can also affect neck tension. Got anything else going on with the ones you shot? Like flat primers?

 

[MFInc]

The ammo inc is jageman, good brass, I'm sure they anneal it ( you can't always tell by looking), aguilar I know nothing about. What are you using as a sizing die? Are you flaring? If using jacketed bullets, especially bt, no need to flare...too much flare can also affect neck tension. Got anything else going on with the ones you shot? Like flat primers?

Yea the AI ammo has a fine polish on it so no telling. I am using an RCBS FL die set for 300 AAC. Did not flare other than what is on the sizing die. I did trim with a WFT and chamfered them, not crazy though. The 2 that shot, those primers are flat and didnt move. I had them loaded with H110 one had 17.2 and the other 17.6 gr's. Bullets are Nosler 130 gr Varmits No Canilure either.

 

[cfullgraf]

I do not crimp my 300 BO ammunition. I make sure I have enough neck tension.

300 BO cases made from once fired 223 Rem/5.56 NATO cases can have varying neck thicknesses. This can affect the amount of neck tension that can be obtained without thinning the neck walls of the case.

In the early days of 300 BO, the main source of cases was once fired 223 Rem/ 5.56 NATO cases. At least today, cases formed from scratch for 300 BO are available.

 

[243winxb]

The fix might be as simple as removing .001" from the expander. But first the Fl dies must be doing its job. Sizing down enough.

Measure neck outside diameter before & after bullet seating. If .002" or less, increase neck tension.

See Neck Tension by Sierra

 

[jmorris]

Does 300AAC require a heavy crimp?​

No, I don’t crimp mine at all.

 

[jmorris]

I am using an RCBS FL die set for 300 AAC. Did not flare other than what is on the sizing die.

If you have a size die that is flaring the case mouth any measurable amount, something is wrong. Rifle or pistol, size dies don’t flare/bell the mouth.

 

[MFInc]

If you have a size die that is flaring the case mouth any measurable amount, something is wrong. Rifle or pistol, size dies don’t flare/bell the mouth.

I may have mis stated, Im just using the sizing die, and not flaring. Perhaps saying the expander was flaring was wrong.

 

[reddog81]

I use converted brass that was never annealed. Bought 1,000 pieces from a vendor on Castboolits.com and have reloaded some of those case probably 20+ times without loosing a single piece due to cracking.

I do use a Lee FCD. It is set to barely touch the brass. Probably 90% of the bullets I use are cast bullets sized to .311, so I do use a separate expander from the sizing die to open the mouth of the case up to .309. This setup has worked well for me.

I am kind of perplexed how cartridge OAL would increase. Is the bullet sticking into the lands of the barrel? Loading into an AR will usually decrease OAL... FWIW .007 isn't much. A burr on the case rim could cause your reading to vary by that much. A human hair measures around .003

 

[n2omike]

I don't crimp 90% of the cartridges that I load... including 300BO. Never an issue. Only ones I crimp are 44 Mag ,50 AE and stuff that gets reloaded into tubular magazines.

If you're shooting Berrys 220 grain plated 300BO bullets with no cannelure, chances are, crimping will do more harm than good.

Good Luck

 

[MFInc]

I don't crimp 90% of the cartridges that I load... including 300BO. Never an issue. Only ones I crimp are 44 Mag ,50 AE and stuff that gets reloaded into tubular magazines.

If you're shooting Berrys 220 grain plated 300BO bullets with no cannelure, chances are, crimping will do more harm than good.

Good Luck

The bullets are 130 gr Speer's no cannelure. Most all of current my bullets dont have a cannelure. But seeing how the bullets came out ugly, I may have another issue causing this. ugh.