Crimp or no crimp for precision 300 blk?

[Odysseus1911]

Here's what I will be loading:
Speer TNT 125,
H110,
CCI BR-4,
Starline 300 blk brass

My reloading setup:
Dillion 550B with UniqueTek clamped, CNC-machined toolhead,
Lee full length sizing die,
Forster Ultra Micrometer seater,
Lee Factory Crimp Die
K&M controlled depth taper reamer to chamfer case necks


They will be fired from an AR-15 that is set up for precision and has a Bartlein cut-rifled 1:8 twist barrel chambered by Craddock Precision. I do not want any risk of bullet set back with recoil, but I don't want to sacrifice any accuracy, either. From reading another thread on here, the consensus seems to be that even for semi-auto, nobody crimps any more -especially with non-cannelured bullets, and the bullets I'm using do not have a cannelure. So if crimping is unnecessary, and may hurt accuracy, should I get some other types of dies to set neck tension? I've reloaded for years, but only for 45 acp.

 

[Choid]

I crimp for semi autos. Don't see a downside to it. I also use a 550 with a factory crimp die. Just a light crimp, not anything extreme.

 

[Skg_Mre_Lght]

I don't crimp for anything but pistols and big bore revolver rounds. No need to, and crimping doesn't help for accuracy. I don't even crimp for any of my gas guns, no need.

 

[db2000]

Never crimped blackout in a gas gun, sub or super. Never had an issue. There’s another recent thread and the vast majority of people that chimed in all said the same thing.

 

[Odysseus1911]

Ok, so if I don't crimp, what would be the ideal setup to set neck tension?

 

[TheOfficeT-Rex]

Ok, so if I don't crimp, what would be the ideal setup to set neck tension?

Is your lee FL die not giving you enough to not experience bullet setback?

Other methods include bushing dies and expanding with a mandrel - And its a separate argument over which is better or if they should both be used...

 

[Odysseus1911]

Is your lee FL die not giving you enough to not experience bullet setback?

Other methods include bushing dies and expanding with a mandrel - And its a separate argument over which is better or if they should both be used...

Don't know, I haven't started to load rounds yet. Just making sure I've got all the right stuff before I start load development. If I don't NEED to crimp and it can possibly have a negative effect on accuracy, then I'm not going to.

If I want to go the mandrel route, what all do I need? Is the mandrel incorporated into the full length sizer, or is it a separate step?

 

[spife7980]

I wouldnt crimp until you find a reason that you think you need to, for yourself.

Mandrel sizing is its own thing, dont worry about it yet. Just use your normal full length die to learn the ropes.

 

[TheOfficeT-Rex]

Don't know, I haven't started to load rounds yet. Just making sure I've got all the right stuff before I start load development. If I don't NEED to crimp and it can possibly have a negative effect on accuracy, then I'm not going to.

Start with just the FL die, right out of the box. Get used to loading bottleneck cases a few times, then you can add crimp to see if it makes a difference for you.

Most guys use it to stop bullet set back - where rounds in the magazine grow longer under recoil; unlike in pistol or straight wall, where you're trying to take out the flare from bullet seating.

I wouldnt crimp until you find a reason that you think you need to, for yourself.

Mandrel sizing is its own thing, dont worry about it yet. Just use your normal full length die to learn the ropes.

^^^This. On both counts.

 

[LastShot300]

I crimp for semi autos. Don't see a downside to it. I also use a 550 with a factory crimp die. Just a light crimp, not anything extreme.

+1

I also crimp for bolt actions and never experienced any detriment in accuracy, ever

 

[db2000]

Ok, so if I don't crimp, what would be the ideal setup to set neck tension?

There’s several threads to search on here but this is one I was reviewing earlier. A lot of good information. I’d ask though..what rifle are you using? Accurate 1680 Blackout powder is small, ball powder. It throws through your hopper very easily and consistently. If you’re shooting/reloading a lot of rounds you can skip all the neck tension business and just FL resize/decap, prime and load powder. I don’t weigh every charge once I’ve got it dialed in...say after 10 or so. I check every 20-30 and they’re money. Also shooting sub a lot and not supersonic for sub MOA accuracy.

Bushing vs. Expander Mandrel For Obtaining Neck Tension

So I know "neck tension" can be a hot debate, but I was wondering if anyone could shed some light on using a bushing vs. an expander mandrel for obtaining a desired amount of neck tension. Right now I run all of my new brass threw a 0.263" expander mandrel (shooting 6.5 creedmoor) to obtain...

www.snipershide.com