Subsonic .308 - desired velocity

[Mike K]

First time making ammo and I decided to go with subsonic. Here is what I got:



Ammo specs:
Brass: Federal (once fired from Federal Premium Gold Medal)
Projectile: SMK 175gr
Powder: Trail Boss
Primer: Federal Rifle Magnum (F210M)
OAL: 2.233

Rifle: Remington 700 SPS Tactical (1:12 twist)

Questions... what is an acceptable velocity variance? It looks like 10.4gr of Trail Boss is the one to go with, but why are the other ones not as consistent? Should I explore going with 10.3 and 10.5 grains? I'm just looking to make plinking ammo.

Just looking for any advice before I go through and make a large batch of them.

[YALE]

You should go as heavy as possible with your projectile. Retained energy is everything, if you have to stay subsonic.

[CJ]

That's not enough twist for real heavy .30 cal bullets. That's going to be your limitation.

Ballistics can be a mystery at times. It could be neck tension playing a part. Primers, col, brass, etc. all play a part.

Have these cases been gauged and trimmed?

[Mike K]

That's not enough twist for real heavy .30 cal bullets. That's going to be your limitation.

And that's why I only went with the 175gr bullets. I know I don't have the best twist rate for shooting subsonic.

Ballistics can be a mystery at times. It could be neck tension playing a part. Primers, col, brass, etc. all play a part.

Have these cases been gauged and trimmed?

Neck tension - I used Redding's full length sizing die, but I also have their separate neck sizing die and body die. I just don't have any bushings for the neck die. With these being my first rounds I was going for the KISS philosophy.

I didn't drill the primer holes like many suggest. I just don't know how I am going to mark the cases so I know which brass has the larger flash hole. I feel that any marking on the outside (paint, permanent marker, dye) will come off when I tumble the brass.

[CJ]

Buy a package of assorted sharpie colors. Use them on the seam between the primer pocket and the primer. It won't tumble off.

In order to set your neck tension to a zero across all cases you'll need to anneal. Pick up some templestik. . I'll give you the proper temp to buy. You just need a drill, socket, and a torch. Real easy. But before that try matching cases and trim/sizing. The first question I always ask is if you have a case gauge.

[dee]

Buy a bump gauge and forget just neck sizing. Set up your fl die to bump the shoulders .002 and you'll be golden.

If your brasd is new them you can get a few firings before having to anneal.

As far as your stability goes you can use bergers online stability calculator and find out if you will be ok or not before hitting the range.

[CJ]

Buy a bump gauge and forget just neck sizing. Set up your fl die to bump the shoulders .002 and you'll be golden.

If you're reloading military cases you'll encounter brass out of spec by more than .002 on the shoulder. I find a case gauge to be a lot more accurate for match shooting, getting trim and head space identical on both sides of the same case. Good call on the stability calculators. They do work.

[dee]

If you're reloading military cases you'll encounter brass out of spec by more than .002 on the shoulder. I find a case gauge to be a lot more accurate for match shooting, getting trim and head space identical on both sides of the same case. Good call on the stability calculators. They do work.

The bump should be performed after firing which will form the brass to the chamber so everything should be the same. After that the bump will work the same as any other brass.

[CJ]

The bump should be performed after firing which will form the brass to the chamber so everything should be the same. After that the bump will work the same as any other brass.

Exactly, he'd have to fire form all the cases before that works. Good if you're low volume. I come from a perspective of high volume, where every case is fired from a gun that wasn't my own. Sometimes I forget about other methods.

[Mike K]

The first question I always ask is if you have a case gauge.

Yes, I have the Dillon gauge.

Exactly, he'd have to fire form all the cases before that works. Good if you're low volume. I come from a perspective of high volume, where every case is fired from a gun that wasn't my own. Sometimes I forget about other methods.

All of this brass is once fired from my gun. It is either Federal brass or Lapua (from southwest ammo), but either way it has all been fired from my Remington 700. This is also the only .308 gun I have.

[CJ]

Yes, I have the Dillon gauge.



All of this brass is once fired from my gun. It is either Federal brass or Lapua (from southwest ammo), but either way it has all been fired from my Remington 700. This is also the only .308 gun I have.

Good that's an LE wilson gauge, same ones I use. So you have the trim and the headspace all exactly the same across the cases you're loading?

[dee]

Good that's an LE wilson gauge, same ones I use. So you have the trim and the headspace all exactly the same across the cases you're loading?

X2 , consistency throughout is the key.

[Mike K]

Good that's an LE wilson gauge, same ones I use. So you have the trim and the headspace all exactly the same across the cases you're loading?

I didn't trim any of the cases. They were all shorter than the max recommended case length, so I used them as is and set aside the few that happen to be over. So, there is probably some inconsistencies there.

I just did a search and found this video:


Interesting, I thought you just threw the bullet in there to make sure it would universally fit in any chamber and you were done. However, now that I have seen that video, I just checked my brass and it is within spec.

I do NOT have a headspace gauge set; the only gauges I have are the Hornady overall length gauge and bullet comparator set. Should I invest in something like this: http://www.midwayusa.com/product/479...ith-comparator

[dee]

You can if you want but there are other methods. I use one that is homemade with a case and sharpie. First take a case and split the neck with a saw or dremel so you can insert and remove various bullets. After the case is cut color your desired bullet and seat it long, then chamber it. After you chamber it remove the case and the bullet will have marks from the lands, from there you can adjust to know where they are.

Fwiw you will likely run out of room in the magazine or the bullet won't be in the case before you hit the lands in most factory rifles, especially a 700. This doesn't mean that it won't be accurate just that you will likely have better luck with a tangent ogive type bullet as they are very jump tolerant.

[CJ]

I just watched the video you posted. Yeah he's way too short on the headspace, that's way low, not okay, despite what he said. Sure it will work, but that's too far out of spec. That's the reason he thinks he needs to trim, he's smashed the case so far down he's got a trim issue now. As long as you're between the shelfs you are fine. There's not much room between them.