.308 Win. Load development

[ADIDAS69]

CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.

So I posted a couple days ago about some awesome results I achieved with my CZ452 chambered in 7.62X39. Yesterday I went through he same testing for my M24. I thought I would post some pictures and a minor warning about expensive rifles. Technically the milspec for a rifle to be designated an M24 demands that it shoot .35 MOA for a specified number of fired cartridges. The rifle did fine and I wasn't using the milspec machine rest nor the powder primer and projectiles but I will admit to some disappointment as my $4K worth of rifle kit and my $0.8K worth of rifle kit performed near identically.

On the plus side the M24 should carry out to a few more yards than the Russian round. Also the incomplete polygons and triangles drawn on the groups were my 4 yr old's idea. the hand writing is however mine.

[ADIDAS69]

bullet is the Nosler 190 hpbt custom competition trimmed and repointed
the powder is H414
primer is CCI large rifle

I included the 46.2 to illustrate just how big a difference .8 grains can make.

[Wayneinky]

I love my CZ452. It shoots .22 LR very well. It must have been a lot of work to chamber yours to 7.62x39.

[Metal god]

If you really want to feel better about those groups you might want to measure them from “center” to center rather then edge to edge as the rest of us do

[ADIDAS69]

Sorry I got my numbers switched my 527 is the 7.62 I also have a 452 with the 28” barrel.

[ADIDAS69]

Yeah the only thing these groups really have over the 7.62X39 is that these are five shot or seven shot groups and the former is a 3 shot group.

[RC20]

5 shots is better indicator, 10 better yet.

Me I am happy with 5 good ones, but I will venture into the 7 area when I have a few extra rounds left.

[cw308]

I'm shooting 308 200 yards , I'm loading on the low side IMR 4064 40.8 grains under a Sierra 168 MK bullet . average 1/2 " 6 five shot groups. Rem 700 M24 5R Rock Creek Barrel 11.27 twist , just love shooting the rifle . This week I'm changing to 3 ten shot groups , hope for nice weather .

[ADIDAS69]

I’ve been shooting 190s cause during the famine I managed to stockpile about 2000 projectiles being distributed amongst my .308 30-06 and 300 Win Mag I’ve also ended up with a boat load of H414. Once I’ve burned all this mess I’m going to upgrade to turned projectiles Vihtavori powder and lapua brass. At present these groups were achieved with a mix of Aguila and IMI brass which maybe makes these groups all the more impressive.

[cw308]

ADIDAS69
Are you full or neck sizing ? I neck sized but found full sizing to .001 case headspace worked much better. I get my brass form a shooting friend that doesn't reload , HSM , ADI & FC all three brass brands the brass is thicker then most , allowed me to keep the charge lower & still fill the case to the base of the neck.

[ADIDAS69]

Shells are full length resized using an RCBS small base die. They’re trimmed to 0.001” shy of saami. They’re also annealed every time. I also reload from and for an AR10 and the small base die makes a difference. I’m not going to spend the time to separating brass by gun till I’ve started the afore mentioned craziness re lapua brass and turned projectiles.

[cw308]

ADIDAS69
Never used a small base die , I'm shooting a bolt action . the trim size for the 308 is 2.005 to 2.015 , I trim to 2.010 every firing . What are you sizing your brass , for a bolt .001 but for a semi . 002 - 3 no more . I haven't tried your powders , have used Varget & RL15 , my rifle didn't like Varget , IMR 4064 & RL15 shot best .My favorite is 4064. Your twist is most likely faster then mine . That changes things a bit.

[Metal god]

the trim size for the 308 is 1.2005 to 1.2015 ,

err wait what ??? that isn't much longer then a 45acp case .

I had to use a small base die for the first time on a batch of once fired LC-14 cases I bought . I kept getting slight resistance when closing the bolt no matter how far I bumped the shoulders back . Turned out my standard die was not able to size them down enough by .0015 right around where you might get case head separation . Bought a small base die for that lot of cases ( 1000 pieces ) and they've been gtg .

[cw308]

Metal god
Thanks for picking up on my screw up , I'll correct my numbers . that sure would be a lot of trimming , would have looked more like a 40.

Metal god
Never had to use a small base die . I size with the RCBS standard die , never had that problem . Does the problem only happen with semi fired rounds? I can't picture what happens , is it the die can't bottom on the shell holder? Most dies over size the brass.

[ADIDAS69]

The problem mostly occurs when going from rifle to rifle with the same brass. Meaning that if I give you brass from either my bolt gun or AR10 there is a likelihood that neither will chamber perfectly in yours. The problem is more likely to occur coming from semi auto rifles and even more likely from full autos. No mater what gun you use there is a slight bulge generated near the head of the case. The standard full length resizing dies don’t actually contact and or reduce those bulges.

[ADIDAS69]

https://youtu.be/7NrKOTFoOrM

[Metal god]

Generally speaking it happens when changing from rifle to rifle . How ever it's most commonly found when using once fired NATO cases that were fired from a full auto machine gun with there generous chambers but still can be found happening in semi auto's as well . Some of those 7.62x51 chambers can be a tad on the larger size which results in the cases expanding larger then usual . This extra expansion can cause a standard FL die to be unable to size the diameter of the body down enough . What appears to happen is the body springs back to much leaving the diameter of the case just a tad to big . Most of the time it's never noticed do to the tolerances built into the chamber and dies . How ever some times you have a chamber on the tighter side and you need a small base die to squeeze those cases down just a bit more in order to fit .

It can happen with bolt guns but you don't see that nearly as much as when buying once fired cases from the military which is what I do .

There's another issue reloaders don't think about when buying those type of cases . Not only were they fired from a chamber allowing them to expand further then normal . Many times the bolt faces are not square to the camber or bore axis . This causes the case to stretch on one side more then the other under pressure to match the alignment of the bolt face . This causes the heads of the case to be out of square to the case body .

How do I know this you ask ? Well I've seen it and have the photos to prove it

Here are some 308 cases that have been fired from my Savage model 10 . Notice they look pretty straight down the line . No necks leaning one way or the other or at least not much .



Now look at these cases I recently bought . These are the cases that needed the small base die . These are leaning all out of whack do to the case heads not being square to the case body .

[cw308]

Thank you guy's . I get my once fired brass from a friend who doesn't reload . Howa & Sako I full size his an they have sized & formed to my chamber without problems , both of his rifles are bolt actions , after your explanations helped me understand small base dies . My dies bottom to the she'll holder , couldn't see how it wouldn't size to fit a chamber , forgetting about spring back from larger chambers or cocked bases from untrued actions.

Luckily I get enough brass from one source & know its once fired from what rifle. Both are very close to mine. Thanks again , Chris

[JeepHammer]

Gotta love friends that give free brass!

[cw308]

For sure.