Mil Brass vs. Comm brass loads .308

[Victory700SS5R]

Newbie here, I am confused, the sierra load manual and speer load manual suggest reducing charge weights by 1 to 1 1/2 grains if using military brass. Have a very large quantity of FA 64 brass from my dad (5000 or so). Anyway, he told me that that reducing the charge is BS. I did not buy that, but using the lighter loads, with 168smk's I'm hitting 6" low at 200 yds, which from what I have read is about 2400 fps at muzzle. Should be 2600 give or take.
Anyway, I weighed some FA 64 brass and came up with an average weight of 184 grains, then weighed Win brass and came up with 164 grains, Federal at 199 grains. The problem is that is about 1 percent difference. But what really got me was that the Fed commercial brass was heavier than the mil brass. So I took this a step further and weighed the .30/06 brass I have, HXP 78 averaged 191 Grains, Remington averaged 200 grains and winchester averaged 186 grains.
So my question, are the load manuals just being cautious for liability reasons ? Because, my loads seem to be not living up to expectation, loading 40 grains of IMR 4064 behind 168smk's and federal 200 primers out of Rem. 700ss5R.

 

[PLeighton]

Re: Mil Brass vs. Comm brass loads .308

Mil brass is thicker and has less case capacity.
Due to this, the chamber pressures run slightly higher.

I know, kind of counter intuitive.
You think that the thicker brass would allow you to run hotter loads, but physics kicks in and trumps intuition...

 

[Victory700SS5R]

Re: Mil Brass vs. Comm brass loads .308

Yeah I understand that, but my friend is using the FA 64 brass in his Remmy and is loading 43.5 grains of Varget behind 168smk's with no signs of pressure. I tried bumping up to the 41.5 grains of IMR 4064 during my work up load and had cratered primers, he shot my loads out of his rifle and did not experience that issue. Could it be the difference with his 1 in 12 twist and my 1 in 11.24 twist ?

 

[PLeighton]

Re: Mil Brass vs. Comm brass loads .308

Could be twist or chamber or difference in bore size.
I've seen nearly identical rifles have pressure problem with one but not the other.

Remember, the manuals provide a safe load for all spec chamberings.
When you start loading close to actual max for an individual rifle everything changes.

 

[Victory700SS5R]

Re: Mil Brass vs. Comm brass loads .308

Thats true. Well, IMR 4064 does not meter well, so I picked up some Ramshot TAC poweder and have loaded 50 rounds from start load in Sierra Manual to Max load in Ramshot Manual in 1/2 grain incraments to see what works. TAC meters very well. My thought is TAC is listed as a slightly faster powder, which from what I've read, the pressures are slightly less than IMR 4064, so out of the 24" barrel maybe I can get the velocity up so I don't have such a lobing trajectory. Since I have all this brass, I can not see buying any for a long time, just have to keep experimenting till I find something that works, the IMR 4064 with 40 Grains and 168smk's shoots awesome at 100 yds, my best 5 shot group measured .439" outside to outside, but my average is around 3/4" outside to outside.

 

[MitchAlsup]

Re: Mil Brass vs. Comm brass loads .308

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Victory5R</div><div class="ubbcode-body">Newbie here, I am confused, the sierra load manual and speer load manual suggest reducing charge weights by 1 to 1 1/2 grains if using military brass. Have a very large quantity of FA 64 brass from my dad (5000 or so). Anyway, he told me that that reducing the charge is BS. </div></div>

{Pedanically}

I agree with your dad, reducing the load is BS*.

{/Pedanically}

However, each case deserves to have a load developed for it and it alone. So, start low, work your way up, and watch for pressure signs on the way up.

In all cases, more accuracy is better than more velocity.

(*) Reducing the load is BS B.E.C.A.U.S.E you should start each load recipie low and work your way up watching for pressure along the journey. You should never assume that a load recipie from one set of components can be transfered to another set of components. Pedanically, that is.

 

[gunsnjeeps]

Re: Mil Brass vs. Comm brass loads .308

Just as Mitch said. Work up the load for the brass and the gun. Your Remington 700 is not the same chamber, bore and twist as the Savage Sierra worked up their loads with. Their Savage is not the same as someone elses Savage. In my AR-15 almost any load shoots 150-200 fps faster than normal. My .308 Garand shoots about average for a gas .308. The point is to work up a load not just pick one. A chronograph will not give you pressure but it will give you a good indication of what's going on with your load, say your first was 2500 not 2400 but the bullet you zeroed was not a 168 Sierra then you bumped up to 41.5 but have a short chamber and were in the rifling so you had a pressure spike and 2700 not 2600. If FGMM w/168's runs at x velocity then you know that you can replicate that velocity with the 168 and set your sizing die by either setting it up with a loaded round or measuring for the same length.

 

[hrt4me]

Re: Mil Brass vs. Comm brass loads .308

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Victory5R</div><div class="ubbcode-body">Well, IMR 4064 does not meter well...</div></div>

That's contrary to my own experience

 

[Victory700SS5R]

Re: Mil Brass vs. Comm brass loads .308

Well once the weather breaks, or at least it gets a little warmer, I will get out and try the TAC loads I made up. Thank you all for the input. I understand that I have to do a work up load for everything. My friend that I shoot with and do some loading with said I should just do another work up load with IMR 4064, he said maybe I had something else out of spec, maybe the C.O.A.L. was too long ? Could be, maybe I just screwed up. Well anyway, this will give me a reason to spend more time in the cave.

 

[Grump]

Re: Mil Brass vs. Comm brass loads .308

You'll never know until you weigh the water capacity.

I have FA63M, M852 LC 86, and something else that are pretty much identical for case capacity, all within .2 grain of water average when weighed.

Hornady brass from Match 155 A-Max loads holds a LOT more water.

FC from various batches ranges all the way from almost identical to the military brass, to holding significantly more. Newer stuff seems military-equivalent, 1980s stuff was much more high-capacity or "roomy".

The most reliable is as-fired from your chamber, but you can still do comparisons and ordinal rankings and probably ratio comparisons if the cases are all sized in the same die.

There is no substitute for measuring what YOU have. What the next guy's got don't mean squat unless you got yours from his same batch.

HIGHLY recommend a chrono. Rule of thumb: if you are getting more speed than the manuals say is the max velocity for your barrel length and that powder, you are probably over spec regardless of absence of voodoo "pressure signs". Lots of reports of false positives, but I'm convinced that there are a huge number of true negatives out there. A lot. Speed will tell you what you need to know long before an boltface artifact on the casehead will.

 

[Victory700SS5R]

Re: Mil Brass vs. Comm brass loads .308

Thank you for the input. I have wanted a Chrony for a while just did not want to spend the cash on it. Probably a good idea. Plus it would be good info to have. My shooting buddy said as long as the loads I work up group well and are below max per the manual who cares if the bullet is going 2400fps or 2600fps. I agree with that, but It as you stated will let me know where we are and also show that maybe the load in the book shows 2400fps, but with my cases, primers and batch of powder I could actually be way over. Well looks like chrony is on top of to get list and new scope got slid down to 2nd on list again. Oh well scope works for now.

 

[Greg Langelius *]

Re: Mil Brass vs. Comm brass loads .308

Mitch is correct. When I weigh for capacity, I use a full charge of the powder I intend to employ. It's just more logical, IMHO.

 

[tomcatfan]

Re: Mil Brass vs. Comm brass loads .308

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Victory5R</div><div class="ubbcode-body">Yeah I understand that, but my friend is using the FA 64 brass in his Remmy and is loading 43.5 grains of Varget behind 168smk's with no signs of pressure. I tried bumping up to the 41.5 grains of IMR 4064 during my work up load and had cratered primers, he shot my loads out of his rifle and did not experience that issue. Could it be the difference with his 1 in 12 twist and my 1 in 11.24 twist ? </div></div>

One point to take into account is that no two rifles are going to be built exactly the same. Each gun will be slightly different. As a result, the manuals have to take that into account so that people don't kill themselves. I have noticed that all of the manuals err on the side of caution. Also just as an FYI 43.5 grns of varget and 41.5 grns of IMR 4064 are two toally different monsters. Varget and 4064 have different burn rates and energy densities.