Sniper & Sharpshooter Forums banner

1 - 9 of 9 Posts

·
Registered
Joined
·
109 Posts
Discussion Starter #1
I don't happen to have Sierras latest manual, and my others don't list the load, so can somebody tell me what the max is for a .308 175 grain Sierra MatchKing over Alliant Reloader-15?
 

·
Registered
Joined
·
109 Posts
Discussion Starter #2
Ok, I called Alliant and got the specs from them for the above combo. 35.8 to 41.3 grains (for a max velocity of 2500 fps).

Here's the rub. My LTR only gets 2480 from it's 20 inch tube with a 42 grain load I tried yesterday (which is certianly in accordance with the Sierra manual), and Alliant lists as much as 44 grains for a 180 grain Speer bullet.

A very common handloading predicament (but one I've never been faced with in 30 years of precision shooting), because I want to get 2580 out of that tube. I have internet friends who insist that they have no pressure signs with a 44 grain load under the sierra 175 grain bullet.

What to do!

I'll kick up the load to 43 and see how the primer looks.
 

·
Registered
Joined
·
1,118 Posts
ive mentioned this is a few other posts, i usually work up by .1 of a grain until i see things start to screw up. Then back off until just before it started happening.

A good way is to measure case length. Mic your cases after you fire em, the moment the web diameter stops stretching, as long as the primer looks fine, use that load.

lemme explain. So if you fire up a bunch of reloads,, ranging from 42.0 to 44 in .1 grain increments. Brand new cases measure (for the sake of argument) .465" at the web. Your starting load gives a fired web diameter of .466." You up the charge a grain, and the web diameter shows just a slight increase. You go up another grain or two, and the web diameter is now .467. Note that I am not talking here about tenths of a thousandth, but rather thousandths that you can readily measure with any decent caliper...... even some of the cheap plastic ones.

f you will very carefully watch the appearance of the SURFACE FINISH of the primers as you go, this will also tell you alot. Note that I did not say flattening of primers..... Flattening of primers is useless as an indicator of pressure. It can be utterly, totally misleading, since much of the flattening has to do with headspace, not pressure. This is another subject. Forget everything you thought you knew about large rifle primer flattening as an indicator of maximum allowable pressure in Contenders.

Ok, you increase the charge another couple grains, and your fired web diameters are now up to .468." Another grain increase, no change in diameter. One more grain, and still no increase in diameter. Gun still opens ok, and you try one more grain. Still no change in diameter.

Go back to the load that gave you the diameter before changes stopped occurring, and call it max.

What happened? The pressure finally exceeded the elasticity of the brass, and further growth of the case was stopped by the diameter of the chamber.

If you watched the primer surface finish very carefully, and I might add even perhaps using a magnifying glass, you should have noticed the primers going from shiny smooth to showing the texture of the breech face imprinted on the primer. When you first get this "signature" of the breech face on the face of the primers, you are within about 5% of max.

Hope this helps.
 

·
Registered
Joined
·
109 Posts
Discussion Starter #4
Hmmm.

I am not a fan of the occasionally touted idea of using web or case head expansion as an indicator for excessive pressure for several reasons.

First, new cases will almost always result in greater expansion than subsequent firings in the same case, at the same pressure. In other words, due to work-hardening of the brass it will take more pressure to expand the case head a similar degree. The techs at Speer discovered this and described the problem in their manual #13 (pages 53 and 54).

Secondly, the manufacturing lots of brass and the alloys therein are inconsistant and, in the opinions of many, the level of expansion shouldn't be relied upon to provide consistant indications (even with the best measuring tool for this technique, a blade-micrometer). When the indications are measured in a miniscule 10,000's of an inch, lot-variations of alloy is a big problem.

In my opinion, lacking a copper-crusher fixure or a piezo-electric stress gage, accurately measuring chamber pressure is a crap-shoot (pun intended).

I agree that the one fair indicator is fired primer ingraving, but ONLY if the cases are of uniform dimensions regarding flash-hole and primer pockets (naturally, I uniform both in my brass with Sinclair tools) and the SAME manufactured lot of primers are used. Bolt handle lift resistance is a good indication, but only when pressures have already reached VERY high levels.

Anyway, yep, they seemed fine today and 43 grains have given me 2550 fps, which is close enough for my purposes.

Thanks for the help!
 

·
Registered
Joined
·
76 Posts
Max Presure

I have to agree with Spade Here, he is talking about testing NEW cases not reloading old cases, but he starts out talking in .1=1/10th grains increments and winds up talking about 1 grain increments and I would not load for max in 1 grain increments.
Making sure that you use the same lot number for your primers and brass is also just as important so combine ideas and lets go to the range LOL

Rusty
 

·
Registered
Joined
·
1,118 Posts
lol was just trying to simplify the progression, i thought it was understood there was a progression up to that point.

LOL yeah dont load for max 1 grain at a time.
 

·
Registered
Joined
·
76 Posts
Reloading Point

Spade: I could probably have explained myself better, I have read a number of tips and hints from you about reloading and knew what you were talking and knew that you knew what you were talking about but some of the other folks that are new to reloading might have tried to take what you said litterally, I will try to make myself clearer in the future----- tried to misdirect everyone to the wrong month G&A Mag. article the other day!!??
I do not have ALTZHIEMERS I HAVE SOME-TIMERZ DISEASE
RUSTY
 

·
Registered
Joined
·
1,118 Posts
lol no prob, i should probably try and be more deliberate with my posts. I do it alot too... type **** and the read it again later and dont knwo why i typed it.
 

·
Registered
Joined
·
109 Posts
Discussion Starter #9
1 - 9 of 9 Posts
Top