View Single Post
Old February 14, 2013, 09:21 AM   #3
Senior Member
Join Date: June 22, 2009
Location: South Carolina
Posts: 167
Well yes, no and maybe. Yes, as indicated the "hash marks" were placed on the cases by LC AAP and it was their decision and not by direction of ARRADCOM(Army Armament Research and Devopment Command)
I was involved in that program and the "load" was developed at Picatinny Arsenal and they could not load the ammo as they did not have any 308 dies. I had to bring my personal dies in and they were used to develop the load for the M852. The test tech that directed the loading was Lou Behling who by the way is one of the foremost ammunition experts in the world. The lady tech that did the actual loading was Betty Babbitt as I watched her doing the loading.

No while I have seen hundreds of exspurt opinions on shortened case life, "ruptured" brass etc I am not aware of any case failures directly attributable to the "hash marks" but then again Murphy's Law is in effect.

Now I can see maybe "hash marked" cases failing from firing in big oversize chambers and then reduced back with smallbase dies numerous times but the condition is also found in non "hash marked" cases. I have seen multiple commercial 308 cases develop insipient separation as (1) they are lighter in weight, (2) they are thinner in the "web area" which corresponds to the "hash mark" area. (3) they are smaller in diameter.

Here is why:

1.Commercial cases I have measured in unfired condition .200" up from case rim measure .465" diameter.

2. LC MATCH 7.62 cases I have measured in unfired condition measure .468" diameter.

3. Most all commercial chambers run between .471 and .473 by the drawings but I have seen numerous fired cases measure as much as .475" which means they are fired in oversize chambers which are caused by misaligned reamer in chambering.

Thusly a LC case should only expand a max of .004" on firing but a commercial case can expand .007" and still be "IN SPEC".

My 308 FL dies size from .468" to .469". If you guys would measure the base of your 308 dies and see what the diameter is or mic FL sized cases and see if you come up with something smaller. Please let us know.

I order my reamers with a base dimension of .4685-.469 tolerance thusly when I load 308 be it commercial cases they come out .004" and LC cases come out only .001" larger.

It is well known excessive case sizing "thins" the cases at the web area which corresponds to the "hash mark" area. Thusly we have a definite "maybe" of whether the "hash marks" cause anything.

Now the original M852 had "NOT FOR COMBAT USE" on the boxes because everyone was a lawyer and no one wanted to be blamed for war crimes against humanity and hung at Nuremburg or sent home with a note to his mother.

Next came the 175 Sierra MK which is load designated as M118LR (Long Range) which is the standard sniper issued round for the M24 rifle now which is much more accurate than the M118 match and does better at long range1000-1200 yards than the M852 with the 168 Matchking which was designed as a 300 meter competition bullet and tends to develop yaw after 900 yards.

The "convention" basically says a bullet will not be designed for increased lethality. The 168 nor the 175, 180, 190, 200 gr. Matchkings were designed for lethality. Only for efficient production cost and maximum accuracy. Now the 165 Sierra (we call it the poor man's Matchking) perform well in competition and are less expensive than the MKs) which is a hunting bullet with a larger hole in meplat and does expand and is listed in their catalog as a hunting bullet where they do not recommend the Matchkings for hunting. I would estimate that Sierra bullets are shot by 95% of highpower shooters.

I estimate 99% of my bullets are from Sierra as they have always been excellent performers for me.

Thusly if you have a big chamber or a much bigger chamber it may well shorten brass life for not only M852 but M118 and all commercial cases.

In my experience Federal Match brass is only reloaded two or three times depending on the "feel" of the primer pockets seating new primers. On the third firing I pick up brass and dump it in my reject barrel.

Winchester cases seem to hold up a tad better and good for about five or six loadings before the primer pockets get loose.

About the same for Remington cases.

Haven't shot enough of the Privi Partisan to determine case life yet.

Now if you want case life as indicated you need to have your own custom reamer made. As indicated my base dimension is .4685-.469 and the neck dimension is .339 to .3395. I have never found a M118 round that would not chamber in reamers of these dimensions.

RECOMMENDATION: If you get a custom min dimension reamer have your gunsmith take a 1" section of take off barrel and run your reamer up to about 1/8" below the shoulder. Then turn off other end till you can see exactly where the neck stops on sized cases. You can try every last round in this "gage" to see if there is a interference before loading rifle to give you complete piece of mind. I call it the Hummer GO GAGE, if it goes it shoots, if it doesn't go it doesn't get shot.

The absolute finest brass I have ever loaded is DWM. Followed by LC Match and FA Match though you won't find much of that if any.

Be advised the neck walls on M118 are much thicker than commercial cases and thusly when they are reloaded I set my Marquart turner about .015" and turn off the thickest part of the neck. Neck walls on M118 can vary .005" per the drawing.

For long range 308 I turn necks thinner as I have a reamer that cuts a .337" neck and that requires removing material 360° so loaded rounds are .336" diameter. A normal neck is in the .344" range.

Bottom line is check your chamber for fired case size and see what you have.

Case life of M118 is superb as I can easily get 100 loadings on LC MATCH cases. I also have min dimension reamers for 30.06 and I have one M72 MATCH case LC66 that I have loaded 157 times and it is still waiting for more.
One reason for such enhanced case life is the LC case heads are very hard and don't expand on firing like the softer commercial cases.

If you properly care for your brass and you run tight chambers brass will last for years. Case in point I have one lot of 500 LC63 and LC66 MATCH brass I have shot out two barrels with since 1981. New barrels were chambered with same reamer so previosly loaded rounds went right in and cycled just fine.

On the other hand if you run big chambers, oversize your brass etc you will get the separations identified.
Distinguished Rifleman High Power & Smallbore Prone
President's Hundred (Rifle) US Palma Teams(2)
US Dewar Team (2),4 Man Natl.Champ Team SB Prone
Cert Test Dir. Sm Arms and Ammo,Aberdeen Pr Ground, Firefighter I, AC4HT
Hummer70 is offline  
Page generated in 0.03721 seconds with 7 queries