Hello again every one. I've been reloading for my 308 for a bit now and have mostly used Winchester brass for my 700p. I picked up some LC brass from the store and loaded some up. I noticed that even after full length sizing my bolt closes much harder on the LC brass. The reloads shot ok so I resized and reloaded them again thinking maybe I didn't size them fully or my die needed some adjustment or some thing. went through die setup and checked all that out. they plunk right into the headspace gage they looked good! so I then chambered some in my rifle and same thing, took a bit of force to close the bolt. they extract fine before and after firing. With the Winchester brass I can run my bolt with just my thumb and fore finger. With the lc brass I need to grip the stock and use 3 fingers with some force to close the bolt. Any ideas in the difference between the 2? obviously one is 308 win and one is 762 but run through the same die and trimmed to the same length... should be same \ same right?
308win brass vs 7.62
- Thread starter 308Loader
- Start date
The LC brass actually is a bit stiffer than commercial brass usually is harder and tougher than most civilian brass. Weigh them empty and deprimed, side-by-side, and you'll see the extra brass weight reflected. They typically need a grain or so less powder than the lightest commercial cases to reach the same peak pressure, but aren't that different from the heaviest commercial cases.
But none of that explains what you describe. If you are reading the chamber gauge correctly, can you see if the reading is shorter for the commercial cases than it is for your LC cases? If so, that likely explains it. Something near the long end of the gage range (the head sticking up near flush with the top of the step at its back end) will have some interference with closing in chamber. The dimensions are such that the room for it to expand as you squeeze with the bolt will still allow you to shoot the gun.
But none of that explains what you describe. If you are reading the chamber gauge correctly, can you see if the reading is shorter for the commercial cases than it is for your LC cases? If so, that likely explains it. Something near the long end of the gage range (the head sticking up near flush with the top of the step at its back end) will have some interference with closing in chamber. The dimensions are such that the room for it to expand as you squeeze with the bolt will still allow you to shoot the gun.
Your gauge will only show length from the shoulder not width of the cases. If your rifle is a 308 instead of a 7.62 NATO your chamber may have been cut closer to specs. for the commercial round than that of the military round. You may need to get a Small Base Resizing Die to insure that the bottom of the case gets put into spec.
Re-size a case and use your rifle to test the re-sized case without any bullet in it. If it closes without any problems, then it might be a OAL issue and not one for the case, if however, without the bullet in the case, you still get the same problem then you will need to get a Small Base Re-sizing Die.
Good luck and stay safe.
Jim
Re-size a case and use your rifle to test the re-sized case without any bullet in it. If it closes without any problems, then it might be a OAL issue and not one for the case, if however, without the bullet in the case, you still get the same problem then you will need to get a Small Base Re-sizing Die.
Good luck and stay safe.
Jim
LC brass designed tough and is almost always fired from a machine gun chamber, unless you are buying unfired pulled components or a surplused component overrun. The exception to the rule is brass marked "LR" on the head stamp, which has a decent chance of being fired through a bolt action rifle, but with the adoption of the M110 SASS and the military transition to 300 Win Mag sniper rifles more and more LR brass will be run solely through gas operated rifles. But the LR brass is a different specification now, although it comes in two flavors Mk316 and standard M118 LR. The Mk316 is Federal brass, the LR is LC brass that is manufactured for sniper ammunition.
So the first thing to do with regular once fired LC 7.62 brass is to anneal the neck and shoulder area. Because the brass is tough to begin with this is my first step in brass prep, followed by a FL resize and then a trim.
It isn't that machine gun chambers are oversize, it is that like normal semi-autos the cases are extracted under pressure and violently at that. At home in a footocker I have a machine gun barrel that I scrounged from a dumpster that still has the front half of a cartridge stuck in the chamber.
Jimro
So the first thing to do with regular once fired LC 7.62 brass is to anneal the neck and shoulder area. Because the brass is tough to begin with this is my first step in brass prep, followed by a FL resize and then a trim.
It isn't that machine gun chambers are oversize, it is that like normal semi-autos the cases are extracted under pressure and violently at that. At home in a footocker I have a machine gun barrel that I scrounged from a dumpster that still has the front half of a cartridge stuck in the chamber.
Jimro
A lot of 700's are slightly "short chambered" I have to set my case shoulders back a few thou more to have proper head clearance for mine.
The somewhat harder LC cases WILL chamber harder than most commercial because of this.
I wound up having to dust off .002 from my shellholder, the bolt closes fine now.
I used my surface grinder, but you can use the flat surface/sandpaper trick.
Your cases aren't too long after sizing are they?
OR it could be your die.
The somewhat harder LC cases WILL chamber harder than most commercial because of this.
I wound up having to dust off .002 from my shellholder, the bolt closes fine now.
I used my surface grinder, but you can use the flat surface/sandpaper trick.
Your cases aren't too long after sizing are they?
OR it could be your die.
I don't have a dog in the fight as far as the 308 rifle goes but I do have a Sav.99 in 300 Sav. of which I have converted many a 308 Win. and LC 7.62 NATO brass to 300 Sav.
All the NATO brass was once fired MG brass and over expanded. I resized my NATO brass in two steps using a 06 FL resizing die to size the lower part of the cartridge and base first then ran the partially size case through my Lyman 300 Sav. FL resizing die to reform the neck and shoulder,it was basically impossible without lot of force to resize and reform the NATO case to 300 Sav. in one step. Final step was to trim the cases to the correct length.
Of all the Mil. spec brass the 7.62 NATO cases overall are thicker and have less case volume than the commercial 308 cases. So you should use the correct load data when using those type cases for use in 308 rifles. Externally there is little to no difference in 7.62 NATO and 308 Win as far as case dimensions,it's all internal and how the weapon is chambered.
Some may find it necessary to ream or turn the case necks to accommodate there rifles chamber dimension using the thicker brass. In my Sav. 99 which has a generous chamber I'm able to chamber and shoot cast lead bullets sized to .311" very easily without doing so. Which is pretty much all I ever shoot in the 99 anyways.
On a side note about the internal case dimensions I get around an extra 75 fps. MV using the LC brass over the converted 308 Win. brass with and identical cast bullet and load of which none of my loads are even near max pressure so it's not an issue.
All the NATO brass was once fired MG brass and over expanded. I resized my NATO brass in two steps using a 06 FL resizing die to size the lower part of the cartridge and base first then ran the partially size case through my Lyman 300 Sav. FL resizing die to reform the neck and shoulder,it was basically impossible without lot of force to resize and reform the NATO case to 300 Sav. in one step. Final step was to trim the cases to the correct length.
Of all the Mil. spec brass the 7.62 NATO cases overall are thicker and have less case volume than the commercial 308 cases. So you should use the correct load data when using those type cases for use in 308 rifles. Externally there is little to no difference in 7.62 NATO and 308 Win as far as case dimensions,it's all internal and how the weapon is chambered.
Some may find it necessary to ream or turn the case necks to accommodate there rifles chamber dimension using the thicker brass. In my Sav. 99 which has a generous chamber I'm able to chamber and shoot cast lead bullets sized to .311" very easily without doing so. Which is pretty much all I ever shoot in the 99 anyways.
On a side note about the internal case dimensions I get around an extra 75 fps. MV using the LC brass over the converted 308 Win. brass with and identical cast bullet and load of which none of my loads are even near max pressure so it's not an issue.
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They look the same in the case gage, below the top cut and above the bottom. They were all trimmed to 2005. I think I might try a sb die and see. Seems to be the most logical answer from what has been posted. I tossed the first 50 I was working with at the range thinking something wasn't right, so I cant measure them. Guess ill ware out my Win brass and save for a sb die set to finish off the rest. A lot of people seem to like the military brass. Is It worth the trouble to reload it for a Win bolt gun? Or is it best used for ar10's and such.
It might be best used for a AR-10 or other 7.62 NATO rifle, but there is nothing wrong with it for a 308 if you can get it sized right. Free brass is free brass and I would not pass it up just because of a little extra work. I have the same issue with 223/5.56 brass and at today's prices for brass, it is well worth it.
Jim
Found an old post from here that pointed to rim thickness. http://thefiringline.com/forums/showthread.php?t=477053
308Loader,
Take a look at the SAAMI drawing. For the case, it matches the military drawing for external dimensions, with the exception that some of the military tolerances are tighter. Mil-spec allows only -0.015" for the case length tolerance, where SAAMI allows -0.020". The SAAMI rim thickness is 0.054" with a tolerance of -0.010", while mil-spec rim thickness is 0.054" with a tolerance of -0.007". SAAMI headspace is 1.634" with -0.007" tolerance, and mil-spec headspace is 1.634" with -0.006" tolerance. The point is, the maximum dimensions are identical and your gun should be made to work with those maximum dimensions from either source.
If you own a caliper, you can certainly make comparative case length measurements to the shoulder, improvised with a spacer, as shown below. Just zero on one case and then measure the other to get the difference. Only the difference matters. Note that without a headspace GO gauge to calibrate to, you can't be sure of what your absolute measurements are. This is due to the radius at the mouth of the spacer and its imprecise diameter.
Take a look at the SAAMI drawing. For the case, it matches the military drawing for external dimensions, with the exception that some of the military tolerances are tighter. Mil-spec allows only -0.015" for the case length tolerance, where SAAMI allows -0.020". The SAAMI rim thickness is 0.054" with a tolerance of -0.010", while mil-spec rim thickness is 0.054" with a tolerance of -0.007". SAAMI headspace is 1.634" with -0.007" tolerance, and mil-spec headspace is 1.634" with -0.006" tolerance. The point is, the maximum dimensions are identical and your gun should be made to work with those maximum dimensions from either source.
If you own a caliper, you can certainly make comparative case length measurements to the shoulder, improvised with a spacer, as shown below. Just zero on one case and then measure the other to get the difference. Only the difference matters. Note that without a headspace GO gauge to calibrate to, you can't be sure of what your absolute measurements are. This is due to the radius at the mouth of the spacer and its imprecise diameter.