newbie needs help AR10 won't chamber

[z7]

I am a long time reader, but just recently joined when i started reloading and ran into a problem recently
my 223 and 40sw are working well, around 100rds each with no problems (plinking ammo for now). the problem i am having is with my 308 setup
loading for a RRA LR8 predator,

before going to the range i read more and saw on conversation on headspace and dies improperly setup, i wanted to verify my rounds would chamber so i took one of my prepped cases that didn't have a primer and i made a dummy round. put it in the magazine, went to chamber the round and it failed to fully chamber. tried to eject it and it was seized pretty tight.
30 mins later i had it out, there are scratches along the body of the case starting around the upper 3rd of the main body and continuing down towards the case head.
i tried re-sizing a few pieces of brass, rotating 180 and then running it through the die again but didn't have any more luck. i measured a few Winchester factory rounds around the case head against my re sized brass and i am about 5 thousands larger at around the case head.
i am yet to fire the rifle, but it chambers factory ammo, so I am blaming my hand loads.
i believe the cases are oversized given the markings, but i realize I may have a headspace issue as well. when i set up the fl sizing die i touch the shell holder +1/4 turn or until it cams over with no light showing between the shell holder and die.
my plan to try and correct this issue is to get a rcbs small base die and a wilson head space gauge. do you all have any suggestions or other wisdom that would help me and or save me $. am i doing something wrong?


hornady single stage press
lee pacesetter dies.
once fired lc brass (in a 240mg, i picked it up from underneath the gun)

Process.
tumble with corn cob
lube with hornady spay lube, following instructions
resize again following instructions,
remove primer crimp
clean primer pockets,
trim with le wilson trimmer, 2.005"
chamfer, debur,
milk jug of soapy water to remove any grime, rinse and air dry
prime
20 rds loaded with 8208 xbr and 165g sgk hpbt and a light crimp

i gained most of my diagnosis from this thread and whatever else the google machine turned up, sorry if i brought up a question that has already been fully answered.

 

[cfullgraf]

once fired lc brass (in a 240mg, i picked it up from underneath the gun)

Cases fired in a machine gun, that is probably your problem.

I would try a small base die.

Machine gun chambers are generous in size and cases do not spring back enough for a standard resizie die to fully resize the body down near the base.

A case gauge can be helpful in insuring that you reset the shoulder to the proper length but it will not tell you anything about the body diameter of the case.

Hope this helps.

 

[Reloadron]

I agree with Chuck as to the possibility you may have gotten once fired machine gun brass. The small base dies and case gauge are a good way to go. For the time being this drawing of a 308 Winchester case may be of some help. The drawings show the MAXIMUM CARTRIDGE / MINIMUM CHAMBER specifications. You should be able to use your caliper and get some basic measurements and see how your cases size up.

Ron

 

[z7]

Thanks for the help. I will eventually get my reloading stuff all purchased. Every week I discover something else I need.

Is the lake city brass always a pain to resize or only that first time? I have a decent source of free brass, a few hundred a year but its all 240 shot.

 

[Poper]

Machine gun fired brass is always a pain, or at least has been in my experience. You may be able to squish 'em back small enough to chamber in your gun with a small base die. Maybe. Then again, maybe not. If you do try a small base die, be sure to use Imperial Sizing Wax to be sure you do not stick a case in the die.

I hope this helps.

Poper

 

[cfullgraf]

Once cases have been fired in your rifle, it can be resized with a standard resize die and it will still work fine in your rifle.

A small base resizing die should resize the cases just fine with no more effort than the standard die.

My M1A does not like once fired machine gun cases unless I small base size them. I just keep using the small base sizer all the time out of convenience. Your cases will fail, or be lost, for other reasons before failing due to any excess working of the case body due to the small base dies.

Some folks small base size the initial time then use a standard die after subsequent firings in their rifle.

If you start with factory ammunition or cases fired in a rifle as opposed to a machine gun, standard resizing dies should be work just fine.

Lake City cases are good quality cases, being fired in a machine gun makes them a pain.

Hope this helps.

 

[mtrmn]

I buy a lot of once-fired brass and use small base dies exclusively for both 223 and 308. I've never once noticed any ill effects from using SB dies. The SB dies, if I understand it correctly, simply size farther down the body of the case than the standard dies. I own several AR-types, and 2 of them demand the use of SB dies for 100% reliability.

The Wilson case gage will check the headspace length and overall case length. Any oversize dimension on the BODY of the case will not be detected.
JP Enterprises makes some case gages in 223 and 308 that DO check every outside dimension of your brass. They are made with chamber reamers rather than simply drilled to a specific depth, so the interior walls are tapered just like your chamber. I bought mine from Brownells. All my loaded rounds drop in one of these gages before final storage.
http://www.jprifles.com/1.5.1.2_maint.php

I'm not saying YOU need this stuff, just telling you MY process. YMMV

 

[Robert101]

I would also try to resize one or two of the brass, separate the rifle (upper from lower), and try to insert the brass case into the chamber. Does it slide in without resistance? My 308 chamber is of moderate width (not too tight and not too loose). Typical Lee Sizing Dies work fine for me. Your chamber might just be on the tight side, so as previously mentioned, require you to full length to minimal cartridge dimensions.

 

[W.E.G.]

If you are not using a CASE GAGE to measure your finished product, you are doing it wrong.