bigedp51

If you look at the OPs left and center cases in his photo the base diameter above the extractor groove is much larger than the inside diameter of the sizing die. If these cases were sized with a standard die then a undersize die would make this look much worse. What is the base diameter measurment just above the extractor groove on these cases? If its over .3910 then my guess is the case bulged due to high pressure, or the inside diameter of your die is on the small side.

Make sure you clean the bolt of your SKS, I had one that went full auto. It has a floating firing pin and dirt, a sliver of brass etc and cause it to go full auto. This means compleatly disembling the bolt and removing the firing pin and cleaning.

CHOOSING THE RIGHT PRIMER - A PRIMER ON PRIMERS http://www.sksboards.com/smf/index.php?topic=56422.0 Small Handgun Standard .017" cup thickness CCI 500Federal 100 - Has a soft cup - good to use if hammer strike is light.Federal 100M - Match version of aboveMagtech PR-SPMagtech PR-SPC - Lead-free "Clean Range" primer for indoor ranges etc. Remington 1 ½RWS 4031Winchester WSPWolf/Tula Small Pistol SP #KVB-9 - brass cup - "For Standard Pistol loads"Wolf/Tula Small Pistol #KVB-9SP - "For 9×19 NATO cartridges"Wolf/Tula Small Pistol #KVB-9S - "For Sporting Pistol loads" Small Rifle StandardCCI 400 -thin .020" cup, not recommended for AR15 use by CCI/Speer. Good for .22 Hornet, .30 Carbine. See Note 1 at the bottom of the page NOTE 1: According to Speer/CCI Technical Services - Both the CCI 550 Small Pistol Magnum and CCI 400 Small Rifle primers are identical in size. Both primers use the same cup metal and share the same cup thickness. Both primers use the same primer compound formula and same amount of primer compound. They can be used interchangeably. The image below shows cup thickness, the thicker .025 cups will be harder to set off.

If you use a .310 flat base bullet with a lead core, when fired and kicked in the seat of the pants the bullet should expand and fill the bore. Many old .303 British Enfield rifles had bores as large as .317 and flat base .312 bullets would work just fine.

If you are not loading "HOT" you could try using small pistol magnum primers. For the AR15 it is recommended to use primers with a cup thickness of .025 to help prevent slam fires. "BUT" many reloaders use the CCI 400 primers without ill effect. CHOOSING THE RIGHT PRIMER - A PRIMER ON PRIMERS http://www.sksboards.com/smf/index.php?topic=56422.0 CCI 400 -thin .020" cup, not recommended for AR15 use by CCI/Speer. Good for .22 Hornet, .30 Carbine. See Note 1 at the bottom of the page NOTE 1: According to Speer/CCI Technical Services - Both the CCI 550 Small Pistol Magnum and CCI 400 Small Rifle primers are identical in size. Both primers use the same cup metal and share the same cup thickness. Both primers use the same primer compound formula and same amount of primer compound. They can be used interchangeably.

RGA I got the least neck runout using Forster full length dies, and the Lee collet die were OK but I saw no sense in sizing the case twice. Meaning using a Redding body die and a Lee collet die when I got the same results with the Forster die and sizing the case once. As a side note I got the most neck runout using bushing dies. And I believe this is due to the amount the neck must be reduced in diameter in SAAMI chambers. Bushing dies work best in custom tight neck chambers with neck turned brass. Below the Forster full length dies have a high mounted floating expander. And the case neck is held and centered in the neck of the die when the expander enters the case neck. This means the expander can not pull the neck off center and induce neck runout and the Forster die produces very concentric cases.

Below is for the .308/7.62 and Forster dies, small base dies reduce the case body diameter approimatly .003, and not just the very base of the case. I would not use a bushing die for a AR15 rifle with larger military chambers. The more the neck is reduced in diameter the greater the chance of inducing neck runout. On top of this the Redding bushing die FAQ tells you if the neck thickness varies .002 or more to use a bushing a few thousandths smaller and use the expander to set the inside neck diameter. Read the links below on bushing dies Tech Line & Tips (FAQs) https://www.redding-reloading.com/tech-line-a-tips-faqs Bushing dies work best with custom tight neck chambers with neck turned brass. All my full length Forster dies produce less neck runout than my bushing dies in standard SAAMI chambers. Below just a few of the .223 dies I have used and tested. In the video below by the 6.5 Guys they tell you they get less neck runout with Forster dies vs Redding bushing dies. Save $$ By Using Lake City 5.56x45mm Once-Fired GI Brass http://bulletin.accurateshooter.com/2019/10/save-by-using-lake-city-5-56x45mm-once-fired-gi-brass/ Accuracy Potential of Mil-Surp 5.56×45 Brass So, how accurate can previously-fired GI surplus brass be in a good National Match AR-15? Well, here’s a data point from many years ago that might be of interest. A High Power shooter who wrote for the late Precision Shooting magazine took a Bill Wylde-built AR match rifle to a registered Benchrest match. His first 5-round group ever fired in a BR match was officially measured at 0.231″ at 200 hundred yards. This was fired in front of witnesses, while using a moving target backer that confirmed all five rounds were fired. He recounted that his ammo was loaded progressively with factory 52gr match bullets and a spherical powder using mixed years of LC brass with no special preparation whatsoever. Obviously, this was “exceptional”. However, he had no difficulty obtaining consistent 0.5-0.6 MOA accuracy at 200 yards using LC brass and a generic “practice” load that was not tuned to his rifle.

In a semi-auto rifle the resized case body should be .003 to .005 smaller in diameter than its fired diameter. This allows the case to spring back from the chamber walls and extract reliably. So measure your fired and resized cases to determine if they are being reduced enough in diameter. Dies and chamber vary in size and the amount of brass spring back can vary also. NOTE, I buy bulk once fired Lake City brass and size it the first time with a small base die. Thereafter my standard Forster .223 die works for my AR-15 rifle, BUT a standard die "might" not work for your rifle. Example I have a standard Lee .223 die that will size the case body smaller than my RCBS small base die.

It also looks like the die is "pushing brass" near the base where your red arrow is. Some guesses on the pushing brass, and the ring on the base. 1. Case off center with the die, meaning the case not centered in the shell holder. 2. Check for a bulge if you are using range pickup brass. 3. The brass is too clean and being grabbed by the carbide ring. Try some Hornady one shot on the cases and inside the die. 4. A undersize die will push even more brass because of it smaller diameter.

The vast majority of rifle case gauges do not check case body diameter. Meaning they just check cartridge headspace and case length. Below are a Wilson, Dillon and JP Enterprise .223/5.56 case gauges with the case placed in base first. This shows that the JP Enterprise gauge is smaller in diameter. I use the JP Enterprise after sizing the case and again to check the loaded rounds. Bottom line if the case fits in the JP Enterprize gauge it will chamber in any rifle. I also use a Hornady gauge below to check the cartridge headspace and set the die up for the proper shoulder bump. Another example with .308 gauges, below a "FIRED" Lake City 7.62 case in a Wilson gauge. And now the same "FIRED" case in a JP Enterprise gauge showing its smaller diameter. A resized case should be .003 to .005 smaller in diameter than its fired diameter. This allows the case to spring back from the chamber walls and extract reliably in a semi-auto rifle. And this is the primary reason I use the JP Enterprise gauges to ensure they chamber and extract reliably.

The U.S. Army Marksmanship Unit uses Hornady OneShot a "dry film" lube and it does not need to be removed. Read the link below. Slick Tricks: Techniques and Tools for Big-Batch Case Lubrication https://bulletin.accurateshooter.com/2018/09/slick-tricks-techniques-and-tools-for-big-batch-case-lubrication/ Any type "wet" lubes should be removed because it increases bolt thrust.

The more the case is resized and reloaded the more work hardened the brass becomes. This causes more brass spring back after sizing and less bullet grip. The undersize dies reduce the case diameter more to counteract brass spring back and less bullet grip. Below is a 9mm cartridge sized with a under size die and the case is wasp waisted that increases bullet grip. (this is good) Two things pistol shooters never do, trim their cases and anneal their cases to make the brass softer. So use the under size die and "Get a grip".

CHOOSING THE RIGHT PRIMER - A PRIMER ON PRIMERS http://www.sksboards.com/smf/index.php?topic=56422.0 Small Handgun Standard .017" cup thickness Small Handgun Magnum .017" cup thicknessCCI 550 See Note 1 at the bottom of page NOTE 1: According to Speer/CCI Technical Services - Both the CCI 550 Small Pistol Magnum and CCI 400 Small Rifle primers are identical in size. Both primers use the same cup metal and share the same cup thickness. Both primers use the same primer compound formula and same amount of primer compound. They can be used interchangeably. Small Rifle StandardCCI 400 -thin .020" cup, not recommended for AR15 use by CCI/Speer. Good for .22 Hornet, .30 Carbine. See Note 1 at the bottom of the pageCCI BR4 - match primer with a thicker .025" cup. Federal 205 - Mil-Spec cup thickness according to Federal - okay for 5.56mm. .0225" cup thickness.Federal 205M - same as the 205 but the match version.Magtech PR-SR - .025" cup thickness (not much feedback yet on this new primer as to AR15 suitability but with the same cup thickness as the Rem 7 1/2 it looks good so far) Remington 6 ½ - thin .020" cup, intended for older, lower pressure rounds Remington says do not use for the .223 Rem or other similar pressure rounds. Good for .22 Hornet, .30 Carbine.Remington 7 ½ BR - A match or "bench rest" primer. Lyman & Nosler classify this primer as a Standard. Remington says the compound is the same as the 6 1/2 but with a thicker .025" cup.RWS 4033Winchester WSR - some piercing issues noted when changed from silver to brass cup. Cup thickness is a bit thinner at .021". Most say they are good to go for the AR15 despite that, probably because of the hardness of the cup. Some feel they are less resistant to higher pressures.Wolf/Tula Small Rifle SR #KVB-223 - soft, sensitive copper cup, not recommended for AR15/military rifle use or high pressure rounds.

I buy bulk once fired Lake city brass and size it the first time with a small base die. This brings the cases back to minimum dimentions and be able to be fired in any chamber. Once fired in my AR15 and bolt action rifles I use a standard Forster full length die. Bottom line if you are resizing range pickup brass and reloading for more than rifle then a small base die would be my choice. And if you are reloading for one rifle with cases only fired in your one rifle a standard full length die should be fine.

A type "M" expander allows the bullet to start straight into the case. And if the seater plug does not fit the shape of the bullet it can cause the buller to be pushed into the case at a angle. Redding now makes their expanders the same as the Lyman type "M" expanders.