SW,
Interesting and broad based post. That being said - when you get into precision reloading, there are very distinct processes that are specific to bolt & gas guns.
So, if up front your looking at the GAP10, then specific items on your list are applicable and different ones are more appropriate for a bolt gun.
I would also offer this one word as the hallmark for anything and everything that is remotely connected to precision / accuracy based reloading practices:
CONSISTENCY - write that on the back of your hand, backwards on your forehead - so you can read it in the mirror
and every flat surface on your reloading bench.
Its that important.
- Turning case necks
Don't bother for either - ESPECIALLY a gas gun. Recipe for major problems. For a bolt gun, this is only needed when your chamber has been cut with a custom reamer designed for specific clearance/dimensioned brass... read high end bench/LR guns. Turning necks is a whole other world and it opens up your wallet and drains your time. I turn necks on a custom / precision .308 40X w/ a 20" Krieger. The reamer is a .339 neck. I turn Lapua to .0145" This gives me .002 clearance. It's finicky - I have to keep the rifle /chamber clean and turning the brass is a labor intensive effort. I use K&M turners and a powered collet to spin the brass. Results??? I'd be hard pressed to quantify it other than it shoots under .5 MOA with boring regularity. When I say .5, I mean .5 - like 30 or 40 rounds will go into a group that I can
cover with a quarter (.955 if you're wondering)
Note: Personal rant / pet peeve - all to often you'll see claims that "My M740A6 blah blah blah shoots .5 MOA or .250 MOA all day long...these claims and the trigger pullers themselves are seriously suspect and are generally the product of a one time 3 shot group.
Remember the important word? Will your rifle / ammo & you CONSISTENTLY generate .5 MOA groups day in day out? That is in reality, a rare feat that lives in the stratosphere of custom guns. I've shot .3 or .4" groups with a rack grade M70 in 30-06 with hunting ammo - BUT they were 3 shot groups and I can't even remotely consistently repeat it. Is it a .5moa gun - sure on the internet.....in reality - not a chance.
Rant off.
- Using bench rest primers VS standard primers - experimentation will show results. In a gas gun - don't bother. Too many other variables. I shot NM High Power Service Rifle for nearly 20 yrs. Made High Master shooting across the course 200/300/600yds - I never ever shot BR or Match primers at 600yds - ever. I shot primed LC 556 brass with the standard GI M-41 primer. Guns shot MOA or better - meaning if I did my part and mother nature didn't offer up a big huff n' puff - the ammo rifle me combo could hold the x ring.
Now - different story at 1K - I always used CCI BR primers for that ammo - but we are talking about HIGHLY developed VLD based loads. At 1k a 20fps velocity dip will take you out of the 10 ring. These loads were HIGHLY developed and had velocity extreme spreads (22rds min) of less than 15fps. I rarely lost a point to elevation. SD's ran in the single digits.
CONSISTENCY
- Using competition seating dies over standard dies - ABSOLUTELY. I load on Redding dies almost exclusively - the adjustability / repeatability is gold. This applies to seaters, neck sizers, body dies and bump dies (shoulder HS) Redding stuff is ground / reamed to superb concentricity - using crappy standard dies vs competition ones can be measured in TIR at the contact point on the bullet ogive. Personally on my 1K ammo - nothing over .001 goes in the chamber. .002 is the cull point for 600yd ammo and .003 is 200/300 ammo. Beyond that - it goes to the practice bin or my son to kill dirt. That being said - he doesn't get much ammo to shoot dirt with. It is rare that I cull 1 or 2% out of a 500 cartridge load session.
Also - use good strong RIGID presses. I load all my ammo on Redding T-6 & T-7 turret presses. I have a box of all brands of cheap single stage presses that I bought, used and learned the had way. Some are relegated to nothing more that punching primers or pulling bullets.
- Crimping and not crimping - NEVER EVER crimp a match bullet EVER. The only time you should even consider it is is the bullet of choice has a canelure in it. If it doesn't - then don't - that simple. Some of the 77gr Mk262Mod1 ammo has a (cough) canelure...ok if you want to call it that - it is the slightest of slight canelures and offers just enough "bite" so that the 77's won't set back under recoil / FA fire. Don't even consider, if they still sel them - the tools that will canelure a bullet - waste of $ and you're wrecking a good match bullet.
- Loading to be just off the lands or kissing the lands - or INTO the lands. Very very complicated topic. I start ALL ammo development with the bullet touching the lands - charges reduced accordingly. This way you are puting the pressure spike up front in your load development. Once you develop the powder type / charge weight, you can use seating depth to tune the load. SMK's are built with relatively thick jackets - so they very tolerant of jump. But..you find that different rifles, barrels, bullets etc have their own individuals likes / dislikes. For a gas gun, I tend to stay away from a load that has to be jammed into the lands. But there are exceptions - my 1K LR service rifle - AR shot 90gr JLK VLD's .005 into the lands - I had to be very very careful if I had to unload a live round - the possibility of extracting the case and leaving the bullet in the throat is real - along with all the powder in the bolt lugs...not cool. Some barrels have a lead / throat cut so long that you CAN'T load to touch the lands - in that case - load to the longest length you can and still feed through the mag. Witht he GAP10 - you'lll be limited to internal mag dimensions. Bolt guns can be single loaded.
Quantifying this - in a specific instance - loading for my 40X .308 - it loves 168SMK's on the lands - to be specific - just touching. The difference? .020 off, opens the group by 30%. The LR AR? from .005 in to say .010 off - would take that group and double its size at 300yds duing one of my velocity test sessions. On target at 1K - it would have been ugly.
- Uniforming primer pockets - easy stuff, one time and you're done. Definitely worth it. It also contributes to CONSISTENCY of the case.
- Deburring flash holes - same as above.
- Bumping shoulders VS resizing to factory specs - in a gas gun - full length resize. If you bump a shoulder in a gas gun reloading - you will be pounding out a stuck case - IF you can even get the bolt to close. Brass is extracted and ejected hot and still under pressure, read "plastic" state - ESPECIALLY in an AR10 type platform. Put a mike on fired brass about 1/3 up from the bottom and compare to new unfired brass - the diameters grow considerably. You will need to full length resize for the GAP10. Bolt guns are happy when you feed them fire formed brass - you've basically custom sized the brass to your chamber. For that, you'll only need to neck size - and maybe every 5 or 6 loadings, bump the shoulder to maintain the right cartridge headspace.
Others have opined about bushing neck dies - great investment - and another tool to fine tune the ammo re: neck tension. It also offers you flexibility - case in point, I can pop out a .332 bushing for that 40X (tight neck/turned brass) and drop a .339 bushing in to load LC brass for my M14. Super simple and precise.
There is a lot of good advice - Accurate Shooter (6BR.com) is excellent.
Final thought - (sorry for the long post)...one aspect that befuddles and confuses reloaders, not to mention wasting bullets, powder, barrel life etc is the actual development process. All too often I see reloaders who have loaded for years, repeat the some old wasteful routine. They'll load 3 - 10 rounds of the same charge and have 10 different charges; 30 -100 rds of ammo and proceed to shoot each charge for group. They end up with a stack of targets with a whole bunch of different groups - they pick the smallest one and declare victory. Wrong wrong wrong.
I would strongly suggest a ladder method or incremental load method where you'd only need to shoot 1, maybe 3 rounds of each charge weight. Based on analysis of vertical stringing, you'll be able to ID the accuracy nodes in your various charges - in a 308 you'll probably see 3 or 4 charges separated by maybe .2/.3grs or a range of .6-.8grs that all shoot to the same elevation - they'll cluster. This is a sweat spot and if you start your fine tuning in the center of that sweat spot (charge weight wise), you'll get to a seriously accurate load far quicker with exponnentially greater confindence that you truly have an accurate load for that rifle. The fine tuning will consist of bumping the charge weight up/down in smaller increments on each side of the sweet spot and playing with seating depth. Loading to the center of that sweet spot will also build in a buffer for atmospheric issues - i.e. temperature changes. That guy who picked that really cool looking group using that outdated inefficient method unknowingly picked one that was right on the hiry edge of a pressure issue. That great group shout in 50deg weather starts pooping primers and leaking gas in his face in the spring time in 70deg weather. The center charge of the sweet spot will prevent that. How do you think that factory loaded match ammo manages to maintain accuracy in nearly every type of condition?
Hope this helps - its only 1% of the the realm....
What are your questions?
Originally Posted by opsoff1
SW,
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) in a neck area process, then expanding on a precision mandrel will help (gets the necks perfectly round) then turn the neck to achieve the exact same wall thickness for a full 360 deg. then run the brass through a bushing neck sizer - you will gain astoundingly consistent neck tension which WILL impove acuracy. If you want to go full psychotic, then get into neck annealing and get a hardness gauge..
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