Bumping Shoulders - Newbie questions

[Chrazy-Chris]

Hello all,

I am shooting a relatively mild .308 load of 43gr IMR4320 under 175TMKs and I'm experiencing some resistance opening the bolt (on a spent case only). Closing the bolt I don't have any resistance. Interestingly enough, I'm also getting some primer cratering even though I'm 2.7gr under max (min 42gr, max 45.7C). Sometimes I have to whack the bolt handle with my palm a few times to get it to open. I'm using fire-formed FC brass from FGMM that has been loaded about three times. I use a lee neck sizing die instead of the FL resizing die and set them .005-.010" off the rifling.

I have a few questions:
1. Could the shoulder needing "bumped" be causing the bolt lift issues? What are the other common contributors to the hard bolt lift?
2. Can I bump the shoulder back using the full length resizing die without losing the benefits of using fire-formed brass or do I need a special die?
3. I have the Hornady shoulder bushing comparator kit - is it possible to use this to confirm whether the shoulders are even an issue or is this only helpful when actually doing the "bumping" process? I don't have any factory ammo handy for comparison but I do have some FL resized ammo.

My assumption is that I can adjust the resizing die down a little at a time until I'm seeing some change using the comparator. If this assumption is correct - how much of a difference should I aim for between fired brass and "bumped" brass?

Thanks all, I'm still learning a lot about reloading for precision with a bolt gun. The good news is that this load shoots great, I've cloverleafed several with it using the factory 10T barrel, it just sucks having to re-establish my shooting position each time I have to hammer on the gun to cycle the action.

Chris

EDIT: I did some more research and this article provided some clarity - thought I would add it in case anyone else came here to learn about the bumping process:
http://www.accurateshooter.com/technical-articles/die-issues-when-bumping-shoulders/

[bigedp51]

Below Kevin Thomas worked in the Sierra Ballistic Test Lab and now shoots for "Team Lapua USA". You might want to think about joining the "rat turd in the violin case" club.

http://i.imgur.com/Y3IiYL5.jpg

[Chrazy-Chris]

Below Kevin Thomas worked in the Sierra Ballistic Test Lab and now shoots for "Team Lapua USA". You might want to think about joining the "rat turd in the violin case" club.

http://i.imgur.com/Y3IiYL5.jpg
Interesting. I have some FL sized brass and I'll have to shoot them side by side next time. After researching this a bit it seems I might have a primary extraction issue. Still figuring it out.

Sent from my XT1254 using Tapatalk

[Chrazy-Chris]

I know I'm in the wrong forum section but might as well ask - is there a troubleshooting guide or comprehensive article of some sort on primary extraction issues? I'm pretty much convinced after my research that something isn't right in my bolt.

[Nor Cal Mikie]

If you like the idea of neck sizing, go for it. I neck size LOTS of my brass or I should say most BUT, over time, the case body will swell and get tight on extraction. Either full length resize or neck size and use a body die to push the body of the case back in place.
Bumping shoulders works BUT again, you still have the rest of the case to deal with. It gets fat and sooner or later you'll have to do something about it.
Either get a bigger hammer to beat the bolt open OR, get the proper die to deal with it. The BEST solution would be to get a custom made die that sizes the brass to your chamber. No more rat turd in the violin case issues.
Bump the shoulders back .001 to .002, bushing size the neck and squeeze the case body down. A custom die will do all of that in one pass.

[Texas10]

First the Brass. The 308 FC brass has a well deserved reputation for being soft and you may get 3 or 4 loads before primers start falling out. FGGM ammo is made to shoot accurately ONCE, so you'll need to eventually buy some better brass. If you'd like some personal experience with determining exactly what soft brass feels like you can do this: Drill and 6-32 tap the flash hole on several pieces of brass with different head stamps. I put the tap in my cordless drill and hold the case in my hand. You get a better feel for just how hard the brass is if you tap it this way. In FC brass the tap will cut like butter. In Rem or Win you probably won't be able to hole the brass from spinning with your hand as you tap. After this exercise, you'll have a pretty good idea what is meant by soft brass and why primers won't stay seated.

If you want to neck size most of the time, and many hand loaders believe in this process because it works the brass less, you should first chamber each piece of shot brass to see if it chambers easily. Neck size only those you feel chamber easily enough. Measure the base to shoulder with a comparator gage of some sort and write down that number. I make a hand drawing of the brass and label important dimensions for quick reference, like caliber, overall length, base to shoulder, gun serial number, and post it on the wall of my reloading room. You'll need to know exactly where each piece of brass measures relative to that snug chamber dimension so you can FL size and bump the shoulder back .001 or .002.

You'll also need to trim necks occasionally. If you're not set up for that, stop and get the tools you need or you'll risk a chamber explosion from pinching a bullet in the throat.

[bigedp51]

Not all brass is created equal and brass hardness and how thick the flash hole web is governs base expansion. I had factory loaded Federal .223/5.56 cases with over sized primer pockets after the first firing.

Below the flash hole web adds radial strength to the base of the case. And this controls how much the base of the case just above the extractor groove expands when fired.

http://i.imgur.com/cYeTsDp.jpg

When full length resizing cases for a semi-auto the case diameter should be .003 to .005 smaller than its fired diameter for reliable extraction.

Below JP Enterprise case gauges are made with a finish chamber reamer cut to minimum SAAMI chamber dimensions and check case diameter. I check my cases with a Hornady cartridge case headspace gauge after firing to adjust the die for proper shoulder bump. And then use the JP Enterprise case gauge as the final "plop test" of the loaded rounds.

https://images-na.ssl-images-amazon.com/images/I/31nmN-cC24L.jpg

Below Wilson, Dillon and JP Enterprise .223/5.56 case gauges with Lake City cases inverted in the gauges. As you can see below the Wilson and Dillon case gauges do not check case diemeter and the JP Enterprise does check case diameter.

http://i.imgur.com/KSB3ZvP.jpg

Bottom line, full length resize your cases and reduce the case diameter, your cases are not springing back from the chamber walls after firing and causing hard bolt lift.

NOTE, soft brass was one of the causes of early M16 jamming and now Lake City cases have the hardest brass and thickest flash hole webs.

http://i.imgur.com/OujD1z7.jpg

[Haiku_Rodney]

Do you have the same difficulty opening the bolt when firing factory ammo?

[Robinhood]

Change your brass. Try LC or Lapua.

[Texas10]

Big Ed, you've been posting those pics of American Eagle brass and Military brass for a while. When I first became aware of your pics a year or two ago, I checked my American Eagle brass salvaged for reloading and found that the web at the flash hole was identical to all others I checked, .070.

Was that a particular batch of A.E. brass you cut apart that has since been superseded? Based upon my experience A.E. is good HARD brass in the head area. I've reloaded some dozens of times, neck sizing only the entire time. Still shoots fine, never a tight bolt lift, never a loose pocket, no neck splits almost never have to trim as it just does not grow, and I am shooting some pretty hot loads at time.

Not trying to call you out on your post, Big ED, just adding my experience to the conversation, FWIW.

[bigedp51]

Big Ed, you've been posting those pics of American Eagle brass and Military brass for a while. When I first became aware of your pics a year or two ago, I checked my American Eagle brass salvaged for reloading and found that the web at the flash hole was identical to all others I checked, .070.

Was that a particular batch of A.E. brass you cut apart that has since been superseded? Based upon my experience A.E. is good HARD brass in the head area. I've reloaded some dozens of times, neck sizing only the entire time. Still shoots fine, never a tight bolt lift, never a loose pocket, no neck splits almost never have to trim as it just does not grow, and I am shooting some pretty hot loads at time.

Not trying to call you out on your post, Big ED, just adding my experience to the conversation, FWIW.

My problem cases were marked FC 05 and this problem lasted for years and just one reason why Federal is noted for soft brass. On the flip side of this Lake City and any commercial contract ammunition made for the military must meet higher standards.

This information and photos came from AR15.com. and other AR15 forums. I also made the two inch rod to check my cases for web thickness that you see at the link below. I also bought pin gauges to check the primer pocket diameter.
http://accurateshooter.net/Blog/brasstest03.png
"Current American Eagle .223 once fire brass" Posted: 4/6/2009
https://www.ar15.com/forums/t_6_42/276154_.htmlhttp://accurateshooter.net/Blog/brasstest03.png

Bottom line I was given three 5 gallon buckets of .223/5.56 brass fired by our local police departments. One of the buckets was all Federal brass and I sized and prepped all this brass only to find out that over 30% of it had over sized primer pockets. I then started checking the cases as above and tossing the bad brass in my scrap brass bucket.

How Hard is Your Brass? 5.56 and .223 Rem Base Hardness Tests
http://bulletin.accurateshooter.com/2014/05/how-hard-is-your-brass-5-56-and-223-rem-base-hardness-tests/

http://accurateshooter.net/Blog/brasstest03.png

[Texas10]

Thanks, Big ED, that was very informative. Love the little web gage. Brilliant idea, and saves cutting cases apart.

[RC20]

I know I'm in the wrong forum section but might as well ask - is there a troubleshooting guide or comprehensive article of some sort on primary extraction issues? I'm pretty much convinced after my research that something isn't right in my bolt.

Just the posts. I am in the camp that believes there is far less primary extraction issues than is proposed.

Neck sizing is one way to create what looks like it, but that's a case that has finally swelled and not shrunk back and its binding.

Chamber cleaning resolved mine and then with after market barrels it stayed gone.

So rule out the other possible causes of what I call FTE (failure to extract) before pre determining its PE

[Robinhood]

I am of the opinion the FTE is "a" problem. Whether it is extraordinary or ordinary.

Primary Extraction (PE) is "an" engineered remedy. Different than "a" brass rod down the bore of the barrel. If you have no primary extraction carry a brass rod. IF you have a problem, fix it.

[Deadshot2]

Just the posts. I am in the camp that believes there is far less primary extraction issues than is proposed.

Neck sizing is one way to create what looks like it, but that's a case that has finally swelled and not shrunk back and its binding.

Chamber cleaning resolved mine and then with after market barrels it stayed gone.

So rule out the other possible causes of what I call FTE (failure to extract) before pre determining its PE

Unless you own a Remington. I have several and it was either remove and re-solder on the handle in the correct position or replace the entire bolt with a One-Piece that also corrected several other problems inherent to their bolt design.

A frequent cause of FTE with hand-loads is setting the seating die to crimp at the same time as the bullet is seated. This often leads to a bulge at the shoulder/side wall junction which in turn often leads to FTE.

Aftermarket barrels are a good cure if the factory barrel has a rough chamber but a little judicious application of polishing compound on an oversized and tight bore mop can fix that. I find that 50 Cal mops work for any .308/30-06 case based calibers to polish a chamber.