Tight Bolt Revisited

T

Twud

Guest
You may remember my sticky bolt problem. Using a conservative load in my new custom 6BR the bolt is really tight on the way upafter firing
I decided to go after the shoulders first. Bought a Hornady Headspace Gauge. The turned Lapua brass is very inconsistent from base to shoulder. A fired round mesures 1.167 with the gauge zeroed out on the bushing.
Fired cases measured:
1.167
1.167
1.167
1.168
Subsequent unfired cases neasure:
1.162
1.168
1.159
1.165
1.162

I'd like to bump the shoulders .002", but where would I start?
Also given the variance they all felt the same resistance when opening the bolt. Extraction is no problem.
The fired cases are a random sample.
Is there a better tool out there for measuring length to shoulder?
Mark


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Because factory brass varies so wildly from out the box it's essentially useless to measure, gauge or headspace from it. Even trimming cases, turning necks or any other brass trimming procedures are simply working off of this variance until you can find a way to pop out the brass for consistency.


Soooo, What I'm saying is, if you chamber SHORT enough you can then re-set each and every shoulder to within half-a-thou of each other so that your fireform (popping out) step is consistent. NOW you can go after the brass.

al
 
...but after you fire the case once you achieve the same effect just be careful not to set the shoulder back too far on resizing.
 
alinwa said:
Because factory brass varies so wildly from out the box it's essentially useless to measure, gauge or headspace from it. Even trimming cases, turning necks or any other brass trimming procedures are simply working off of this variance until you can find a way to pop out the brass for consistency.

Soooo, What I'm saying is, if you chamber SHORT enough you can then re-set each and every shoulder to within half-a-thou of each other so that your fireform (popping out) step is consistent. NOW you can go after the brass.

al
Click to expand...
Al,

I was chambering right at the min. but discovered that sometimes I could not get any "bump" with a standard Redding die. So I now choose to go about min. +.003 or .004 and use the redding "tall" shell holders to fine tune the amount of bump.
But I reserve the right to change direction again, maybe......

Jay
 
Start with your longest fired cases.

Screw the die in slowly keeping an eye on the headspace measurement. Use one piece of brass and remove the expander ball if your die is using one.

When your getting the die close you should actually see the headspace measurement increase very slightly. Thats simply because your squishing the brass forward due to the body sizing taking place. (Not applicable to shoulder bump neck sizing dies)

Keep screwing your die in until you've reached your desired headspace.

During all this you should be testing "the feel" by chambering in your rifle.

Hope thats clear as mud.
 
TWUD...If you cannot adjust your sizing die to get the .002" bump...try putting the die in a lathe (using a carbide tool bit) lathe off about .005-.007" off the base of the die then polish the bottom of the die with some 420/600 grit paper..you will be able to adjust the bump exactly where you want it..
I neck size and bump in seperate operations (2 presses) but a FL sizing die modified for your chamber dimension is the best for straight ammo..
 
1. Why do you want to bump .002? That's really a bunch for a custom chamber in my opinion. .0005 is where you should be.

2. Why worry about bumping unfired cases? What's the point. Fire the cases twice and them set you sizing die and go at it.


Hovis
 
HovisKM said:
1. Why do you want to bump .002? That's really a bunch for a custom chamber in my opinion. .0005 is where you should be.

2. Why worry about bumping unfired cases? What's the point. Fire the cases twice and them set you sizing die and go at it.


Hovis
Click to expand...
I'm bumping them as a potential solution to the tight bolt problem. I don't know if it will work, but can it hurt.
Mark
 
Stephen Perry said:
It's entirely possible you did not completely fire form your cases to the chamber. Now your cases have taken a set where they are constantly trying to complete the fire form process but will never get there. If it were me I would make new brass this time go for the max fire form load to get that 98% fire form on the first firing with the 2nd shot being a sealer fire form shot.
This should make it so that FL sizing each time will eliminate tight bolt.

Stephen Perry
Angeles BR
Click to expand...

Wow, I couldn't agree with this more.

Nicely put.

al
 
Twud

Twud
In a nutshell the newer Lapua 6BR brass isn't as good as it was 4 years ago or older.
I will be fireforming sunday 1-4-09 and my load will be 28.0 grains for the first firing.After that it will be 31.5 grains.
If you try the max load on your fireforming make sure your wearing eye protection and your insurance premiums are paid up.You will be popping primers right out of the cases.
All your new brass cycles just fine because it is 1.168 or shorter.Your chamber is probaly 1.169 judging from your fireformed measurements.
Your problem isn't your shoulders.
You need the Redding 6mm BR REM SB Body W4 to size near the base.
After that your headspace number at 1.168 now will get slightly longer.If your brass doesn't fit you then need the Redding 6mm BR Body P2 to push the shoulder back to 1.168 inches.If this die won't move the shoulder enough and it probaly won't grind the bottom off of it and polish it with a Norton wheel.
If you don't want to go through all of that shoot your new brass 3 times and have Harrels send you a fitted die.
Lynn
 
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Taking skim cut off die

eww1350 said:
TWUD...If you cannot adjust your sizing die to get the .002" bump...try putting the die in a lathe (using a carbide tool bit) lathe off about .005-.007" off the base of the die then polish the bottom of the die with some 420/600 grit paper..you will be able to adjust the bump exactly where you want it..
I neck size and bump in seperate operations (2 presses) but a FL sizing die modified for your chamber dimension is the best for straight ammo..
Click to expand...

I've had to do this with Redding body as well as Redding small base body dies for chambers reamed by the same gunsmith Twud is using. It's not the fault of the gunsmith or his reamer (Henricksen). It's just that standard Redding dies are manufactured to tolerances that are more open or sloppy than this gunsmith and Henricksen reamers produce. This is a well known established benchrest gunsmith renowned for the quality of his work. He's in the Benchrest Hall of Fame and the quality of Henricksen reamers is known to the most discerning practitioners of the accuracy quest. No foul or error in either of these areas that I can see.

I've taken a skim cut of .005 off the base of every Redding die I use for chambers done by this gunsmith and my brass gets sized as minimal as I want. I take the firing pin out of my bolt and beginning with Redding competition shellholders @ .010, begin sizing, chambering and measuring the resultant shoulder bump, going down in shell holder/die shim thickness, until I get exactly .001 decrease in headspace and the brass chambers easily. I write down the shellholder dimension (.010 down to .002) along with the die shim thickness and I'm done. I also do all the above in addition to sending my dies along with five or six 3X fired cases to Jim Carstensen for the final touch.

Lou Baccino
 
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Incomplete fireforming

alinwa said:
Wow, I couldn't agree with this more.

Nicely put.

al
Click to expand...

I agree, that is well put. Part of the problem is the shooter being new to this chamber and as a result, the fireforming load being a little on the anemic side; educated guess on my part. The reason I say this is that I have a 6mm BR 1:14" twist that I've developed tested pet loads with. I have another barrel chambered by Twud's gunsmith using the same reamer Twud's chamber was reamed with along with using the same gunsmith. My second barrel is a
1:7.5" twist I use for the heavy 6MM VLDs. When I fireformed brass for that brand new barrel I was using a beginning load a friend gave to me who has the same chamber by the same gunsmith. You might say I was operating in a 'comfort zone' envelope with respect to pressures, etc. My brass came out perfect the first time.

Many people, when fireforming a load in a new chamber they are unfamiliar with, default to the standard maxim of reducing their load by 10%. I found this out on my own by beginning with a rather timid load with my first .22-250 AI. Now when fireforming for an Ackley I go straight to the max. load for the parent cartridge for my initial fireforming load and as the low end start for subsequent load development. In some cases, depending on the Ackley caliber, I end up 2 or three grains or more beyond the max. parent load; that's the whole point of paying homage to the Ackley altar. Ackley himself referred to using a 'snappy load' for intitial fireforming.

The bottom line is the more you're in this game, the more you learn and can pass the info. on to others. That is what I really like about this sport; the camraderie and willingness to share information. The other thing I've noticed is that old maxims, while being accurate 70 to 90% of the time, aren't necessarily cast in stone. One has to be willing to get away from pre-conceived patterns and methods sometimes.

Example: Everyone mostly follows the standard practice of loading their bullets into or touching the lands during load development as a starting point. In my 1:7.5" Kreiger 6mm BR, I was shooting the 105 grn. Bergers by loading touching the lands. The rifle was shooting ok but I knew it had to shoot better. Of course, I tried going further into the lands with no improvement. I e-mailed Eric Stecker (Berger bullets) with my dilemma. Eric suggested I jump the bullets as much as .040. Well, I went to the range with rounds loaded long, accompanied by a Wilson seater, set of calipers with a bullet comparator and began shooting. I tried .010 off the lands and when I got to .063 from the lands, I hit paydirt. My groups were the one hole groups I was looking for @200 meters. I went past .063 and the groups began to open a little. I repeated the process several times to validate my initial discovery and my load is now 30.2 grn. of Varget with Berger 105 grn. VLDs .063 off the lands. I probably would have never gone that far away from the lands on my own because my thinking was hampered by traditional methodology that works most of the time; but not in this situation.

Lou Baccino
 
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A little note that may not apply

Several years ago, two friends had custom, slow twist, 6BRs built, by excellent gunsmiths. Despite the fact that I advised them to order Harrell FL dies, they both bought Redding type S FL dies. Their dies were too large at the back for their chambers, and after I got it through their heads that no amount of fiddling with the adjustment would result in a proper amount of bump and sizing just in front of the case head, they both sent off fired brass to Lynwood Harrell and got back dies that were properly fitted to their chambers...end of problem.

You can order a reamer to match sized brass from a particular die, or order a die to match brass from a particular chamber, but the chance of getting a perfect match between die and chamber with an off the shelf die are not nearly as good. If you want different results, do something different.

Another thing, if new brass is too close a fit at the back of the chamber, you will have tight bolt problems after firing with a moderate load. If, as some have reported, Lapua 6BR brass is being made larger in the back than it was before, a reamer that was a close fit to the earlier brass might be too small. Even though unfired cases would chamber without resistance, they would get tight that would not cause a problem with a larger chamber. If the chamber was right on the edge of this situation, some cases would be tight, before others. If this is the case, I think that a new reamer is the best answer. Having your own reamer is cheap insurance that your dies will continue to work properly for new barrels.

I have discussed this issue with a fellow shooter who found out that a closer fit is not always a good idea. He tightened the fit of his brass (unfired) to the back of his chamber too much (He had his 6PPC reamer reground smaller in the back.) and had to order a new reamer. His cases were having bolt lift issues with loads that had not caused a problem before. The new reamer solved the problem. Being able to easily chamber a new or sized case does not necessarily mean that it has adequate clearance at the back of the chamber to prevent premature (in terms of load pressure) bolt lift problems.

The relationship of the dimensions of chambers to FL dies to brass, is one of the keys to getting the most out of our rifles, no matter what the caliber. The size of the brass determines the proper chamber size ( at the back) and that determines the proper die dimension. Within a range, you can work from the die to to chamber or from chamber to die to get this fit, but if you go too small with the chamber, nothing else that you do can properly fix the situation.
 
Harrel

Boyd,
The round is fired. The brass expands to fit the limits of the chamber and then springs back, more so in the body than in the base. The bolt handle is hard to raise, but does raise. Bolt is drawn back with no resistance and round is ejected. You chamber the same pc. of brass it goes in without a hitch, the bolt closes without a problem and opens back up without a problem.
What changed? Shouldn't the bolt be just as hard on the second chambering?
I'm not arguing your point, I just don't understand mine.
Mark
 
Try this. Put a bullet in the neck of a piece of fired brass and chuck the neck of the case in a cordless drill that is set to low RPM range. (The bullet is to keep the neck from collapsing.) Lay the drill on its side with the back of the case supported. I used the side of an open wooden drawer. (at right angle to case) Use a coarse diamond lap or some wet and dry wrapped around something flat, held parallel to the CL of the case. Spin the case and take no more than .002 off of the diameter at the front of the extractor groove, holding the abrasive parallel to the case CL. Polish with 0000. Now refire the case with the same load that caused the problem (assuming that there were no other pressure signs) If the problem persists, I don't know what is causing it, if it does not, your chamber is a bit small in the back. This can be remedied with a different reamer that is larger in the back, or polishing out the back of the chamber. Either operation will require a lathe and an experienced operator.
 
Stephen,

My point was that his die and or chamber might indeed need to change. You might have missed that little point. Also, What I suggested that he do, I have done myself, with a case that had developed a click at the top of the bolt opening, so I wasn't flying blind. BTW I got the idea from an article in an old black and white issue of PS that mentioned something about Tony Boyer something similar to a set of problem cases at a match. In my case, making the well worn case a couple of thousandths smaller where the FL die couldn't quite reach solved the problem, and showed just where the problem was coming from, something I was trying to find out about Twud's situation. This is all a lot easier with equipment and cases in hand.

Boyd
 
Chino69 And Stephen Perry

Your shooting max loads in new brass tells me you've not been shooting a 6BR for very long.
I also would never advise anybody to shoot book max loads in a Ackley Chambering without first working up to that point with sacrificial cases.I see this in print all of the time and on cases like the 22-250 or 223 it probaly doesn't matter.
On a case like the 300 Weatherby it matters a whole lot.
Lynn
 
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Eric Stecker's advice

Stephen Perry said:
Chino
I couldn't have written your Thread any different or any better. You gave a clinic on bullet seating that some might never consider. Congrats on nailing what it takes to fireform cases and seeking out Eric's help.

Stephen Perry
Angeles BR
Click to expand...

Stephen,
Thank you; I figured this might be informative to others. Isn't that what's it's all about? Sharing knowledge gained and seeking when one doesn't understand?

Interesting similar experience two years ago. I have a NEF Handi Rifle that I use for walk around critter whacking. I don't care if it gets scratched, dropped, or otherwise mishandled; took a spill over slippery rocks in Vermont several years ago. You get the picture; a basic utilitarian rifle. I had it re-barrelled by NEF with a 1:9" barrel. The day I went to shoot this barrel for the first time, I brought along my Mini-14. The rounds loaded for the Mini-14 are dependent on fitting into a magazine, and the bullets are seated much deeper into the case to function flawlessly. Now the rounds I had loaded for the Handi Rifle were with the bullets touching the lands as I was in the beginning stages of load development. These rounds were starting to show promise with some decent groups starting to show. Just for the hell of it I shot a five shot group with rds. that were loaded for the Mini-14. I thought the first two shots were just lucky as they went into one hole. The next three rounds went into the same hole! These bullets were a full .106 from the lands and they were performing like that. I've repeated the above many times @100 yds. All this from a rough $110.00 fitted new barrel. The point I am trying to make is that I would have never gotten to .106 off the lands in the course of my load development had I not tried this.

I don't know about you but when I can get a factory rifle to shoot that well I'm more thrilled than when my benchrest quality rigs perform. I've invested thousands of dollars in these rifles, custom barrels, reamers, match grade barrels, high quality optics, benchrest renowned gunsmiths, Jewell triggers, etc. They damned well better shoot one hole groups but to get a cheap rifle to shoot as well as my Handi Rifle shoots is kind of like the meaning in the parable of 'The Prodigal Son'.

Happy New Year to you and good conversing with you.

Lou Baccino
 
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