FL sizing - inconsistent bolt tension

[roklock]

Hello,

Been Shooting giving Fclass & benchrest (groundhog matches) a try this year. Been a reloader , hunting and high volume but not for these disciplines

Background...forester coax press, redding FL S die, once fired lapua 6.5 x 284 brass necked up with a .282 mandrel and shot in a .284 win. Brass annealed cleaned and lubed (one shot) Custom chamber, no turn nk at .3175., bat action.

Setting up die, for bump of 2 thousand but also checking bolt tension with firing pin and ejector removed. Assume adjusting has been completed and then ran 10 pieces of brass, 7 out of 10 the bolt either dropped freely or stopped traveling roughly 3/4-7/8 and just needed very slight assistance with a finger. The other three the bolt didn't free drop at all and needed assistance to travel the entire way, not hard but more than light pressure.

OK, now the question(s),

1. Do I turn the die another 1/16 or so until those three also have the same consistency?
2. Do I ignore and keep going on? Meaning, worry more about neck tension, seating pressure, ect.

Thanks in advance for any feedback

Steve

 

[BoydAllen]

Too much bump will shorten case life, and could lead to incipient and actual separations. Having said that, we need more information. Have you verified the shoulder bump of the cases for which the handle does not drop. Also, how much reduction of fired case diameters are you getting of fired cases, by sizing, at the shoulder and at the largest diameter above the extractor groove? With that information we can do a better job of diagnosing the cause of your issue. While I am at it, have you seen any issues with accuracy that you can correlate with the tighter cases. Recently, I did a little experiment on some 6PPC brass that had plenty of body clearance after sizing. The difference between very light feel and a gravity drop was .0005 of bump. That is why I have asked for your after sizing body diameters chamber clearance.

 

[Richard Coody]

I believe i would check the diameter of the case near the base. Compare easily chambered and tight chambering. When setting up a proper shoulder bump sometimes the die doesn't size the base enough. 6.5 x 284 works that brass pretty hard.

 

[jepp2]

once fired lapua 6.5 x 284 brass

It normally takes several (at least more than 1) firings for the brass to be the length of the chamber. So how do you know your case head to datum for bolt contact?

Since the brass was probably undersize due to once fired, if your die was set high, then it could move the shoulder forward as you sized. Differences in case length would give different sized results. Did you measure the case head to datum on the ones that had free drop vs the ones that didn't?

 

[joshb]

Boyd is on it. I get the same results as you, sometimes. My thought is that the brass springs back a little more on some cases. That’s why I anneal every time. It doesn’t completely solve the problem, but helps a lot with the shoulder bumping.

 

[Richard Coody]

I normally takes several (at least more than 1) firings for the brass to be the length of the chamber. So how do you know your case head to datum for bolt contact?

Since the brass was probably undersize due to once fired, if your die was set high, then it could move the shoulder forward as you sized. Differences in case length would give different sized results. Did you measure the case head to datum on the ones that had free drop vs the ones that didn't?

Missed.that one. Don't ever set your shoulder bump.until you have.fully fireformed brass. Just size the neck until then. You can tell by when brass starts to chamber tight and the base to shiulder datam measurement stabilizes.

 

[roklock]

Too much bump will shorten case life, and could lead to incipient and actual separations. Having said that, we need more information. Have you verified the shoulder bump of the cases for which the handle does not drop. Also, how much reduction of fired case diameters are you getting of fired cases, by sizing, at the shoulder and at the largest diameter above the extractor groove? With that information we can do a better job of diagnosing the cause of your issue. While I am at it, have you seen any issues with accuracy that you can correlate with the tighter cases. Recently, I did a little experiment on some 6PPC brass that had plenty of body clearance after sizing. The difference between very light feel and a gravity drop was .0005 of bump. That is why I have asked for your after sizing body diameters chamber clearance.

Hi Boyd,

First, I bought 400 pieces of brass when back in July, so I don't have data on the second firings. Thanks for the thought. To answer your other questions and based on all 10 cases.

Base: right next to extractor groove, once fired .4995-.5000, after sizing .4990-.4995
Shoulder: once fired .4770-.4775, after sizing .4750
Bump: once fired 1.7805-1.7815, after sizing 1.7770-1.7780 (two of the three "tight" ones measured 1.7770)

I actually did another test, I took some once fired (not resized) and ran them in and out of the action. Quite a few of them the bolt dropped freely. Of which I was surprised.

 

[roklock]

It normally takes several (at least more than 1) firings for the brass to be the length of the chamber. So how do you know your case head to datum for bolt contact?

Since the brass was probably undersize due to once fired, if your die was set high, then it could move the shoulder forward as you sized. Differences in case length would give different sized results. Did you measure the case head to datum on the ones that had free drop vs the ones that didn't?

I don't know the measurement from bolt face to datum but I did check case head to datum, measurements posted in response to Boyd. I do agree the cases aren't long enough for trimming yet.

 

[Terry]

Where is Donovan?

He taught me to use dwell time to get consistency.
Run the ram up, count to 5 or 10, repeat. It solved the problem for me.

 

[roklock]

Where is Donovan?

He taught me to use dwell time to get consistency.
Run the ram up, count to 5 or 10, repeat. It solved the problem for me.

Currently counting to 3 but can count more if longer is better

 

[jepp2]

I don't know the measurement from bolt face to datum but I did check case head to datum, measurements posted in response to Boyd.

I saw those. What I record for each of my rifles:
A. once fired - case head to datum
B. bolt contact - case head to datum
C. what I size to - which is B. - 0.002"
But I also like to record the case head to datum on new brass (tells me if I need to size or not, and if I might have issues). Did you measure any of your new brass? And how about the once fired, unsized, the bolt dropped freely?

For my first sizings, I actually more the shoulder forward, by sizing with the die set high so it doesn't bump the shoulder. Shortens the number of firings for me to determine B. on a new to me rifle, and gets the shoulder closer to my desired length (C.).

 

[BoydAllen]

I tried this lately so that I could help people with the whole bump thing. Strip the bolt of its striker assembly and if it has a spring plunger ejector, carefully remove it. None of what is to follow requires a decapping stem, expander, or neck bushing in the die, so remove them before you start. Take one of your longest (at the shoulder) once fired cases, write down the number, and then deprime it, without sizing. Double over a piece of Scotch tape sticky to sticky and measure it. Half of that is the thickness of your tape. Put a piece of tape on the head of the case and use a sharp knife to trim it flush with the flat of the head, including taking out the piece over the primer pocket. Measure the case with tape. Put a light film of bolt grease on the back face of your bolt locking lugs and chamber the case. It should require some effort. Remeasure the case that you just chambered. The shoulder may have been bumped back a bit. Now comes the delicate part, for which a PMA Micro Die Adjuster would be handy but not mandatory. Remember that a full turn of your die will raise or lower the die .071 so even sixteenths of a turn are too coarse when trying to pick of thousandths. Carefully, by trial and error lower the die until the case measures .001 less than your last measurement. Try it in your rifle. If it is still pretty tight, adjust the die down another thousandth and try again. At some point it will take very light effort to close the bolt and it will stay where ever you stop closing it. Of course ever time that you change the die and chamber the case you should measure the case and record that number. Doing this with a 6PPC case, chambered the way that it was, the very light closing effort came at SAAMI minumum plus .0015 and a gravity drop to the bottom a half thousandth shorter. This was with a custom action, and brass that had a body diameter smaller than my chamber by a good margin. It was from another rifle. I put this together for the guys that have a problem with loading at the range so that they can neck size and load the hottest safe load several times to produce a case that is as large in the body and from shoulder to head as their rifle can produce, with that barrel.

Generally, I tell people that one should only bump back from the actual measurement of a tight case, and that for once fired, they should adjust their die to give the same head to shoulder dimension as the once fired case, and try it in the rifle. We only bump to create clearance, if it is needed. There is no other reason for doing so.

 

[fyrewall]

I ran into this problem while loading some Hornady brand .204 R ammo. I stripped the control feed bolt (Ruger M77 Hawkeye) then ran 100 sized cases into the chamber. 15 cases exhibited excessive tightness - noticeable force to close bolt. I marked the tight ones with a felt tip pen. Using the same Redding body die (no effect on neck) I ran the entire 100 through the die again but ran the case into the die 3 times with 1 second between sizing. I then ran the 100 cases into the chamber, marked tight ones first - no marked resistance; the other 85 chambered easily. My guess is that inadequate dwell time affected the 15 cases that would not chamber. Upon closing the bolt on an empty chamber there is a noticeable allowance for lateral movement, possibly an unmeasured .005 - .006. Upon chambering on an easy close sized case the lateral movement is zippo. After this I sized another 250 with three strokes and random tested 35 and had no problems.

I have been told that a tiny amount of headspace is more desirable for accuracy vs. tight with forceful bolt closing. I neck size my .204 brass, neck turned to .225, using a Lee collet die. Brass life is very good with 8-10 loadings. My Redding .204 body die is used with its own ground down shell holder - light contact.

 

[carlsbad]

This is normal. Sizing doesn't provide perfectly identical results. either don't worry about it or add .001" to your shoulder bump. I had pretty much the same thing today and I'll add .001" shoulder bump when I remember to.

 

[243winxb]

Buy Redding.

Now you can control headspace. The new Redding Competition Shellholders are packaged in five piece sets in .002” increments (+.002”, +.004”. +.006”, +.008” and +.010”). Each shellholder has a distinct black oxide finish and is clearly marked to indicate the amount it will decrease case-to-chamber headspace. You can now easily adjust the shoulder bump to customize cases to your specific chamber

This removes slop in the press linkage.

forester coax press,

Not for this press.

 

[Iowa Fox]

Where is Donovan?

He taught me to use dwell time to get consistency.
Run the ram up, count to 5 or 10, repeat. It solved the problem for me.

This and good lube.

 

[Arky]

Last line second paragraph Custom chamber. Last line third paragraph three required assistance the whole way. A custom die may be needed for this chamber.

 

[Uncle Ed]

Currently counting to 3 but can count more if longer is better

I would pause longer because this reduces the amount of brass spring back.