Inconsistent Shoulder bump

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RDavies
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Re: Inconsistent Shoulder bump

#16 Postby RDavies » Fri Dec 09, 2016 9:55 am

Barry Davies wrote:Why " bump " the shoulder at all?
Talking .308.
If your head space is set at say 1.630" then all fired cases won't come out at 1.630". There will be a variation of maybe a thou either side.
I set my body die to give an average of 1.630" ( my rifles are 1.630" ) in other words some shoulders are bumped a thou some are not touched.
Someone tell me what does it matter if some cases when chambered have a thou crush ( which you won't feel ) and some have a thou clearance?
Does it make a significant ( or any ) difference to grouping capabilities? I doubt it.
You will always get some variation because there are variations in every sizing such as -- more or less sizing lubricant, case hardness, slop in the press pivot pins etc. but as long as you are within a thou or so of rifle head space what does it matter?
Jase PTRC, Your measurements 0f 1.618 etc are not correct for a 308. 1.630/1.634 are Min/ Max so there seems to be something not correct with your gauge, I would fix that first.

Whether a tight case affects accuracy or not, I don't think it has MUCH effect. Maybe a better shot than me could tell the difference? Where I think a case with .001" crush will matter is gun handling if it is hard to close the bolt. I'm probably not the only one out there with a limited attention span and if I am struggling to close the bolt, my mind wonders away from what was happening down range. Maybe those who are lucky enough to have one of the lovely actions which Barry Davies makes won't feel much with tight cases but I know with the actions I use I can feel it and try to maintain some clearance. I would rather too much (.003") clearance than too little to make for easier bolt closing and less lug wear.

Razer
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Location: Orange,N.S.W.

Re: Inconsistent Shoulder bump

#17 Postby Razer » Fri Dec 09, 2016 1:36 pm

I am a bit of a dinosaur when it comes to"some" reloading practices so once brass has been fire formed in a particular chamber it doesn't get used in any other while ever I use that barrel.
After firing I chuck the cases into a tumbler for 3 hours, neck size with a Lee Collet die, clean primer pocket , reprime and load. Have no trouble with case length changing so cases don't need trimming.
Have also reloaded my sons Angel with Winchester brass over 40 firings with no bolt closure problems.
Also no split necks, head separation, loose primer pockets, etc.
Also never had any trouble with maintaining 1000yd elevations in spite of using a moderate load of 45.6 gas 2208.
I shoot(or used to) a choice of rifles and barrels in 308 but over come the odds of mismatching the brass by using different brands such as Lapua, Lapua Palma, RWS, HPS.
Only full resize when shooting new barrel or after a re-chamber and never saw any reason to down load at all, even though my personal loads start at 46grs of 2208 and more.
I always full resize hunting cases and the use the Lee Collet die just to make sure every round fits and neck tension and runout are constant.

bsouthernau
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Re: Inconsistent Shoulder bump

#18 Postby bsouthernau » Sat Dec 10, 2016 8:26 am

mike H wrote:Barry,
I have a Hornady gauge,the same as the one mentioned,mine gives identical measurements to those of Jase.My son,Chris has a gauge Adam Davies made for him,whenI measured my fired cases with it,they measured 1.630".I think the gauge body has a slight bevel on the entrance,causing the odd measurement.


That's interesting. I have the Hornady gauge and my cases measure 1.630". There's no bevel on the gauge body. Doesn't fill you with confidence in their quality control.

Barry

Barry Davies
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Re: Inconsistent Shoulder bump

#19 Postby Barry Davies » Sat Dec 10, 2016 9:30 am

Maybe the 1.618 reading is correct and these cases are being run with 12 or so thou head space??

bsouthernau
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Re: Inconsistent Shoulder bump

#20 Postby bsouthernau » Sat Dec 10, 2016 9:41 am

Barry Davies wrote:Maybe the 1.618 reading is correct and these cases are being run with 12 or so thou head space??


But Mike H is getting different readings on the same case. If he uses his Hornady gauge he gets 1.618 which is the same as Jase gets. If he uses Chris's gauge made by Adam he gets the correct 1.630.

Jase PTRC
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Location: Adelaide SA "PTRC"

Re: Inconsistent Shoulder bump

#21 Postby Jase PTRC » Sat Dec 10, 2016 4:31 pm

Barry Davies wrote:Maybe the 1.618 reading is correct and these cases are being run with 12 or so thou head space??


I can feel a little sarcasm maybe in this post Barry? :lol: I can guarantee there is not .012 head space...i dont think my cases would have lasted much more than one firing. New unfired cases measure 1.617 or 1.618 on my gauge. Of the 100 fired cases i measured all except 1 measured 1.619 the odd one measured 1.6195

mike H
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Re: Inconsistent Shoulder bump

#22 Postby mike H » Sat Dec 10, 2016 5:18 pm

Let us not get too wound up about this,I know that my Hornady gauge measures differently to my Adam Davies gauge,as well my fired cases are around three thousands of an inch longer than New In Box Lapua cases.What I think is the important point,does one or two thousand inches matter in the scheme of things,base diameter of the case is also important for ease of loading and extraction.

Jase PTRC
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Location: Adelaide SA "PTRC"

Re: Inconsistent Shoulder bump

#23 Postby Jase PTRC » Sat Dec 10, 2016 7:29 pm

mike H wrote:Let us not get too wound up about this,I know that my Hornady gauge measures differently to my Adam Davies gauge,as well my fired cases are around three thousands of an inch longer than New In Box Lapua cases.What I think is the important point,does one or two thousand inches matter in the scheme of things,base diameter of the case is also important for ease of loading and extraction.


I hope no one is getting worked up. Im going to try using a competition shell holder and camming the press right over and see if it gives me more consistent shoulder bump. The rifle is shooting well, it held x ring elevation at 700 mtrs today for my second round. Maybe im being anal about measuring stuff but a .002 variation in shoulder bump just seems wrong. Im going to anneal the cases before i re size this time and make sure my lube is as close to the same for each case. Extraction has been good so far, a couple of the longer cases (i marked them) were a bit more firm to close the bolt on today.

Barry Davies
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Re: Inconsistent Shoulder bump

#24 Postby Barry Davies » Sun Dec 11, 2016 7:57 am

Hey Jase,
No sarcasm intended.
It just doesn't make sense to me to have an instrument that does not read correctly. If it was mine I would return it and request one that read correctly--- better still have Adam make you one that reads as it should. What you have is not a gauge as such, it's a comparator.

Jase PTRC
Posts: 221
Joined: Sat Nov 29, 2014 11:15 pm
Location: Adelaide SA "PTRC"

Re: Inconsistent Shoulder bump

#25 Postby Jase PTRC » Sun Dec 11, 2016 9:02 am

Barry Davies wrote:Hey Jase,
No sarcasm intended.
It just doesn't make sense to me to have an instrument that does not read correctly. If it was mine I would return it and request one that read correctly--- better still have Adam make you one that reads as it should. What you have is not a gauge as such, it's a comparator.


You are dead right Barry. It doesnt make sense to use a tool that is not correct for the job. I will get in touch with Adam and get one made up. Thanks for your replies.

XCALIBRE
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Re: Inconsistent Shoulder bump

#26 Postby XCALIBRE » Sun Dec 11, 2016 3:00 pm

One of the main factors that appear to be overlooked is unequal case neck and partial shoulder annealing hardness of the cases. If not equal in those respects the case length will tend to and grow and resist spring spring back after multiple firings, the case neck hardens and increases tension on the bullet seating process giving variations in bullet length protrusion. Proper and semi regular annealing of these areas will make loading, firing and extraction trouble free without having to reset dies.
F TROOP, SHOOTING F CLASS.


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