Seating into the lands , Pressures & velocities
- Thread starter Metal god
- Start date
Nick, I don't think anyone will argue that when changing to a different style bullet with a different ogive will it require that you adjust the seating die to accommodate the new ogive profile. If you change from a Berger 105 Hybrid Target bullet to a Berger 105 VLD Target and yes you will have to re measure and re adjust the seating depth to get the same amount of "jump".
On shoulder differences once again it is obvious. I have no idea why anyone would use different shoulder bumps and expect the same results.
I know above someone stated their shoulders ended up in different places after shooting, that would fall into the what the heck category for me, however just out of curiosity I did measure 15 fired cases from fired from the same barrel and all were exactly in the same place.
Kudos for a nice graphic but most of this is common sense, not rocket surgery
On shoulder differences once again it is obvious. I have no idea why anyone would use different shoulder bumps and expect the same results.
I know above someone stated their shoulders ended up in different places after shooting, that would fall into the what the heck category for me, however just out of curiosity I did measure 15 fired cases from fired from the same barrel and all were exactly in the same place.
Kudos for a nice graphic but most of this is common sense, not rocket surgery
I've had shoulders set back several thousandths with reduced loads.
And moved forward with normal loads.
All with the same barrel.
I agree but at the same time , sometimes I like talking 50 shades of grey .
Like
Although 100% correct , I've pointed out on numerous occasions that when using the competition shell holders my shoulders are in the same place from case to case , case headspace is incredibly consistent from case to case or my head to shoulder datum measurement are virtually the same from case to case . How ever you want to say it , I'm very confident that what I'm producing is very consistent as a whole . How consistent ? My "Guess" is +/- .0015 or an ES of .003 . when you stack all the variables together .
So the real question or shade of grey if you will is . How much does that .003 effect pressure , accuracy , velocity etc in a real world application . Well Berger seems to think changing seating depths in .020 increments at minimum is likely best and I think they go as much as .040 increments . I've also read several times adjusting seating depth .005 or less is a waste of time when fine tuning a load . So how much does the .003 extreme variance I'm working with really going to matter when I know or have reasonable confidence that my bullet has a minimum of a .010 jam and "may" have as much as a .013 jam .
Does anyone talking in all these shades of grey think , "wow he's just wasting his time with such an inconsistent load" ?
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I'm getting ready to try the Berger test. I do not plan on using jam myself, I'm just not comfortable in that area yet.
https://bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/
https://bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/
hounddawg said:
And I'm not arguing that either. That's a gross difference. But if you look at the standard deviations in the table of my measurements of the MatchKings for the two different comparator diameters, you see the SD's are different by about half a thousandth. With a sample size of 15, that tells us the average extreme spread for the difference in the two measurings points was almost 0.002", so the jump to the lands based on the smaller hole ogive measurement will vary about 0.002" more than when measured from the throat contact point with those bullets. Bryan Litz points out he measures about 3% variation in BC within a box of bullets and small shape inconsistencies would contribute to that.
As to rocket science and brain surgery, the facts don't care whether we find them simple or complex. They just are whatever they are. We measure them and test them to see if they are important by looking for any effect they produce. If we see none, then we can put them on the list of things to ignore. But not before.
As I said earlier, I am not expecting a small difference (like 0.002") to normally make a difference. You then said you had seen 0.003" make a difference. I have not, but since 0.002" is 2/3 of that, perhaps the variation is stopping you from seeing an even smaller jump difference make a difference? I am not sticking my speculative neck out far enough to say that it is, but I would have supposed the experiment would interest you.
Metal god said:
Yep. They keep the amount of press stretch consistent. Those having shoulder position variations are the ones I want to make aware that having that variation contributes to variation in bullet jump and that measures to eliminate, like those shell holders, help keep bullet jump consistent.
Honestly Nick, I don't think that 99.99% of the shooters would notice a difference of .005. That .003 number came from a national level BR shooter using a 5K custom chambered in 6 PPC who thinks .25 MOA is a bad group. He uses custom bullets from a small manufacturer who caters to the BR crowd. I just checked 15 Bergers (105 hybrids) out of curiosity and found a ES of .002
Alright I'm shooting tomorrow and finally have my rifle Ruger PR 308Win . I went ahead and darkened a bullet and chambered a cartridge to see if I'm even in the lands . I did all those measurements over a year ago maybe pushing two years now . I do have a pretty low round count down the bore though . Under 1k easy and maybe not even 700 rounds shot from this rifle . Like I said , been shooting pistol a lot recently .
Anyways correct me if I'm wrong but it looks like I'm exactly where I want to be . There are 6 little dots with a thin scratchy line in between them all . I was actually surprised how concentric the marks are .
These marks just repeat them selves all the way around the bullet . I'll add that my ejector is pushing hard on the base of the cartridge so I'm assuming the case shoulder is headspacing on the chambers shoulder .
Anyways correct me if I'm wrong but it looks like I'm exactly where I want to be . There are 6 little dots with a thin scratchy line in between them all . I was actually surprised how concentric the marks are .
These marks just repeat them selves all the way around the bullet . I'll add that my ejector is pushing hard on the base of the cartridge so I'm assuming the case shoulder is headspacing on the chambers shoulder .
Metal god,
Rereading your posts, the variation you see with the Sinclair is because the smaller diameter hole in your seating die ram pressed against the ogive at a location that had that amount of inconsistency with respect to the actual bullet throat contact location. The smaller comparator hole is closer to the seating die's contact point diameter, so it agrees better with the seating die. But the Sinclair insert's measurement relative to the shoulder location tell you what bullet jump consistency will be. If your shoulders are perfectly consistent with the head and the heads are flat and perfectly square to the case body, then the head-to-comparator insert measurement will tell you the actual bullet jump consistency as well.
The only commercial gauge I am aware of that tries to make a direct shoulder-to-bullet ogive measurement in the Redding Instant Indicator. Its limitation is that it uses an undersized (for caliber) bushing die neck bushing to provide the hole diameter that meets the bullet. If I owned one, I would replace the bushing with my own that I had bored and reamed with my chamber reamer to provide a matching throat profile to contact the bullet. I assume there is enough range of movement in the shoulder contact sleeve in those tools to let the bullet reach that far. There probably is.
The reason I don't own one of the Redding gauges is that about three years before it came on the market I designed my own gauge for this with both the shoulder contact (knurled nut on the end, below) and bullet contact location on the gauge plunger plug cut with my chamber reamer (actually cut simultaneously in a single piece of stock which I parted between the throat and shoulder afterward). So when I want to add a cartridge, I make a shoulder nut and indicator plunger for that chambering using my chamber reamer.
Rereading your posts, the variation you see with the Sinclair is because the smaller diameter hole in your seating die ram pressed against the ogive at a location that had that amount of inconsistency with respect to the actual bullet throat contact location. The smaller comparator hole is closer to the seating die's contact point diameter, so it agrees better with the seating die. But the Sinclair insert's measurement relative to the shoulder location tell you what bullet jump consistency will be. If your shoulders are perfectly consistent with the head and the heads are flat and perfectly square to the case body, then the head-to-comparator insert measurement will tell you the actual bullet jump consistency as well.
The only commercial gauge I am aware of that tries to make a direct shoulder-to-bullet ogive measurement in the Redding Instant Indicator. Its limitation is that it uses an undersized (for caliber) bushing die neck bushing to provide the hole diameter that meets the bullet. If I owned one, I would replace the bushing with my own that I had bored and reamed with my chamber reamer to provide a matching throat profile to contact the bullet. I assume there is enough range of movement in the shoulder contact sleeve in those tools to let the bullet reach that far. There probably is.
The reason I don't own one of the Redding gauges is that about three years before it came on the market I designed my own gauge for this with both the shoulder contact (knurled nut on the end, below) and bullet contact location on the gauge plunger plug cut with my chamber reamer (actually cut simultaneously in a single piece of stock which I parted between the throat and shoulder afterward). So when I want to add a cartridge, I make a shoulder nut and indicator plunger for that chambering using my chamber reamer.
36.2gr avg 2290fps which makes me think I started way to low . My max load is only 37.8 and based on my experience I’ll likely not get to the velocities I’m looking for . Im going to stop shooting all 5 rounds for groups and only shoot 2 per charge wieght throgh the chrono just checking velocities and for pressure signs
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I may abandon this seating in the throat idea . This will be the second load I have that yhe COAL is not only to long to fit in the mag but it’s also to long to be ejected/removed from the receiver if not fired . I tried to eject a round and they are to long to clear the port . The issue is that the cartridge is still locked into the bolt by the ejector and extractor . It’s a real pane to deal with .
I think my next loads will have a COAL that just clears the port . I don’t know what that is yet .
I think my next loads will have a COAL that just clears the port . I don’t know what that is yet .