Correlating seating force with... anything?

[memilanuk]

Just curious

In all seriousness: a few years ago I got a new K&M arbor press, and splurged for the 'force indicator' setup with the bellville washer stack and mount for a dial indicator. At the time it didn't get a whole lot of use, because most of the ammo I was loading at the time had enough neck tension that it was *really* hard to see anything meaningful - i.e. when your loads have 40-50 'pounds' (supposedly the reading on the indicator are supposed to be a rough analog to 'pounds' of force, as I understand it) its difficult to tell when the seater is bottomed out on the die body, at least for me.

With lighter neck tension, in the 20-30 range, its easier to tell when the seater has reached the bottom and you're against the die body. Still seems like a process with a large degree of subjective 'feel' to it - i.e. hard to get repeatable numbers. I haven't intentionally gone with neck tension less than that as of yet.

I am curious if anyone, whether using heavy or light neck tension, has gotten repeatable results that reliably correlate to anything - reduced group size, lower ES/SD for muzzle velocity, tighter pressure traces with some device like an RSI Pressure Trace II, less vertical on target at distance, etc.

Monte

 

[johara1]

I did and do load by the indicator reading. i separate by 2 lb. and color code the bullet tips so i don't mix them up. Does it work? yes check the records…….. jim

 

[memilanuk]

Hello Jim,

Cool! Hopefully I can learn how to refine my usage to where I'm getting better info out of it.

What metric are you using - group size, vertical dispersion, MV, etc.?

How did you decide on 2 lbs as your increment of choice?

How much neck tension are you using? 0.001", 0.002", more, less?

How many lbs force are you averaging for seating? 10, 20, 30?

Are you doing anything in particular as far as case neck cleaning/prep/lube? Brushing the insides of case necks? Polishing? Dry lube?

Anything else significant that you think matters or would otherwise affect the readings?

I am having a tough time differentiating where the seater bottoms out... seems like the force just keeps going up and up and up and then at some point I realize that probably about 5-10 lbs back was where it hit bottom and I have to mentally go back and subtract the appropriate amount, etc. Doesn't seem very precise... which is why I question whether I'm doing it right at all.

Thanks,

Monte

 

[Shynloco]

I'm not Jim, but thought I'd jump in here because of the title of your post...Correlating seating force with...anything." I use a Sinclair Arbor press (w/Wilson seaters for all my calibers) that doesn't have any measuring instrument that tells me how much pressure I'm exerting to seat a bullet. Rather, that "feel" of the action of seating tells me a good deal about the status of my Lapua (Norma or LC brass) and it's neck tension. I specifically look for uniformity in the seating process and can actually tell when one piece of brass is either too soft or too hard, possibly due to aging or some other factor, like that piece needs annealing. But I'm curious that you appear concerned about when you seater bottoms out. It strikes me that when I can't pull on the lever anymore, she's hit bottom and a visual look confirms the feeling of having hit bottom. I then measure the ojive on each seated casing to verify the proper seating depth of the bullet.

I use the .002 neck tension and also Imperial Dry lube by dipping each casing neck into the dry lube and shaking off the excess before seating the bullet. This process has proven successful for me and it shows on my targets downrange. BTW, I've tested this by separating out the harder seating bullets which aren't hitting or grouping as accurately as the consistent feeling seated bullets. The softer seated one don't seem to make a difference. Probably not very scientific, but it works for me. Info only.

Alex

 

[memilanuk]

But I'm curious that you appear concerned about when you seater bottoms out. It strikes me that when I can't pull on the lever anymore, she's hit bottom and a visual look confirms the feeling of having hit bottom.

True... but when you go to the trouble/expense of using something that shows the actual force being exerted, don't you think you would want to be able to get a stable reading, not an 'aw crap, seating force started climbing, the seater plug must have bottomed out X amount ago'?

I use the .002 neck tension and also Imperial Dry lube by dipping each casing neck into the dry lube and shaking off the excess before seating the bullet. This process has proven successful for me and it shows on my targets downrange. BTW, I've tested this by separating out the harder seating bullets which aren't hitting or grouping as accurately as the consistent feeling seated bullets. The softer seated one don't seem to make a difference. Probably not very scientific, but it works for me. Info only.

So you're seeing primarily smaller/tighter groups overall? Ever tried comparing hard vs soft seating rounds over a chrono?

Thanks,

Monte

 

[johara1]

2 lb.or .002 seems to keep the groups small and .002 neck tension middle of the road numbers would be 30lb…….. jim

 

[Shynloco]

True... but when you go to the trouble/expense of using something that shows the actual force being exerted, don't you think you would want to be able to get a stable reading, not an 'aw crap, seating force started climbing, the seater plug must have bottomed out X amount ago'?

So you're seeing primarily smaller/tighter groups overall? Ever tried comparing hard vs soft seating rounds over a chrono?

Thanks,

Monte

Monte,
As to the "don't you think" question to me requires what I believe is an assumption on my part about something I've not experienced, so I'd rather not comment.

As to the accuracy issue, yes I've found that when seating bullets that present more resistance (more pressure to seat) during seating tend not to be as accurate or gropup as well as the ones that I feel a consistent seating/even resistance. I usual separate those out (uneven resistance) and use them as foulers and then anneal them and conduct a closer look as to what could have caused that "more resistance" in seating. And unfortunately, I don't own a chrony and actually have never used one in all my 45+ years of shooting. Honestly have never gotten excited about using one as I don't compete, except for Rimfire and that's all at 50 yds.

Alex

 

[lrgoodger]

When I first got my K&M arbor press, I thought that if seating force really does make a difference, then I should be able to load five rounds and the ones that seat with the most force will have the highest pressure and therefore the highest MV. So I did exactly that. I loaded five rounds exactly the same and sorted them from highest to lowest seating force and shot them over the chrono. They went right down the line, highest to lowest seating force yielded highest to lowest MV. The difference was not much, but it was there and in the right order. I was actually pleasantly surprised. Later I wondered if the barrel heating a little more on each shot had more effect than the seating force difference (doubtful), or maybe added to it, making the order even more pronounced, but I never re-did the experiment shooting them in reverse seating force order.

I carefully watch the gap on the Wilson seater and seat slowly so I can tell about when the press bottoms out. You can group the loads just fine by noting where the force is at the point just before the gap closes. I usually go ahead and run the dial all the way up after noting that force. I find that gives me more consistent seating depths.

 

[Ray Gross]

Monte,

If I am being careful and trying to apply uniform force to my arbor press lever, I cannot positively feel the stem stop against the die body. At some indistinct point, I just realize it is not moving anymore. Perhaps a longer lever would aid in giving more sensitive feedback.

Ray

 

[PMA3]

Let's say that you scientifically figure out the arbor press force measurement number, go to the range and verify your findings and then load prior to your next match.

For a normal 1000 yard match, lets say you load 40 rounds....10 for sighters...10 for record... and then another 20 hoping you win a relay to get in the shoot off. You don't get in the shoot off and the next match is another 2 weeks out. Now you have 20 rounds loaded that have been sitting for 2 weeks with "XXX" number of neck tension change that can't be measured. How do you feel about these 20 compared to the 20 loaded the night before the last match with a precise force measurement number...just food for thought.

 

[memilanuk]

Haven't had much opportunity to shoot LR BR around here; F-Class is more my game. I'd love to give it a try, though.

By those standards, given the logistics involved in getting large amounts of ammo ready for multi-day matches - sometimes where the ammo has to be shipped ahead for domestic events where the round count is more than I can fly with, or where the ammo has to be ready weeks or even *months* before so it can go through international customs, secure storage, etc.... I'll take my chances with the pre-loaded ammo thats been sitting there a while vs. scrambling every night to get stuff loaded for the next day or trying to scrape together components/tools locally. ;D

 

[ALppc]

I did a neck tension test last summer on my 308.

What I was looking for was “what neck tension it would take to have the bullet not move with the pressure of the primer alone”.
Thinking that maybe the pressure from the primer going off is changing the seating depth on the bullet before the powder is lit.

What I did was take 5 Lapua cases (unturned necks) with new primers (BR2) and seat bullets .030” off the lands with no powder in the cases. Measuring the overall length before and after I chambered the round and fired the primer.

Starting with my normal neck tension of .0015” the results were surprising. All bullets moved from .000” to .030” (on the lands) but no two were the same within the five cases. Bullet 1 moved .030”, bullet 2 moved .000”, bullet 3 moved .020”, bullet 4 moved .015”, and bullet moved .000”.

No inside neck lube was used just once fired grit in the neck. Brass was once fired.

So I next increased the neck tension to .0025” same result. Increasing neck tension all the way to .007” (.001” at a time) I could not stop the bullets from moving with just the primer going off.

All neck tensions had at least one bullet that did not move and most had one that went all the way to the lands, but it was with a different case each time.

My engineer friend Jeff M insisted the test was flawed as I had not used some kind of buffer in place of the powder so the hydraulic effect would be similar. So I redid the .007” test with corn meal replacing the powder. This of course turned the corn meal into something that houses could be built from. But the results were the same.

All bullets moved and all were different although the deviation was less when the neck tension went up.

I pondered over the results for days. I was sure I could make the bullet not change seating depth with enough neck tension. I could not. Then I wondered why I always seem to end up with a seating depth under .010” to the lands when I settle on a final load, not being able to make the longer bullet jump work. Could it be that starting with bullets close to the lands leaves less room for seating depth deviation?

Al Barnhart

 

[memilanuk]

Thats some great info, Al! I bet seating the bullets against 7 thou of neck tension was not so much fun

Info like that makes me wonder if maybe thats why techniques like soft seating or jamming into the lands works so well for a lot of folks - the bullet is already touching/into the lands and the variations in neck tension and/or primer brissance can't cause the varying bullet jump that you observed?

Then again, I've had a couple guns where jumping the snot out of bullets (40-50 thou or more) was the 'answer'. ???

 

[nra-for-life]

Interesting topic. I for one have struggled with my km force indicator... You really have to be paying attention so you can get the reading before it bottoms out. It has been frustrating to me because it I seem to struggle to get cases that all seat with the same amount of force. Ill have two or three in a row then Ill get one that is way high or way low... The amount of variables in precision hand loading makes my brain hurt sometimes lol!

 

[ALppc]

Yes the .007” was almost two hands on the press handle.

Next I will try inside neck lube. And redo the test just to see if I can make the bullet movement more consistent. I would just jam the bullets but it tends to make the wind coaches nervous.

Al Barnhart

 

[David Christian]

Greetings everyone,

Jumping in on this thread from a few years ago, as I have been trying to understand how bullet seating force (using a K&M arbor press) correlates to muzzle velocity (using a Magneto V3) and I have yet to see any statistical connection, nor difference on the target. (twice fired Lapua brass, CCI 450 primers, Berger 140 Hybrids)

This weekend I tested 80 rounds, all prepped at the same time in the same exact manner.

Prep steps:
-Deprime
-Anneal with AMP
-F/L size bumping .002
-Tumble in STM
-Trim & Chamfer with Wilson
-Ream case with gauge pin
-Prime, powder, seat bullets

I entered all of my data from the fired rounds into an excel spreadsheet comparing the variation from average speed to the variation from average seating force. See here:

I also ran the correlation (correl) calculation within excel on the data. Here is the truncated result:

Does anyone else have empirical data that shows a positive correlation?

Thanks
David

 

[mikecr]

Honestly, you really can't tell when you've reached the end of seating -with an inline die & arbor press?

 

[David Christian]

Honestly, you really can't tell when you've reached the end of seating -with an inline die & arbor press?

Mikecr,

I find that if I slowly pull down on the handle while watching the dial indicator then stop the pull with about a 1/16th of an inch before the seater bottoms out, I can see a stable max force on the gauge. I record this figure for my measurement then continue the down stroke ensuring a full and repeatable seating depth.

 

[memilanuk]

Honestly, you really can't tell when you've reached the end of seating -with an inline die & arbor press?

With neck tension at 0.002 and above, generally no. Not reliably enough to count on. Even four and a half years later

 

[Alex Wheeler]

Do this test.
Take 3 cases. Use 3 different bushings for the neck. Use a stiff nylon brush in the neck and seat bullets.
record the numbers
Take 3 more, use the same bushing. Dont touch the inside of one neck, use a nylon brush in one and a steel wool wrapped brush in the other. Seat bullets and record the numbers.
I have done it so I'll go ahead and give you my opinion. Seating force measures friction mainly. The actual neck tension has a small effect on the seating force. Neck tension shows on target. Im not saying not to sort, its easy, so do it. But its down my list of importance. Sort by oal to the bullet ogive, it will give you a similar result. Longer oal had more resistance to seating. Then go shoot them and see how much it matters.