Question on cartridge length consistency

[AxlMyk]

Originally Posted by cdoc42

Then I happened to put a charged and primed case on the bench rather than in the die until I reached for a bullet to seat and noticed the case rocked a bit. I reseated the primer a bit more and that completely eliminated the discrepancy I have been seeing. Check your primers.

This was my first thought. The primers.

[Arbrn Rngr]

44 amp, If you are measuring your coal and pulling back .03 or less, you will not be able to eyeball that and must use a caliper. Jamming that bullet into the lands could increase pressures that would make one unhappy.

[Arbrn Rngr]

Ammo.crafter, I use the exact same technique. Then I check it with a 2 foot 1/4" threaded rod that screws into my fire formed brass, drilled and tapped for my 1/4" threaded rod. I check it 5-6 times both ways for consistency. I use a single stage Lee cast Iron press and the Lee seating dies give me spot on accuracy for my C.O.A.L ( minus .02). Hornady Steel manual dial calipers lock down and each finished round is a perfect match.

[Wrought]

I always assumed that its safe to shoot shorter necked cases just not long ones. I set my bullet seat down onto a test round, once i load a test round to my desired depth with no primer or powder.. I make sure most cases are the same length but theres always a couple shorter ones but my dies are set to load them to the same col regardless of case length. I also never crimp for a bolt action, only pistols and pumps/levers. My old pump .35 rem can shoot pointed bullets, i crimp them real good and the tips usually dont get to nicked up

[cw308]

You can use the short cases for foul shots until the grow , I trim every firing , find your trim range an trim in the mid range . the only way to accurately measure your rounds is from base to ogive .OAL is important when feeding from a magazine . Fire your new brass then concentrate on accurate case measurements.

[cw308]

Unclenick
Your diagrams are the best .

[RC20]

Primers should be at least .003 below back of the case.

[Unclenick]

Originally Posted by F. Guffey

I go to the range, get set up, load a round and then fire it. I take the next round and place the bullet into the neck of the fired case. If the bullet touches the neck of the fired case I put the rifle away and will not fire it until I have clearance for the neck to expand, if the end of my case neck is reduce in diameter I shorten the length of the neck to prevent it from getting into the throat of the chamber.

I have never had a case bevel inward when firing.

This is very interesting to me, because I have seen it frequently, just as the sectioned case shows. The case mouth may have sprung back enough that it won't allow a bullet to slip in without friction, but the neck behind the mouth is large enough to, so I've never considered it a sign of a problem. How hot the loads are seems to affect how much of it there is, too, with milder loads leaving the brass less completely formed to the neck area of the chamber.

[RC20]

Question:

If you know where the bullet touches the lands, and then regardless of where, have reference on the OGIVE of the bullet, does it matter where that tool you use and its line is?

[cw308]

Jamesf553
Is having a problem getting his bullets the same length , if the bullets were exact they would , but the bullets aren't exact , that's why for the seating distance to the lands is measured from the ogive . if his seating die is set properly , his OAL wouldn't be consistent but his ogive setting would be exact . By changing the die adjustments to make the rounds the same length his ogive settings would be all different . Ogive setting is most important .

[Dufus]

I have found the only way to have consistent exact ogive to lands is to use CNC made bullets.

Otherwise, manufacturing tolerances will prevent most any other bullet to be the exact measurement as the one before or the one after.

[hounddawg]

I have found the only way to have consistent exact ogive to lands is to use CNC made bullets.

Otherwise, manufacturing tolerances will prevent most any other bullet to be the exact measurement as the one before or the one after.

That is exactly right.



here are 15 Sierra 69 gr .223's.BTM is overall length or base to metplat, 2nd number is base to ogive. If your seating die is seating off the metplat the ogive to landing (jump) numbers will vary and if seating off the ogive the COL will vary.

btm bto	
0.902	0.509	
0.902	0.512	
0.9	0.509	
0.901	0.509	
0.903	0.51	
0.899	0.508	
0.899	0.51	
0.899	0.512	
0.899	0.509	
0.902	0.511	
0.9	0.509	
0.903	0.509	
0.898	0.509	
0.899	0.512	
0.901	0.512

[44 AMP]

ok, so a couple folks agreed I'm right, but thought my answer could have been better framed for a beginner, so I'll try again, and try to explain some basics.

The first question was about the difference in length in the first time fired cases.

The answer is that this is perfectly normal. Generally speaking the first time brass is fired, it stretches the most. And, each individual case, even from the same maker and lot#, fired in the same chamber with the same load, has the potential to stretch slightly differently than the other cases. so some will be slightly longer or shorter than the average length of the other fired cases.

The next question was about the difference in length of loaded rounds. The answer here again, is this is normal, given the very small differences in length, production tolerances of the bullets, and your seating stem type and where it contacts the bullet.

Most rifle seating stems are made with a cone shaped hollow, to all clearance for the tip of the bullet (so a soft point won't get mashed). The stem contacts the bullet ogive (the sloped/curved tapering part of the bullet) and that contact happens on the bullet at the same point of bullet width (diameter).

That point on the bullet can be varying distances from the bullet tip, depending on the bullet design, and the tolerances involved with both the bullet and the seating stem "hole" size.

SO, it is the difference in individual bullet length, between where the seating stem touches them and the bullet tip that gives you the slight variance in loaded overall length.

Consider, the next time you get new brass and new bullets you measure them, to see just how uniform they are before you start.

First question; How do I determine what length to trim to?

Anything below listed max will work. How many firings do you want before you need to trim them again?? The trim to length is not a set in stone number, it is a convenience number, to give you a few loadings (usually) before the case has stretched back to max length. The usual trim to length for most calibers is 0.01 less than max case length. Some cartridges are listed with trim to lengths 0.005" less than case max length.

Second question; Are cases that fall below saami specs useless? If not how far below can I go?

Useless? No. Not useful for a specific purpose, possibly. As long as there is enough case neck left to securely hold the bullet, the case can be used, meaning it can be loaded and fired safely. Accuracy, on the other hand could be different, every rifle has its own quirks.

I once had a trimmer setting "accident" and cut some .223 cases way too short. Like, the necks were only half as long as they should have been, short.
And, of course the error wasn't caught before loading them. I fired them in a Mini 14. There was no detectable difference in function or accuracy in that gun. In a precision bolt gun? who knows??

Third question; How important is the amount of "hold" on the bullet in the case neck?

The amount of "grip" in units of measure, I don't know, all I know is that it has to be enough, and it has to be uniform for accuracy. The old rule is at least one caliber length of case neck in contact with the bullet as a minimum.
Some folks say they get fine results seating to only a half caliber "depth". If you aren't loading "long" there's usually well more than one caliber of case neck gripping the bullet.

44 amp, If you are measuring your coal and pulling back .03 or less, you will not be able to eyeball that and must use a caliper

I'm not sure where this comes from, as I didn't mention anything about how I measure or load anything. and I know I didn't say anything about "pulling back .03" or anything like that.

if it is a comment on my comment " if you, and your rifle can't tell the difference, except with a caliper,.." let me explain what I meant by that.

What I was referring to was all the "measuring to the ogive" and "bumping the shoulder back .xxx" using different gauges to measure to the lands, and the other "tricks" that have been mentioned.

Say for example, you do all the tricks, checks, etc., and with your best loads you get 3/4" groups. Now say you load the same loads, but without ensuring each case is exactly the same length (just all below max), and you seat to a bit below the max listed loaded length, and don't do anything else, and you still get 3/4" groups.

IF that is the case, then the extra work ensuring maximum uniformity of each round is essentially wasted. YOUR rifle may, or may not shoot the precision crafted ammo significantly better than "regular" ammo. The only way to know for sure is to try ammo loaded both ways (with your most accurate load), and see.

[jamaica]

Dufus: "Case length has nothing to do with COL.

Differences in bullet ogive is what is screwing you up."

Yes, this.

Here is what I do: Adjust the seating die to give you the bullet length I want with the first bullet. Then load and seat bullets. The calipers are put out of reach. Don't worry about a slight difference in OAL as long as they go in the magazine and load OK. Then go shoot and have fun!

About trimming cases, I shot a 30-30 for many years in a lever action rifle. These cases did stretch and I would have to trim them. These are the only cases I have ever needed to trim.

44 AMP gives good advice above.

[Unclenick]

You can minimize the variables in the above by measuring enough bullets to know their average length. Pick two that are as close to average as you have. Use the first one to adjust the seating die. Use the second to make a final adjustment. Then all the errors will be plus or minus, but center around the average.

Some bullets have bearing surfaces that are shorter than a caliber, so these obviously cannot be seated to provide a caliber of bullet grip (the old M1 Type military match bullet or the current Sierra .308 155 grain Palma bullet, for example). Just sure these shorties don't get loose in the case going up the feed ramp, and you are seated deeply enough and will have to depend on load tuning to make further improvements.

What you will find is that different tools "find" the ogive at different places. The Sinclair bullet comparator inserts and hex nut tool both seem to match chamber reamer throats well, so they catch the ogive pretty far down. A lot of seating dies catch it rather further up. This, IME, results in up to around a 0.002" discrepancy comparing a Redding Competition Seating Die to what the Sinclair insert finds on a 168 grain .308" SMK. A Lee Dead Length Seating Die catches them still closer to the nose. So you just have to accept there will be some degree of imprecision in bullet jump imposed by this. The best cure is to find a seating depth that isn't particularly sensitive to exact bullet location, but that still minimizes group size. This is why I am always suspicious of what shooters are getting with seating depths purportedly less than five thousandths off the lands. I know that in that range they could go from wider open to touching the lands just based on some bullet's tolerances.

[RC20]

Not that there is any question Uncleick knows where of he speak, but as more of a test it and then work from there type, all true.

I have had bullets seat back that I thought were ok, some would get into the lands and stick (if I tired to jack them out when a cease fire was called)

In reality it does not matter what your baseline of your seater be at the same point as your checker (I actually made my own insert of case shoulder bump back out of an insert for a caliber I will never use, it doe not match anything anyone uses but all I have to know is the shoulder moved back at least .001)

I don't zero out the mike for bullets, sure its an 1.004 longer than anything anyone else uses, but I am not using that in their guns, only mine. As long as I know its moved .0XX is all I care about (in or out)

I know where the lands are for any given bullet with that setup (logged and tested by actual bullets in a cartridge to where they stick in the lads not the Hornady throat unit that is about .015 short. I will use the Hornady and it case but also assume its short (and I check bullets to work)

I then adjust them back .020 (at least to start).

Any close than .010 I get random lands sticking. So no more than .015 close to my spec of sticking in the lands.

I am not close to Tubbs so I am not after the last tiny bit of precision. If I can shoot sub 1/2 inch groups with a good load, I am happy.

So what works for me is not Tubbs class but how many of us are.

I can always refine if that magic day happens!

[cw308]

My system in sizing an seating . Sizing , I'm using the standard RCBS Standard F/L sizing die with the Redding Precision shell holders . sizing my brass to .001space in my chamber . Seating I use the Redding competition seating die . My way of thinking is the case fits inside the sleeve from the shoulder to the shellholder with no slack . With the bullet on top of the case mouth raising the ram , the seating stem set for ogive setting . My thinking is the bullet side OD would stop at that point pressing the bullet into the case as the ram raises without the tip of the bullet hitting the top of the stem . How else could the ogive setting be exact , or am I missing something .

[Unclenick]

That will mean base-to-ogive measurements for different rounds match at the ogive diameter where the Redding die leaves its little ring mark. That diameter, from my measuring, will not be the exact same distance to the bullet base from one bullet to the next, nor do we know it will be the same distance from the wider diameter ogive shoulder of the bullet that actually meets the throat, though I expect the bullet-to-bullet difference to be small. The problem is the bullets are the mixed output of more than one set of tooling and the toolmakers never seem to get quite exactly the same exact ogive radius established on each forming die.

[cw308]

Unclenick
Let's say the OD on the die at ogive ring is .305 for a 308 cal. even though the bullet may have a slight difference but stops at the .305 wouldn't that bullet from base to ogive ring be the same making the ogive to the lands the same ? I can see the bullet may be seated at slightly different depths . Tip of bullet to base was never a concern of mine , only base to ogive . When I measure my reloads with the RCBS Precision Mic all are dead on . I shoot with a .002 jump
P.S. I only shoot Sierra 168gr. HPBT MatchKing Bullets

[Metal god]

For the OP's sake I'd like to add ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,Well nothing

I don't care what anybody says , I still crack me up

[cw308]

Metal god
I understand completely , when everyone answers to help in every possible example . It opens up other ways of thinking , that opens up other conversations . That one post may help not only the OP but others like me . Im sure the OP can chime in when the post goes south . Don't you think if we were all in the same room , the same thing would happen . I could talk on this subject all day . Be Well , Chris
P.S. When I'm not shooting or reloading , I talk about reloading or shooting . There isn't many in my neck of the woods that do . So keep it coming.

[Metal god]

Don't you think if we were all in the same room , the same thing would happen . I could talk on this subject all day

Absolutely , there is more info in this thread then the OP could have asked for . It's the great thing that happens when people that know what they're talking about , speak .

One of the best things about this forum .

[Unclenick]

Let's say the OD on the die at ogive ring is .305 for a 308 cal. even though the bullet may have a slight difference but stops at the .305 wouldn't that bullet from base to ogive ring be the same making the ogive to the lands the same ?

Why would it? What dependency do the two have inside the chamber? The back end of the case doesn't determine how far forward in the chamber the cartridge and bullet go during firing. The headspace determining surface does that. Additionally, because the seating die doesn't push down on the bullet at the .305" diameter point, if there is a difference in ogive radius among the bullets in the box, it won't seat every bullet with the exact same head-to-.305" diameter ring each time, anyway.

Keep in mind, as we get down into the last thousandths of jump, we are probably wasting time better spent shooting. The reason I pointed these sources of error out is just to say we probably can't control the actual distance of the .305 ring from the lands reliably to better than about 0.005" (±0.0025"), cartridge-to-cartridge, by normal loading practices. As a result, someone thinking they are loading to get a jump of 0.002" (I've seen this claim made) is probably actually jamming the lands sometimes and not others. Therefore, any benefit claimed for such tight none-touching spacing is suspect and the group size is likely to turn out to be just as good seated another 0.005 in either direction. Or more.

[Metal god]

As a result, someone thinking they are loading to get a jump of 0.002" (I've seen this claim made) is probably actually jamming the lands sometimes and not others.

I think this would be an accurate statement , at least for me . I have a very accurate 168gr HPBT 308 load that measures 2.855 just off the lands . I estimate it to be .003 to .005 off the lands . I how ever believe maybe 1 in 10 to maybe 1-15 rounds I can feel slight resistance when closing the bolt which I believe is the bullet being pushed into the lands .

This load is my accurate plinking load . I say plinking because it does not use the "usual" known match components like match primers , Lapua brass , IMR 4064 , Varget or other powders everybody else uses for there best loads . It how ever may be the best load I've ever worked up as far as consistently preforming every time out .

I mention that because the fact I consider these a plinking load I've not tested if those rounds I feel get pressed in the lands shoot any different then the ones that I believe to be just off . They all go where I want them to so I've not found the need to find out .

[cw308]

Unclenick
I first size the case , I know the length of my chamber . What I did was strip my bolt on my Rem. 700 inserted a go gauge 1.630 then added shims the the base until the bolt closed with resistance 1.632 I did the same thing with a fired case an size the case to .001 headspace bolt would close with a slight hint of resistance to zero . I did the same with the bullet by seating it long an lowering the stem leaving no marks or resistance .Both measurements for headspace an base to ogive I now have , an can adjust my dies to give me the same .001 headspace an jump or jam settings every time . If I'm missing something , I don't understand why all my reloads are exact. The stripped bolt closures by feel for me is pretty accurate . What is your system . Chris