Question about loading bullets to jam into the lands

[stubbicatt]

I am in the information gathering stage here, so I read all I can find on the 6.5x47. I am finding a great deal of consensus with respect to seating bullets into the lands. The amount of "jam" I read about differs from a few thou to 20 thousandths into the lands.

I have never tried this technique, at least not on purpose, but it seems to me that at some point when one "jams" the bullet, it won't go any further into the lands, and will simply seat deeper into the case as you close the bolt.

Anybody know what "that point" is, or might be?

Thanks in advance.

 

[USSR]

stubbicatt,

When I was shooting 1,000 yard F Class competitively with my 6.5X55, I would go with minimal neck tension (.001") and seat the bullet so that it would be .020" into the lands. As you noted, the bullet simply seats itself a little deeper into the case when you chamber the round. I also found out through load development, that a reduction of 0.9gr in charge weight was necessary to duplicate the velocity of the same bullet seated 0.010" to 0.015" off the lands. Hope that helps.

Don

 

[Walkalong]

Yep, light neck tension and let the round seat its self into the lands. Load just a hair longer and let the lands push the bullet in a hair.

With heavy neck tension, just barely touching, just barely shy, or just barely into the lands is all about the same.

You need a short throat, a match quality rifle, match quality bullets, and match quality loading to utilize the advantage it can give. Not necessarily give, but can give.

 

[MtnCreek]

What bullet are you planning on using? About 0.020 off the rifling w/ a 140 a-max in 6.5 creedmoor is doing well for me.

If you decide to finish seating on chambering, reduce neck tension so you're not 'jamming' the bullet into the rifling, otherwise you may have issues removing a complete, live rd from the chamber.

 

[MtnCreek]

...With heavy neck tension, just barely touching, just barely shy, or just barely into the lands is all about the same.

You need a short throat, a match quality rifle, match quality bullets, and match quality loading to utilize the advantage it can give. Not necessarily give, but can give.

I lacked the match quality loading needed to succeed at that. Consistently seating the ojive to rifling is harder than it sounds. YMMV.

 

[tyeo098]

Use light neck tension, load a dummy round slightly long, close bolt and measure the setback.

That should tell you for far away your lands directly are. Load to, or a few thou longer than this measurement and you will be just kissing the lands.

...right?

 

[MtnCreek]

IME, it's not accurate enough for seating to lands. It will get you within ~0.005.

 

[docsleepy]

Try the Hornady OAL measurement gizmo Make several measurements.

Sometimes seating into the lands a few thousandsths improves the group size. In famous tests conducted in a windless indoor range, with groups of .030, seating into the lands was necessary. But my ability to control seating is generally only .002-.004 (using a comparator to attempt to measure ogive) so sometimes it isn't worth it. Backing off .010 to .020 might be prudent.

It does raise the pressure. VEry useful information above that it was worth about 0.9 grains of powder!

 

[Walkalong]

Consistently seating the ojive to rifling is harder than it sounds.

Yes it is.

 

[Walkalong]

It does raise the pressure.

If you are planning on loading this way, you start low doing it and work up. You don't suddenly take a load and change the seating depth to seat into the lands. Normal good reloading practice tells us this. Change something? Back off and start again.

 

[stubbicatt]

As a followup, I am finding that with the tools I have at my disposal, and measuring using the Stoney Point (now Hornady) comparator tool, my seating depths have a variance of about .003 to .004" to a datum point on the ogive.

Does anybody load their ammo to tighter seating depth tolerances, and if so, what tools do you use?

I do not know these answers, but over the years I have noticed that the seating plug (what I call the gizmo in the seating die which actually contacts the bullet) will tend to touch the bullet at a point somewhere between the nose of a spitzer bullet and the spot on the bullet ogive where the comparator tool contacts the bullet. I suspect my .003 to .004 variance is due in part to the vagaries of the actual shapes of these ogives, or maybe if the bullet has a VLD profile, perhaps the pointy nose is bottoming out in the plug, and it is no longer touching the bullet at the ogive. --With the inconsistencies in the meplats of bullets I have used, I would think that if the plug is pressing the bullet in by the meplat, that would account for a good bit of differences in seating depths.

If you guys are obtaining really consistent seating depths as measured to the ogive, what tools are you using?

Thanks again.

 

[Walkalong]

With the only load I have seated into the lands I never measured it to see if there was a variance, I simply seated a bit long with light neck tension and let the lands finish seating the bullet. Not jammed into the lands, simply pushed lightly into them.

.020 off the lands? I get an average of what a bullet is "at" the lands" and an avg of .020 "off" the lands. You'll never get it exactly the same each time, even with the best bullets (As in custom Benchrest bullets all made in the same exact bullet swagging die). Close, but not exactly.

You'll never see a .004 ogive variance on target. At least not at 300 and under. After that the only difference it might make is a larger ES, which hurts at long distance. I would think .020 into or off the lands would be more consistent in that regard than trying to be exactly at the lands, but I can't prove it.

 

[MtnCreek]

What seating die are you using?

What bullet are you using?

Does anybody load their ammo to tighter seating depth tolerances, and if so, what tools do you use?

Anything from RCBS to Redding give me tighter tolerances measuring from case head to ojive.

 

[stubbicatt]

What seating die are you using?

What bullet are you using?


Anything from RCBS to Redding give me tighter tolerances measuring from case head to ojive.

I am using a Lee seating die with either the 308 155 Lapua Scenar or the 175 SMK bullets.

The Scenars have an extreme spread of .003", out of 5 cartridges measured, but the if I remove one of them, other 4 are .001"

The SMK have an extreme spread of .004", out of 5 cartridges measured, but if I remove one of them, the other 4 are .002"

Of some interest, the chamber neck dimension on fired brass is .3444 to .34805" The as loaded neck diameter is .3391" That seems like a lot of expansion there on that 308 neck!, .005" to .009"

 

[MtnCreek]

Odd. 0.004 variance is too much. Try cleaning the die (special attn to stem) and shell holder. Check to see if linkage in the press is worn. Measure a cartridge several times, adjusting measure tool between measuring to confirm it's working properly. If you have another lot # of bullets, try them to see if you get same results. 175smk should not bottom out in std stem; I'm not sure about the scenar, but wouldn't think it would either.

I have some lee dies and have loaded good ammo w/ them, but not ammo where I was measuring for precision. New dies could make the difference.

Edit: Measure the bullets before loading, then measure the complete cartridge after loading.

 

[USSR]

Agree with MtnCreek, .004" is too much of a variance, and I would be looking into a higher quality seater die such as the Redding or Forster. Of course, if you decide to seat the bullets long so that the bullets are softseated into the neck upon chambering, then the variance becomes moot.

Don

 

[docsleepy]

I agree with earlier poster Walkalong that if you are backed off from the lands a bit, a few thousandths doesn't make much difference. If you are right on the lands, it can make considerable difference at least in my experience.

I have Wilson seaters, RCBS seaters, and Lee seaters. Most of the time I just use the Lee seaters. I can generally keep it within + or - .002 if I am really trying.

I have found that what makes the difference is different case mouth tension: if the case has higher tension, the bullet doesn't go in as far!

One solution I've found with my simple equipment is to use the same cadence and stroke each time, and then to do a SECOND touch with the handle right after the first -- so every tip gets touched twice. The first seats, the second seems to make the variance decrease significantly.

I happen to use Sierra bullets mostly, though I do have a bunch of benchrest speciality bullets. My measurements above are from 7mm Sierra spire point bullets, where the variability of the lead tip is a factor. But then, if you want to hunt deer, you can't use a hollowpoint varmint match bullet!

 

[docsleepy]

I think Lee and probably other manufacturers will cut you a seater stem that exactly fits the bullet you prefer, if you want.

 

[BullfrogKen]

Anybody know what "that point" is, or might be?

I wouldn't do it.


Let me rephrase that. I would only think about doing it if I were a really good benchrest shooter. The slight gain in accuracy would be worth the trouble.

But anywhere else, not at all. If you have to remove a round from the chamber, you run the risk of pulling out the bullet and having the powder dump into your action. I've seen it happen at local matches several times.

The reward is not worth it outside of a highly competitive sport like benchrest competition.

 

[KUSA]

Yep, light neck tension and let the round seat its self into the lands.

An easy way of doing this is to take a used case and pinch the end a little with some pliers.



Sent from my Galaxy S3 using Tapatalk 2.

 

[243winxb]

Jam

Anybody know what "that point" is, or might be?

Jam is done so there is no pressure spike when the jumped bullet engages the rifling. The 2nd reason, to center the round in the chamber, if not a "tight neck" . Not fun when a safety condition requires you to unload. Bullet sits in barrel, powder in action. Did it in my single shot with light neck tension. Bushing dies work well.

 

[Bruno2]

The dummy round is good advice. I have dumped powder in the action and what a mess. The technique I use is to smoke the lands. I seat a bullet at different and use a birthday cake candle to smoke the end of it so that it turns black. This way when the action is closed and the dummy is removed I can see when the bullet starts to make contact. I have never gone much beyond starting to touch the lands. Another thing to look at is a lot of box magazines in bolt guns wont allow you to be able to use the magazine and get the lowest amount of neck tension. This isn't a big deal if you plan on loading one at a time or have a break action like a Thompson.

I don't shoot BR so I usually stop at the point where I can still use the magazine if I want to.

 

[gandog56]

Anybody know what "that point" is, or might be?

That would depend I guess on the cartridge used, and the bullet's ogive.

 

[Walkalong]

I have found that what makes the difference is different case mouth tension

When loading my 15 to 20 cases I laboriously prepared, if any one had a different seating oressure (Hand die and arbor press) it was put on the "sighter" side of the block. If it was really off it was tossed.

Let me rephrase that. I would only think about doing it if I were a really good benchrest shooter. The slight gain in accuracy would be worth the trouble.

This is the only application I have used this technique on.

you run the risk of pulling out the bullet and having the powder dump into your action

Yes, if you have a dud, you have to be very careful removing the round, and may still spill powder all in the action. If I was running out of time I would never put another round in if I could not get it fired on record in time. That made me fire when not ready or in horrible conditions before, but that is the risk if you wait too long for your pet condition of the day. You do not want to remove a live round when using such light neck tension and seated into the lands if you can help it.

My super accurate .222 Mag heavy barrel Sako will shoot great .040 off the lands. I use medium neck tension and jump .040. It will shoot bug holes if you do your part.

 

[cacoltguy]

A good competition style seating die made by Redding or Forster (with a micrometer adjustment knob) is a good investment regarding getting more reliable bullet seating. Dont discount the resizing process as a cause for excessively large variances in seating depths though. In my experience this is actually more often the cause than the bullet seating process. As the necks become work hardened it makes for a rougher passage of the bullet through the neck as you seat it and hence increasingly more inconsistent seating the more times the case is reloaded. For my long range accuracy loads I anneal after every firing it it does wonders for the consistency of my seating depth.

On a side note, I don't think there is any good reason to jam Sierra Matchkings against the lands. Tangent bullets are very "jump" tolerant and doing so only unnecessarily complicates things. Secant (VLD) bullets are a different story. Jamming bullets into the lands requires you to develop a load with this in mind to avoid pressure spikes. As the throat of your barrel erodes over time, so does the bullet's contact with the lands. Now your pressure and ballistics have changed and you have to keep chasing the lands to keep everything the same. Too much of a headache and its one of the reasons I dont bother with VLD or secant shaped bullets. I did testing with my SMK's at varying seating depths and saw no discernible difference in accuracy and just shoot them .02 off the lands