Chasing lands for increased accuracy

[Knightrunner]

So I spent a couple hours watching videos and reading texts about determining the true OAL of a rifle cartridge and seating the bullet closer to the lands in an effort to increase accuracy.
My .308 modified case hasn't arrived yet, so I cut a slit in the neck of a once-fired, resized, and trimmed cartridge with a dremel. Pushing in a bullet and clambering it showed a measurement of 2.313" @ the ogive using Hornady's bullet comparator. I then subtracted .030" to arrive at an OAL @ the ogive of 2.283". I then assembled a cartridge, (minus powder/primer), to use as a model to help set up my seating die.
It was at this point that I realized this wasn't going to work.
Case trimmed to the book-specified trim length of 2.005"...

OAL length @ the ogive of 2.283" with a .030" jump to the lands...

As assembled...

The bullet is seated nowhere near the cannelure! Also, the book calls for a COL of 2.700" with this bullet and the COL of this model bullet is 2.874"...


Either I have done something very wrong or this process only works in certain applications...
The rookie question of the day is...would it make more sense at my current level of (in)experience, to forget about bullet jump and just follow the book's recommended COL? Or am I just stupidly missing something simple?

 

[z7]

So you need to start low and work up with powder at that oal. Choosing oal is a decision tree, here is my process, find the lands and what oal would be needed to get close.

now, the decision to try that load depends on what sort of gun? What purpose? Do you need the cannelure? If it’s a bolt gun you are probably safe either way. You should still be able to feed from the magazine at that oal. Semi auto, I might not chase the lands and use the cannelure instead

Finally, is there enough bullet in the neck of the case? Looks iffy with that bullet. Also looks like a FMJ bullet, not sure if the bullet is good enough to matter.

I run my 308 match loads .01 off the lands at an oal of 2.83”

my process for a load, kiss the lands with the bullet, then do a full load work up until i find a powder node I like, then I take that same load, load 5rds each at .005”, .01”, .015” And .02” off the lands, all working from jammed away from the rifling thus not risking unexpected high pressure

I use a chrono and group size and pick a load that gives a right group and tight velocity spread/SD/ES

Remember to start low and work up slowly, and start at the lands and work away, I only adjust oal after I’ve worked up to whatever my max working powder load is, (published max or when then chrono shows similar speed)

 

[Walkalong]

Also looks like a FMJ bullet, not sure if the bullet is good enough to matter.

Amen to that.

 

[Walkalong]

Best way to find the lands or set up a sizer.

 

[frankmako]

a easy way to get a starting point is to take a cleaning rod and run it from the muzzle end to the closed bolt. mark the rod at the muzzle end when it stops. take a bullet and mount it on the end of a chop stick. push the bullet all the way in from the chamber stopping when it hit the lands. hold in place while running the cleaning rod back down the barrel. when rod stops on bullet make a second mark on the rod. measure between the two marks to get the oal of the round with the bullet making contact on the lands. this gives you a good starting point to start the chase.

 

[Knightrunner]

now, the decision to try that load depends on what sort of gun? What purpose?

Sorry, yes it is a bolt gun. A remington 700 magpul enhanced tactical.

Finally, is there enough bullet in the neck of the case? Looks iffy with that bullet. Also looks like a FMJ bullet, not sure if the bullet is good enough to matter.

I don't believe there is enough bullet in the neck. It is a Hornady 150gr FMJ/BT. I was looking for a 150gr Hornady bullet at Bass Pro for 200 yd target shooting and it was that or the Interlock, (hunting bullet). I would have chosen one of Nosler's offerings, but Bass Pro didn't have any of the powders listed in Nosler's reloading manual for my application.
Also, I am currently shooting 40gr of H4895 behind these bullets seated to the cannelure at the specified 2.700" COL. It's my understanding that pulling the bullet out to get it closer to the lands will decrease pressure. Meaning if there was enough bullet in the case neck, I could simply begin working up from where I'm at now correct?

 

[Knightrunner]

Best way to find the lands or set up a sizer.

No arguing with that! Looking into 700 ejector removal next! Thanks!

 

[z7]

@Knightrunner moving toward the lands increases pressure because the bullet gets less of a running start before it is jammed into the rifling,

It is also true that jamming the bullet deeper in the case raises pressure, so a departure from published oal and powder should be done carefully and thoughtfully

If you can help it, don’t buy bullets or powder from bass pro, they charge way too
Much. Get the promo emails from midway, midsoutu etc and get in a position to buy two or three boxes, it pays for shipping. I’m shouting 178 ELD M’s form $34 per hundred after shipping


To your data, you should be safe working up from 40 grains, hodgdon’s online data for h4895 shows 41-43 grains as a starting load and 45ish as a max load for two different Nosler 150’s with Winchester brass, LC of FC brass i would expect to take 1.0-2.0 Grains off of that 45g max

With the rem 700 factory barrel you will probably struggle to get close to the lands, those barrels have a long throat as a safety measure but many of them shoot well anyway, if you just want to have fun shooting at targets, my advice is to get a box or two of FGMM ammo, 168 or 175 smk’s and see how accurate you and your gun are. Then go to Midsouth shooters supply and buy 3 boxes in the 160-180 range of target bullets (Sierra March king, Nosler Rdf, Hornady ELD or Hp match) and see what your gun likes, if the fgmm and your reloads show similar groups, you are reloading well

 

[Muddydogs]

Your figuring out that the book COAL means very little compared to your firearms. If you worked up your measurements right there is nothing wrong with the cannelure being that high. I like to keep a caliber of bullet in the case for optimal neck tension. Do the rounds fit in your mag if they need to?

 

[Demi-human]

If you have a bullet with a cannelure, seat to that.
If you are looking for more precision, you are not using bullets with cannelures, let alone FMJs.

Many of the newer Match bullets like a longer jump anyway. Leaps in accuracy can be had with the proper bullet.

 

[Knightrunner]

Do the rounds fit in your mag if they need to?

Just barely...

 

[Walkalong]

No arguing with that! Looking into 700 ejector removal next! Thanks!

Sinclair International/Brownells
SKU #: 080-520-375WS (5/64x3/8 roll pins) Fits Rem 700 bolt.

Bench block for Remington bolt

You'll want a 5/64 pin punch, although you can get by with a flat 5/64 punch. Replace the roll pin.

Ejector spring tool

It can be done without special tools, but they make it a LOT easier.

 

[Walkalong]

Buy some Sierra 168 Gr SMKs, load them to fit the mag, and let them jump, they don't mind. I load them to 2.800 and they shoot great.

 

[Telekinesis]

My .308 modified case hasn't arrived yet

The rookie question of the day is...would it make more sense at my current level of (in)experience, to forget about bullet jump and just follow the book's recommended COL?

I would honestly wait for your modified case to arrive and repeat your measurements, especially for someone new to this.

On the other hand, Remington 700 factory barrels have very long throats. On mine, if I want to get close to the lands I have to single load the cartridges because they are way too long for my mags. I’d recommend finding some good bullets like 168 or 178 grain SMKs or ELD-X and load to magazine length and go from there.

 

[Knightrunner]

Buy some Sierra 168 Gr SMKs, load them to fit the mag, and let them jump, they don't mind. I load them to 2.800 and they shoot great.

It appears that I can continue using the H4895 powder with these, but Hodgdon's recipe shows match primers. I am currently using WLR and CCI 200 primers. What is special about a match primer?

 

[Hooda Thunkit]

It appears that I can continue using the H4895 powder with these, but Hodgdon's recipe shows match primers. I am currently using WLR and CCI 200 primers. What is special about a match primer?

Match primers are reputed to be more consistent than regular.

I have never used match primers, so I have no first hand knowledge.

FWIW, I also never win at the matches in which I compete. I just figured it's my lack of experience, equipment, and competitiveness.
Coupled with old eyes.
I just go to shoot. I usually end up in the middle of the pack, so I'm good with that.

 

[z7]

It appears that I can continue using the H4895 powder with these, but Hodgdon's recipe shows match primers. I am currently using WLR and CCI 200 primers. What is special about a match primer?

If you start low and work up, primers are not an issue, the load data lists the primer just as a data point, either primer you have will be fine

match primers are the same as the other primers but are made a bit more consistently and checked more

 

[bob4]

What is special about a match primer?

I personally get my groups as tight as I can with my favorite primer. Last thing I do is swap out primers to see if any tighten that group any more. My understanding is match primers should ignite almost exactly the same each time. And for accuracy we like reputability.

 

[Jack B.]

I spent weeks chasing cartridge length to get the bullet to headspace within several thousands of an inch to the lands. Then I loaded some ammo to what the manual I was using said and realized I was wasting my time. As the shorter length cartridge shot better than my custom reloads Then I got away from all that and realized that for my rifle a Remington 700 BDL. The manual recommendations for O.A.L. shot better in my rifle. It's the only bolt rifle I own and I don't compete in any competitions, it's not a precision target rifle. So I quit messing around with Cartridge O.A.L. and concentrated making other things better. Like powder, bullet ,cartridge concentricity , trigger, scope and other aspects of making it a better shooter.

 

[Walkalong]

What is special about a match primer?

Made by the most skilled workers for more consistency. Don't expect magical results merely changing to match primer.

 

[jmr40]

If they fit the magazine, and chamber without hitting lands I'm good. If I'm not satisfied with accuracy I may try seating them a bit deeper for a little shorter OAL. But I'm almost always good to go at that length. I don't even bother measuring.

I think the OAL can be a factor with some bullets. I don't use those bullets. Others are much more forgiving, those are the ones I use.

 

[Rule3]

Made by the most skilled workers for more consistency. Don't expect magical results merely changing to match primer.

But with match primers, match bullets, and match powder (opposed to tactical) you will be a Winner!

 

[Varminterror]

Shotgun blasting some thoughts here:

@Walkalong shared the best method for finding the lands. Having the bolt torn down is also an opportunity to determine the appropriate headspace for your sizing die - attempt to close on a piece of fired and partial sized/neck sized brass, progressively lower your sizing die until the bolt handle just barely drags to close. If it drops on fired brass, then add shim layers of packing tape to the base until it doesn’t close.

The cannelure is irrelevant. You’re shooting a bolt gun, there’s no reason to crimp, so the cannelure is a useless artifact. Don’t get distracted.

You should not be talking about “chasing the lands” with an FMJ - or concerning yourself with match primers. A cheap blasting bullet like this really isn’t going to yield spectacular results, so be sure you calibrate and balance your expectations and investments. As they say - a $5 horse and a $40 saddle. Chasing lands and using match primers with a blasting bullet is a lot of work and added expense for nothing.

But you are not really talking about “chasing the lands” anyway. ”Chasing lands” in the reloaders’ vernacular is a progressive process of increasing your COAL as your throat (lands) erode with barrel wear. Effectively keeping the same jump to the lands as the lands move away. What you are really describing here is “establishing seating depth” or COAL for that particular bullet in your chamber. @walkalong’s video above well describes the process.

The importance depth, or COAL criticality, varies from bullet to bullet. Some bullets will be happy whether they start 60 thou off of the lands or 10 thou jammed. Some bullets will really want to be 50-60 off, some want to be 5thou off to 15 thou jammed. Knowing your particular bullet helps a lot.

If you have ~1 caliber in the neck, or the full length of the case neck making contact with the bearing surface, fit in the mag, and have a suitable jump for the bullet, then call it a day. You might be a little shallow in the pictures above, but a quick measurement will determine how well calibrated my eye might be.

Match primers, in the case of CCI, are the same as their standard primers, but primer cups and anvils used in match lots have gone through additional weight sorting for consistency, and supposedly assembled by someone other than the slack-jawed summer intern who may or may not have passed his last urinalysis. I have shot some of my smallest groups with non-match primers, including WLR’s. Spending extra on match primers is typically an investment in a small improvement in peace of mind, but often doesn’t deliver a tangible and measurable improvement in group size or velocity variability.

 

[Knightrunner]

Lots of great information coming my way! I appreciate all of you taking the time to share your comments.

Perhaps I should have started at the beginning in my original post. I took some of these rounds with me to the 200 yard range last week and struggled to shoot a tight group. I was chasing holes around the target trying to get a decent group. I was positive it wasn't me or the rifle. In fact, just a few days prior I was shooting quarter-size groups at the same distance with factory Hornady Black 155gr A-max .308 bullets. I had read that a great way to improve accuracy was to establish a true COAL for your particular rifle. And that is how I got to this point...

What has become glaringly obvious in the responses that I have received is that the real problem is the FMJ bullets I loaded with. It didn't seem like such a bad idea when I chose them...I mean after all, there was a time when I could consistently place FMJ bullets in the small ring from 500 meters with iron sights...especially from the prone position...

That said, I have zero intention of switching to match primers. I was only asking what was special about them because I found a recipe on Hodgdon"s website for the 168gr SMK bullets that Walkalong referenced above and it calls out match primers.
Thank you for pointing to that @Walkalong, I am heeding the advice and have already ordered that bullet. I will hold off on any further COL adjustments until after I try that combination at the length specified to see how they do in my rifle.

Thanks for the comments all! I'm listening...

 

[forrest r]

Typically you want a minimum neck tension to equal the diameter of the bullet. Meaning a .308" bullet should be seated deep enough so that .308" of the bullets body is in the cases neck. Bullet body ='s the distance from the base of the bullet for flat based bullets or where the boat tail ends and the bullets body begins until the octave on the nose of any fmj/rn/fn/xxr bullet or where the top drive band ends on swc's.

Not judging, just find it odd you didn't use the same a-max bullets and see if you could tweak the reloads to improve on what you bought/used/tested/benchmarked.