Experimenting with COAL...tips?

Pr589

Pr589

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Folks,

Starting to reload for my M305 and wanted to start experimenting with COAL. Any tricks for determining the distance to the lands without special tools? I don't have a way of opening the cartridge neck to allow the bullet to slide to starting COAL when chambered.

Also noticed that when my sized brass is inserted into the chamber, it doesn't allow the bolt to lock when the bolt is eased down. Should I be concerned? Some commercial cartridges will allow the bolt to close while others won't. The case length is to spec using a Lyman case gauge.
 
Be your own best friend, stick to mil specs.

This is a military fire arm, it is not meant to be coddled. Rip her back and let her fly(stripping a round from a mag only, never load a single round in the tube and drop the bolt)
 
Well normally the bolt gets slammed in there good and hard but I was trying to see if I could ease the bolt in with a sized case, bullet seated long with no powder, to start seeing when the bullets started touching the lands. I was surprised that I couldn't close the bolt and checked some of my commercial ammo as a comparison. I'm not worried given the amount of commercial and Norc ammo I've put through her with no problems but thought I'd ask.

So does everyone seat only to a maximum of the SAAMI spec length?
 
I seat to max mag length. I very highly doubt you will get to the lands and mag feed with the m305. Perhaps with a match barrel. If you have a dremel or even a hack saw you can put a few slits in the neck of a resized case. And it will hold a bullet well enough to get a good idea of where to seat a bullet to get to the lands.
 
"...doesn't allow the bolt to lock..." Cases aren't sized properly. Did you full length resize? It's required for semi-autos. Don't 'ease' the bolt closed either.
"...bullet seated long with no powder..." Doing that with no primer and crimping at all will give you the length to the lands. However, like CanuckR says, the max length given in your manual will save you a lot of screwing around. 'Just off the lands' is a bolt action target rifle technique you don't need to bother with.
 
to measure coal for your rifle and bullet combination. Open the action and put a bullet ( not a cartridge) into the chamber, tip gun down so the bullet slides forward and lodges in the lands, hold it there with a pencil. next insert a flat ended cleaning rod into the muzzle. When the end of the rod touches the bullet point make a mark with a felt pen on the cleaning rod. Remove the bullet and close the bolt. re-insert the cleaning rod down the muzzle until it touches the bolt, mark this on the cleaning rod. the length between your two marks is the COAL for your gun and bullet. I would bet that you can't load the bullet out that far due to the amount of free-bore in a military rifle.
 
Thanks folks. Good ideas. I've been seating to COAL Of 2.8" so far but wanted to fiddle.
So far only 168 grain bullets get any thing close to the max COAL. 155 grain and lighter are down at 1.75-ish but shoot great.
This has made me wonder how much of an effect COAL really has on group size.
 
Pr589 said:
Folks,

Starting to reload for my M305 and wanted to start experimenting with COAL. Any tricks for determining the distance to the lands without special tools? I don't have a way of opening the cartridge neck to allow the bullet to slide to starting COAL when chambered.
Click to expand...

Probably not worth bothering - loading your bullets to magazine length (2.800") or a bit less, is probably your best bet.

If you do want to know how to make the measurement:
- a modified cartridge case (as you're aware) is one good way
- with a great deal of care and fuss, one can push a bullet into the lands, and then find the location of its tip with a cleaning rod. Then push the bullet out and using the same cleaning rod, determine where the bolt face is (bolt closed and locked, no brass in the chamber). The difference between these two fussy and imprecise measurements, is the C.O.A.L. you need to load *that* bullet to in order to touch the lands.
- I think there is a version of the Hornady tool (the one with the special dummy case) made that you can use in a gas gun (a curved rod so you can get around the corner)

Also noticed that when my sized brass is inserted into the chamber, it doesn't allow the bolt to lock when the bolt is eased down. Should I be concerned? Some commercial cartridges will allow the bolt to close while others won't. The case length is to spec using a Lyman case gauge.
Click to expand...

Presumably the Lyman case gauge is telling you whether or not the case mouth has been trimmed short enough? (with calipers, the maximum length from case head to case mouth is 2.015").

In addition to this measurement, you also want to ensure that your shoulder (the case's "headspace" dimension) is pushed back far enough by your full length sizing die, to allow the case to chamber freely.

If your F/L sizing die has not been adjusted to make firm contact with your shellholder, try screwing it in in 1/8-turn increments, until it sizes the case enough that the case chambers as freely as a brand new unfired factory case.
 
Pr589 said:
Thanks folks. Good ideas. I've been seating to COAL Of 2.8" so far but wanted to fiddle.
So far only 168 grain bullets get any thing close to the max COAL. 155 grain and lighter are down at 1.75-ish but shoot great.
This has made me wonder how much of an effect COAL really has on group size.
Click to expand...

Sorry for the second post.

Are these Sierra 168s? You'll be very hard pressed to get better results than you will get by seating them to 2.80", loaded up with a sensible charge of a suitable powder (forty-something grains of a medium rate rifle powder).

Same with the Sierra 175s and the older Sierra 155s (part #2155) - load them to 2.80" just like the 168s. They all share the same nose shape, and they all work very (very!) well loaded to 2.80"
 
Using Hornady 168s under IMR4895. The lighter bullets have all been canellured and getting to 2.80 would have seated way short of the cannelure.

Thought that anything heavier than a 168 was not recommended without an adjustable gas plug.
 
174gr is the rifle's max under design specs. I doubt 175's will harm her.

Lots of awesome info/technique being shared here, I too am soaking it up :rockOn:
 
CanuckR said:
I seat to max mag length. I very highly doubt you will get to the lands and mag feed with the m305. Perhaps with a match barrel. If you have a dremel or even a hack saw you can put a few slits in the neck of a resized case. And it will hold a bullet well enough to get a good idea of where to seat a bullet to get to the lands.
Click to expand...

Like he said. Your limit is the magazine, not the chamber throat.
 
Max mag length is as close as your going to get to the lands
Seems to work out for most..........just one of them things.
Like my gun groups better with 150 FMJBTs than it does with 168 SMK.......just one of them things.
Still get that sh$tty grin every time she goes bang :))
 
So I dremmeled the neck of a full-length-sized cartridge and removed the rim. It turns out that the reason the bolt wasn't closing when the cartridges were inserted into the chamber is due to the extractor (doh šŸ˜³!). A bullet was then seated long (with some sharpie on the tip down to the ogive) then chambered. The sharpie shows that the bullet is hitting the lands but not getting embedded (no grooves in the bullet). I then opened the bolt and used a cleaning rod to ease out the cartridge - no force was needed - slid right out.

It turns out that OAL (not measured from the reference point on the ogive) tip-to-catridge-base for my rifle seems to be 2.83" +/- 0.002" (4 measurements). This is much shorter than I would have thought and well within what will fit in my mags. Time to start playing with OAL although I've heard from others at the range that they have gone down this path and have had inconclusive results.

Thanks all for the advice.
 
45ACPKING said:
174gr is the rifle's max under design specs. I doubt 175's will harm her.

Lots of awesome info/technique being shared here, I too am soaking it up :rockOn:
Click to expand...

180's won't hard her either IF you load them right. Problem is you can't expect the performance you want out of them.

My memory is a bit vague on this topic, but I did research it quite a bit. I could be wrong.

As I understand it, the army experimented with the diff' bullet weights. They wanted specific performance and ballistics out of the machine.
They tried the heavier bullets but found they could not get the ballistics they wanted without driving the action too hard. This included the 174's they shot great, but they couldn't quite get the speed they wanted out of them while still assuring the longevity of the rifle. It's one of the reasons the 168 became the standard. It was the heaviest bullet they found they could use, that gave them the performance they wanted, without beating up the rifle.

Something to that effect anyway. Bare in mind, the military likes to run things hot and was expecting a lot. The 174g loads they were using were probably a lot hotter then the stuff we are loading up for accuracy shooting.

Again tho', this is a rough memory recall, I could be wrong.

I've shot probably a 1000 180g Hornday SP's out my M305 with no ill effect. My rifle loves the bullet in fact. I could not get it to shoot the more expensive 168g bullets any more consistently then those plain jane 180 SP's. However, they were under a mild load of only 38g of 3031, and only left the muzzle at 2400fps.
Shot great at 100.

In practice, my experience with the M305 shattered a few myths about what it could and could not do. Just have to know what you're doing as a reloader, and know what the risks and machines limits are when you do.
 
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