.308 cannelure placement different than Min OAL?

[Falconeer]

Hay folks!
I've started reloading .308 for my new Savage rifle (first time reloading for rifle, I normally reload 9mm, 357 Sig, & 12 gauge), and I have a question. First, some background (doing ALL this from memory). I'm using Lake City 91 brass (from GI Brass), primer pocket cleaned & processed, full length resized and trimmed. The bullets are 150grn Remmington Corelokt (on special from MidwayUSA). I'm using the Lee Modern Reloading manual for 150grn FMJ. Powder is 44grn (Lee's starting load) of Varget.

My quandry is when I seat the bullet to match the cannelure to the top of the brass, I'm too short.

Min OAL is listed as 2.8" (SAMMI spec for OAL is 2.81").
Seated to 2.8" and there's a approx 1/8th inch gap between top of brass to bottom of cannelure.

Is this normal? When I seat the round in the chamber the bullet gets pushed in til top of brass is just touching the bottom of the cannelure. I'm hoping to shoot this rifle for the first time this weekend. Am I doing something wrong? Help!!

 

[dakotasin]

ignore the cannelure. seat the bullet where you want it, and let the cannelure be where it is.

 

[USSR]

What dakotasin said. Overall lengths listed in reloading manuals are just the length that they used. Load to an OAL that fits your rifle's chamber.

Don

 

[Falconeer]

I had thought the purpose of Min OAL was to ensure the volume inside the case wasn't decreased to an unsafe point?

 

[dakotasin]

i wouldn't seat to less than minimum specs because accuracy is most likely to suffer.

moving the bullet in and out will increase/decrease volume some, but in a bottleneck case, it won't have catastrophic results. it may do something annoying, like stiffen up the bolt, but that's about it.

i'd load as long as i could and maintain reliable feeding, or until i jammed the lands. surely wouldn't go shorter. (if you jam the lands, be prepared for the possibility of extraction troubles of unfired cartridges... specifically, pulling the bullet out of the case).

 

[Falconeer]

i wouldn't seat to less than minimum specs because accuracy is most likely to suffer.

That leaves me in a quandry. The manual says seat to 2.8" (Min OAL), but when loaded into rifle the bullet gets pushed in to the lower edge of the cannelure (need to confirm if this is only when fed from magazine, or also when loaded manually). Do I need to crimp the bullet in place in it's 2.8" pre-cannelure postition?

moving the bullet in and out will increase/decrease volume some, but in a bottleneck case, it won't have catastrophic results. it may do something annoying, like stiffen up the bolt, but that's about it.

Ah, alrighty. Is that general rule for rifle ammo only, or does it also apply to bottle neck pistol cartridges, like my 357 Sig?

i'd load as long as i could and maintain reliable feeding, or until i jammed the lands. surely wouldn't go shorter. (if you jam the lands, be prepared for the possibility of extraction troubles of unfired cartridges... specifically, pulling the bullet out of the case).

Rgr that! I'm guessing easiest way to do that is to load a dummy round progressively longer until the lands catch the bullet?

Thanks much for the help/advice!

 

[Ol` Joe]

The lenght listed is the max SAAMI lenght for the 308 cartridge. Some manuals use the max OAL to work up their loads, and some load to their own OAL and list it seperatly from the SAAMI max. The SAAMI max is simpily the longest a cartridge can be and fit in ANY factory rifle chambered for that cartridges magazine, nothing more.

The rifle cartridges aren`t as picky about OAL in reguards to pressure as pistol rounds. The case volume of a straight walled case changes drasticly compared to the volume of the neck of a bottle neck cartridge with changes in seating depth. The over all case volume to bore changes the ratio of volume change too.
The bullet companies put the cannular on the bullet at a spot that will give the most cartridges a fit in the rifles mag. The groove on the 308 caliber bullets may be designed for the 30-06 or 308, maybe the 300 Win mag. The bullets cannular won`t be a good fit in all cartridges. I believe Hornady still loads their bullets to the center of the groove when developing their data for their manual and that is the loaded lenght given in their books. Nosler uses a Universal reciever and SAAMI spec barrels and loads at the SAMI max lenght for their data.

The best way to figure seating depth in a rifle is to find the OAL that has the bullet touching the leade and start load development there. When you find your max load start dropping the OAL in 0.005" increments until you find a spot that gives you the best accuracy. I load 3 rds at various lenghts and usually go past the "sweet spot" and see my groups start growing again. I then reload 6 rds at the lenght I think gives the best accuracy and 6rds at both the 0.005" longer and shorter lenght to verify I have it. I may play a bit with powder charge at this point to see if I can get any more improvment, but don`t exceed the manuals max!
The best accuracy I seem to find is at a lenght of 0.005"-0.020" off the lands but I do have a rifle or two that likes them still farther out.

EDITED TO ADD, I wouldn`t worry about crimping either unless you are loading for a semi-auto. Rifle cartridges don`t need a crimp in 99% of the cases.

The easiest way to find the lands of the chamber is to slightly squeeze the neck on a fired case, just enough the case will still chamber but hold a bullet. seat a bullet out past the SAAMI reccomended OAL and chamber the dummy rd. The lands will push the bullet back as it contacts the leade. measure the OAL repete to verify the lenght. Use this as your starting point for your loads.
"A Stoney Point tool or other comparator makes this a much easier and more accurate task"

BTW
The OAL you find at this point will likely be longer then the SAAMI max, if the cartridge will fit your mag at this lenght you can use it as is. IF best accuracy is found here. If your rifle has a long action and is chambered for a 308 or other short cartridge you can likely go way past the SAAMI recomedation.

 

[WayneConrad]

I'm guessing easiest way to do that is to load a dummy round progressively longer until the lands catch the bullet?

I think you can do it like this:

Size and trim a case. Now use hacksaw to make two vertical cuts in the neck, 180 degrees from each other. Deburr the cuts. You are making a springy neck that will allow a bullet to move easily when pushed on but stay put otherwise.

Stick a bullet in the neck. Chamber the round slowly so that the lands will push the bullet back in the case without grabbing the bullet. Remove the case carefully so you don't bump the bullet and move it. Measure the length. Now you have the OAL that for that rifle and that bullet will contact the lands.

This isn't your max OAL, though. I read that if the bullet is touching the lands when chambered, pressures will be much higher than otherwise, so you should back off some distance from the lands.

 

[dakotasin]

i think joe addressed most of your questions. as far as the 357 sig goes, i don't have an answer because i've never loaded for it. if i were to guess, i would say it may be a little finicky on cartridge length vs pressure, but not as finicky as a straightwall case. i would err on the side of caution w/ it because it is a high-pressure cartridge, and would start loading for it very close to book specs and get a feel for it before i started experimenting.

on jamming the lands in a rifle... i always at least experiment w/ this because it does sometimes lead to phoenomenal accuracy. the last load i devloped was for a 300 win mag. using my method of load development, i found a good solid load at max pressure. then, i seated the bullet deeper, and seated the bullet to hard jam, and tried those. in both cases, accuracy suffered, but! the loads w/ the bullet seated to a hard jam did exhibit slightly raised pressures. the bolt was a little sticky, but extraction/ejection, and primers were fine (this is typical behavior).

try this: seat a bullet just barely into the case (i never used the hacksaw, but it would work) and start it in the chamber. w/ constant, steady pressure force the bolt closed. remove your case, and note the land marks. polish the marks out w/ steel wool. adjust your seating die to this new length, then go 1/4 turn deeper. re-seat the bullet, and do the process again. the marks won't be as deep or as long, but still there. repeat the process until the marks are very faint. label the case w/ the gun and bullet and put it in your die box. this is your max. load 3 or 4 dummies and make sure they'll fit in your mag, and feed. adjust seating depth if need be. once you have this established, you're ready to start dumping powder and doing load development.

good luck!

 

[dakotasin]

forgot to mention... rifle brass grows w/ each firing, sometimes significantly. if you continue to chase the cannelure, you are setting yourself up for a ton of work on the bench in the form of brass prep... don't worry about the cannelure. it isn't good or bad, it just is.

 

[azredhawk44]

In my experience/knowledge, 2.800 is MAX OAL for 308. If you load a cartridge over 2.800 into a M14 or FAL mag, the tip of the bullet will rub against the front of the mag. That will give feeding issues.

I personally load Remington 150 SP's in Winchester brass to 2.790" OAL. Feeds great, pretty consistent too. I ignore the cannelure.

 

[dakotasin]

bolt actions rarely have the same constraints auto-loaders do...

 

[USSR]

When I seat the round in the chamber the bullet gets pushed in til top of brass is just touching the bottom of the cannelure.

Falconeer,

Seat your bullets so that the "top of brass is just touching the bottom of the cannelure" and the bullets don't get pushed in when chambering. The OAL means diddly-squat in this case. Crimping is unnecessary -- proper neck tension holds the bullet in the case.

Don

 

[Falconeer]

Thanks for all the great advice, folks! I'm going to spend some time this weekend determining a good starting point for OAL for this rifle and make notes. So begins the quest for better, longer accuracy!

Summarized this would probably make a good sticky. Opinions?

 

[azredhawk44]

bolt actions rarely have the same constraints auto-loaders do...

Bolt actions do have magazines, though.

The bullet still has to be held in the space allotted in the mag. Whether it's an M14 or a bolt action with a trapdoor floorplate. There's still a maximum length.

In a M14 mag, it's around 2.810" before the tip of the bullet rubs against the mag wall. I don't know where that is for a bolt action, but it's there somewhere.

Unless it's a single shot rifle.

 

[dakotasin]

yes, but, the mag constraints in bolts are rarely as confining as they are in autoloaders. ie, my ar-15's cannot be loaded longer than spec because of the mag, but my bolt 223's can be loaded a lot longer, and still run right thru the mag.

all i was pointing out is the mag constraints between different manufacture guns can be very different - even among bolt guns. a savage 110 in 223 can be loaded so that the bullet is barely held in and still run thru the mag (chambering is a different story), while that isn't true of a rem 700...

 

[azredhawk44]

okay, dakota, i hear you.

I don't own a bolt action yet, just some leverguns and an M14. In another year or two, you know?

I assumed that the internal magazine of a bolt gun had similar dimensions to a removeable magazine.

Sorry for the assumption, folks.

 

[Delmar]

You're not kiddin, Dakotasin about the Rem 700. The most I can get out of my Rem VS in 308, thanks to the mag box is 2.820. Fortunately, thats what the rifle seems to like best, even though the chamber will take a longer oal. Strange-almost like those Weatherby's and their "free space". That they will even hold an inch at a hundred makes me scratch my head, but out of the 4 I have loaded for, they all come in at about 3/4".

 

[dakotasin]

well, the 30 cal is a special case. you can blame hornady for that w/ their 220 round nose, and the companies that load for 'em. as soon as those become obsolete enough that nobody buys them in loaded form anymore, we'll get realistic throats in the rifles.

long throats: anything in 30 cal, wby, and ruger tang safety. most other guns are very average.

 

[USSR]

For some reason, Remington seems to excel at long throats and short mag wells. My FN SPR is not bad at all -- Will mag feed at 2.845" which is only .012" off the lands.

Don

 

[Falconeer]

Welp, I still haven't had a chance to actually SHOOT this rifle yet (along with the Sig P229 I've had FOUR weeks :banghead: ), but I did some checking on the seating depth. If I manually place a round in the chamber, close the bolt, then carefully remove the round, it measures to 2.77". I reset my bullet seating die to that depth. Thanks for the info folks!

 

[Ol` Joe]

If I manually place a round in the chamber, close the bolt, then carefully remove the round, it measures to 2.77".

As a double check I`d color a bullet at the ogive at that lenght with magic marker and rechamber it then check for rub marks. If the lands gripped the bullet and pulled it back out a couple thousanths when extracted you will see it. If marks appear, measure the lenght of the marks as best you can and seat the bullet that much deeper and recheck. When the marks disapear you will be right "at the lands".
Remember every time you change the brand, wgt or style of bullet the lenght to the leade will change also and you`ll have to refigure the lenght all over again.
Ain`t reloading fun........

Tip;

When you find the oal you want, lock the die lock ring to the die and DON`T move or loosen it from the die body, leave it be!

Now measure the lenght of the seating die with your caliper from the top of the stem to the base of the die.
Record the measurement and put it in the box of bullets you are loading.

Now whenever you`ve switched to another bullet and want to return the one you were loading simply adjust the seating stem to give you recorded lenght for that bullet and put it back in the press, start loading and double check that you are back at your desired lenght, you should be. Every time you try a new bullet record the die lenght and you will be able to return to the desired die setting quickly and easily........Remember there will be some lenght variation unless a comparator tool is used in measuring bullet lenght. The seater works off the ogive not the tip and will be seating repetably even though you see some variation when measuring to the tip. Trust your die

 

[30Cal]

FWIW, I doubt that varying OAL is going to matter much. It's important for really long, high BC bullets. For everything else, it's generally not something that's going to make a lot of difference one way or the other.

In a M14 mag, it's around 2.810" before the tip of the bullet rubs against the mag wall.

I know I shot 168s at 2.825" for at least 2 seasons. If I remember right, I started having malfunctions at 2.835".

Ty

 

[Falconeer]

As a double check I`d color a bullet at the ogive at that lenght with magic marker and rechamber it then check for rub marks. If the lands gripped the bullet and pulled it back out a couple thousanths when extracted you will see it. If marks appear, measure the lenght of the marks as best you can and seat the bullet that much deeper and recheck. When the marks disapear you will be right "at the lands".

Good way to check, thanks!

FWIW, I doubt that varying OAL is going to matter much. It's important for really long, high BC bullets. For everything else, it's generally not something that's going to make a lot of difference one way or the other.

I'm sure it won't matter much at my current level of expertise. But hopefully I can get myself in good habits now so when it does make a difference I won't have to switch my procedures around.