Acceptable tolerances in C.O.A.L. for .308

[5RWannabe]

Acceptable tolerances in C.O.A.L. ??????????

so im new to reloading, my grandfather used to reload, now that im shooting more I choose to pick up this art also.

Currently I am only reloading .308 win.

using my friends press and some forester dies i bought.

I understand that some shooters say to load to the rifling, but I am told that most Remmy 700 have a long way to go and you probably wont be able to get there. I have a new SS 5R milspec, and am currently loading to the C.O.A.L. length until can figure more things out. (and due to the fact that these rounds have to work in at lesat 3 diff firearms, another bolt Remmy 788, and an old French MAS 1949/56


as for my reloads im using Win Brass, Varget, CCI 200, and 168 SMK's . I will be switching to 175 for load development, its just that my local store only stocks the 168, and i wanted the practice.


I have noticed different lengths (due i think partally to the hollow point feature of the SMK's sometimes is not even,( i know there is a tool for this but im not that anal yet) I understand that i should be using a comparator (i think its called) the thingies that attach to your calipers and read from the widest part of the bullet instead of the tip. but besides me not having one of those....



my question is : WHat are the acceptable tolerances for C.O.A.L. for the .308 it says its supposed to be 2.800

My first batch of reloads have about a +/- 0.005 from the 2.8 mark. what is the acceptable range?

 

[bm11]

Re: Acceptable tolerances in C.O.A.L. for .308

That's about the range I've seen in SMK's, from what I've seen. It's because of inconsistent tips, not because of your die or anything you are doing wrong.

 

[RobG]

Re: Acceptable tolerances in C.O.A.L. for .308

Sinclair makes a seating depth tool to measure your chamber depth. That way you will have an accurate measurement for <span style="font-style: italic">your</span> rifles chamber. You can also use a bullet comparator to get a better measurement since the tips are inconsistent. I have and use both with good results.

 

[Fuzzball]

Re: Acceptable tolerances in C.O.A.L. for .308

"WHat are the acceptable tolerances for C.O.A.L. for the .308 it says its supposed to be 2.800"

There is no "supposed to be" about it, what the book lists is the OAL they used to develop the data.

A 10 thou OAL range isn't going to make any difference in your accuracy or safety at this point, your rifle couldn't care less where a bullet point hangs in space.

 

[gvanhyning]

Re: Acceptable tolerances in C.O.A.L. for .308

C.O.A.L. is also for standard magazine length. Magazines for the AICS will easily accommodate 2.850. Different bullets like different amounts of "jump" to the lands. I start all my loads at the C.O.A.L. to establish the best powder charge weight. I then play with the bullet seating depth and will work higher and lower in terms of length. Pay special attention to seating the bullet deeper with compressed powder loads as this can and will significantly change your chamber pressures. I use Quickload to get an idea of forecast pressure and velocity. While it is not perfect, it is an excellent tool. Here's the Quickload link:
www.neconos.com/

 

[gvanhyning]

Re: Acceptable tolerances in C.O.A.L. for .308

I disagree with Fuzzball ... While the load data is developed at that C.O.A.L., the load manuals also point out that every weapon is different and every load approaching maximum should be done with a high degree of caution. Example: I have a Remington 700 5R SS that I gave to the gunsmith for an extreme makeover, i.e., Rock Creek 5R barrel, oversize bolt w/Sako extractor, action trued, and a SAAMI spec match chamber. When I got the gun back I full length re-sized all the brass and it still would not fit the new chamber. I bought a tight body Redding full length re-sizing die and problem was solved. I did do some thorough testing with the loads I had previously developed.

 

[sniperaviator]

Re: Acceptable tolerances in C.O.A.L. for .308

The COAL listed on the Hodgdon website where they have the powder loads is a minimum. As you move the bullet out further, it reduces pressure. Need to understand that.

Ignoring magazine length and ignoring the reciever's limit on loading long rounds, the place to start is just kissing the lands. Now load a batch of rounds, each batch going shorter and see if COAL makes a difference in accuracy. If it doesn't a lenght of about 50 thousandths less than magazine length works well.

However, if you are going to use a magazine, then load COAL to the maximum length the magazine will hold. Then vary COAL down from this and see if it affects accuracy.

There really is no maximum COAL short of jamming to the lands. You need enough bullet in the case so the bullet stays straight and won't fall out.

Some rifles are more sensitive to COAL variations than others. Only way to know is to try varying COAL, shooting the rounds and comparing them to rounds with other COAL.

Hope that helps.

 

[marksman25]

Re: Acceptable tolerances in C.O.A.L. for .308

I recomend getting a bullet comparator and a Hornady O.A.L. gauge. This will tell you where the bullet ogive is contacting the rifling on your rifle. This gives you the COAL on your rifle. Depending on the leade in your chamber, this may or may not fit in your magazine. Since you are loading for 3 different rifles, you will have to load your ammo to fit the shortest chamber length. Similar to specs that factory ammo is loaded to so that it can be chambered in a variety of firearms. If you really want to get anal(and I would but that is just me) I would create a load specific for each firearm. It will give the best accuracy potential from each.

My .308 with 168gr A-max touching the lands is 2.821 COAL and still fits in the mag, but that is my rifle. May not work for you. The only way to know is to measure with the appropriate tools.

 

[sniperaviator]

Re: Acceptable tolerances in C.O.A.L. for .308

You can determine the OAL that touches the lands by loading just a bullet (no primer or powder) in a somewhat loose neck of a case. Just enough neck tension so you can barely move the bullet with your fingers. Now pull it out as far as it will go and chamber it carefully. The bullet will be pushed back into the case. Eject the round (again carefully) and measure. You should see some scratch marks where the lands touch the bullet. Some people mark the bullet with magic marker or smoke from a lighter so the lands leave a mark. Anyway, you get the idea. You may have to do it several times to get a confindent number. Tends to vary a bit.

 

[notquiteright]

Re: Acceptable tolerances in C.O.A.L. for .308

If you are just starting out I'd stick to whatever your smallest magazine length is. Conventional LR bullets in the 168-175 range really dont seem to mind whatever leap or jam you think is the cat's ass.

With the variety of rifles you own, it probably wont be ideal in them all but after seeing so many rifles use one common round between them I wouldnt sweat it too much.

My F-Class rifle is always single loaded, none of this from the mag stuff, however it uses the same length ammo my other 308s and a few friends can use it as well.

Use mag length as your standard for now and you can tweak later-

or not.

 

[5RWannabe]

Re: Acceptable tolerances in C.O.A.L. for .308

Thanks guys for the words of wisdom. I really appreciate the comments and the time you took to respond to my current issues.

I now understand more about how and why this number is used.

im going to be getting me some of those comparators.

and testing the bullet seating measuring system.

 

[Chanonry]

Re: Acceptable tolerances in C.O.A.L. for .308

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RobG</div><div class="ubbcode-body">Sinclair makes a seating depth tool to measure your chamber depth. That way you will have an accurate measurement for <span style="font-style: italic">your</span> rifles chamber. You can also use a bullet comparator to get a better measurement since the tips are inconsistent. I have and use both with good results.</div></div>

+1 then you can ignore the manuals and tailor for your barrel or magazine.

 

[223ai]

Re: Acceptable tolerances in C.O.A.L. for .308

Just be aware to not fall in the trap that most, including myself, fall into...chasing the perfect load. Load to what you find acceptable, and then shoot the barrel out.

Of course, some would argue that reloading is another hobby unto itself.

Good luck.

 

[Chanonry]

Re: Acceptable tolerances in C.O.A.L. for .308

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JPipes</div><div class="ubbcode-body">Just be aware to not fall in the trap that most, including myself, fall into...chasing the perfect load. Load to what you find acceptable, and then shoot the barrel out.

Of course, some would argue that reloading is another hobby unto itself.

Good luck.</div></div>

absolutely, 'tailor' was the wrong word, set it up would have been more appropriate. Once you get something that is good enough there is more to be gained from shooting than reloading imo

 

[samnev]

Re: Acceptable tolerances in C.O.A.L. for .308

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bm11</div><div class="ubbcode-body">That's about the range I've seen in SMK's, from what I've seen. It's because of inconsistent tips, not because of your die or anything you are doing wrong. </div></div>

+1 Same here with about the same variation in COAL using SMK's and Forster micrometer seating die.

 

[Nessal]

Re: Acceptable tolerances in C.O.A.L. for .308

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bm11</div><div class="ubbcode-body">That's about the range I've seen in SMK's, from what I've seen. It's because of inconsistent tips, not because of your die or anything you are doing wrong. </div></div>

That's one of the things that bug the crap out of me with SMK.

 

[Fuzzball]

Re: Acceptable tolerances in C.O.A.L. for .308

"I disagree with Fuzzball ... While the load data is developed at that C.O.A.L., the load manuals also point out that every weapon is different and every load approaching maximum should be done with a high degree of caution."


Hummm...what part of a simple statement like:

"There is no "supposed to be" about it, what the book lists is the OAL they used to develop the data." don't you understand?

 

[9H_Cracka]

Re: Acceptable tolerances in C.O.A.L. for .308

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gvanhyning</div><div class="ubbcode-body">I disagree with Fuzzball ... While the load data is developed at that C.O.A.L., the load manuals also point out that every weapon is different and every load approaching maximum should be done with a high degree of caution. Example: I have a Remington 700 5R SS that I gave to the gunsmith for an extreme makeover, i.e., Rock Creek 5R barrel, oversize bolt w/Sako extractor, action trued, and a SAAMI spec match chamber. When I got the gun back I full length re-sized all the brass and it still would not fit the new chamber. I bought a tight body Redding full length re-sizing die and problem was solved. I did do some thorough testing with the loads I had previously developed. </div></div>

This has nothing to do with COAL, and COAL also should not be confused with the SAAMI spec for MAX OAL for whatever chambering you are running. COAL is a static measurement independent of MAX OAL SAAMI for a particular chambering, as is the COAL that your magazine is capable of taking.

Untipped SMKs generally vary in the .005" range as stated above. In addition to that, the seating process we use with a rather universal seating stem designed to accommodate several bullet shapes generally introduces another .002-.004" COAL variance as well.

We are more concerned about the base-to-ogive dimension when it comes to accuracy, not COAL. COAL is a factor for functioning; base-to-ogive, or "jump length" is a factor for accuracy.

There are a few ways to try to shrink the variance of this number (COAL). One is to use tipped bullets. The Sierra 2156 is the only SMK I know of that is factory tipped, and they are very uniform in bullet OAL. To address the seating stem, M.l. ("Mic") McPherson did some articles a decade ago in Precision Shooting magazine about matching your specific bullet shape to your seating stem. He took the next size smaller stem, machined it close to the bullet shape, then final lapped in using a bullet and Clover compound. This reduced his base-to-ogive variance introduced by the seating process down to .001" on average.

Net/net on your original question, you are within range of normal for the equipment you are using. Dragging bullet tips and causing malfunctions is your biggest concern here, so make sure you are not doing that at 2.806". If you are, then drop the seater another .006" making your long ones at 2.800" and your short ones 2.794".

I was diagnosing a $5000 KAC rifle feeding "problem" using the ammo specified in KAC's manual recently. The factory LC M852 ammo was having cycling issues. The bullet tips were dragging. HUMM.... some of the rounds measured COAL 2.806", longer than SAAMI spec... A quick call to KAC figured out that someone has substituted a CMMG mag for the KAC mag, which was dead on 2.800" internal dimension. The KAC mag was another .015" deeper front-to-back (as were the Magpuls), so a mag switch fixed the "problem".