So about OAL for accurate rifle rounds

GymB

GymB

Picking it up slowly.
2A Bourbon Hound 2024
2A Bourbon Hound OG
Charter Life Member
Benefactor
Joined
Dec 16, 2016
Messages
14,678
Location
Waxhaw
Rating - 100%
45   0   0
Really started playing with reloading 223 a couple weeks ago, my first bottleneck rifle cartridge. Have been loading to 2.20” because it feeds through the mag and lines up in the middle of the cannelure on a 55g fmj bullet. Last night I tried to measure the optimal OAL using traditional methods and couldn’t make it work, so today I went and bought the Hornady doodad, now I see what my problem was last night.

8FC870E0-51AB-405A-9B03-28D6E9A7EAAA.jpeg

Obviously even if I back off the lands a couple thou I’m not going to have enough neck engaged.

A heavier bullet will be longer so I will try that, but am limited by the 1:9 barrel and the magazine.

Could not trim brass for 10 firings to get a long-neck 223, but I’d still have the OAL well beyond what would feed.

Gonna go shoot it at 100-300 before I do anything, but thought I’d get the question out there. Any ideas?

Thanks
 
Buy a short chambered barrel or find a manufacturer that will chamber a barrel to your COAL and bullet type.
It's a common practice in bolt guns.

I think GAP offers AR platform rifles with short/custom chambers.
 
Common problem in reloading for accuracy in most autoloaders and very misunderstood by noobs. COAL is a function of the overall length of the cartridge to allow the gun to feed and fire, not for accuracy. For optimum accuracy as you're attempting to do, you'll probably need a custom cut chamber so the ogive radius will be a couple thou off the rifling and still keep cartridge length in a range the rifle can function with.
 
Slacker said:
Buy a short chambered barrel or find a manufacturer that will chamber a barrel to your COAL and bullet type.
It's a common practice in bolt guns.

I think GAP offers AR platform rifles with short/custom chambers.
Click to expand...

Curious that S&W would cut the chamber significantly longer than a magazine would feed, but I’ll use it for short range stuff and add another gun for long range rather than swap the barrel.

Dave951 said:
Common problem in reloading for accuracy in most autoloaders and very misunderstood by noobs. COAL is a function of the overall length of the cartridge to allow the gun to feed and fire, not for accuracy. For optimum accuracy as you're attempting to do, you'll probably need a custom cut chamber so the ogive radius will be a couple thou off the rifling and still keep cartridge length in a range the rifle can function with.
Click to expand...
Yes, I understand the relationships.

Bailey Boat said:
OR... have a thread or half cut off your barrel and re-chamber it to your desired OAL.......
You can rent the chambering tools here www.4-dproducts.com
Click to expand...
Have never done this, but it sounds like it would require removing the barrel extension, cutting the barrel, rechamber the barrel, threading the barrel for the barrel extension, installing the barrel extension, sealing the port for the gas block, drilling a new hole for the gas block. That’s a whole lot of effort to save a stock barrel. Is it less complicated than I imagine?
 
JimB said:
Curious that S&W would cut the chamber significantly longer than a magazine would feed, but I’ll use it for short range stuff and add another gun for long range rather
Click to expand...

Almost all manufacturers do it these days.
The older Rem 700's are shorter chambered than those made today.
My theory is lawyers are driving the engineering. More leade = less pressure.
 
How important is a short leade to accuracy? Does a shorter leade always equate to better accuracy? I am not a long range precision shooter but do have some rather accurate rifles, by my standards, that have fairly long leades. Don't Weatherby rifles generally have chambers that have long leades?

I am just wondering whether chasing a shorter leade would have a significant benefit?
 
Charlie said:
How important is a short leade to accuracy? Does a shorter leade always equate to better accuracy? I am not a long range precision shooter but do have some rather accurate rifles, by my standards, that have fairly long leades. Don't Weatherby rifles generally have chambers that have long leades?

I am just wondering whether chasing a shorter leade would have a significant benefit?
Click to expand...

Great question, I’ve just assumed that it matters, and I think it does, but I don’t know how much.
 
Assume you are loading for an AR. Brass needs to be trimmed to length. See reloading manual for max length. New brass should be OK and not need trimming. 55gr bullet can go 2.26" COL but not needed. I set mine at just being able to see cannelure at the case neck. 21.5grs Reloader#7...tried and true Sierra accuracy load. Med to heavy crimp and you should be good to go.
 
Jim I’m having a little trouble with this based on your picture...seems super long. What’s the OAL of the chamber based on that test? Is that normal for the host rifle? Which is what, by the way?
 
As I understand it, the leade in the AR type guns (or anything stamped 5.56) is long for reliability purposes. A 223 Rem chamber has a shorter leade which can give more accuracy. While the chambers of the two are pretty much identical from the case mouth back to the breech, the differences are forward of the case mouth. A 223 Wylde chamber is a compromise of the two, as it can handle 5.56 pressures, but the leade is tighter than a 5.56.

This isn't to say that a 5.56 can't be accurate, you will just have to find a bullet that doesn't mind jumping to the lands. Some of the Berger bullets are known to be more accurate with a longer than normal jump.
 
JimB said:
Great question, I’ve just assumed that it matters, and I think it does, but I don’t know how much.
Click to expand...

In my super tight chambered 5.56 sabre defense AR, it makes a huge difference.
Of course they don't fit the mag, but they print teeny tiny clover leafs.
(77 gr SMK over Varget)
 
jimmyjames8 said:
Assume you are loading for an AR. Brass needs to be trimmed to length. See reloading manual for max length. New brass should be OK and not need trimming. 55gr bullet can go 2.26" COL but not needed. I set mine at just being able to see cannelure at the case neck. 21.5grs Reloader#7...tried and true Sierra accuracy load. Med to heavy crimp and you should be good to go.
Click to expand...

Rifle is a S&W M&P, brass is trimmed, am loading a 55g Hornady FMJBT over 25g H335 with no crimp.

11B CIB said:
Jim I’m having a little trouble with this based on your picture...seems super long. What’s the OAL of the chamber based on that test? Is that normal for the host rifle? Which is what, by the way?
Click to expand...

Yes, it is super long, didn’t even bother to measure it because it obviously wouldn’t feed through the magazine even if the bullet would stay in the case, but if I had to guess, 2.5”. I don’t understand the question about it being normal, I do own two of them so will measure the second later today, be great if it had a more reasonable chamber length.

Toprudder said:
As I understand it, the leade in the AR type guns (or anything stamped 5.56) is long for reliability purposes. A 223 Rem chamber has a shorter leade which can give more accuracy. While the chambers of the two are pretty much identical from the case mouth back to the breech, the differences are forward of the case mouth. A 223 Wylde chamber is a compromise of the two, as it can handle 5.56 pressures, but the leade is tighter than a 5.56.

This isn't to say that a 5.56 can't be accurate, you will just have to find a bullet that doesn't mind jumping to the lands. Some of the Berger bullets are known to be more accurate with a longer than normal jump.
Click to expand...

I had forgotten that 5.56 has a longer leade, thanks for the reminder. Never did know why it has a longer leade, but nonetheless I’ll check to see if it is within spec.

Strange that some bullets like a little more jump, or at least tolerate it better. Thanks I’ll go do some reading on that and try some Berger bullets.

Ikarus1 said:
This. All. Day.

Barnes TSX is another.
Click to expand...

I think I can find those easily enough. Pretty soon I’ll have more boxes of bullets that I don’t shoot than holsters that I don’t wear.

Slacker said:
In my super tight chambered 5.56 sabre defense AR, it makes a huge difference.
Of course they don't fit the mag, but they print teeny tiny clover leafs.
(77 gr SMK over Varget)
Click to expand...

Nice, but if I’m not feeding from a magazine then I’m disinclined to stay with the AR platform, maybe even go blue and walnut in a single shot, and if I’m doing that then maybe go on up to 30cal. So many choices.
 
JimB said:
Nice, but if I’m not feeding from a magazine then I’m disinclined to stay with the AR platform, maybe even go blue and walnut in a single shot, and if I’m doing that then maybe go on up to 30cal. So many choices.
Click to expand...
Or go to a different caliber in the AR platform that is inherently more accurate. There has been lots of buzz about the 224 Valkyrie lately.

OTOH, if you really are considering going to a single-shot, then why not consider single-feeding your accuracy rounds in your AR? It would be a single-shot accuracy rifle that has the option to feed plinking ammo from the magazine.
 
JimB said:
Rifle is a S&W M&P, brass is trimmed, am loading a 55g Hornady FMJBT over 25g H335 with no crimp.



Yes, it is super long, didn’t even bother to measure it because it obviously wouldn’t feed through the magazine even if the bullet would stay in the case, but if I had to guess, 2.5”. I don’t understand the question about it being normal, I do own two of them so will measure the second later today, be great if it had a more reasonable chamber length.



I had forgotten that 5.56 has a longer leade, thanks for the reminder. Never did know why it has a longer leade, but nonetheless I’ll check to see if it is within spec.

Strange that some bullets like a little more jump, or at least tolerate it better. Thanks I’ll go do some reading on that and try some Berger bullets.



I think I can find those easily enough. Pretty soon I’ll have more boxes of bullets that I don’t shoot than holsters that I don’t wear.



Nice, but if I’m not feeding from a magazine then I’m disinclined to stay with the AR platform, maybe even go blue and walnut in a single shot, and if I’m doing that then maybe go on up to 30cal. So many choices.
Click to expand...

What I meant the normal comment as in since I wasn’t sure what the rifle was, were your results in line with other barrels from the same manufacturer or is yours an outlier
 
Toprudder said:
then why not consider single-feeding your accuracy rounds in your AR?
Click to expand...
Well, if I need to load close to the lands for accuracy I’ll need a bullet that’s at least 1/4” longer, but I can’t go that long because the barrel has a 1:9.25 twist.
 
AR rounds fed from a mag need crimping or extreme neck tension or you will have reliability problems. The kinetic energy of the bolt slapping home a round will push the bullet forward into the throat even if single loading. A 9 twist will stabilize 55 to 77 gr bullets despite what all the bullet and powder mfrs say.
 
jimmyjames8 said:
AR rounds fed from a mag need crimping or extreme neck tension or you will have reliability problems. The kinetic energy of the bolt slapping home a round will push the bullet forward into the throat even if single loading. A 9 twist will stabilize 55 to 77 gr bullets despite what all the bullet and powder mfrs say.
Click to expand...

This... ^^^


9T will work for sure, What kind of accuracy are you looking to achieve and at what distance(s)?

For a great, practical, accurate, precision AR rifle build reference, look at the:

  • Army Designated Marksman Rifle Specs (SDM-R ).. They spec a 20" S.S. 1-8 barrel for precision shots out to 600 meters. 5.56mm chamber
  • Navy SPR specs.. They spec an 18" S.S 1-7 barrel with 77g ammo. 5.56mm chamber




I have an 8T 16" barrel chambered in 5.56 that shoots extremely well out to 200 yards using 75g Hornady Superperformance ammo..
 
jimmyjames8 said:
AR rounds fed from a mag need crimping or extreme neck tension or you will have reliability problems. The kinetic energy of the bolt slapping home a round will push the bullet forward into the throat even if single loading. A 9 twist will stabilize 55 to 77 gr bullets despite what all the bullet and powder mfrs say.
Click to expand...

I have the Lee FCD, just haven’t used it. Read that Sierra did some testing and found that factory ammo lengthens by .003” to .007” upon chambering...I have no reason not to believe them, but then it looks like half the folks think you must crimp and half think you need not, so the science isn’t well settled.

Once I find a 2moa load I’ll start playing with crimp and heavier bullets, thanks for the info.
 
Longer Throat = less pressure, even when bubba is reloading. Thank lawyers for this.

****If you have a used barrel you should not consider re-chambering it this. Carbon is absolute hell on reamers***

You will see short throats (leads) in rifles so the shooter can chase the lands as the barrel wears, especially the throat.

Finding bullets that like jump is easy...Serria Match kings, Berger Hybirds are the top two. There are a few others as well.


Talk to OCD (Ogburn Combat Development) Good friend of mine near Myrtle Beach that is a PRS shooter and chambers AR-15's He has a absolute nail drive 6SLR, thing is nuts.


Tell'em Dustin sent you: http://www.ogburnrifles.com/
 
Last edited:
The crimp thing - well, that depends. Let the gun tell you whether to crimp or not.

I have tested dummy loads in my AR by chambering the rounds a few times, and neck tension is enough to hold them. I also ran a test between no-crimp, light-crimp, and heavy-crimp rounds, and the difference was very noticeable. The no-crimp rounds had a standard deviation in velocity that was half what the other two were, and the group size was also smaller. The heavy crimp was the worst in both cases. This was with Hornady 55SP bullets. If I had a heavier buffer spring, or a lightened bolt carrier, it might slam the round in hard enough to cause bullet-jump, but that is not the case for my rifle. Heavier bullets might need crimping, but I've had good luck with minimal crimping on 75gn bullets.

On the other hand, I have a Ruger Mini-30 that I could use as a kinetic bullet puller. I have to put a heavy crimp on those to keep them from jumping.
 
Toprudder said:
The crimp thing - well, that depends. Let the gun tell you whether to crimp or not.

I have tested dummy loads in my AR by chambering the rounds a few times, and neck tension is enough to hold them. I also ran a test between no-crimp, light-crimp, and heavy-crimp rounds, and the difference was very noticeable. The no-crimp rounds had a standard deviation in velocity that was half what the other two were, and the group size was also smaller. The heavy crimp was the worst in both cases. This was with Hornady 55SP bullets. If I had a heavier buffer spring, or a lightened bolt carrier, it might slam the round in hard enough to cause bullet-jump, but that is not the case for my rifle. Heavier bullets might need crimping, but I've had good luck with minimal crimping on 75gn bullets.

On the other hand, I have a Ruger Mini-30 that I could use as a kinetic bullet puller. I have to put a heavy crimp on those to keep them from jumping.
Click to expand...


Bingo^^ It’s not one size fits all

jimmyjames8 said:
AR rounds fed from a mag need crimping or extreme neck tension or you will have reliability problems. The kinetic energy of the bolt slapping home a round will push the bullet forward into the throat even if single loading. A 9 twist will stabilize 55 to 77 gr bullets despite what all the bullet and powder mfrs say.
Click to expand...


Saying every AR loader needs to crimp their rounds is inaccurate. I haven’t crimped a SINGLE ONE of the tens of thousands of rounds I’ve shot through a dozen or more ARs. My dies are set up correctly and neck tension is more than enough. And I’m not just talking about plinking ammo. If you want to see 100 or 300 yard groups, let me know.
 
11B CIB said:
Bingo^^ It’s not one size fits all




Saying every AR loader needs to crimp their rounds is inaccurate. I haven’t crimped a SINGLE ONE of the tens of thousands of rounds I’ve shot through a dozen or more ARs. My dies are set up correctly and neck tension is more than enough. And I’m not just talking about plinking ammo. If you want to see 100 or 300 yard groups, let me know.
Click to expand...

We just became best friends, again. lol. People's jaw drop when shooting ipsc (fullsize) at 900 yards with my 18". 8 for 10 shots.


Neck tension at .003 to .004 (.004 is the diameter of 2 human hairs)
 
Last edited:
11B CIB said:
Bingo^^ It’s not one size fits all




Saying every AR loader needs to crimp their rounds is inaccurate. I haven’t crimped a SINGLE ONE of the tens of thousands of rounds I’ve shot through a dozen or more ARs. My dies are set up correctly and neck tension is more than enough. And I’m not just talking about plinking ammo. If you want to see 100 or 300 yard groups, let me know.
Click to expand...


One size does not fit all for sure... It does payoff to test and do the R&D to find what the gun likes.. Post some pics of your rifle and some groups!!
 
Hashknife said:
One size does not fit all for sure... It does payoff to test and do the R&D to find what the gun likes.. Post some pics of your rifle and some groups!!
Click to expand...

I’ve spread some around here so it’ll take me getting home from work to aggregate them here.

I’ve been playing with a lot of bullets: regular SMKs (52, 69, 77gr) 77gr TMKs, 73gr ELD, 75gr Hornady BTHP, 62gr TTSX, and of course 55gr FMJs. Finally got my work done and can focus on dope, shooting, drills, etc
 
Yeah, gonna have to decide on an accuracy objective, otherwise I’ll become the half deranged looking guy at the end of the firing line with a 250lb trunk of gear including a shelter for my scale, a press and a variety of components.

Which, btw is how I now picture @11B CIB , and most benchrest shooters when they aren’t competing, the mad scientists of the shooting sports.
 
Toprudder said:
The crimp thing - well, that depends. Let the gun tell you whether to crimp or not.

I have tested dummy loads in my AR by chambering the rounds a few times, and neck tension is enough to hold them. I also ran a test between no-crimp, light-crimp, and heavy-crimp rounds, and the difference was very noticeable. The no-crimp rounds had a standard deviation in velocity that was half what the other two were, and the group size was also smaller. The heavy crimp was the worst in both cases. This was with Hornady 55SP bullets. If I had a heavier buffer spring, or a lightened bolt carrier, it might slam the round in hard enough to cause bullet-jump, but that is not the case for my rifle. Heavier bullets might need crimping, but I've had good luck with minimal crimping on 75gn bullets.

On the other hand, I have a Ruger Mini-30 that I could use as a kinetic bullet puller. I have to put a heavy crimp on those to keep them from jumping.
Click to expand...

I crimp the hell out of 55gr and 77gr cannelured bullets. Non cannelure bullets, not so much. All my loads and guns are sub moa accurate or i sell and move on. Interesting about the mini 30. I wonder if a mini 14 does the same. Has to have something to do with the location of the spring being forward of the the bolt.
 
jimmyjames8 said:
Interesting about the mini 30. I wonder if a mini 14 does the same. Has to have something to do with the location of the spring being forward of the the bolt.
Click to expand...
I'm not sure why. The bolt appears to be small and probably light, and I suspect the recoil spring is heavy as a result. Plus, they tend to be over-gassed, mine spits the brass out as much as 30 feet. I've been toying with the idea of tuning the gas block and trying different springs.
 
JimB said:
Yeah, gonna have to decide on an accuracy objective, otherwise I’ll become the half deranged looking guy at the end of the firing line with a 250lb trunk of gear including a shelter for my scale, a press and a variety of components.

Which, btw is how I now picture @11B CIB , and most benchrest shooters when they aren’t competing, the mad scientists of the shooting sports.
Click to expand...

After the last “famine” post Sandy Hook, powder was harder to find locally. I had to learn to use some powders that weren’t my go-to so I wouldn’t deplete my reserves of my favorites. This prepared me should the situation happen again I’d have pre-worked loads so no wasting components trying to find a winner.

And now that things are good again, I still try and snag a powder every so often I don’t have data for and see what unfolds
 
11B CIB said:
After the last “famine” post Sandy Hook, powder was harder to find locally. I had to learn to use some powders that weren’t my go-to so I wouldn’t deplete my reserves of my favorites. This prepared me should the situation happen again I’d have pre-worked loads so no wasting components trying to find a winner.

And now that things are good again, I still try and snag a powder every so often I don’t have data for and see what unfolds
Click to expand...

That’d be great, but I’m finding that a pound of powder doesn’t go very far in rifle loads!
 
You must log in or register to reply here.
Back
Top Bottom