book suggested OAL or your own OAL determination

[hounddawg]

have to respectfully disagree there Nick, SAMMI does have a specification that is generally heeded in the making of magazines. While each bullet has it's own unique COAL recommended by the manufacturer that does not over ride the fact that SAMMI does indeed have a COAL for each cartridge

here is what Berger has to say about it


http://bulletin.accurateshooter.com/...base-to-ogive/

[gwpercle]

Being " well seasoned" , started reloading in 1967 , I make my own determination .
This comes from the days when OAL's were not listed in books and/or the average reloader measured things with a foot ruler, yard stick or tape measure .

Having learned how to do without the book OAL I know the secrete and it's not hard .

Although reloading for over 50 years I never owned a Dial Caliper until 12 years ago .
I only bought it to slug some barrels and measure their diameters , not to measure OAL .
Gary

[old roper]

Berger may suggestion something but in their manual they list SAAMI Max COAL and that's what they used to test loads with.

I don't have every manual but Hodgdon data doesn't list SAAMI Max COAL and they do have some loads over Max COAL.

I got Nosler first manual 1976 and they have section "How to determine bullet seating depth in relation to lands of the barrel". It wasn't too hard to figure out base to ogive back then if you had interest.

[F. Guffey]

Having learned how to do without the book OAL I know the secrete and it's not hard .

Again; Jimmy Dean tried to explain to his fans why the chicken crossed the road. He said the chicken crossed the road to show the opossum it could be done. Many reloaders stick the bullet into the lands because they heard that was the cool think to do while they were at the pool hall.

I want my bullet to have that running start, I want my bullets to have 'that bullet jump' before hitting the lands. But at the same time I want to know where the lands are located.

A friend build magnificent rifles, he made the dies, reamer and cut the stock. My opinion he was a most talented individual. He built 4 rifles 4 rifles with 03 receivers. Something went wrong with one of them; he took the rifle to different smiths, the best he got from them was some rubbed their heads and others shrugged their shoulders, And then he called me, he explained to me the rifle just did not shoot; he asked me where would I start? I told him I would check the chamber starting with the length/distance from the beginning of the rifling to the bolt face. And of course he did not believe I was listening because he build 4 rifles and cut the chamber with his reamer.

SO? He got onto the Internet and signed into a reloading forum ' and then? in a few days he called back. He started to explain to me how it was explained to him. I reminded him he started with; "Where would you start? "And now you are explaining to me how someone else would 'do it' "

There method was not that accurate nor was it simple as it "anyone can do it".

I checked his rifle, the throat was so long the bullet came out of the case neck before the bullet contacted the lands..

I used the heaviest/longest bullet I had; the bullet traveled .250"+ without contacting the case neck and or rifling. He wanted to know how that could happen I had to say "I do not know". I then went through my reamers to determine if I could lengthen the chamber to reduce the free bore, The 7mm/8mmm Remington was not long enough without moving the barrel back. I reminded him all he wanted me to do is to determine why the rifle scattered bullets like a shot gun.

F. Guffey

[Rimfire5]

After 25 posts, no one has answered the OPs question.

The answer is the O.A.L. recommendation is generally related to SAAMI recommended overall length for most calibers.
Page 148 of the Berger Reloading Manual has a very good discussion of the "Effects of Cartridge Over All Length (COAL) and Cartridge Base to Ogive (CBTO)" by Bryan Litz.

In my experience, many manufacturers seem to make recommendations within 0.010 of the SAMMI number depending upon their knowledge of where the ogive is on their particular bullets.

However, there are exceptions.
For example, Sierra recommends an O.A.L. of 2.260 for both their 77 SMK and 77 TMK bullets. The bullet base to ogive measurement for both bullets are no more than 0.010 different but the TMK has an extra 0.070 tip so the O.A.L. for the TMK should be 0.060 longer than the SMK if the O.A.L was intended to keep the cartridge base to ogive length the same. they do the same thing for the 69 grain SMK and TMK bullets.

I asked Sierra why they didn't account for the tip length difference of the TMKs in recommending the O.A.L. and asked if it was because the standard AR magazine only accommodated 2.272 to 2.274 O.A.L. They admitted that the AR magazine length was a factor.

Interestingly, they do the same thing for their .308 155, 168, 175 and 195 TMKs versus their 150, 168, 175 and 190 SMKs. Oh yeah, there are also AR-10s with magazine limitations in the .308 environment as well.

For the second part of th OP's question, about a particular bullet's performance in a specific caliber, some bullets (like the .308 180 grain SMK) are a different design than the other bullets from the same manufacturer (.308 175 and 190 grain SMKs). The amount of bullet body touching the rifling in the 180 grain bullet is different than the others and, that difference seems to effect the performance. Therefore, you need to experiment with the seating depth to find what your rifle might like.

As for me, I have never been able to get the 180 grain SMKs to shoot anywhere near as accurately as the 175 and 190 SMKs. Maybe I gave up on the 180s too soon but it wasn't worth the effort when a 175 or 190 grain would shoot much better.

[Unclenick]

Right. I never said there was no SAAMI standard for COL; I only intended to contradict T. O' Heir's gratuitous assertion that load books universally adhere to them. Additionally, SAAMI has standard velocity ranges for common bullet weights for each cartridge, but published loads go outside those ranges routinely. SAAMI also has a system of maximum pressure determination that manual authors don't typically use the same way manufacturers do.

Examples of books ignoring the SAAMI Standard limitations:

SAAMI standard for .223 Remington says C.O.L. should be in the range of 2.125-2.260 inches.

Sierra book:
80 -grain Sierra Matchking COL: 2.550"

Hornady book:
75-grain A-Max COL: 2.390"
75-grain ELD COL: 2.390"
80-grain A-Max COL: 2.390"
80- Grain ELD COL: 2.390"

Speer book:

40-grain SP COL: 2.060"

Nosler book:

34-grain FBHP COL: 2.080"

Norma book:

55-grain Oryx bullet COL: 2.106"


SAAMI Standard Velocity for a 55-grain bullet in the 223 and fired from a 24" test barrel calls for a range of 3050 fps to 3215 fps.

The Hornady book loads for most of their 55-grain bullets have a range of:
2800 fps to 3300 fps, (they use a 26" barrel, but in a 24" they would still be outside the SAAMI range at both ends).

Norma has 55's at:
2887 to 3307 fps with 24" barrel

Nosler has 55's with various powders at:
2805 to 3302 fps with a 24" barrel

Speer has 55's as low as 2805 fps.

So those are all outside the SAAMI velocity standard. If you look at other bullet weight velocity ranges you find the same thing. I'm just limiting my examples because there is way too much material out there to include it all.

And note that was just one cartridge; the 223 Remington. The same applies to other cartridges. Speer has several light bullets loads for .30-06 as short as 2.419", where the SAAMI minimum COL is 2.490". Hornady lists its 212-grain ELD-X in .308 Winchester with a COL of 3.000" when the SAAMI max COL is 2.810", and so on and so forth. Shooters just have to be aware the rounds that exceed the SAAMI maximum COL will have to be loaded singly if they don't fit a particular gun's magazine, and the very short ones may have to be loaded singly if they won't feed well from the shooter's magazine.

Pressures in manuals generally do not follow the SAAMI method, either. The Maximum pressure listed by SAAMI is called the MAP (Maximum Average Pressure), which means the average peak pressure value of a single random 10 round sample from a freshly loaded lot cannot exceed that number. Individual rounds can be both above and below it, and additional 10-round samples can be a couple of standard errors above it. They specify a maximum extreme spread for peak pressures which winds up limiting how far above MAP the hottest load in the average can go to just over a theoretical 18% above the MAP, but in practical terms, the worst load is usually under 15% over-MAP, which is the percentage the CIP uses in its requirements.

Most load manuals (read the Hodgdon print manual for a description of this) don't give you maximum pressures that meet the SAAMI MAP. They normally try not to let their hottest round in a sample of 10 go over the MAP. They do this both to err on the side of safety, and so handloaders have the widest powder selection possible so they can use something they may have on hand even if it isn't the best choice and has too much pressure SD to be loaded to SAAMI MAP. Hodgdon points out the shooter can take advantage of this when choosing a powder because it means the powder producing the least pressure (and velocity) variation in Hodgdon's testing was the one with the highest listed maximum load pressure.

Anyway, my point is the load manuals include listed loads that are often not adhering to the SAAMI standards in various ways. It doesn't create a problem. SAAMI standards exist so manufacturers can mass produce ammunition that will work in any gun chambered for it that is in good condition. SAAMI is not a handloading standards organization. Handloaders are loading for a specific gun the commercial ammunition manufacturers never get to see. It is a different problem. Your rifle's magazine may be able to handle longer cartridges than the SAAMI standard assumes a magazine can. You have to look and see.


For the OP:

Reading Litz's article at Berger's site on the effects of seating depth is a good start. It has one error and one, to me, glaring omission. The error is that it uses "throat" to define what SAAMI and the reamer makers all call "freebore". What SAAMI (see the SAAMI glossary) and those reamer makers call the "throat" is the tapered transition from the freebore onto the rifling. It is also called the "leade". This is why there is a throat angle specification. Odd mistake to see Litz make, but we've all got one lurking in us somewhere.

The omission is that as the bullet gets close enough to the lands, the increase in powder space behind the bullet ceases to be the dominant term in determining peak pressure and gas bypass cutoff starts to take over. For a typical tangent ogive bullet shape, contact with the throat can raise pressure about 20% as compared to having about 0.030" of jump. QuickLOAD even notes the way to address this is to increase start pressure by about 7200 lbs.

Here's are two measured examples. The pressure change with bullet jump is much more gradual in the second example because the round nose bullet used has a very gradual side taper and has to move a lot to change gas bypass:





So, the moral is to make your changes in seating depth while carefully watching for pressure signs.

As to why changing bullet seating depth affects accuracy, it appears to be due to two things: Most rifles have vertical and at least some horizontal muzzle swing due to recoil moments at firing, and both the vertical and horizontal swings have flat spots on an Audette ladder if you plot the vertical and horizontal displacement of each ladder shot separately. The flat spots don't automatically coincide exactly in the middle of their flats. Adjusting bullet jump, as the second curve above shows, will change velocity and barrel time by varying pressure. This means it tweaks the bullet exit timing with respect to the flat spots until you find the best compromise between them. I believe this is what Tony Boyer is doing in the tuning Chapter (22) of his book. His illustration at the top of page 249 shows the vertical muzzle swing, but there is almost always a horizontal component also occurring, and the two need optimized coordination for best grouping.

A second factor is something I have a theory about (and some pressure data to corroborate it), but it is not ready for prime time. It is a third vibration factor that has to be synchronized with the other two, and changing bullet seating depth seems to tune it almost independently of the others. I'll put it up here in detail if the testing this summer goes as anticipated. Meanwhile, read this paper at Berger to get some idea of the combined effect. Since the secant ogive VLDs the Berger article addresses need to have their jump changed more than a shorter radius ogive bullet does to achieve a given degree of gas bypass, figure to adjust conventional bullet seating in 0.020" steps instead of the 0.030" and 0.040" increments Berger describes. Afterward, you may want to narrow the steps between the seating depths that produced the best results to better center on a sweet spot afterward.

[noylj]

COL Note:
Determine COL BEFORE you start working up loads.
Per Ramshot (and all other reloading suppliers):
“SPECIAL NOTE ON CARTRIDGE OVERALL LENGTH (COL)
It is important to note that the SAAMI COL values are for the firearms and ammunition manufacturers industry and must be seen as a guideline only.
The individual reloader is free to adjust this dimension to suit their particular firearm-component-weapon combination.
This parameter is determined by various dimensions such as
1) magazine length (space),
2) freebore-lead dimensions of
the barrel,
3) ogive or profile of the projectile and
4) position of cannelure or crimp groove.
• Always begin loading at the minimum "Start Load".
• Increase in 2% increments towards the Maximum Load.
• Watch for signs of excessive pressure.
• Never exceed the Maximum Load.”

Your COL (OAL) is determined by your barrel and your gun and your magazine and the specific bullet you are using.
What worked in a pressure barrel or in my gun has very little to do with what will work in your gun. Load a couple of dummy rounds (no powder and no primer) to the max. COL (OAL) and see if it fits your magazine, feeds in your gun, and chambers in your barrel.
Seat the bullet slightly deeper until you achieve all three of these goals. This is the COL (OAL) for you in your gun with that make of bullet. You are the one in control. Enjoy it. You can make ammunition tailored to your gun and not have to load to the minimum COL (OAL) as do the factories for pressure testing.

[old roper]

Brian Litz Company made ammo using Berger bullets and now that Berger has been sold Berger going to make their own ammo.

https://bergerbullets.com/abm-ammo-n...er-ammunition/

[F. Guffey]

So the difference in pressure between into the lands and backed off .030" is 10,000 psi +/- a few. And then we leave out the part where we suggest into the lands is a bod habit when firing max loads or the bullet could have a difficult time getting past the lands or the bullet is not soften up with lead.

Again, I am the fan of the running start, I want my bullet past the rifling before my bullets knows it is there. I did not say jamming the bullet up at the lands is not cute, I said I want my bullet past the lands before the pressure in the case gets serious.

F. Guffey

[Unclenick]

Originally Posted by Raikiri

Well, I guess that shows my "newbieness" ( is that a word? ).

It is now.

The reason for sandbag or machine rest testing is to try to segregate shooter error from mechanical error in the overall shooting system (shooter, gun, ammo, range, and target). It's the scientific principle of independence of variables. The reason for doing it is that if you shoot from a rest and the group isn't appreciably smaller and doesn't change shape as compared to shooting "freestyle", then you are pretty certain the gun-and-ammo are the accuracy limiting factor and not the shooter. But if the groups get much smaller shooting from the rest, then you know the shooter and not the gun is the main cause off point of impact error.

Occasionally, I've come across cases where the above doesn't work out simply. I've seen persons with such a bad flinch that they can't group well even with a sandbag (though the sandbag usually changes the shape of their group some, which is why I mentioned watching out for shape change). I've also seen a couple of guns with such extremely hard and creepy triggers with lots of overtravel slap that only a very experienced shooter can get better groups out of them (and even that shooter still doesn't enjoy the experience). If you have trouble seeing the difference in group size with the sandbags, find a more experienced shooter who is willing to try to get the gun to group just to make sure it isn't you.

A Ransom Rest would be still better, but it's expensive enough that most are owned by people who like to work on guns to improve accuracy and function. It lets them discern "improvements" that work from those that don't. Generally, for handguns these tests are done at 25 yards or 50 yards to make mechanical grouping errors clear even with precise guns. For rifles, 100 yards is usually minimum for this.

[cw308]

ReloadKy
Book suggestions or my own for OAL. I like to keep things simple . Book OAL are in spec to work in all rifles , magazines , tubes and bolt actions . I shoot a Rem 700 bolt action , I load one at a time so I can jump or jam , when I started I follower the OAL measurement and worked with different owder charges , after a while after reading up on reloading I only measure from the case base to the ogive measurement , OAL measurements when looking for accuracy is not the way to go , just use it as a starting point , check the ogive measurement and go from there .

[jmr40]

I load one round just as long as possible that will fit the magazine of my rifles. If I have multiple rifles in the same cartridge I make sure it fits all of them. If the round chambers without hitting the lands that is the OAL where I start. If it hits the lands I seat it deeper. And virtually all of the time where I finish. That usually gives me the best accuracy. If the 1st round checks out then I load a batch up and head to the range.

In rare cases I've not been happy and experimented seating bullets a bit deeper. But by doing it this way I only have one direction to experiment. Unless I want a single shot, and I don't. Most of the time I don't even know the OAL, but the few times I've measured and compared my loads to book loads I'm close, but usually a tad longer than they suggest.

Factory loads, and most hand load manuals err on the side of loading the ammo on the short side to ensure they will fit any rifle without causing problems.

[hdwhit]

ReloadKY asked:
How many of you all use the published / suggested OAL in reloading manuals...

When starting with a new load, I ALWAYs use the published COAL measurement. Once I have a thousand or so rounds downrange from different powders, bullet weights and different COALs I would CONSIDER making changes based on my own experience, but I generally hewed close to the loads in published manuals and they have always worked out well.

[std7mag]

I can't think of a single cartridge i load to SAAMI spec...
And i load a bunch of different cartridges, with a lot of different bullets, different weight bullets.

My most consistant bullet weight would be my 1911 in 45 ACP. I run 185gr consistently.

[Bart B.]

Originally Posted by Rimfire5

For the second part of th OP's question, about a particular bullet's performance in a specific caliber, some bullets (like the .308 180 grain SMK) are a different design than the other bullets from the same manufacturer (.308 175 and 190 grain SMKs). The amount of bullet body touching the rifling in the 180 grain bullet is different than the others and, that difference seems to effect the performance. Therefore, you need to experiment with the seating depth to find what your rifle might like.

As for me, I have never been able to get the 180 grain SMKs to shoot anywhere near as accurately as the 175 and 190 SMKs. Maybe I gave up on the 180s too soon but it wasn't worth the effort when a 175 or 190 grain would shoot much better.

Sierra changed their 30 caliber 180 HPMK boattail angle from 9 to 13 degrees in the 1980's. It is now the same as their 168 grain HPMK. This newer 180 has more drag (less BC) than their original but is equally as accurate as the other 30 caliber match bullets if they stay supersonic at target range.

All 30 caliber HPMK bullets gave different bearing lengths. Sierra's HPMK accuracy spec is 1/4th MOA maximum 10 shot group average at 200 yards and all under 1/2 MOA. I had 1000 of one lot of the new 180 HPMK bulllets that Sierra tested .15 MOA average, all groups under .25 MOA.