Questions about OAL vs Factory ammo

[TacticalBacon]

Ok so... i understand the logic behind seating depth and its effects on accuracy and mechanical function. And i know what SAMMI specs are and how to find them

But.. how do the factorys gauge their seating depth in order to achieve a cartridge that works in almost every firearm?

I ask because its a goal of mine as it pertains to my plinking reloads

I dont want nessarly to replicate the proformance of factory ammo as i know reloading can exceed factory ammo proformance drastically, but what i do want is to understand the formula they use to make their cartridges so versatile among firearms within the same caliber

Like do they have a team of developers who go out and test their ammo in every single gun on the market then its a law of averages

Or is there a magic depth in relation to SAMMI that makes it just work

 

[drband]

Work up your loads in your shortest chamber for whatever caliber you are loading. It should work in any other gun of that caliber you have.

 

[TacticalBacon]

Work up your loads in your shortest chamber for whatever caliber you are loading. It should work in any other gun of that caliber you have.

Ok but then how can i generate average accuracy node so to speak

Like for example if i buy a box of Winchesters its a safe bet that its going to work in almost every gun its chambered with of course there being outlyers

But also generally speaking the perceived accuracy is pretty close aswell granted there are factors that play into the accuracy that seperate firearms experience but generally speaking they are fairly close to one another in terms of spread and velocity how do they achieve that

I mean sure a carbine firing a 9mm will experience different perceived accuracy than a handgun but in general if 2 hand guns or 2 equal catagory firearms square off using the same box of ammo there spreads and velocitys are relatively similar

 

[TacticalBacon]

Or am i reading to much into this and im incorrect in my inital thesis

Iv notice that when firing my reloads in my own firearms i have very noticeable inconsistencies and one firearm that wont even cycle the cartridges

But those same 4 guns cycle and are relatively consistent using factory ammo i had laying around

 

[Varminterror]

what i do want is to understand the formula they use to make their cartridges so versatile among firearms within the same caliber

The answer really isn’t terribly satisfying.

“If it fits, it ships.”

SAAMI prints minimum chamber dimensions. Reamers made for and used by firearm manufacturers will have a certain minimum dimension. Ammunition manufacturers then fit their ammo to that minimum dimension. If their ammo ever does NOT fit into a specific firearm then, they immediately know the chamber is smaller than SAAMI spec, and they’re absolved of burden. And in reality, most firearm manufacturers will lean towards the LARGER end of SAAMI maximum dimensional spec, to ensure their firearms aren’t the root cause of an issue where SAAMI spec ammo doesn’t fit.

This is one of the reasons you commonly see the question online that once fired brass from factory ammo is often shorter than minimum trim-to length in a reloading manual. Why? Because jamming case neck into chamber throat is a dangerous issue, and not all reamers are identical, so factory ammo will often be made with a short neck to ensure that interference never happens.

It is also why we rarely ever see chambering issues for base or shoulder diameter on factory ammo, BUT we so commonly see diameter fit issues when we reload ammo and use brass fired from one rifle into another - they all swallowed the undersized factory ammo, but once brass was blown out to the bigger chamber, it no longer really wants to fit into the rifle with a slightly smaller chamber.

Or am i reading to much into this and im incorrect in my inital thesis

Yes, you’re reading too much into it.

Ammo manufacturers simply use gauges cut with minimum specs, so if their ammo fits their gauge, it will fit any firearm which meets SAAMI specs. It’s as simple as that.

 

[TacticalBacon]

The answer really isn’t terribly satisfying.

“If it fits, it ships.”

SAAMI prints minimum chamber dimensions. Reamers made for and used by firearm manufacturers will have a certain minimum dimension. Ammunition manufacturers then fit their ammo to that minimum dimension. If their ammo ever does NOT fit into a specific firearm then, they immediately know the chamber is smaller than SAAMI spec, and they’re absolved of burden. And in reality, most firearm manufacturers will lean towards the LARGER end of SAAMI maximum dimensional spec, to ensure their firearms aren’t the root cause of an issue where SAAMI spec ammo doesn’t fit.

This is one of the reasons you commonly see the question online that once fired brass from factory ammo is often shorter than minimum trim-to length in a reloading manual. Why? Because jamming case neck into chamber throat is a dangerous issue, and not all reamers are identical, so factory ammo will often be made with a short neck to ensure that interference never happens.

It is also why we rarely ever see chambering issues for base or shoulder diameter on factory ammo, BUT we so commonly see diameter fit issues when we reload ammo and use brass fired from one rifle into another - they all swallowed the undersized factory ammo, but once brass was blown out to the bigger chamber, it no longer really wants to fit into the rifle with a slightly smaller chamber.



Yes, you’re reading too much into it.

Ammo manufacturers simply use gauges cut with minimum specs, so if their ammo fits their gauge, it will fit any firearm which meets SAAMI specs. It’s as simple as that.

Ok.. so does that mean that the relative, similar/ predictable accuracy among same category firearms is more of a placebo and that though the groups are similar in term of tightness that its more of an illusion

Because i feel it would be almost impossible to advertise for example 2 moa accuracy and velocitys if the cartridges are all loosly fitted

Or am i thinking too much on this aswell and that so long as they fit and the cartridge desined is constant than a constant result will be achieved

 

[TacticalBacon]

Well loosly fitted is prolly not the correct term i ment more minimum fitted

 

[Varminterror]

Because i feel it would be almost impossible to advertise for example 2 moa accuracy and velocitys if the cartridges are all loosly fitted

You don’t have to like the answer, but your feelings are wrong.

It’s incredibly simple to expect 2moa, even 1moa, from most factory rifles and quality ammo.

Or am i thinking too much on this aswell

Yes.

I’m telling you, with direct manufacturing experience, how firearm and ammunition manufacturers ensure ammunition fits and functions in firearms. Which is largely why everyone involved is so willing to accept voluntary compliance of SAAMI standards.

The specification span isn’t large, so building rifles with maximum spec chambers and ammo with minimum spec chambers is only a matter of a few thousandths of an inch. Often less than half of the thickness of a piece of paper - but enough to ensure the dimension of the chamber is always larger than the dimension of the ammo, so the round always fits into the chamber.

 

[Varminterror]

How about we pose this in a different way: have you ever questioned why EVERY bolt of a given size at every hardware store in America fits into EVERY nut of the same size? Specification tolerances. Bolts HAVE to fit into nuts, so they’re made with specification tolerances such the biggest bolt will fit the smallest nut. Some big bolts might fit extremely tightly into some tighter nuts, while some others might have looser fit, but ALL of them fit together.

It’s not complicated, no conspiracy, no magic, and not even any luck. We make holes big enough to fit plugs, and we make plugs small enough to fit holes… pretty simple.

 

[TacticalBacon]

How about we pose this in a different way: have you ever questioned why EVERY bolt of a given size at every hardware store in America fits into EVERY nut of the same size? Specification tolerances. Bolts HAVE to fit into nuts, so they’re made with specification tolerances such the biggest bolt will fit the smallest nut. Some big bolts might fit extremely tightly into some tighter nuts, while some others might have looser fit, but ALL of them fit together.

It’s not complicated, no conspiracy, no magic, and not even any luck. We make holes big enough to fit plugs, and we make plugs small enough to fit holes… pretty simple.

Oh ok srry i didnt intend to make it sound like i was challenging your knowledge i was genuinly unsure if i was incorrect or not

But i do understand now and i never though about it in the same light as fasteners
I just though because we where dealing with a tool that have a massive varants in accuracy capabilities amung diffrent firearms that there was like a magic formula or equation that preduces averge results

So would it be safe to say that if i reload a cartridge to minimum sammi spec i should receive the same result or is there any saftey concerns that say a factory would have covered that i may not

Like cases being too long or too short for this application, bullet design incompatibilities , ext

 

[NMexJim]

The pursuit of accuracy has driven many a soul over the edge not to mention breaking their wallet. To get very far along on one's own can be a long road. First to consider is the rifle capability - chambers follow the same manufacturing tolerances as cartridges. Then the shooter. Finding someone with a lot of experience can really help explain all your questions. These forums too, but hands-on is priceless. Does reloading help? You bet. Anything you can do to tighten up tolerances is a good thing. Just be aware that nothing concerning accuracy comes cheaply.

 

[Varminterror]

So would it be safe to say that if i reload a cartridge to minimum sammi spec i should receive the same result

In general, if you follow the process steps described in reloading manuals, set up your sizing dies in the way the die instructions suggest, trim to the minimum length listed in manuals, and seat your bullets to the COALs listed in their manufacturers’ reloading manuals, you will also be producing very near minimally spec’d ammunition, very similar to factory ammo dimensions. Just dimensions.

What the factory ammo will have which yours will not is their completed load development which promotes that particular bullet over their particular powder should shoot consistently, whereas you could choose some arbitrary powder charge which happens to be in an antinode, so your ammo would be less accurate than theirs. OR, you can tune your powder charge and end up with ammo more consistent than typical factory ammo.

OR… you can size your cases to perfectly suit your chamber, seat your bullets to perfectly suit your rifling leade and the particular optimum jump for your chosen bullet, and tune your powder charges for consistency, and end up with ammunition which greatly exceeds the performance of factory ammo.

 

[.45Coltguy]

We, as handloaders, can set our OAL as we would like with our dies. On the other hand, you buy a box of factory, lets say, .357 mag, in 158gr JSP, you're going to get varying OAL's often.
They may, and probably do shoot rather well, but, with your own handloads you gain consistency. Mostly. This is why we handload.

 

[Soonerpesek]

Oh ok srry i didnt intend to make it sound like i was challenging your knowledge i was genuinly unsure if i was incorrect or not

Whilst most all “bolts” ( cartridges) can be crafted to the same SAAMI specs, not all “nuts” ( chambers) are the same….ie CZ, Glock, Baer, etc., so that’s kind of a poor analogy.

While you are being told you don’t like sourdough, you have to look for more research than one outlet and there are many here with expansive knowledge that will share it freely for you to take for what it’s worth.

All knowledge is good, even the poor stuff as it teaches a lesson, albeit sometimes hard.

Nice setup BTW….. HAVE FUN ….!!

 

[Varminterror]

Whilst most all “bolts” ( cartridges) can be crafted to the same SAAMI specs, not all “nuts” ( chambers) are the same….ie CZ, Glock, Baer, etc., so that’s kind of a poor analogy.

Can you share specific provenance that CZ, Glock, and Baer, or other manufacturers don’t follow SAAMI or CIP chamber specifications?

 

[BJung]

The more I learn, the more variables I find. SAMMI specs are relative. First. You can make things very easy for yourself and copy the factory dimensions: same case length from the factory, same bullet, case, etc. Or if you change your components, you'll have to experiment using maybe a load manual, trim your case to SAMMI specs and find the load that prints those bullets into the tightest group within your load range. There is more than one accuracy load though. And if you have more than one firearm chambered for the same round, you could most possibly find an average load that both will shoot ok. I don't have two guns shooting the same cartridge by theoretically, I think it's possible. For example. 2.7-2.8gr Bullseye for 38-148WC bullets shoots well in practically any 38 special. SAMMI specs are within a safe range. But, you can load outside it when you become more skilled. You watch for pressure signs.

 

[Soonerpesek]

Can you share specific provenance that CZ, Glock, and Baer, or other manufacturers don’t follow SAAMI or CIP chamber specifications?

Never stated they didn't, but not all SAAMI spec ammo will fit..........It's pretty widely known.......

And since all SAAMI spec ammo may not fit said SAAMI/CIP chambers, they bolt/nut anaogy is a poor one......

 

[AJC1]

Can you share specific provenance that CZ, Glock, and Baer, or other manufacturers don’t follow SAAMI or CIP chamber specifications?

You jumped right on it. CIP is a different standard and I've not studied their drawings or specifications enough to be knowledgeable. I would be interested in knowing if that is the reason cz pistols have notoriously short leads.

 

[joneb]

It should work in any other gun of that caliber you have.

Do you mean cartridge? I have 30-30 Win, 308 Win and 30-06 these are the same Caliber. should I load all to the same COAL?

 

[Varminterror]

Never stated they didn't, but not all SAAMI spec ammo will fit..........It's pretty widely known.......

And since all SAAMI spec ammo may not fit said SAAMI/CIP chambers, they bolt/nut anaogy is a poor one......

Pat yourself on the back, I guess, for your personal victory here, as idiotic as the argument you’re proposing has to be to do so. Yes, SAAMI and CIP chamber and cartridge specs have tighter tolerances than ASTM and SAE fastener specs, so yes, we’re more apt to see interference issues in rifles than nuts and bolts. But the same principles apply - manufacturers plan product specifications for any part which has to fit inside another to align sizes such the part going in should always be smaller than the part it goes into.

We can be certain, that no ammo manufacturer is walking around to every firearm in the country to make sure they have their sizing dies in their machines set to fit all of them. They make ammo on the smaller side of the published spec, and odds are, they avoid running into any issues with any chamber in the market.

 

[eddiememphis]

But.. how do the factorys gauge their seating depth in order to achieve a cartridge that works in almost every firearm?

They keep it short.

 

[Soonerpesek]

as idiotic as the argument you’re proposing has to be to do so

You are the one who proposed it with yout bolt/nut analogy..............so, you're saying that you are the idiotic one.....??................okay, if you say so...........

 

[Varminterror]

You are the one who proposed it with yout bolt/nut analogy..............so, you're saying that you are the idiotic one.....??................okay, if you say so...........

I drew the apt parallel between familiar items to explain the unfamiliar.

You chose to split hairs that tighter tolerance requirements defy the fact tolerance specifications exist. Which is false.

 

[Varminterror]

They keep it short.

Sometimes, we do see some things get sideways.

Some of the early 6 ARC ammo from Hornady was seated way too long, and caused pressure issues for a lot of folks. A few guys I know, and I, would set up a seating die to press factory rounds just a hair deeper to clear ammo in those chambers. Savage 12’s in 223 were another rifle which commonly had pretty short throats, and could end up jamming bullets into the lands - while most factory rifles have rather long throats to avoid that from happening.

But typically, specification tolerances do what they’re supposed to do, and things fit where they should, because the dimensional specs are to make smaller ammo and bigger chambers.

 

[jmorris]

Ok so... i understand the logic behind seating depth and its effects on accuracy and mechanical function. And i know what SAMMI specs are and how to find them

But.. how do the factorys gauge their seating depth in order to achieve a cartridge that works in almost every firearm?

The only way they could, you load for the smallest sample you can get your hands on.

SAMMI doesn’t have any ogive or throat dimensions, so that’s useless.


So, your stuck with going minimum on everything, kind of like the folks that use small base dies, even if it’s sized more than needed it will still fit in a normal sized chamber…