Beyond SAAMI Specs?

D

Dr Killdeer

New member
I need some feedback about SAAMI Specifications. I'm loading for A Browning Medallion in 300 Winchester Magnum caliber with a 26 inch barrel. I'm loading a 165 grain Nosler AccuBond bullet. The actual load specs don't apply to my question, so I ommitted them.

I use the Hornady Lock n Load OAL gauge to determine the exact OAL from the bullet ogive to the base of the brass. Today I decided to move the bullet to within .020 of the rifling to reduce the distance it has to jump into the lands. The rounds chamber properly and cycle through the magazine without any issues. I haven't tested them yet, but here's my concern.

In all the reloading manuals the MAXIMUM OAL for the 300 Win Mag is 3.340. That's the SAAMI SPEC number. The actual OAL on mine, from bullet tip to the base of the brass is 3.563. That's a difference of .223, which is pretty substantial. So, I guess my question is; is that normal? Somehow, I can't believe the throat in that rifle could be that long! And since I'm a half a mile beyond the SAMMI specs, what are the evils that I need to know about, if any?
 
SAAMI specs are how we can stagger into a store, buy a gun, buy ammo, stagger out, and it works.
In the 1974 movie Towering Inferno, Paul Newman is a grumpy architect:
Roger Simmons: Every piece of wire I put in that building is strictly up to code, inspected and approved.
Doug Roberts: The code's not enough for that building. And you know it. That's why I asked for installations that were way, way above standard!
I make some chambers bigger and some smaller than SAAMI spec. But usually per SAAMI spec.
I load some ammo longer and some shorter than SAAMI spec. But usually per SAAMI spec.
I load some ammo higher and some lower pressure than SAAMI spec. But usually per SAAMI spec.
It is ok when I deviate on purpose for MY stuff. I would not like it if I bought something and it was deviate. I don't think anyone would like it if I gave them something that deviated.
 
I want to know the length of the chamber from the rifling to the bolt face. I make transfers, I transfer the dimensions of the chamber to the seating die, then I zero the seating die with a height gage. After that I save the transfer because? Above all I do not like starting over every day like it was a new day.

Off the lands, I am the fan of the running start, I want my bullets to have 'that jump'. For me there is nothing interesting about a bullet setting at the lands trying to make up its little mind if it going down the barrel.

F. Guffey
 
I load my rifle rounds to fit inside the magazine. I load 1, then test it for function. If it bumps the lands I seat it deeper until it chambers easily. I rarely have to go any deeper. I'll then load a few and head to the range. If they do what I want I go home and load a bunch. If not I'll seat a touch deeper and go back to the range. This rarely happens.

I also watch the chronograph. If they are shooting at the expected speed that is my concern. Faster than expected means they are over pressure for some reason. Only had that happen one time with one rifle and one powder. Stopped using that powder and the problem went away.

I rarely measure OAL or how far from the lands. The ones I have measured are usually pretty close. But as long as the speed is not too fast and if feeding and ejection is working I'm good to go.
 
I benched the rifle today and tested my out of spec rounds. No complaints! They printed tighter than I expected them to and there were no signs of any pressure problems with the brass after firing. The Chrony told me that they were close to book specs. No flyers either. I'm a happy camper.
I like jmr40's method, but higgite, you nailed it. SAAMI didn't use my rifle for their tests, so I'm not using their standards.
Thanks for the feedback guys.
 
In all the reloading manuals the MAXIMUM OAL for the 300 Win Mag is 3.340. That's the SAAMI SPEC number. The actual OAL on mine, from bullet tip to the base of the brass is 3.563. That's a difference of .223, which is pretty substantial. So, I guess my question is; is that normal?
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If your measurements are correct, then no it is not normal. What you are doing is extending the life of that barrel somewhat. Both you and I know you are beyond the useful life of that barrel and the gun needs to be re-barreled.

You may be a happy camper right now but that will change with time and continued firing of that rifle as accuracy keeps falling off.

To use a pun, bite the bullet and re-barrel the rifle for proper specks.

Stay safe and be well.
Jim
 
higgite said:
SAAMI specs are a firearms industry standard, not a personal standard... unless you want them to be.
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This is the correct answer.

Here is what Accurate Powders has to say about SAAMI OAL/COAL and handloading.

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.
Click to expand...

http://www.accuratepowder.com/wp-content/uploads/2011/01/accurate_load_data_3.5.pdf
 
If your longer than book number rounds fit the magazine, feed from magazine to chamber, and don't jam into the rifling, I see nothing to worry about.

I don't know how Jim243 concludes that the long throat is a sign you are "beyond the useful life." Have you shot it so much as to advance the throat like that? Or did Browning just ream it long? I have read many Internet Complaints about Remingtons being throated so long that you cannot have both short jump and magazine fit. You are better off than that.
 
I bought the rifle from a friend. It belonged to his father who was an avid hunter for many years. The rifle is pristine and it sat in my gun safe for a few years before I decided to work up a good load for it and use it as a back up to my Sako 7mm Mag.
The previous owner had several hunting rifles and he only shot factory ammo. And besides, the 300 Win Mag is not the kind of rifle that you plink with, so I suspect it didn't see a lot of use.

Every reloading source, from Nosler to Lee states the COL as 3.340, but Steve 4102 posted the amendment to the SAAMI specs and it makes sense. I adjusted my COL to fit my chamber and it works. I'm just surprised at the length of the throat. The rounds feed and chamber flawlessly and the 165 grain Nosler bullet gave me sub MOA at 100 yards with the initial test. I still going to tweak the load, but at least I'm off to a good start.
I inspected the rifling and the chamber and everything looks fine, but I don't have a bore scope and the truth is, I wouldn't know an eroded throat from shinola if it sent me a text message!
I'm happy with the way it shoots and the only change I'm going to make is to the trigger pull. Beyond that, if I can work up a good 300 yard load that prints, it will be my backup Montana rifle.

As an FYI, I use Forster dies. I bump the shoulder to .0002 headspace on the fire formed brass. I anneal the necks and use a .334 collet size for minimum bullet pull. I turn any out of spec necks to .0005 for uniform thickness. I reduce bullet runout to absolute zero on the digital concentricity gauge. I ream the primer pockets and flash holes for uniformity as well. I decided to put the bullet .0020 off the rifling to start and that's when I realized how long the throat is in that rifle.
 
Dr K: be advised that if you load long (which is fine), your velocity will probably be lower because of the greater volume in the cartridge.
 
I don't know how Jim243 concludes that the long throat is a sign you are "beyond the useful life."
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Because 1/4 inch is way beyond spec and either the barrel was cut (reamed) wrong or has been fire cut to those dimensions. This is a 300 Win Mag people not a 22 LR and you will not be adding any additional metal to the barrel by additional firing but fire cutting it more.

If you are happy with it's current accuracy, fine, if not then re-barrel it.

Jim

Useful life (accuracy) will depend on what you shoot and how often

http://www.accurateshooter.com/technical-articles/excel-formula-predicts-useful-barrel-life/
 
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Jim243,

I understand your reasoning, but its a tough call to make accurately these days. Lots of reports of Remington chambers with longer-than-SAAMI-spec freebores. Weatherby used to make pretty long ones, too. And with bullet makers now frequently using secant ogives to get higher BC's, longer COL's are bound to result¹. We don't know what his rifle is or what bullet design he's using.



¹Secant ogives typically contact the throat closer to the bullet's ogive shoulder than tangent ogives do. Thus, for two same-length ogives, one of each type, a secant ogive will need a longer COL to have the same jump to the lands as a tangent ogive bullet does. Plastic tips, with their small meplat radii, typically extend ogive length and thus COL even further, and they are increasingly common, too.
 
Dave P said:
Dr K: be advised that if you load long (which is fine), your velocity will probably be lower because of the greater volume in the cartridge.
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Actually Pressures will prolly be higher as the closer to the lands the pressure is often times increased. With increased pressure increased velocity may follow.
 
Yes. Here's a plot of pressure vs. seating depth for a round nose bullet. It will have the greatest change in seating depth to see a pressure change. Pointed bullets will see pressure change more for a given change in seating depth, but they, too, will have a pressure minimum.

seatingdepthvpressure_zps326eb859.gif
 
You guys aroused my curiosity, especially since Unclenick mentioned Weatherby. A friend has a 300 Weatherby mag, so I called him and I'm going to test the freebore in his rifle by pushing the bullet right onto the lands and and then measuring the OAL.

He only shoots factory ammo and I know his Weatherby is more of a show piece than a hunting rifle. I doubt if he's put more than 100 rounds through it. ( I wish I had his money.) Thereafter, I'll post the results. I don't know anybody else that has a Browning 300 Win Mag for me to test, so for now, the Weatherby will have to do.
 
In the last couple years most tool shops have gone over to CNC grinders. The OP makes it sound as if the rifle in question is an older model. 20-25 years ago I was using a well known reamer maker for the gun industry and had so many problems I started making my own. The newer CNC grinders repeat better on different set ups. Some of the older grinders it was a crap shoot.
 
You guys aroused my curiosity, especially since Unclenick mentioned Weatherby. A friend has a 300 Weatherby mag, so I called him and I'm going to test the freebore in his rifle by pushing the bullet right onto the lands and and then measuring the OAL.
Click to expand...

Whatherby published their free bore and the rational. I have pushed bullets out of the case whole the bullet skidded along until it stopped against the rifling. And then? The owner asked me "How could that happen?" And I respond with "I do not know". He was the builder and he made the reamer.

F. Guffey
 
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