Question about OAL

Josh · April 29, 2000, 05:02 PM

Question-I measured where my lands are with a technique that I got from one of the Sierra Techs. My measurment was 2.938.
They told me to back off about .010 and keep working back until I find the best OAL for the particular load I am using.
Now to my question. The Sierra manuel gives 2.800 for the maximum length. If I start .010 from the lands then I am at 2.928. This is above the maximum length listed. Is there a problem if I were to start with it at 2.938?

EQP · April 29, 2000, 09:22 PM

What caliber are you working with? By the nearly 3" length, I am guessing your working with a rifle cartridge. First thing to check is will the weapon load a cartridge at 2.938? Let us know what the caliber and type of weapon your using is so we can help you a little bit better.

Evan

Josh · April 30, 2000, 08:24 AM

I'm sorry I did not give more info.

I am working with a Remington .308 PSS bolt with detachable magazine. I am limited to OAL because of the magazine and want to see if there is any increase in the accuracy of the rifle by seating closer to the lands. I loaded up five at 2.928, 2.918, and five at 2.908 backing off .010 from the origional figure of 2.938 where the lands are.

After loading these 15 up I checked again to make sure everything was right and saw the maximum OAL was 2.800.

My question is being that the gun has such a long throat area would these shells I loaded
cause any problems?

If there is a big increase in accuracy then I have to decide if I want the barrel set back.

Josh · April 30, 2000, 08:25 AM

By the way the 15 that I loaded all chamber without any problems.

Big Bunny · April 30, 2000, 09:43 PM

Try "smoking" your bullet and see whether it contacts the lands. Every barrel is differentand SAMI cant cover them all!

Some benchresters contact the lands on purpose and then work up a load to suit.

If yours shoots OK leave it alone, but be careful of high pressures with a too long case and the above !!!

------------------
***Big Bunny***

**Mal H** · April 30, 2000, 10:22 PM

What was the technique that the Sierra tech rep gave you? If it gave you an accurate measurement of your maximum OAL with that particular bullet then the answer to your question is no, the rounds you loaded should cause no problems assuming there is enough bullet left in the case to hold it hard and straight.

The SAAMI max OAL is a standard so that any factory round for any given caliber will work in [almost] any gun chambered for that caliber. It is certainly an excellent place to start, but if you do your homework and know exactly what you are doing and the signs to look for (and the consequences) if you do something wrong, then you can tailor your cartridges to your particular rifle. The homework part is very important and it certainly sounds like you're doing that.

alan · April 30, 2000, 10:45 PM

Josh:

You are talking about the .308 Winchester, aren't you". The length you mentioned, 2.9" plus a bit, would most likely NOT work through the magazine of a rifle with a 308 length magazine. 2.8" oal is the specified length for magazine feed. I have seen National Match ammumnition with a oal of 2.820, which would feed through a integral box magazine, bolt action rifle, but that was about the longest.

Josh · May 1, 2000, 04:54 PM

Mal H.

the technique that a Sierra Tech gave me was to take a .308 case, FL re size it, trim it, make a verticle cut in the neck with a fine blade hacksaw. At this point start the bullet of choice in the case. Next open your bolt and place it in the chamber. Close the bolt gently and then open it making sure it extracts into you hand. Use calpier to measure it. Do this 5 times and take the avg of the 5 cases. Now back off .010 and start loading of course starting at the suggested starting point and go from there. I have done this before on my other rifles and it works very well. The problem that the I had this time was that there did not appear to be much bullet in the case.
Anyhow I loaded up 15 starting as they suggested .010 from the lands seating the head back in .005 increaments.
I found after I reached .020 from the start that my groups were cut in half. Yes half.
I could not buy a group under one inch no matter what I did changing powder/primers etc.
I shot a group-5 shots- at 100 yards into 1/2"

I was doubtful thinking this was a fluke so I loaded up more last night and came home today and did it again.
I am going to have to decide if I want a riflesmith to bring the barrel back to wher I can get this accuracy and still load out of a detachable magazine.

**Mal H** · May 1, 2000, 06:03 PM

Josh - I had the same concern about how much bullet in the case is enough. I was chatting with a Speer rep a while back and he said there is no hard and fast rule about this. He had a rule-of-thumb that makes sense, you should have at least 1/2 of a caliber in the case if you are shooting bench rest and don't have to load from a magazine. If the cartridges will take a little abuse, like when hunting then you should leave at least 3/4 caliber. And if you are using boattails be sure to take that into account. The 1/2 caliber refers to the amount of bearing surface, not necessarily from the base of the bullet.

It sounds like you have already found your optimum OAL for that bullet and your rifle. I guess the only thing is that you will have to live with your gun now being a single shot when you want optimal accuracy. When that isn't necessary and you need to use the mag, you'll still have an accurate rifle even if you have to use the 2.80 OAL.

I don't know if a smith can do much with your current barrel to help that situation. But then again, new barrels really aren't all that expensive if you want to try making a rifle that gets the same optimal accuracy and still be able to use a mag. Just be aware there is no guarantee that if you have a barrel chambered/thoated the way you want that it will have the same accuracy you just achieved. There are too many variables at work.

April 29, 2000, 05:02 PM	#1
Josh Member Join Date: January 31, 1999 Posts: 77	Question-I measured where my lands are with a technique that I got from one of the Sierra Techs. My measurment was 2.938. They told me to back off about .010 and keep working back until I find the best OAL for the particular load I am using. Now to my question. The Sierra manuel gives 2.800 for the maximum length. If I start .010 from the lands then I am at 2.928. This is above the maximum length listed. Is there a problem if I were to start with it at 2.938?

April 29, 2000, 09:22 PM	#2
EQP Senior Member Join Date: March 31, 2000 Location: Schaumburg, IL Posts: 154	What caliber are you working with? By the nearly 3" length, I am guessing your working with a rifle cartridge. First thing to check is will the weapon load a cartridge at 2.938? Let us know what the caliber and type of weapon your using is so we can help you a little bit better. Evan

April 30, 2000, 08:24 AM	#3
Josh Member Join Date: January 31, 1999 Posts: 77	I'm sorry I did not give more info. I am working with a Remington .308 PSS bolt with detachable magazine. I am limited to OAL because of the magazine and want to see if there is any increase in the accuracy of the rifle by seating closer to the lands. I loaded up five at 2.928, 2.918, and five at 2.908 backing off .010 from the origional figure of 2.938 where the lands are. After loading these 15 up I checked again to make sure everything was right and saw the maximum OAL was 2.800. My question is being that the gun has such a long throat area would these shells I loaded cause any problems? If there is a big increase in accuracy then I have to decide if I want the barrel set back.

April 30, 2000, 08:25 AM	#4
Josh Member Join Date: January 31, 1999 Posts: 77	By the way the 15 that I loaded all chamber without any problems.

April 30, 2000, 09:43 PM	#5
Big Bunny Senior Member Join Date: August 9, 1999 Location: New South Wales - Australia Posts: 605	Try "smoking" your bullet and see whether it contacts the lands. Every barrel is differentand SAMI cant cover them all! Some benchresters contact the lands on purpose and then work up a load to suit. If yours shoots OK leave it alone, but be careful of high pressures with a too long case and the above !!! ------------------ *Big Bunny*

April 30, 2000, 10:22 PM	#6
Mal H Staff Join Date: March 20, 1999 Location: Somewhere in the woods of Northern Virginia Posts: 16,955	What was the technique that the Sierra tech rep gave you? If it gave you an accurate measurement of your maximum OAL with that particular bullet then the answer to your question is no, the rounds you loaded should cause no problems assuming there is enough bullet left in the case to hold it hard and straight. The SAAMI max OAL is a standard so that any factory round for any given caliber will work in [almost] any gun chambered for that caliber. It is certainly an excellent place to start, but if you do your homework and know exactly what you are doing and the signs to look for (and the consequences) if you do something wrong, then you can tailor your cartridges to your particular rifle. The homework part is very important and it certainly sounds like you're doing that.

April 30, 2000, 10:45 PM	#7
alan Senior Member Join Date: June 7, 1999 Posts: 3,847	Josh: You are talking about the .308 Winchester, aren't you". The length you mentioned, 2.9" plus a bit, would most likely NOT work through the magazine of a rifle with a 308 length magazine. 2.8" oal is the specified length for magazine feed. I have seen National Match ammumnition with a oal of 2.820, which would feed through a integral box magazine, bolt action rifle, but that was about the longest.

May 1, 2000, 04:54 PM	#8
Josh Member Join Date: January 31, 1999 Posts: 77	Mal H. the technique that a Sierra Tech gave me was to take a .308 case, FL re size it, trim it, make a verticle cut in the neck with a fine blade hacksaw. At this point start the bullet of choice in the case. Next open your bolt and place it in the chamber. Close the bolt gently and then open it making sure it extracts into you hand. Use calpier to measure it. Do this 5 times and take the avg of the 5 cases. Now back off .010 and start loading of course starting at the suggested starting point and go from there. I have done this before on my other rifles and it works very well. The problem that the I had this time was that there did not appear to be much bullet in the case. Anyhow I loaded up 15 starting as they suggested .010 from the lands seating the head back in .005 increaments. I found after I reached .020 from the start that my groups were cut in half. Yes half. I could not buy a group under one inch no matter what I did changing powder/primers etc. I shot a group-5 shots- at 100 yards into 1/2" I was doubtful thinking this was a fluke so I loaded up more last night and came home today and did it again. I am going to have to decide if I want a riflesmith to bring the barrel back to wher I can get this accuracy and still load out of a detachable magazine.

May 1, 2000, 06:03 PM	#9
Mal H Staff Join Date: March 20, 1999 Location: Somewhere in the woods of Northern Virginia Posts: 16,955	Josh - I had the same concern about how much bullet in the case is enough. I was chatting with a Speer rep a while back and he said there is no hard and fast rule about this. He had a rule-of-thumb that makes sense, you should have at least 1/2 of a caliber in the case if you are shooting bench rest and don't have to load from a magazine. If the cartridges will take a little abuse, like when hunting then you should leave at least 3/4 caliber. And if you are using boattails be sure to take that into account. The 1/2 caliber refers to the amount of bearing surface, not necessarily from the base of the bullet. It sounds like you have already found your optimum OAL for that bullet and your rifle. I guess the only thing is that you will have to live with your gun now being a single shot when you want optimal accuracy. When that isn't necessary and you need to use the mag, you'll still have an accurate rifle even if you have to use the 2.80 OAL. I don't know if a smith can do much with your current barrel to help that situation. But then again, new barrels really aren't all that expensive if you want to try making a rifle that gets the same optimal accuracy and still be able to use a mag. Just be aware there is no guarantee that if you have a barrel chambered/thoated the way you want that it will have the same accuracy you just achieved. There are too many variables at work.