Too much difference in OAL?

jackwillis · February 27, 2008, 04:36 PM

Noobie here. I have yet to load my first round. I am taking some so called baby steps in order to get that first loaded round. Case in point. I am working on finding the correct OAL for my rifle (Ruger M77 Target Grey in .204 caliber). I used a Stoney Mt. OAL gauge tipped with a Sierra 32g bullet. After 3 measurements I found the tolal chamber length to be 2.424". This compares with the Hodgdon's manual listed COL of 2.250. After subracting the recommended 0.03" to 0.04" from the 2.424" measured, I made a dummy round that is 2.390" OAL. I also ran it through my rifle and it went in and out smooth as butter. My question is, is there too much difference between the published COL of 2.250" and my measured and set back 2.390 OAL? Oh yeah, using my bullet comparater I measured 1.883" on a Hornady factory round (.204) and I measured 2.022" on my dummy round.

steve4102 · February 27, 2008, 05:57 PM

COL listed in the manuals means very little. It is only to inform you as to what length they used. COL is rifle specific. Here is a quote from AA Powders on COL.

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.

saudst · February 27, 2008, 06:14 PM

I agree with Steve, industry standards on O.A.L. is a minimum. Every rifle chamber and headspace is as different as a fingerprint.

cdoc42 · February 27, 2008, 06:27 PM

Are you measuring from the tip of the bullet to the base of the case or from the ogive? I think if you do a search on these threads for bullet seating you'll find a more detailed discussion on the subject.

jackwillis · February 27, 2008, 07:20 PM

I measured from the tip to the base and got 2.424". Using my bullet comparator (which I believe measures from the ogive to the base) I got 2.022"

February 27, 2008, 04:36 PM	#1
jackwillis Junior Member Join Date: January 23, 2008 Location: Los Osos, Ca. Posts: 12	Too much difference in OAL? Noobie here. I have yet to load my first round. I am taking some so called baby steps in order to get that first loaded round. Case in point. I am working on finding the correct OAL for my rifle (Ruger M77 Target Grey in .204 caliber). I used a Stoney Mt. OAL gauge tipped with a Sierra 32g bullet. After 3 measurements I found the tolal chamber length to be 2.424". This compares with the Hodgdon's manual listed COL of 2.250. After subracting the recommended 0.03" to 0.04" from the 2.424" measured, I made a dummy round that is 2.390" OAL. I also ran it through my rifle and it went in and out smooth as butter. My question is, is there too much difference between the published COL of 2.250" and my measured and set back 2.390 OAL? Oh yeah, using my bullet comparater I measured 1.883" on a Hornady factory round (.204) and I measured 2.022" on my dummy round. Last edited by jackwillis; February 27, 2008 at 05:16 PM. Reason: forgot the last sentence

February 27, 2008, 06:14 PM	#3
saudst Senior Member Join Date: February 20, 2008 Location: Central Wisconsin Posts: 184	O.A.L. I agree with Steve, industry standards on O.A.L. is a minimum. Every rifle chamber and headspace is as different as a fingerprint.

February 27, 2008, 05:57 PM	#2
steve4102 Senior Member Join Date: December 23, 2005 Location: Minnesota Posts: 2,955	COL listed in the manuals means very little. It is only to inform you as to what length they used. COL is rifle specific. Here is a quote from AA Powders on COL. 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.

February 27, 2008, 06:27 PM	#4
cdoc42 Senior Member Join Date: March 13, 2005 Location: Pennsylvania Posts: 1,687	Are you measuring from the tip of the bullet to the base of the case or from the ogive? I think if you do a search on these threads for bullet seating you'll find a more detailed discussion on the subject.

February 27, 2008, 07:20 PM	#5
jackwillis Junior Member Join Date: January 23, 2008 Location: Los Osos, Ca. Posts: 12	I measured from the tip to the base and got 2.424". Using my bullet comparator (which I believe measures from the ogive to the base) I got 2.022"