O A Length

nazier · January 10, 2012, 12:50 PM

[email protected]Hi I am new here and have lots of questions

I have a problem with O A L in my 270 and 375 H&H.. I used a O A L gauge with a modified case i now have seat my heads upto 4mm longer then the recomended lenth, as for the 375 if i seat the heads to the gauged lenth it will not fit into the magazine of my browning A bolt, to have it fit in the magazine i have to seat the heads 5mm shorter then the gauged lenth... will this create a problem ? can heads be seated upto 4mm below the crimping grove ?

can sombody help ?
Nazier

243winxb · January 10, 2012, 08:10 PM

Quote:

i have to seat the heads 5mm shorter then the gauged lenth... will this create a problem ?

Not if you use the starting load of powder and work your way up to maximum, while watching for pressure signs.

Quote:

can heads be seated upto 4mm below the crimping grove ?

Yes, if done so the loaded round will fit the magazine. Again, use a starting load of powder and work you way up to maximum per the reloading manual. Watch for pressure signs.

PA-Joe · January 10, 2012, 09:38 PM

You will find that some barrels have long throats. If you use max COL then it will not feed correctly out of the magazine. As you noted. You can use these rounds single shot or your can reduce the COL until you get consistent feeding. It may or may not affect accuracy.

steve4102 · January 10, 2012, 10:49 PM

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.

nazier · January 11, 2012, 01:04 AM

Thanks for the info, what i meant by seating 4mm below the crimping grove is that my o a l is now 4mm longer then the recommended length for my 270, and it fits the magazine and there are no feeding problems. would it still be safe to use my normal load of 53.3 grains of s.365 powder ( somcem south africa ) with a 130 grain hornady sp head

243winxb · January 11, 2012, 10:10 AM

Quote:

my o a l is now 4mm longer then the recommended length for my 270, and it fits the magazine and there are no feeding problems. would it still be safe to use my normal load of 53.3 grains of s.365 powder

270 win. S365 powder start 50.4 gr to 54.0 gr Maximum-130 gr PMP SP COL 80.3mm If you have used the same components with 53.3 gr before and the only change is a longer OAL, then Yes, it is safe. Do not Seat the bullet into or touching the rifling, this will raise pressure. Loading data for that powder > http://www.jjwapens.com/somchemballisticdata.htm

nazier · January 13, 2012, 04:00 AM

Thanks for info, will give it a go at the range...

January 10, 2012, 12:50 PM	#1
nazier Junior Member Join Date: January 9, 2012 Location: cape town south africa Posts: 5	O A Length [email protected]Hi I am new here and have lots of questions I have a problem with O A L in my 270 and 375 H&H.. I used a O A L gauge with a modified case i now have seat my heads upto 4mm longer then the recomended lenth, as for the 375 if i seat the heads to the gauged lenth it will not fit into the magazine of my browning A bolt, to have it fit in the magazine i have to seat the heads 5mm shorter then the gauged lenth... will this create a problem ? can heads be seated upto 4mm below the crimping grove ? can sombody help ? Nazier Last edited by nazier; January 10, 2012 at 02:01 PM.

January 11, 2012, 01:04 AM	#5
nazier Junior Member Join Date: January 9, 2012 Location: cape town south africa Posts: 5	C O Lenth Thanks for the info, what i meant by seating 4mm below the crimping grove is that my o a l is now 4mm longer then the recommended length for my 270, and it fits the magazine and there are no feeding problems. would it still be safe to use my normal load of 53.3 grains of s.365 powder ( somcem south africa ) with a 130 grain hornady sp head

January 13, 2012, 04:00 AM	#7
nazier Junior Member Join Date: January 9, 2012 Location: cape town south africa Posts: 5	O A Lenth Thanks for info, will give it a go at the range...

January 10, 2012, 09:38 PM	#3
PA-Joe Senior Member Join Date: June 9, 2010 Location: NEPA Posts: 909	You will find that some barrels have long throats. If you use max COL then it will not feed correctly out of the magazine. As you noted. You can use these rounds single shot or your can reduce the COL until you get consistent feeding. It may or may not affect accuracy.

January 10, 2012, 10:49 PM	#4
steve4102 Senior Member Join Date: December 23, 2005 Location: Minnesota Posts: 2,955	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.