C.O.L Questions

[josmund]

Rookie Reloader here with a few questions on COL.

I've loaded up some Hornady Vmax 110 Grain bullets for my 270 Win.

I've carefully seated the bullets to a COL of 3.165 which is listed in the Horandy Book, 8th Edition. SAAMI list max COL at 3.340 which looks to be a pretty significant jump margin. I know each bullet is shaped differently which effect COL. Should I look at extending my COL? I've yet to fire one of these rounds.

Thanks,

 

[mxjunky78]

Each rifles chamber/throat is different. I find the max COAL for the particular rifle I'm loading for then decide if, and how much "jump" I want. Some bullets will simply not allow you to load right at the "lands", especially with the notoriously long throated Rem700. YMMV.

 

[243winxb]

I like to start with the bullets base at the neck/shoulder junction, if possible. If loading 223/69gr bullets, the base will be much deeper into the neck. This is ok when using a starting load and working up the powder charge.. If the bullet has little contact with the neck when trying to reach the rifling, bullets may become crooked when contacting the feed ram on chambering the round. On firing, the bullet may move before pressure is high enough to burn the power correctly. This is because of light neck tension when the COL is to long. This happens sometime, when using slow burn rates of powder in larger Weatherby type rounds. . Accuracy can be very good with the bullet jumping to the rifling in a factory rifle.

 

[witchhunter]

Your bullets are probably too short to reach the lands. You can try with a dummy round. Use a sharpie to mark the bullet, seat it too long and chamber it. Look for marks on the bullet. adjust your seater to get it where you want. A caliber seated in the neck is a good rule of thumb. In your case .277 of the bullet in the neck.

 

[RAT807]

Once you find a load that shoots good, adjust your seating depth and work your way out to the lands. Shoot groups of 5 at each length to find what your rifle likes with this bullet. With the 110 VMax, you may not be able to get to the lands.
Get a Hornady Bullet Comparator and use it to measure to the ogive of the bullet and not the OAL or to the tip of the bullet. The ogive is the point of the bullet that makes contact with the lands. This is where you measure from, to the base of the case, to find a measurement that can be used on any different bullet profile, as bullets will have different OAL.
My rifle likes 2.7 - 2.705 length rounds. I have worked up loads with Hornady 120gr HP, 140gr Berger VLD's, and a few 150gr Nosler and Sierra's. While the OAL varies a good bit with these rounds, the ogive length only varies .005. If the Bergers weren't so long, they would be at 2.705 also.

 

[josmund]

Thanks Guys,

Great info!

 

[Vol46]

If Hornady gives 3.165 for that weight v max in that caliber, they will shoot fine. I load everything to book length to start, find an accurate powder/bullet combination, & then play with seating depth to fine tune. In my experience, you can get excellent accuracy without being right up against the lands.

 

[gamestalker]

OAL is firearm specific. Every throat is different. The general rule of thumb, but not etched in stone, is one bullet diameter in the neck, or in this case .277". But again, this is not absolute. I have yet to come across more than one or two with a throat or magazine that won't let me seat to the lands, but I know they exist.

So far as I'm concerned, published OAL's are only a guide when loading for a bottle neck. Personally, I don't even look at published OAL's for a bottle neck, the firearm will determine that aspect.

GS

 

[Shortstop]

While reading another thread on the HighRoad forum today, I was led to this web site from Berger Bullets that gives you good information on COAL and CBTO:

http://www.bergerbullets.com/effect...coal-and-cartridge-base-to-ogive-cbto-part-1/

 

[gamestalker]

From what I understand, Berger bullets do not represent the typical bullet profile due to the longer profile nose. So they may not experience the same pressure effects that a typical profiled bullet. Being that they are designed to engage the lands with far less resistance, so they don't produce as much spike when making that push into the lands.

Just my .02

GS

 

[Shortstop]

I actually thought about that myself, but it seemed to me that they were not talking specifically about their bullet.