Exceeding Max COL?

[DanTheFarmer]

Good Evening,

I'm trying to work up a load for my 7mm-08 using H414 and a Hornady 154 gr Spitzer. I got my "One Caliber" book and used the Hornady load data. It seemed a bit heavier than the comparable loads but I'm starting low and working up. I'll keep a close eye out for pressure signs.

After I loaded up a bunch of 6 round batches, sneaking up near Max Load I noticed the COL they had me load to (2.835") exceeds the normal max COL of 2.800".

Is this a non-issue as long as the ammo properly feeds and cycles? (I checked, it does, JUST barely).

Could the longer length result in lower pressure, accounting for the slightly heavier loads Hornady says are o.k.?

Thanks for any and all advice.

Dan

 

[cfullgraf]

There are a number of reasons for a particular cartridge overall length. One is whether it fits in a magazine or not.

This is not an issue if you want to single load the ammo.

Generally, accuracy is improved if the bullet is set close to the rifling. There are recommended starting points but generally you have to find the sweet spot for your rifle. There are a variety of tools and aids to determine the starting point. Bullets set near the rifling usually are longer than magazine length.

For two cartridges with the bullets set to different depths, the longer cartridge should generate less pressure. But there are situations where that is not true like where the bullet is jammed up against the rifling.

Can you see a pressure difference for a difference of .035"? Probably not for the most part until you start to approach maximum loads.

There are lots of variables that go into one company's load data. Bullet seating depth is one of them but ther are many others including the rifle, the chamber, case, primer, lawyers, and some others.

It is not unusual to see data vary from different sources. Just work up the loads as you are doing. If the slightly longer cartridge fits and feeds, that is fine.

 

[USSR]

After I loaded up a bunch of 6 round batches, sneaking up near Max Load I noticed the COL they had me load to (2.835") exceeds the normal max COL of 2.800".

Is this a non-issue as long as the ammo properly feeds and cycles? (I checked, it does, JUST barely).

Yep, the Max COL is rifle specific, not something set in stone.

Don

 

[243winxb]

COL- as long as it feeds and chambers your OK.

Hodgdons website has your bullet/load listed as starting 43.0gr and Maximum of 46.0gr; COl at 2.800" COL-This is a non-issue as long as the ammo properly feeds and cycles.

Could the longer length result in lower pressure,

Not that you could notice. Seating into the rifling will raise pressure, so its been said. But only a problem if you start with a maximum loading thats jumping the bullet to the leade/rifling. You can get great accuracy with bullets that jump to the riflling.

 

[doorman]

I use the Hornady overall length gauge to determine the COL to the rifling. I don't measure just one bullet but 10 then average. The bullet profile also mean a possible COL greater than stated in a load manual. When I loaded up some Nosler Accu-bombs I was a little worried since they were so long. They actually fit the magazine and chambered just fine. I started out at .02 off the lands and eventually settled on .01.

 

[NCsmitty]

Often with short action rifles, it's a balancing act between ammo fitting the magazine and getting it to have a nominal jump to the lands for the sake of accuracy.
I personally try to set my ogive at .020" off the lands, and find that dimension usually allows for the minor variations that can occur with production bullets, and keeps them out of the lands.
That dimension is sometimes not possible, varying with cartridge and bullets used.

IMO, the 7mm-08 is a happier cartridge with 140gr class bullets, especially flat base. They provide more case capacity and resulting velocity. Leave the 154gr to the 7mm mags



NCsmitty

 

[steve4102]

The Max OAL is for Ammunition manufactures, it insures that their factory ammo will fit every rifle chambered in that round. It has nothing to do with handloading. The handloader is free to set his or her OAL to what ever works. What works is determined by such things as Mag length, Cannelure, distance to the lands etc.

 

[ranger335v]

"I noticed the COL they had me load to (2.835") exceeds the normal max COL of 2.800""

Sorta makes a feller suspect it ain't all that critical, don't it?

 

[JDGray]

Bullet shape has alot to do with OAL. The chamber in my Savage 10FP, would allow me to seat 168gr SMKs out to 2.813" before I hit the rifling, 168gr Amaxes could seat out .030"+ farther before they hit. Every bullet type will be different, so check your chamber and record the distance to the lands, with each bullet type. My Savage likes .010" off the lands, yours will be different

 

[DanTheFarmer]

NCsmitty (and all others),

You said in your post "Leave the 154gr to the 7mm mags."

I checked out the www.hornady.com ballistics calculator for heavy 7mm bullets to get down range velocities. I checked out www.hodgdon.com to get muzzle velocities.
I compared 7mm-08 to 7mm Remington Magnum.

It seemed that the Magnum was a "100 yard further" gun. Whatever velocity the Rem Mag had at 400 yards the 7mm-08 had at 300 yards. Whatever the Mag was doing at 300 the 08 was doing at 200.

Since 200 - 300 yards is a loooong shot here in heavily wooded New England are there other reasons I should avoid heavy bullets in the 7mm-08? Accuracy problems? Just a sense that they don't work quite right?

I'm new to this and looking for input. I do my research and value the book knowledge I can gain but I recognize there is no substitute for real world experience.

Thanks again for any input.

Dan

 

[NCsmitty]

I'm new to this and looking for input.

I'm only voicing my opinion, and in no way mean to confuse. If you have 154gr bullets and wish to use them, they will work ok. You just have to test work up loads to make sure that they shoot ok for you.
If you can keep all your shots on a 9" paper plate at 200yds, you have a good load. That's about the size of the kill zone on a deer.
Good shooting.



NCsmitty

 

[steve4102]

You said in your post "Leave the 154gr to the 7mm mags."

I used to load 160gr Partitions in my sons 7mm-08 Savage to 2720fps with Ramshot Hunter. Devastating on Whitetails. Now it's a 7mm-08 AI running the 160's at 2850+.
Load your 154's and enjoy, they will knock-em dead.