O.A.L. Gauge Readings 6.5-284

[Ccctennis]

I have been powder testing for my 6.5/284 and have narrowed my powder and charge weight down.
The next step i took was using the hornady OAL gauge to find my seating depth.
I am a bit inexperienced in using it. My reading which i took 6 times was 3.140 with a 140 grain 6.5 sierra matchking

I am a bit concerned because at that depth very little of the bullet is in the case mouth. Actually just barely past the boat tail contour makes it into the case mouth.

I do know i would back of the lands a touch but this seems to far to seat this particular projectile.
Anyone reloading for 6.5 have some advice on it?
Thanks

 

[Leatherstocking]

It is generally advised to have at least one calbre of bearing surface inserted in the case. This means the boat tail does not count.
Bullets not seated deep eneough can experience set back due to recoil, or be mis aligned due to handling. Do not forget about fitting your magazine, longer COL cartridges may not, if that matters.

 

[fguffey]

The next step i took was using the hornady OAL gauge to find my seating depth.

I would think you are looking for maximum overall length. If the boat tail bullet does not offer bullet hold I would use flat base bullets. And then before that; I would determine the length of the chamber from bullet contact with the rifling to the bolt face. I am not the fan of seating bullets at or into the rifling. I want all the bullet hold I can get and I want my bullets to have that running start.

F. Guffey

 

[243winxb]

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[Bart B.]

I've no idea where that "bullet diameter" minimum seating depth came from nor the rational for it. It's not the spec or standard for military and commercial ammo nor for any match grade ammo I know of.

Seat bullets deep enough so they don't shift in handling, loading and firing. If a 1/10 inch depth is what you want but bullets don't stay in place in these conditions, size case mouths smaller.

Freebore, if it exists, is the chamber's constant diameter from its mouth to start of rifling. Throat, or leave as it's also called, is the rifling angling down from freebore diameter to bore diameter. So says SAAMI's glossary of terms. The .30-06 SAAMI spec chamber has no freebore. It's leade starts at the chamber mouth.

 

[Blue68f100]

The purpose of the gauge is to determine the MAX OAL that will fit your gun with a particular bullet. Some guns have a generous free bore which does not allow you to reach the rifling while others are min spec. Like said you generally want one Caliber length of bullet seated in the neck. This is to ensure proper neck tension, plus it must fit the magazine. I always start off my OAL at what the reloading books tell me to use for starting. Then I work from there. There is no problem loading them long as long as they fit the magazine and you have proper neck tension. I have 1 ar that is next to impossible to reach the lands with some bullets. And another one that has a min spec chamber which I have to load short with some bullets.

My suggestion is start with the suggest OAL and go form there. You will be surprised on how may guns shoot well with very long jumps to the lands.

Some bench rest shooters have their OAL set for the bullet to be seated contacting the lands. They use very light neck tension and single load 1 round at a time. They have worked their loads up doing this, for it's safe for their gun only. Taking that some load to another gun may result in catastrophic failure.

 

[Bart B.]

Like said you generally want one Caliber length of bullet seated in the neck. This is to ensure proper neck tension,

What is "proper" neck tension for the OP's cartridge, or any cartridge?

Are there any standards and tolerances for it?

What's the correct way to measure neck tension?

 

[Blue68f100]

You want enough tension so the bullet does not move during feeding or under recoil. Normally it's in the 40# range. The way to check is see if you can push the bullet down while pushing against a bench (or scales). When loading for a simi-auto the bullet may move (0.002-0.003") when slammed home during chamber due to the violent action. This is fine as long as you don't load to the lands or repeatedly unload the chamber the same round. If your expander ball is the right size where you have ~0.001"-0.002" interface fit you should be fine. The only time it may be problem is if the brass is annealed after sizing.

 

[Bart B.]

In part of MIL SPEC MIL-P-3984J, the following test states the standard for neck tension to be bullet pull measured in pounds for 7.62 NATO ammo made in government arsenals:

4.5.2.1.1 Bullet Pull test. To assure that the sample test cartridges have been properly assembled and crimped a bullet Pull test shall be performed on 20 random samples of the test cartridges for the first article test and all production lot testing. The force required to extract the bullet from the cartridge case shall not be less than 45 pounds (The 7.62MFl,M852 and M118 Cartridges, shall not be crimped and the force required to extract the bullet from the cartridge case shall not be less than 10 pounds).

For what its worth, I’ve shot 7.62 Garands with .3082" diameter 190's having measured bullet pulls less than 10 pounds; they don’t shift forward in case mouths of the M118 new cases .3086" diameter 172-gr. bullets were pulled from, powder charge put in then seated without any case neck prep at all.

There is no standard for bullet insertion force; neither in SAAMI or MIL SPEC standards. If the case mouth diameter is smaller at the shoulder than the mouth, typical for all cases not neck turned for uniform thickness, it'll take more push force to seat one deeper than the pull force to get it out. Otherwise, seating force closely equals pulling force.

Bullet energy at bolt speed when loaded cartridge stops against chamber and bullets seated one caliber deep:

* M1, 30 caliber 175 gr. with about .30 square inch of case neck grip, bolt closing at 9 fps: 314 ft-lbs.

* AR15, 22 caliber 55 gr. with about .15 square inch of case neck grip, bolt closing at 7 fps: .060 ft-lbs.

 

[Ccctennis]

Thanks for your replies. One thing is for sure I have fairly deep free bore. I wasn't looking to seat bullet super close to lands but did want to test seating depth vs accuracy. I will start with book suggestion first then work my way out little by little. I definitely know now I have room to go outwards