Seating depth of bullets

[Irish]

Right all you experienced reloaders I am hoping for some advice.

I am currently reloading for a 270 and all is going well in so far as I have discovered a sweet load that is consistently giving me 3 shot group under .5 inch at 100 yards. However I have seated all my bullets irrespective of shape or size to the same depth as commercially produced ammo.

What I want to know is there any way of knowing what depth to seat a bullet to of does it depend on each rifle. How one start to determine what would be the best depth? Is there a safe and conversely an unsafe practice?

 

[JD338]

I always load my bullets .015-.020" off the lands or as long as the magazine will allow. This is the case for my 338 RUM so I have a lot of free bore. I am still getting .5 MOA.

Try loading off the lands and see what kind of accuracy you get. Sounds like you already have a good load to fall back on.

JD338

 

[Scott in Michigan]

To be able to measure land-to-ogive distance with both precision and repetition, you will need special gauges like those made by Stoney Point. This is necessary because the land-to-ogive distance will change with different bullet shapes even when seated to the same depth. Actual bullet length will be different between both bullets in the same box and different lots. Bullets with plastic tips tend to be the most consistant.

The procedure I use is to start with the bullet seated to either max magazine length or 0.015" off the lands, whichever is longer. I load five rounds, screw the seating die in 0.005", load five more and repeat until I have 10 loads.

When actually shooting these loads, there is usually a single distance off the lands that is significantly better than the others. I'll then load up 25 rounds of the best load or two if another is close, and shoot five 5-shot groups for repeatability and consistancy.

The best ogive-to-land distance will change between rifles, bullet weights and sometimes even brands. However, usually bullets of the same weight shoot fairly well at the same distance off the lands.

FWIW, the best ogive-to-land distance may change with different powder charges or primers, so work up your max load in the usual manner first.

 

[rick smith]

Irish,there is no set seating depth for any particular caliber/rifle. All rifles are individuals and have definite preferences. Magazine box length will control bullet seating for certain calibers/rifles. You may not be able to seat anywhere near the lands. Most factory 308s have that. I just finished loading for a friend's 270 Browning A-Bolt that has a magazine block and doesn't allow seating to the lands. The front of the block is part of the feed ramp so I had to find a load that shot well and be approx. 60thou. off the lands.
If you want to be able to seat to the lands, you need a repeatable method of finding the lands and a way to measure onto the ogive of the bullet, not the tip of the bullet. The Stoney Point, as mentioned by Scott, is an excellent tool for that. It has a learning curve so be patient. After you find the lands, make a dummy round using brass fired in your rifle and try it in your chamber. I make modified cases from brass fired in my rifle so they tend to measure better than Stoney's modified cases in my rifles.
You will find there is more than one sweet spot for any particular load in your rifle.Rick.