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brando
02-16-2007, 9:03 AM
I'm getting back into reloading after a 15 year hiatus and having some issues with bullet seating depth.

I'm currently working on .223 loads for an SPR build that I've had good performance shooting BH 77gr ammo, but naturally I want to work up a more accurate and consistent load. I'm re-using the brass from the BH ammo I've already shot, CCI primers, SMK 77gr HPBT bullets and working up loads between 22.3 - 24.1 grains of Vihtavuori N140 to try to find the sweet spot.

Now the problem is that when I was doing loads in the Army, I was in a Arms Room surrounded by guys who really knew this stuff and guided me through the process every time. I obviously don't have that anymore, so I'm going off of my memory and manuals.

I started seating the bullets last night and was having a devil of a time getting consistent COAL of 2.26. I suspect the first thing I need to do is get a decent COAL comparator that uses the bullet ogive instead of the tip. But the seating die itself (Lee) just doesn't seem to be doing a consistent job. I installed the die until it touched the ram, lowered the ram and added another 1/4 turn, then used an unprimed case to test the bullet depth. Once I got one that matched the COAL I started seating bullets on my charged cases. The first five were all off, some too deep at 2.25 and others not deep enough at 2.28. This obviously concerns me as I've seen first hand what consistent bullet depth can do for accuracy.

Do you guys have any advice or recommendations on this?

ocabj
02-16-2007, 9:20 AM
The problem is that the meplat of the Sierra Match Kings are not consistent. I'm sure if you used a bullet comparator to measure your rounds, they will all be seated consistently with respect to the ogive.

If you are seating mag length loads using a 77gr SMK, I would suggest sticking with 2.250" as your average. Depending on the mag, up to 2.270" shouldn't be a problem.

Also, seating depth has some bearing on your powder. A 77gr SMK is pretty long, and you are packing the powder into that case. Sometimes the powder just doesn't crush consistently when you seat the bullet. This is why some people prefer less powder or a powder with smaller granules when loading heavy bullets in the AR.

You *could* also use a meplat trimmer, but a meplat trimmer wasn't meant to trim the meplat down so you can fit your rounds in the mag. They were meant to make the meplats consistent in your lot of bullets. I have the Sinclair meplat trimmer and I honestly haven't tested it out thoroughly. I trimmed a batch of 100 rounds (77gr SMK) that I used for the short lines (200/300 yards), but I couldn't tell you if it made a difference as far as making the groups more consistent. I have yet to experiment with meplat trimmed bullets in a controlled environment.

Anyway, don't sweat the consistency of your overall length. As long as you're within 2.255" give or take .015", you should be ok.

brando
02-16-2007, 10:06 AM
Ah, very interesting. So it sounds like I need to get a good bullet comparator and just stick to a single setting on the seating die? I seem to remember certain seating dies having measurement dials to set the depth?

ocabj
02-16-2007, 10:26 AM
Yes, Redding and Forster both make a micrometer seating die. I have the Redding.

But the seating die makes contact with the ogive, not the tip. So even with a micrometer seating die, you will still have varying overall lengths if you measure from base to tip of a loaded round. With my 77gr Noslers, the cartridge overall lengths measured from base to tip vary from 2.250" to 2.265".

Again, don't stress over the COL. Just get it so that they hover around 2.250" or so and be done with it. If you find one that is exceptionally long and won't seat in the mag, just set it aside in your practice batch to be single loaded.

thmpr
02-16-2007, 10:59 AM
If you really want to be anal on it, buy a giraud trimmer and purchase the meplat trimmer, this device will trim each bullet to the exact same length. The main reasons why the OAL is critical is for feeding and proper seating depth vs pressure. Make sure the case are trimmed to its min COAL.

ocabj
02-16-2007, 11:14 AM
If you really want to be anal on it, buy a giraud trimmer and purchase the meplat trimmer, this device will trim each bullet to the exact same length. The main reasons why the OAL is critical is for feeding and proper seating depth vs pressure. Make sure the case are trimmed to its min COAL.

Well, seating depth for a good die isn't based on the tip or meplat. So trimming the meplat won't affect seating depth. Thus, it will not affect pressure.

But again, you should not trim a meplat so your cartridges have the same COL. You trim the meplat to make them all consistent so the BC of your bullets are consistent. Thus, this makes the group consistent. I'm pretty sure 99% of highpower AR shooters don't use a meplat trimmer. I own one, and like I said, I don't really use it, yet. From what the experts claim who have used this, they claim as much as a 1/2MOA improvement in group size.

As far as OAL affecting feeding, the variances of the COL due to the inconsistent meplat on OTM (open tip match) style bullets such as the Sierra Match King, there is no issue.

Trimming a case to it's "min COAL" is not correct terminology. COAL or Cartridge Overall Length (or more correctly abbreviated, COL) is the length of the loaded cartridge from base to tip. Trimming a case affects the length of the case itself, not the length of the cartridge.

thmpr
02-16-2007, 11:20 AM
I have been following several gun tactcal match masters on how they have been reloading their 77 grain SMK loads and had no issues with their setup and process, but it helps to have the right tools and a chrono to see what your loads are actually doing. But their was a post C.G posted awhile back concerning that it doesnt really matter if you clean your brass and etc. But what I am more worried about is the seating depth vs charge.

tteng
02-16-2007, 11:37 AM
I installed the die until it touched the ram, lowered the ram and added another 1/4 turn

I thought the above is for sizing die setup.

For seating die, I thought you're suppose to ram-up w/ a empty case in the shell-holder. Screw down the die till you feel the case touch, then backoff 1/4 turn for non-crimp (or in 1/4 turn for crimp). I use a lee die (for 308, 30-06) and don't crimp. If my ram-up/down stroke are consistant, I find COL are pretty much consistant, +-0.005" or so. I think by adding crimp, you add more non-uniform friction, thus the larger tolerance variation.

ocabj
02-16-2007, 11:40 AM
I thought the above is for sizing die setup.

For seating die, I thought you're suppose to ram-up w/ a empty case in the shell-holder. Screw down the die till you feel the case touch, then backoff 1/4 turn for non-crimp (or in 1/4 turn for crimp). I use a lee die (for 308, 30-06) and don't crimp. If my ram-up/down stroke are consistant, I find COL are pretty much consistant, +-0.005" or so. I think by adding crimp, you add more non-uniform friction, thus the larger tolerance variation.

Oh crap, I didn't catch that in the original poster's message. tteng is correct. Screwing the seating die all they way down is bad because it will add crimp. Follow his instructions for adjusting the seating die with no crimp. It is the correct method.

Fjold
02-16-2007, 11:44 AM
I thought the above is for sizing die setup.

For seating die, I thought you're suppose to ram-up w/ a empty case in the shell-holder. Screw down the die till you feel the case touch, then backoff 1/4 turn for non-crimp (or in 1/4 turn for crimp). I use a lee die (for 308, 30-06) and don't crimp. If my ram-up/down stroke are consistant, I find COL are pretty much consistant, +-0.005" or so. I think by adding crimp, you add more non-uniform friction, thus the larger tolerance variation.


+1,000 That jumped right out at me on the original post but I finished reading the string and saw that tteng covered it.

brando
02-16-2007, 11:49 AM
Looks like I need to go back and re-read the manual on seating dies ;)

Thanks.

tteng
02-16-2007, 11:58 AM
I do add that I don't like the rubber-ring underneath the die lock-nut because it'll give gradually under force (when you screw down finger-tight) thus changing the die-height. So if you're doing different batch between days, the COL will be different. I always keep my first cartridge (dummy, no powder) as a template for future reference.

Omega13device
02-16-2007, 12:29 PM
For those who may not have seen this article on Mk262 Mod 1 ammo...

http://www.gunsandammomag.com/ammunition/mk262_080105/

Btw does anyone know what powder and load Black Hills uses in the Mk262?

ocabj
02-16-2007, 12:44 PM
For those who may not have seen this article on Mk262 Mod 1 ammo...

http://www.gunsandammomag.com/ammunition/mk262_080105/

Btw does anyone know what powder and load Black Hills uses in the Mk262?

I read that article. I based my duplication recipe based on the muzzle velocities for the 18" listed in that article.

NOTE: THE FOLLOWING DATA IS OVER SAAMI SPEC. DO NOT USE THE DATA WITHOUT PROPERLY WORKING UP THE LOAD FOR YOUR SPECIFIC RIFLE. USING THIS DATA MAY RESULT IN DAMAGE TO YOUR FIREARM OR BODILY INJURY, OR DEATH.

I used 25.3gr of Varget behind a 77gr SMK in an LC case and a Winchester SR primer to get 2787fps in an 18" SPR barrel.