Seating depth with FMJ bullets bolt action

L

Lange

New member
Hello,

Searched around for info and can't find much info on this. I have been loading 150 Hornady FMJs and 55 FMJs for a .308 and .223 bolt rifle respectively. Goal is to shoot this type ammo with more accuracy than factory loads of these rounds and something else to load for cheaper.

Both these bullets have cantalures likely because they are often used in semi autos with a crimp I assume. Few questions is it beneficial to load these type of bullets past the standard OAL closer to the lands? Can I seat below the cantalure so the bullet is seated further out? Also can any accuracy even small be gained by this? No crimp on the bullet fine as well?

Also wondering if these type of bullets like more jump than most? Maybe 40-30 thou from the lands tops if I can seat them further?

Not sure if many people load this ammo as much outside of semi auto rifles so these kinds of loading practices maybe aren't done so much.

Thanks kindly
 
Also wondering if these type of bullets like more jump than most? Maybe 40-30 thou from the lands tops if I can seat them further?
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If I am going to crimp and the bullet has a cannelure I crimp at the cannular. If I have a bullet that does not have a cannula I have a machine that will install it.

When it comes to maximum over all length I an the fan of the jump start, I want my bullet to have that running start. If I have a rifle that insists the bullet be seated into the lands it does not get shot.

F. Guffey
 
F. Guffey said:
If I am going to crimp and the bullet has a cannelure I crimp at the cannular. If I have a bullet that does not have a cannula I have a machine that will install it.

When it comes to maximum over all length I an the fan of the jump start, I want my bullet to have that running start. If I have a rifle that insists the bullet be seated into the lands it does not get shot.

F. Guffey
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Thanks for the info. My guns don't seem to need to seat close for accuracy just looking for that little bit extra since well have the freedom to seat closer in a bolt gun. If they had to have bullets seated close yes there would be a problem.

Suppose another factor is guns are both Remington 700s, the .308 long throat but the .223 seems average or moderate. The .223 can seat any load I've tried close to the lands and still clear the mag. The .308 with 150s can go 40-30 thou and still make the mag length.
 
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My advice would be to work up loads with powder types, powder charges, different bullets, then work on OAL. I would use the bullet manufacturers recommended OAL for the specific bullet being used and get the best groups you can with varying powder charges. Then work on OAL...

For a bolt gun without crimping, disregard the cannalure. I use the same bullets in my Garand as I do in my Ruger 308 bolt gun. I lightly crimp my Garand ammo, but no crimp in my Ruger and I seat the bullet depth according to my Hornady manual (when I'm using Hornady bullets)...
 
You can forget the cannelure altogether and just load 'em to the Max OAL with bullet given in your manual. That'd be 2.800" for .308. And 2.260" for .223.
If you want extreme accuracy, use match grade bullets.
No crimp is required for an M1 Rifle. Been thumping loaded clips on my rifle's butt plate for eons with no fuss.
"...from the lands..." Is a load tweaking technique. Work up the load first, then fiddle with the length afterwards. Every rifle will prefer a different distance from the lands as every chamber, even in two identical consecutively numbers rifles, is slightly different from every other rifle.
 
Okay I have found the nodes with these loads I believe. Would be 43.5 IMR 4064 for my 5r .308, and 23 grains H335 for my .223. Chrono 2700 FPS with the 150s and 2800 with the 55s. I am just asking about seating depths because I just want to get the most out of my loads not that I am expecting match accuracy from FMJs.

I will try 40 thou from the lands possibly but not sure if any closer is beneficial. To my understanding FMJ bullets are designed to have a bit of jump.

On another note I am wondering about the charges. 43.5 4064 was most accurate for my rifle but is 2700 FPS too slow for a 150 optimally? Also I read something that the Hornady data for h335 for 55 FMJs was conservative. I may try to go 24.0 grain and look for pressure signs.

Also will disregard the cantalure since seems no purpose in my case.
 
You might find that shooting under 300 yards likes flat bullets better than boat tails and over 300 like BT's better if your rifle can realize the difference. I've never needed to touch the lands.
 
I load the hornady 150gr FMJBT in 30-06 bolt & garand and 308 bolt. They can be had around my parts for less than $20/100 so I load them for plinking/target practice. For 308 I load to the book spec OAL, got sub-MOA accuracy from it so I didn't mess around seating any closer (for now). I load with IMR 4895 but also got good results with 4064. 2700fps is on the slow end for 150s out of a 308 but if accuracy is your goal I don't see any reason to push it. I believe my 150gr/308 load chrono'd around 2750 and it stays sub-MOA out to 300yds for me (the longest I've tried with it so far).

I'm of no help in the 223 department
 
I would recommend that you measure the chamber of both rifles before trying to extend seating depth. Individual rifles do vary, even ones in the same caliber from the same manufacturer.

I have two Savage .308s, the oldest one that I bought in 2008 had chamber that was .070 deeper than SAAMI. The second one I bought in 2014 had a chamber that was 0.010 under SAAMI. After about 6,000 rounds, I was seating the bullets in the older Savage out so far (2.970+ OAL) that I couldn't maintain accuracy with the bullet seated out so far into the neck. In 2015, Savage put a new barrel on the old Savage after 6,300 rounds after the chamber eroded another 0.090. The rifle with the new barrel came back with its chamber also 0.010 under SAAMI. (Apparently Savage changed it barrel chamber seating specs over the 6 years in the interim.) At the rate that a .308 chamber erodes, I figure the shorter chambers just gained me about another 5,000 rounds of shooting before they start to lose accuracy.

One thing to note however is that the characteristics of the bullets you load can change the OAL for the same jump to the rifling even for the same bullet weights. With .308 Sierra 168 SMKs for example, The short chambers now seat at a max OAL of 2.805 after about 1700 rounds. But with the .308 Sierra 168 TMKs, the tip makes the OAL longer and the max OAL becomes almost 2.900 with the same jump to the rifling. Even when you know your chamber depth you still have to know the bullet shape and position of the bullet ogive to decide on your OAL when you choose a new bullet shape.

I have never had a factory .223 bolt action that came with a short chamber and neither have any of my range buddies. In fact, none of us can even seat a Sierra or Berger 52 or 53 grain match bullet near the rifling because the bullet falls out of the neck. It doesn't seem to cause a problem with accuracy though. I generally seat my .223 match bullets out at 2.260 to 2.270 OAL and they shoot very accurately. The jump to the rifling is over 0.100 but the results in my rifles are just fine.
 
I have a boatload of 147gr FMJBT in .308" I bought in bulk years ago, and don't know the MFG, but I have never been excited about their accuracy in any load in my M1A, Garand, or SKS. Maybe it's just my bullets, whatever they are, but I get far better accuracy from other bullet designs in these same rifles.
 
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