150 gr. 308 load question

[csterl]

I am loading some Hornady 150 gr. FMJBT .308 loads, I am using LC brass, Winchester LR primers and 45 gr of IMR4064. My question is the Hornady bullets appear to be shorter than other 150 gr pills that I have. The Lyman book lists a 150 gr. FMJSP at 2.735 COL but I don't know how different that bullet is. My Lee manual lists the 150 gr. FMJBT at 2.755. If I seat to the cannelure I am at 2.735 COL, should I seat to the cannelure or seat to 2.755? Do I need to adjust my powder load if I am compressing it a little to seat at 2.735?

Thanks for any insight!

[Fjold]

A .002" difference COL isn't going to make any difference to your load.

Safe powder loads are determined by weight as long as you're charge is in a safe weight for your load then compressing the load won't hurt you. I shoot many compressed loads in different cartridges.

[csterl]

Thanks for the reply Fjold, I agree that .002" wont matter but I am actually talking about a .02" difference, any concerns?

Thanks for the info on the compressed load!

[Fjold]

Sorry, math error. Even .02" isn't going to affect your load noticeably.

Having too short of a COL for a load is kind of self compensating. It reduces the amount of powder space in the case by a small amount which raises pressure slightly at the start of the powder burn but it increases the jump to the lands which gives the bullet a running start before it has to squeeze down to fit the bore so it also has a tendency to lower peak pressures of the load.

That's one of the big reasons that you can't run 5.56 ammo in a 223, the leade (throat) of the 223 chamber is cut shorter and peak pressure goes a lot higher.

[csterl]

Thanks Fjold, that makes a lot of sense. I have loaded up quite a few loads over the last year or so but I am constantly realizing how much there is to learn about reloading! At least I am having fun while I learn. Thanks again for the info!!!

[TestPilot]

Quick Load shows following results for .308 Hornady 150gr FMJBT with a COL of 2.755 and 2.735 and 45gr IMR 4064 in a 26" barrel.

COL: 2.735 2.755
PMax 53844 52996 psi
MVel 2849 2840 fps
Barrel T 1.195 1.202
The 26" Barrel OBT Nodes 3,4 & 5 are 1.1057 1.1905 1.3295 so I'd go with the shorter COL which sits almost exactly on node 4. Might even try working the COL down by another .01 if you don't see any pressure signs...That would put you directly on Node 4 with a barrel T of 1.191...But there are other ways to get there with different powder that don't produce a compressed load.
H4895 at 44.6 is a 98% load density with equal Barrel Time
H322 at 41.6 is a 94% load density with equal Barrel Time.

All these loads are HOT loads and should be worked up to...

[Fjold]

Hodgdon lists the 150 grain bullet load as

150 GR. NOS BT using IMR 4064 at a COL of 2.800"

The starting load is 43.0 grains to get 2663 fps at 44,700 PSI and the maximum load is 47.7 (Compressed load) to get 2903 fps at 57,100 PSI

[csterl]

Hodgdon lists the 150 grain bullet load as

150 GR. NOS BT using IMR 4064 at a COL of 2.800"

The starting load is 43.0 grains to get 2663 fps at 44,700 PSI and the maximum load is 47.7 (Compressed load) to get 2903 fps at 57,100 PSI

Yeah Frank, that's what I am concerned with. If I seat to the cannelure I am at 2.735" and if I seat at 2.755 or 2.800" the cannelure is not in the case?

[Fjold]

I don't pay attention to the cannelure and don't care where it is in relation to the case mouth. I load to fit my chamber or magazine length if the chamber is too long. I usually measure my chamber throat with a dummy case sized enough to allow a slip fit of the bullet. I then set my COL at .010 short of that as long s the fit in the magazine.

[jimbo1747]

I bought 1K of the Hornady 150 grn. FMJ from surplusammo.com and had the same problem. I load my 308 ammo to COL 2.775" and found that the cannelure sticks out from the case. Did a little searching and found that I wasn't the only one with this problem. Check out some of the reviewers comments.

http://www.midwayusa.com/viewProduct/?productNumber=1165163765

I've fired over 200 rounds with these bullets out of my M1A using a very slight roll crimp and have not experience any problems with setback.