"Compressed" loads using IMR 4064?

[mpthole]

In my Sierra manual, it says that some of the .308 Win loads may be a "compressed" load with certain bullets. When I was doing some loading last night, my 45 gr powder charge darn near filled the case and it was obvious that when seating the bullet, the powder would inevitably be compressed.

My question is... how do I know how much powder compression is reasonable? I mean, I don't want to blow up my gun or risk injury because I've got to much pressure build up.

 

[Dave P]

Well, follow the book of course... and if your bullets start backing out, you have too much powder! I do quite a bit of crunching every so often, with no ill effects.

Dave

 

[mpthole]

When setting up my dies, I was able to seat the bullet - without powder in the case - to a perfect 2.800 OAL. After filling the case with powder, the OAL came out to anywhere from 2.825 - 2.850. That seems like an awful lot.

Don't flame me too bad now.... but would it be ok to "re-seat" these loaded rounds to the correct 2.800?

 

[Poodleshooter]

If you haven't crimped, you can always try reseating deeper. As mentioned, the bullets will either back out or some part of the case will deform or collapse. I'd check the final product in a case gauge or a sample chamber (preferably no firing pin in the bolt).

 

[Mark whiz]

The problem with 4064 is that the grains are SO long that you're not so much compressing the powder, but trying to force it into filing all the extra gaps the long grain creates.

To combat this, try the old Black Powder cartridge trick of using a LONG funnel tube to fill the case. Doing so tends to make the grains fall lengthwise in the case, leaving less gaps to compress into. Then tap the case a couple times and then press in the bullet and see if it goes down to spec.

 

[ocabj]

You could always switch to Varget...

I do use IMR 4064 in .223 for my AR and 4064 does tend to take up lots of room in the case because the granules are too long. Someone mentioned that there is dead space between the granules because they don't fall in perfectly straight. This is true. When I drop the 4064 into the .223 case, I tend to tap the side of the case to get the granules to settle in. This helps a little.

As far as compressed loads, you should work them up. Start a grain or two lower than your target weight and work up to make sure you don't see overpressure signs.

 

[Dave P]

but would it be ok to "re-seat" these loaded rounds to the correct 2.800? Yes - no problemo. But 2.85 is very long: could be reaching the lands, making a potentially dangreaous pressure by jamming the bullet into them. You better double check your chamber and load book!

Also next time, fill the case and then tap it a bunch of times - it will ususally do a lot of settling.

 

[Coltdriver]

I would just chime in and add that you should either reload to the OAL spec or you should absolutely know your actual chamber dimensions before you use a reload that is any longer.

I recently had some reloads that were a tad too long and resulted in pressures that ruined the brass. With other than a Ruger #1 chamber this could have been a blow up type disaster. My actual chamber dimensions turned out to be less than .020 over max standard OAL.

 

[mpthole]

Thanks everyone for the feedback. I had no plans on shooting these rounds when the OAL was .050 over the maximum listed in the manual. I just wanted to be sure that seating them a little deeper and compressing the powder even more wasn't going to be hazardous.

I have been working up this load from a lower powder charge. My last time out gave pretty piss poor velocity performance, so that's why I've had to up the powder charge.

Thanks again!

 

[GooseGestapo]

Just last night, I did the same thing loading up some various different powders in the 7mm-08, experimenting with a given bullet (Remington 140gr Cor-lokt) and previously determined seating depth (2.830"; 2.850" touches the lands in the throat).

When charging with 41.0gr of RL-15 (VERY ACCURATE, btw.) I had a bit of space left in the case.

When using RL-19, the 48.0gr charge came half way up the neck. Upon seating the bullet with the same setting on the seating stem, I got an OAL of 2.838", requiring me to reset the seating stem to get the proper OAL of 2.830". The resistance of compressing the powder resulted in a slighty longer OAL. This is due to "tolerances" in the press/loader "springing" or flexing under the increased pressure of seating the bullet and compressing the powder charge.

Both loads chrono's ~2,750fps, and both are amoung the 3 most accurate loads I've used. It just requires a little "manipulation" to get things right.

BTW, the Rl-15 load is 2.0gr below the book max. (Alliants), and the RL-15 load is 2-5gr below listed max, depending on who you reference. How Alliant got 50+ grains in that case and seated a bullet over it is beyond me! I used both a drop tube, and touched the case head to a running vibratory tumbler to get it to settle. I still can't get over about 49.5gr of RL-19 in the case, either PMC or Winchester, and seat a bullet over it.

So, thats why reloading is both an ART and SCIENCE.


(I suspect that the lot# of the Data powder, was a bit denser than the one I have. Kinda funny, as I get higher velocities at the same charge weights with RL-22 as compared to RL-19 in the .30/06, both being compressed charges! RL-22 is SUPPOSED to be slower burning than RL-19. Kinda like H4831 compared to H4350.

P.S. The RL-15 load under a Sierra 140gr BTSP loaded to 2.815" (2.825" touches the lands) gave me the best accuracy to date from my Rem Mod-7; 4rds touched, with #4 of 5rds going ~1/2" high for a ctc. 0.850" load. (the four touching were under 1/2" ctc.) Chron'o showed 2,740fps, with max spread of 62fps. A real winner for a 7lb rifle! The Sierra's are a bit tighter in weight tolerance. Uniformity of the jacket and core seem to be a bit better.

The Cor-lokts performed exemplarily on the deer I've shot with them though.