Loading for an HK 770 or other roller locked semi

[Carphunter]

I'm going to start trying to make a deer load for my HK 770.

Normally, I'd grab my can of Hodgdon h4350 that I use for everything and start working.

But, I'm wondering if this powder is appropriate for roller-locked weapons.

I know from other sites, that some semi's are very particular about whether they use a fast or slow powder to make their pressure and for the gun to operate correctly.

Just checking to see if someone here has first-hand knowledge on this.

thanks

 

[Johnny Guest]

roller locked semi rifles

I have but limited experience with the type. I owned an HK91 for several years, probably 1978 -- 85 and that was what got me started loading .308/7.62x51 ammo.

Once, fairly early on, I loaded up about 30 --40 rounds with 150 gr FMJ bullets and IMR 4895 powder. Then I realized I had made an error in setting my scale and, instead of loading 43.0 grains, I had set the scale ten grains light, so the load was 33 grains. I didn't have a collet bullet puller, so I called my gunsmith and asked what I could expect. He suggested, since I wasn't using premium bullets, that I just use the loads for plinking and close range rifle drills. I asked, "What? You mean manually loading them?" He said that the roller locking setup tended to hold only so long as the pressure was high enough to need the locking and then release. I was dubious, but it worked exactly that way! Semiautomatic functioning was flawless, and, certainly the recoil was very mild.

I fired a few rounds at 100 yards, and the bullets struck lower than they should, of course. Happily, the HK military drum rear sight is easy to rotate, and I found that the 300 yard aperture gave me point of impact very close to point of aim at 100.

Anyhow, while I don't suggest loading THIS light, I doubt that anything like a normal load think there would present functioning problems.

I llike IMR 4350 and have used a LOT of it in various cartridges, but the manuals indicate that 4350 is not the most efficient powder for .308. RL15, IMR 3031 and 4895 do quite well. Some years back, NRA tested some military style 147 gr FMJ bullets using 748 powder, and they liked the results. My most accurate load for my Savage Scout is with the Sierra 165 GameKing and IMR 4895.

Please let us know what all you try, and the results.

Best of luck
Johnny