Hi pressure problems. - Page 2

**Unclenick** · April 4, 2010, 06:37 PM

I just pulled three more LC Match cases from the same lot, and they averaged 179, not 189. I'd remembered them being 181, but that may have been non-match cases I have from some '79 M118 Special Ball. I'd remembered the IMI Match brass as averaging 186 grains, but for five to average a grain lower would be well within there normal variance.

In any event, this, to me, confirms the theory that the fault for the sticky bolt lift lies with the old GI brass. It is probably over-stretched from machine gun firing. If they were in good shape they would have handled the same load as the IMI Match brass did without the bolt sticking, since the IMI's smaller capacity will have increased the pressure a bit. As a result, I think you'll need to keep an eye peeled for head separations with the old brass.

Some degree of primer flattening is normal at full pressure in the .308. Your Remington probably has the new firing pin tunnel chamfer that causes cratering even when pressure is fine (look at the bolt face to see?). Sounds like the SAKO barrel launched the lower load on the down swing of the muzzle, so that just wasn't a sweet spot load for it. You'll want to tune these before deciding on a final charge. Note that load will change with different capacity cases, like commercial cases.

If you haven't looked yet, try Dan Newberry's load tuning method, now that you have a range you want to work with.

On the case dimensions, that looks pretty normal to me. Resizing never returns diameters 100% to new size (except the necks), but they are smaller than the fired size, and that's what counts. The fired shoulder to head length is the only oddity. It's probably an artifact of the shoulder radius in the chamber, where measuring to the headspace datum (where the shoulder is 0.400" diameter) might provide a changed ranking?

greco · April 4, 2010, 07:07 PM

UncleNick..thanks for the post. I too am wondering about this brass. I think I will just fill them up with GI surplus hardball and keep them stashed. I just ordered a batch of LC match brass. I will do all my loading from this point with fresh brass. Yes, i will tune the loads to the barrel vibes (sweet spots). Thanks again...

April 4, 2010, 06:37 PM	#26
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,732	I just pulled three more LC Match cases from the same lot, and they averaged 179, not 189. I'd remembered them being 181, but that may have been non-match cases I have from some '79 M118 Special Ball. I'd remembered the IMI Match brass as averaging 186 grains, but for five to average a grain lower would be well within there normal variance. In any event, this, to me, confirms the theory that the fault for the sticky bolt lift lies with the old GI brass. It is probably over-stretched from machine gun firing. If they were in good shape they would have handled the same load as the IMI Match brass did without the bolt sticking, since the IMI's smaller capacity will have increased the pressure a bit. As a result, I think you'll need to keep an eye peeled for head separations with the old brass. Some degree of primer flattening is normal at full pressure in the .308. Your Remington probably has the new firing pin tunnel chamfer that causes cratering even when pressure is fine (look at the bolt face to see?). Sounds like the SAKO barrel launched the lower load on the down swing of the muzzle, so that just wasn't a sweet spot load for it. You'll want to tune these before deciding on a final charge. Note that load will change with different capacity cases, like commercial cases. If you haven't looked yet, try Dan Newberry's load tuning method, now that you have a range you want to work with. On the case dimensions, that looks pretty normal to me. Resizing never returns diameters 100% to new size (except the necks), but they are smaller than the fired size, and that's what counts. The fired shoulder to head length is the only oddity. It's probably an artifact of the shoulder radius in the chamber, where measuring to the headspace datum (where the shoulder is 0.400" diameter) might provide a changed ranking? __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle Last edited by Unclenick; April 4, 2010 at 06:46 PM.

April 4, 2010, 07:07 PM	#27
greco Senior Member Join Date: September 12, 2005 Posts: 125	UncleNick..thanks for the post. I too am wondering about this brass. I think I will just fill them up with GI surplus hardball and keep them stashed. I just ordered a batch of LC match brass. I will do all my loading from this point with fresh brass. Yes, i will tune the loads to the barrel vibes (sweet spots). Thanks again...