Pressure signs

[Pyscodog]

Working with a Howa Carbon Elevate, 6.5 CM with 1-8 twist carbon barrel. Shopping yeaterday, I picked up a box of Sierra 144 gr Match Kings. I had never seen that grain weight before so I thought I'd try them. Using a Hornady OAL modified case the OAL was 2.786 which seemed rather short to me but I seated one round a little long and it wouldn't let me close the bolt so I shortened the length to 2.782. That's just a ,004 jump and I don't use precision dies so lengths can vary a little +/-. Powder was H4350 and a Winchester primer in Hornady brass. Starting load was 40.5 then 41, 41.5, 42. AT 42, five of each. I was getting the best accuracy with 42 grains but getting a faint ejector swipe and the bolt lift was getting a little heavy. Nothing serious but heavier than normal. If I seat my bullets deeper will it possibly lower the pressure or should I try to find a load somewhere between 41.5 and 42? I may try a different primer as well but only one thing at a time.

 

[C.E.Smith043]

Changing seating depth will definitely alter the pressure. But imo, the only way to know to what degree or effect is to shoot it.

I've seen it cause the pressure to increase on some loads and decrease the pressure on others.

 

[Pyscodog]

I very seldom run my bullets that close to the lands. I guess loading a few with different seating depths will be the only answer. I use to have a 243AI and if I seated the bullets touching it caused the pressure to spike. Back it off .020 and it got happy again. I'll try different seating depths next time out. Maybe it will tighten the groups up a little in the process.

 

[gunsandgunsmithing]

Working with a Howa Carbon Elevate, 6.5 CM with 1-8 twist carbon barrel. Shopping yeaterday, I picked up a box of Sierra 144 gr Match Kings. I had never seen that grain weight before so I thought I'd try them. Using a Hornady OAL modified case the OAL was 2.786 which seemed rather short to me but I seated one round a little long and it wouldn't let me close the bolt so I shortened the length to 2.782. That's just a ,004 jump and I don't use precision dies so lengths can vary a little +/-. Powder was H4350 and a Winchester primer in Hornady brass. Starting load was 40.5 then 41, 41.5, 42. AT 42, five of each. I was getting the best accuracy with 42 grains but getting a faint ejector swipe and the bolt lift was getting a little heavy. Nothing serious but heavier than normal. If I seat my bullets deeper will it possibly lower the pressure or should I try to find a load somewhere between 41.5 and 42? I may try a different primer as well but only one thing at a time.

It can go either way with seating depth. It's not 100% as simple as saying deeper into the lands = more pressure. Id'd back down at least .5, maybe a full grain and do a seating test. It might surprise ya.

 

[Pyscodog]

The lighter loads produced sub standard groups but when I got to the 42 grain load is when the group tightened up. But I will do as suggested and back off the load and work with seating depth also. I think the accuracy is there. I just have to find it. Keeps me occupied so all is good!!

 

[JFrank]

The lighter loads produced sub standard groups but when I got to the 42 grain load is when the group tightened up. But I will do as suggested and back off the load and work with seating depth also. I think the accuracy is there. I just have to find it. Keeps me occupied so all is good!!

Just don’t back the load down into the anti node.

 

[K22]

Personally, I would avoid any reloading recipe, regardless of accuracy on target that produces positive signs of excessive or approaching excessive pressure. Ejector marks on the case head and hard bolt lift are typical signs of high pressure.

Also, for me, .004" is too close to the lands because even the high-quality hunting bullets I use vary in base to ogive measurement, sometime at least that much. Regardless of the pressure consequences of seating bullet close or into the lands, I do not want to have a bullet stick in the lands and dump powder in the mag well when I eject an unfired round, especially if I am in the field. For me, functionality and reliability are as important as accuracy considerations, maybe even more so.

I also start load development at .020 off the lands, sometimes more for rifles with long throats (free bore) like the Remington bolt rifles. I have regularly obtained outstanding varmint grade accuracy with Remington rifles with bullet seated well off the lands out of necessity due to the long throats.

One question you may want to ask yourself is the level of accuracy I need from my system (rifle / reload / shooting position) to satisfy my needs. If it is hunting, this a fairly straight forward assessment.