Seating deeper to reduce pressure

[Jinx]

I only started hand loading. I have a 264 Win Mag Sako Finnbear. I loaded 129 grain Sierra tips. After the first shot my bolt was sticky to open. The gunsmith I use said I should seat the tips 1 millimeter deeper, it will help lesson the pressure. Is this true or not? Should I take out all the tips and reduce the loads?

[Varmint Hunter]

Originally Posted by Jinx

I only started hand loading. I have a 264 Win Mag Sako Finnbear. I loaded 129 grain Sierra tips. After the first shot my bolt was sticky to open. The gunsmith I use said I should seat the tips 1 millimeter deeper, it will help lesson the pressure. Is this true or not? Should I take out all the tips and reduce the loads?

I would disagree with your gunsmith, primarily because there doesn't seem to be any reason to suspect that is the problem. The FIRST thing I would check is the powder charge. You shoud be starting with loads that are 15% below maximum or just use the lighter charges listed in a reloading manual. You may also want to confirm that you are using the EXACT same powder as is indicated in whatever source that you used. I might add that you should NEVER use unconfirmed loads that are listed on ANY web site.

There could be other possible causes of excessive pressure like cases that are too long, wrong primers, etc but I'd look at the powder charge first and then look at less likely causes. Arbitrarily seating bullets deeper into a case could actually cause pressure to climb, however, 1 millimeter shouldn't make that much difference. If bullets are loaded to the length that is indicated in the appropiate manual then you should be fine when using a factory barrel or SAMMI chamber.

[.280Rem]

There's little info to go on there, but on the face either your smith may be a competent smith, but not a competent hand loader, or you misunderstood what he said. In any event, like said above, if you seated it to SAAMI OAL, then, I'd look elsewhere for the cause of the problem. Seating deeper in the case can raise pressure. Seating further out, has been shown to have little effect on lowering pressure, but can a little bit. Think of it this way...seating deeper decreases case capacity/increases pressure. Seating further out increases case capacity/decreases pressure. I don't hold to the 15% thing on starting loads. In my opinion, 10% should be plenty off of max to start safe in a case like your loading for. Go back, check all your components, load data, COAL, and restart the load. If you're loading well under max loads, and your measurements are right, then it could be a gun problem, like headspace for instance. Eliminate the loading, and your procedures first.

By the way, what is the load you're using?

[jwp475]

If you are seating into the lands, then seating a little deeper can indeed lower pressure..

[eddybo]

Agreed, but unless that load is well below max and seated into the lands I would pull the bullets and try a lower charge.

Originally Posted by jwp475

If you are seating into the lands, then seating a little deeper can indeed lower pressure..

[britz]

I agree w/ Edd and JWP in saying that seating to the lands can and will raise pressure. Allowing the bullet a "jump start" prior to hitting the lands can possibly reduce the pressure. HOWEVER!!! you shouldn't ever start loading with a hot charge. If you are already at minimum charge than think about seating deeper, but if not, pull the bullets and lower the charge. The best thing you can do is to purchase a good reloading manual and read the reloading procedures several times until you can recite and explain them to a novice yourself. We could use a little more information to help you farther such as case prep steps, primers, powder distance from the lands...

[boomtube]

You have told us what cartridge and bullet you are shooting but not what powder and charge you put under it. That data would help a lot.