how much should case expand in chamber?

[jcvititow]

I have been shooting some 165 bthp target ammo thru my rem 700 .308 and it seems to require a little extra to extract this round then my standard 150 federal I have been shooting. Should this be a concern or is it just the higher pressure of the new round?

 

[highstandard40]

Are both loads factory ammo?

 

[LACamper]

I have been shooting some 165 bthp target ammo thru my rem 700 .308 and it seems to require a little extra to extract this round then my standard 150 federal I have been shooting. Should this be a concern or is it just the higher pressure of the new round?

I'd stop using it. There are plenty of other good loads in .308. Just my humble opinion though...

 

[sksshooter]

im with lacamper, if your getting sticky extraction that is a good sign of pressure. take a look at the case heads and see if there is any smearing of the headstamp, also compare the primers in the fired cases to the non fired. your primers should still be rounded on the edges like the unfired ones. if they are smashed out or show any signs of metal flowing those are all signs of high pressure. ive had a box of factory ammo that was a bit hot in my rifle but it wasn't o the point of sticky extraction though as your describing.

 

[jcvititow]

Yes both are factory loads. One is federal blue box and other is hsm target loads. Primer on fired round is flush with base of hull no indention around the primer like an infired hull. Ammo is listed at 2625fps on a 168 I would not think that is very hot unless the powder has something to do with it? I was really liking the groups and price of it. What causes the high pressure?

 

[highstandard40]

Is it bolt lift effort or actual extraction (pulling the bolt rearward) that is difficult...and how much? As the others said, if you have doubts stop using the ammo in question or get someone experienced in these matters to take a look at this for you. This is very hard to fully diagnose except in person by an experienced person.

 

[sksshooter]

im no expert so ill try to explain it the way it was explained to me. basically no 2 guns are the same. there are many different reasons why the pressure could be high. a barrel that was chambered with a new reamer is going to be tighter than a barrel that was chambered with a reamer that is towards the end of its life. they can both be within sammi specs but at both ends of the spec. factory ammo is loaded to sammi specs and "should" be safe in all sammi chambers but that is not always the case. if you take a tight chamber and a round that is at the top of the pressure scale you can end up with higher pressures in that tight chamber the ammo could have been loaded in a much different climate and the temp differences could be making it show pressure signs. it could be as simple as you just got a bad lot of ammo that was loaded a bit hot (wouldn't be the first time that has ever happend) to many things to speculate on and no way to really find the answer as there is no way to know what components the ammo was loaded with. you could very well be fine firing the whole box of ammo through it or even 4 more boxes through it but it only takes one round to lock up an action or even worse break the action. a damaged gun or worse a bolt stuck in the face isn't really worth the price of a box of bullets. pitch them, sale them for components or something.

 

[highstandard40]

A barrel that was chambered with a new reamer is going to be tighter than a barrel that was chambered with a reamer that is towards the end of its life.

Actually the opposite is the case. As a reamer wears, it cuts a tighter chamber, not larger. Also reamer specs vary from one manufacturer to another.

 

[sksshooter]

Actually the opposite is the case. As a reamer wears, it cuts a tighter chamber, not larger. Also reamer specs vary from one manufacturer to another.

ill take your word for it. im far from a gun smith just passing along what ive picked up from other who are far more knowledgable than i am. i could have very well have turned that around.

jc good luck hope you got something from the all the info here. i would agree with highstandard at minimum before shooting anymore of that ammo have someone who knows what they are looking at take a look at what is going on. also remember if that rifle shot that load good it will no doubt shoot another just as well you just might have to do a little trial and error to find out which one it is.

 

[LACamper]

im with lacamper, if your getting sticky extraction that is a good sign of pressure. take a look at the case heads and see if there is any smearing of the headstamp, also compare the primers in the fired cases to the non fired. your primers should still be rounded on the edges like the unfired ones. if they are smashed out or show any signs of metal flowing those are all signs of high pressure. ive had a box of factory ammo that was a bit hot in my rifle but it wasn't o the point of sticky extraction though as your describing.

Good answer.
Why not post a pic of the fired brass next to a new round. Then the headstamp.

Another thought. Compare these rounds to another brand of .308 you have around. OAL the same? Also, if all looks good then give a couple of rounds to someone else that has a .308 and see how it runs in that gun.

 

[jcvititow]

Thinking back it is actually lifting the handle that it is tighter not imposible but noticeably tighter. I only have internet on my phone but I can email a picture of the brass to someone if they will post it for me. Like I said out of 4 brands this is the only one so far that has done it.

 

[highstandard40]

Thinking back it is actually lifting the handle that it is tighter not imposible but noticeably tighter. I only have internet on my phone but I can email a picture of the brass to someone if they will post it for me. Like I said out of 4 brands this is the only one so far that has done it.

There is a difference between increased resistance of bolt lift and excessive resistance. I have fired some ammo that required a bolt lift that was no different that if the round had never been fired (very mild pressure). Something just north of that is not automatically an indication of excessive pressure. It could be just a very tight headspace on that target load. There are just so many variables that there is no way to be certain by anything we can say with the written word here. As always, err on the side of safety until a knowledgeable shooter can substantiate or ease your concern.

 

[jcvititow]

Here is a picture of the rounds. From left to right it goes hsm unfired,hsm fired,federal fired and the second set is a repeat. I was kinda concerned about the flattened out primers but they are all like that on that round. Who counld I go to or talk to in person to figure out if the ammo is a no go in my gun?

 

[highstandard40]

Primer appearance can be used to judge chamber pressure to a certain extent but is not the only factor to consider. Looking at your photo, first impressions are that the HSM rounds exhibit higher pressure than the Federal, and that may very well be the case. But we have no way of knowing if the HSM primers have a thinner cup metal than the Federal. Thinner primer cups will appear more flattened even at normal pressure, and these do look more flat than the Federal. I don't see any sign of excess pressure on the headstamp though. If you have a micrometer, you could measure an unfired and a fired case to determine the extent of case expansion just ahead of the case web. This will yield another clue as to chamber pressure but is still not all the information that is needed to make a determination because again you are comparing apples and oranges.........Federal vs HSM......so different manufacturer, different brass case.

Based only on this photo, I don't see anything that I would fear would blow up any modern firearm in good condition.