Extreme ES caused by barrel?

[epags]

Are you recording the velocity of each shot? My chrono prints out a record of each shot's velocity. A lot of the posters seem to believe the first shot is different then the rest. Is that the case?
I was testing for pressure changes with virgin Lapua brass last week with my 243 Rem 700 and in my testing (four sets(varying powder loads) of 5 shots each set) I found the velocity of the third and fourth rounds were lower than the first and last. ES for all sets varied from `25 to `45. However I was not 'shooting' for a low ES but only testing for changing pressure signs.

 

[TRG65]

Right now 75g hp and 85 sierra bthp but I've shot many through it.

With a 243, one question I'd have is how many are many? One of the issues I have when a barrel starts to go is increased SD and ES and random flyers. However, the 100 yard groups are still great. But the ability to hit at 600-1000 yards is severely impacted. I had one barrel in 6.5x47 that kept the same average, but the SD went from about 6 to 16 and got random at 1000.

Large ES loads can be 100 yard accurate, I have a 223 load that absolutely drills at 100 yards in multiple rifles, but it is a range brass special. The brass fluctuation give it an ES of about 150 and an SD of 50 according to my magnetospeed. At 300 it does ok, more than enough for practice. But I would expect a lot of issues to show up past there.

 

[jdavistx]

Lots of questions... Are your temperatures constant. What is the temperature coefficient for the powder. How far you off the lands? Etc.

 

[StumpGrinder]

Are you recording the velocity of each shot? My chrono prints out a record of each shot's velocity. A lot of the posters seem to believe the first shot is different then the rest. Is that the case?
I was testing for pressure changes with virgin Lapua brass last week with my 243 Rem 700 and in my testing (four sets(varying powder loads) of 5 shots each set) I found the velocity of the third and fourth rounds were lower than the first and last. ES for all sets varied from `25 to `45. However I was not 'shooting' for a low ES but only testing for changing pressure signs.

Yes, I believe he stated in the original post that the velocity most often slowed down with successive shots. This to me says barrel heating or fouling.

 

[jdavistx]

Magnetospeed is good, however it effects POI.

 

[jdavistx]

Yes, I believe he stated in the original post that the velocity most often slowed down with successive shots. This to me says barrel heating or fouling.

Usually if the barrel heats up, velocity goes up?

 

[jdavistx]

Strange problem.

 

[StumpGrinder]

Usually if the barrel heats up, velocity goes up?

velocity goes up when the powder temperature goes up. Unless it is very temp insensitive. If you are putting a cold round in a warm barrel and fireing relatively quickly I don't think you would see much difference in velocity. Now if the barrel was hot and you lingered over the shot, then yes I could see the powder temperature going up as well as velocity. I don't have a chronograph so I can't test that. I only shot for groups and hunt. As long as I can get under 1 moa I'm good. 4 inch group at 500 yds all day long. I load slowly and consistently, measuring every third or so round and work up loads in .2 to .3 grain increments. I usually use the loading manuel col and I have no idea what my ES is, I just know I always have meat in the freezer. Sometimes we make things to hard!

 

[epags]

Yes, I believe he stated in the original post that the velocity most often slowed down with successive shots. This to me says barrel heating or fouling.

You're right about the OP's comment. I missed that part and fouling would/could decrease velocity but I agree with StumpGrinder about warming barrel raising velocities....that has been my experience.

 

[jdavistx]

I think it's the lands.

 

[jdavistx]

I think it's the lands.

I shoot Bergers at 0.26 MOA.

 

[jdavistx]

7mm rem mag.

 

[jdavistx]

velocity goes up when the powder temperature goes up. Unless it is very temp insensitive. If you are putting a cold round in a warm barrel and fireing relatively quickly I don't think you would see much difference in velocity. Now if the barrel was hot and you lingered over the shot, then yes I could see the powder temperature going up as well as velocity. I don't have a chronograph so I can't test that. I only shot for groups and hunt. As long as I can get under 1 moa I'm good. 4 inch group at 500 yds all day long. I load slowly and consistently, measuring every third or so round and work up loads in .2 to .3 grain increments. I usually use the loading manuel col and I have no idea what my ES is, I just know I always have meat in the freezer. Sometimes we make things to hard!

The are charts on that.

 

[Zink14]

Es if a function of many factors (charge, primer seating, case wall, ogive consistency, seating depth, neck tension, etc) you need to start eliminating factors to variation ie if the load worlds in other firearms with acceptable es it's your fire arm, if not it's within the load....eliminating factors are key to solving your problems