Extreme ES caused by barrel?

[Aviator]

Do you trust your chronograph?


This

 

[Greyfox]

My checks:
-chronograph
-barrel crown
-powder/primer
-bullet
-brass(seating tension, runout)
-barrel flaws

 

[parker33]

Chrono

 

[Muledeerhuntingfreak]

For New bees working up loads in the Reloading process what does ES mean

 

[Doom2]

Extreme spread (highest velocity-lowest velocity).

 

[StumpGrinder]

I've got a TC venture in 243 Win that is giving me fits with ES. Ive ran different powder/bullet/brass/primer combos but this particular rifle has ES of around 150fps(sometimes higher) regardless. Its shoots 1/2moa groups @100y but of course with those ES it would probably string at longer ranges. It will normally start out high and the velocity will decrease with every shot, not always but common. Same powder scale and same chronograph used with diffrent rifles that have low ES. Is there something with the chamber/barrel that could be causing this?

First shot out of a cold bore will be diffrent. Also freshly cleaned and oiled bores will increase velocity due to reduced friction. This is the reason for fouling shots, to stabilize the string. As metal heats up it expands causing reduced surface contact on the bullet. This is why heating the nut on a stuck bolt will often free it up. There are 2 schools of thought in long range shooting which is determined by how you shoot. Hunters usually only get one or two shots at game so it is better to tune for first shot/cold bore accuracy. Competition shooters start a match by shooting warm up shots and therefore tune to a warm or hot barrel. Few rifles will shot to the same point in both situations. If you are primarily a hunter don't let your barrel heat up to much. 3 to 5 shots then let it cool. If compitition then don't even look at groups untill the barrel is warm. I'm a hunter and this is just my opinion from reasearch I have done. Half inch 100 yd groups would be fine with me regardless of velocity spread. Have you tried a barrel tuner to shrink them down?

 

[StumpGrinder]

Possible the barrel is touching stock as it warms up. Something could be loose... Check action screws and scope mounts, then go from there.

that wouldn't cause velocity change and would cause stringing in his group.

 

[Muledeerhuntingfreak]

Thank you you so much

 

[StumpGrinder]

Yes, this is the only rifle I have this issue with. Ive got Nosler brass and Remington brass both new and once fired. Ive ran H4350, superformance and R15 though it with the same results. I ran standard and Mag primers with superformance with no change. Maybe I should try neck sizing only a few pieces of once fired and see what happens. I normally bump .002 with a FL die on fired brass but I have a Lee Neck die laying around somewhere i could try.

how is your neck tension? That can mess with velocity because it will change pressure. But that would be random not increase as barrel heats.

 

[Bro Dave]

Might be the chronograph, if the barrel was so erratic that it gives you150 es, it shouldn't be sub moa

here is an analysis of error in different chronos. It is about 2/3rds of the way thru the article but is very interesting. Look for a table.

Practical statistics for shooters (autotrickler.com)

 

[Hard Head]

Usually ES is caused by a single or multiple problems with reloading components ,how they are assembled. I recently was out shooting my .454,was using cast with mu lube and powder coated cast bullets of my making. I loaded up 3 cases of Starline with lubed, 3 with powder coated in starline and 3 in winchester with powder coated all loads were assembled with cases that were with in .01 in weight and powder was H110 and cast all were .453 in dia.and with in 1/10 gr. in weight all were the same length win went 1470 fps sd was 18,starline went 1422 fps sd 30, lubed with starline were 1354,1320 then the kicker was the 3rd shot,small rifle primers can be hard to set off in cold weather was 15 out it was a miss fire,God I hate them as you always wonder if it will go off when you rotate the cylinder or remove it,rotated and fired again and it went off 1220 fps. 100fps slower. so there are many variables that how it goes bang,first look at case length and crimp and neck tension are the first things ,then primers are the next things and are usually the first thing I play with,different primers act different with the same powder. One day during the summer I loaded my .338 Lapua and shot some loads that had a SD of 2.25 for 10 shots,I was astonished, went out with the same cases in the fall was in the 40's verses the 80's in the summer and it shot a15.75 spread, the air was dry in the fall compared the the summer heat and very humid,, unless you are shooting 1000 yds. don't worry too much but be aware the temp., and humidity along with a lot of other things affect extreme spread, an animal very rarely says,that bullet was a little slower than the first,ya better run!!!! HardHead

 

[StumpGrinder]

ES speed has much to do with bullet seating and neck tension
Keep your load!! But start at jam +20k then add 3k until you find 2 rifle nodes (tightest groups) together. Then choose a seating depth. Neck tension can play a part also . Less neck tension for long range. More neck tension for hunting just make sure you are getting the exact seating depth and neck tension so everything is the same

I think you mean jam minus 20k! You will shorten col by 20k. Some bullets like jump some like jam. Jam will increase pressures significantly. Be careful!!! I have heard Berger bullets like jam, elds like 10k jump and shorter bullets are fine with 20k or more.

 

[StumpGrinder]

That's a good idea. Hadnt really thought if test it that way.

I'm using a rcbs fl but I'm going to pull my Lee collet die out and try neck sizing some of the once fired and see what happens.

Aaccording to Eric Cortina, a pro shooter, all the best competitors full length size.

 

[StumpGrinder]

Have you used a bore scope on it? How many rounds down the pipe? Have you noticed a great deal of fouling? How often do you clean it? If it progressively slows down shot after shot consistently, I'd look at the barrel.
@DJFergus has a great idea. If you find the barrel is extremely rough, you might consider JB bore Paste or fire lapping with David Tubbs kit. Maybe keep shooting it till it stabilizes, go home and without cleaning, shoot another day and ser if it still does the same thing with repeatable velocities. Just some suggestions

If this is a new gun it may just need to break in. Some barrels have more tool markes than others. Howa recommend a break in process on my 1500 when I bought it.