260 Rem case pressure signs

[Tappets]

Have a new 260 Remington I would like to start learning to shoot long range. Working a load based on 139/140 grain 6.5's and using AR2208, 2209 and 2213SC just breaking in barrel with 1/2 grain less of max in ADI book using 5 rounds of each with 140 grain pill 0.010 of lands. My problems are all cases (new Lapua) show signs of high pressure, cases are around 90 to 95% full but I have a very short throat and I have to sit the long pill way back inside the case the base of the boattail is back to the start of the shoulder taper. If I ream out the throat so I can load the pill out I am not sure if I solve much, meaning will I still have high pressure with more case space with the same amount of powder or will it lower pressure so I could top up space in case. Does anyone have idea on this am I using the right powders?http://ozfclass.com/phpbb/posting.php?mode=post&f=5#

[Frank Green]

What are your pressure signs? Ejector mark on the brass? Bolt lifting hard?

What barrel is on the gun? Factory? Custom? What are the bore and groove sizes of the barrel if they are known?

If custom barrel what chamber spec. reamer was used in it?

What velocity are you getting?

My normal everyday working load with the 139gr./140gr. bullets is 42.0 of H4350. Not sure which powder that is similar to yours that is the same or close to the H4350. I can go slightly hotter with that load.

Later, Frank
Bartlein Barrels

[macguru]

42gr 2209 (140gr proj) sounds about right but you should not get too much pressure there. Are the cases resized enough for your chamber , or are they tight on bolt closure ?
I use this as a fireform load for my 260AI but it should be ok in a straight 260 as well. If not you may be right about the lead being too short. I know this was not your question but if you ream it out to a 260 Ackley improved you will get another 100 fps easily with 43.5 gr 2209. This again is a comfortable load with no pressure signs in my rifle and makes the 6.5 alot better...

(2208 is too fast for the 260 and 2213sc ok but i found 2209 (equiv~ 4350) to be the best)

[mike H]

ADI currently shows 3 grains difference between starting and maximum loads,so you start 2.5 grains above their starting load,how about being a bit more cautious.Seating depth and cartridge overall length make a huge difference to case volume and the powder charge that can be used.For single loading in F/Class shooting it is usual to have the throat long enough that the projectile is not seated down into the case below the neck shoulder junction .

Mike.

[chrisw91]

ADI currently shows 3 grains difference between starting and maximum loads,so you start 2.5 grains above their starting load,how about being a bit more cautious.Seating depth and cartridge overall length make a huge difference to case volume and the powder charge that can be used.For single loading in F/Class shooting it is usual to have the throat long enough that the projectile is not seated down into the case below the neck shoulder junction .

Mike.

As mike said drop back to the minimum charge and work up from there. I use a lighter load to run the barrel in until the throat has smoothed out then start using full power charges. If the boat tail is all the way back down the the shoulder body junction there is no where near enough freebore to use the 140's.

[williada]

Tappets, the guys give good advice. A new barrel not only needs the throat polishing by break in loads, the whole barrel needs conditioning as stainless work hardens. This is another reason why the boys use lower charge weights for about 100 rounds as separate from breaking in the throat. Hot loads at this early stage can lead to premature erosion.

The same deal applies with new cases if you want to condition them before using full bottle loads. It would be better if you get an armourer to use a Universal throat reamer in a five minute job to take the throat out further so that the base of your projectile does not go below the junction of the neck and shoulder on the case. Otherwise you will be strangling the efficiency of the case an putting pressures up too much.

[Tappets]

Thanks you people for you inputs, MikeH and Chrisw91 your right I was trying to speed up the processes, but I have learnt a lot in a short time and its only cost me 10 new cases.
Frank I have ejector marks flat primers with a slight crater but I guess the +0 .0007" at the case head area tell the story. Been out in the garage measuring. The Barrel is a True Flight and is a tight no turn chamber I don't know the bore or grove size. What I have found is that the good once fired cases are just over 0.010 longer from the base to shoulder datum than the new cases which is what I was using to run in the barrel and fire form the cases at the same time, I was sort of hoping that the new cases was part of the problem with the pill back in the case, but I think you blokes nail it. Too much to quick.
The run in showed a lot of copper up to 8 rounds and by the twelfth it clean up real well. Over the Christmas break I will fireform the rest of my cases and in the new year will have the throat taken out a tad so the 140 pills sit out as per your recommended. I like your advice thanks

[Frank Green]

If the copper fouling subsided/stopped then that shouldn't be your cause. I've seen barrels where they we're copper fouling bad and had pressure issues. What was causing the problems varied.

As others recommended I would back of the load a bit and go from there. Making the throat longer can help but I would back of the loads and see what happens first.

If the bore especially the grooves are running tight they can raise pressures. Usually changing the groove size has the biggest impact. If your still having problems with the pressure give Truflite a call and talk to them. Maybe have them look at the barrel and recheck it for sizes.

The chamber reamer in my .260 Rem. barrels that I have on guns the throat is approx. .030" to .055" shorter. Depending on where your measuring it from. Case mouth or from the end of the chambers chamfer. Also instead of a .265" throat diameter like the standard .260 rem. is my is .2645". So slightly tighter there. I run the same loads thru my gun as a standard chamber .260 barrel. My chamber isn't a tight neck or anything like that. Just the throat is different.

I've used the same reamer in three different barrels/rifle builds for myself. We also use it a lot for customers builds. All with no issues.

Later, Frank