throat erosion

[paulT]

would the use of slower burning powder say 48.6g vit n165 with 95 grain bergers which produce exellent groups at 200y in my 243 give slightly extended barrel life than the use of faster burning propellents such as vit n150 or n160 etc, i know that there is a slight increase in charge with the slower powders and on inspection after firing seems to be a little more carbon fouling left in bore in comparission to the faster powders, your views would be apprecited regards paul T.

 

[rhino]

In theory from what I have read, yes. I am doing the same thing with my 6.5x.284 and so far after 415 rounds down the tube the throat hasn't moved.


RHINOUT!

 

[chuckw2]

Rhino,
What are you burning in your 6.5??

Chuck

 

[paulT]

Rhino, are you using vit n165 or similar burning propellent and what primer mag or standard, also have you seen an increase in carbon buildup with the use of slower powder regards paul T.

 

[palma]

I thought the theory was that more throat errosion would occur with a slower burning powder in a .243 since more of the powder would be burning in the throat/barrel rather than in the case.

 

[chrisj]

With the slower powder....more powder will burn going down the barrel than with a fast powder which will burn more in the throat.

Chris

 

[paulT]

Chris, would the use of the slower 165vit powder in 243 produce extra carbon fouling in barrel as aposed to the faster propellents, also would a 24 inch tube be long enough to fully ignite a fairly large charge say 48.6 of vit n165, maybe the foulung that is left in my 24 inch barrel could be a mixture of carbon plus traces of unburnt powder, but works extreamly well in my rifle, regards paul T

 

[joesr]

Yes the slower burning powder does leave more carbon in the barrel. However, I have shot several 100 round matches and it does not seem to affect the accuracy.

On the 24" tube. That is not long enough to get the full affect from the slower burning powders. With a 243 Win sized case a 28" to 30" barrel is optimum for this recipe.

Joe H

 

[Bob3700]

Have you considered using a throat maintenance system,abrasive coated bullets) or a lapping regime to keep the throat smooth.

Am not sure that the throat moving is a cause for lost accuracy, but a rough throat certainly would be.

If smoothing the damage done by the burning powder keeps the rifle shooting accurately, the only limitation on accuracy life would be the amount of seating depth for the bullet.

Perhaps powder choices are important but would not overlook the smooth throat issue.

Just my .02.

Bob

 

[paulT]

Bob, would jb paste be up to the job of keeping throat smooth, regards paul T.

 

[Bob3700]

Paul,

JB is not agressive enough to actually polish any bbl material.

What some of the better LR shooters have been doing is to order some diamond lapping paste. McMaster-Carr carries the stuff in several different grades.

They are using a #1 grade to break in new bbls. and keep them polished in the throat for the first 1000 rds. Then, the #3 paste,more agressive)is used to keep the frosted metal from forming in the throat. IF you can keep the frosting from forming in the throat, the cracking that usually forms takes much longer to appear. The cracking damages the bullet jacket and affects accuracy. Delay the cracking, keep your accuracy longer.

Is the throat dimension moving longer during this process? Sure it is, but the accuracy remains longer using the diamond lapping process.

Shooters who developed this process are using borescopes to track progess and they are top level guys who know when a bbl. has stopped shooting.

If you have a high intensity ctg, like a 6XC or a 6.5x284, this lapping regiment will add many accurate rds to your bbls.

Just my .02 worth.

Bob

 

[paulT]

Thanks for info Bob, paul T.