Effect of fouling on OAL

P

pisces

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Hi,

I have a Remington Model 7 CDL in .17 Rem Fireball which, when the barrel has been freshly cleaned, has a maximum cartridge OAL of 1.850" - as measured with a dummy round. However, when the barrel is fouled, after 50 or so shots, the maximum OAL is now only about 1.820".

So, the fouling has effectively reduced the maximum OAL by 30 thou. Does this sound about right ?
 
Nope....doesn't sound right to me. Are you using the exact same bullet as before. Not out of the same box.....but the same bullet? If not, and your measureing to the tip of the bullet and not using a comparator, it is common for factory bullets to vary a lot in a box.

hovis
 
I repeated the measurements using several bullets, 25 gn Hornady HP and 25 gn Berger Match HP, to confirm the readings.

Is the max OAL about right for a factory rifle ?
 
How many pills down the tube? You may not know that carbon builds up right in front of the case mouth, and this ring needs to be thoroughly removed from time to time. Ordinary cleaning is not enough. And .17 cals have a reputation for fouling. I cannot state with certainty that this is your problem, but it very well could be. Insert a bore guide and then a cleaning rod with bronze brush. Fill the brush with JB bore cleaner. Rotate the cleaning rod numerous times (maybe 20 - 40), and then try your OAL guage again. Better yet, locate someone with a bore scope who can examine the chamber before and after you try this. After you finish, flush the JB out completely with a good solvent.
 
Pisces:

I would agree with Tenring that a carbon build up at end of throat is causing this problem.

When beginning to clean bore, if an abnormal amount of pressure has to be placed on cleaning rod to force wet brush down first few inches of bore, my experience with same has been due to carbon build up.

Carbon kills accuracy, and if you are using light neck tension on bullet, could very easily be changing bullet OAL.

Slip 2000 Carbon Killer has worked for me, and in more severe cases GM Top Engine Cleaner seems to work nicely.

You might consider using Slip 2000 Carbon Killer after your choice of bore solvent as part of a normal cleaning regiment after every 25 rounds maximum.

Hope this helps.

Cob
 
Thanks for the advice. :)

Unfortunately I don't have a borescope; I guess I'll have to pay more attention to throat/leade fouling.
 
Are you using a comparator or meausuring to the bullet tip??? How are you taking the measurements?

The problem just might be the procedure...not the gun.

Hovis
 
I am using a dummy cartridge with the case neck slightly enlarged to allow bullet movement with firm finger pressure. I measure the OAL before and after insertion into the chamber, when there is a difference I back off and retry until there is no change - at that point I note the OAL as being the maximum.
Measurements were made from the case base to bullet tip.
 
Ok, I think we are getting somewhere now. I have one more question for you. Are you using Exactly the same bullet when you check the OAL at different intervals? I don't mean in one setting, I mean when you check them on differnet days? Measuring to bullet tip can vary greatly between bullets in the same box. Buy a comparator, which measures on the Ogive of the bullet, it will open your eyes and make you life a lot easier. After a while, you'll find it's the best single investment you have ever made in reloading.

Hovis
 
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