Worn "leade / throat in M70??

jrothWA · November 10, 2014, 10:15 PM

Have first series, Post 64 M70, that doesn't group with commercial ammo, shoot groups within a paper plate but nothing tight.

SAAMI chamber drawing indicates length from bolt face to "leade / throat"
@ 2.725", I have measured actual length @ 2.792, difference of 0.068".

What options to rework this area to "ease" the bullet transition?

Polish that area? or re-barrel???

Thanks for responses.

James K · November 10, 2014, 11:18 PM

The rifle might not shoot for several reasons, but I rather doubt that that leade is the reason. How long have you had the gun? Has it ever shot well, or has it changed suddenly? What caliber is it? You say it doesn't shoot with commercial ammo? Does it shoot well with any ammo?

What other areas have you tried, like checking the bedding or cleaning the barrel with an electronic cleaner? What does the barrel look like? Is the rifling strong? Have you checked the muzzle crown?

Sorry to ask so many questions, but a Winchester 70 would take a lot of shooting to wear out the barrel or have enough throat erosion to make that kind of difference.

Jim

Scorch · November 12, 2014, 02:01 AM

1- Check the bedding
2- Check the barrel inletting
3- Check the trigger
4- Check the scope
5- Check the scope bases
6- Do some load development
7- Check the action screw torque
8- Notice I have not gotten to "check the barrel" yet? The barrel is always what people point at, but is seldom the culprit. Early post-64 M70s were notorious for poor bedding and poor barrel inletting. Check the easiest to fix first, then worry about major overhaul.

Dixie Gunsmithing · November 12, 2014, 07:05 AM

I'm not sure what caliber that is, as it doesn't look to be a 30-06. Anyhow, manufacturers have been known to fudge that dimension to what they want, and that could be the case. Anyhow, how did you make the measurement, and what is the cartridge?

Last, as mentioned above, there are several things to look at before the barrel throat, and most of the time, it is the stock or in the sighting.

November 10, 2014, 10:15 PM	#1
jrothWA Senior Member Join Date: November 11, 2006 Posts: 2,519	Worn "leade / throat in M70?? Have first series, Post 64 M70, that doesn't group with commercial ammo, shoot groups within a paper plate but nothing tight. SAAMI chamber drawing indicates length from bolt face to "leade / throat" @ 2.725", I have measured actual length @ 2.792, difference of 0.068". What options to rework this area to "ease" the bullet transition? Polish that area? or re-barrel??? Thanks for responses.

November 12, 2014, 02:01 AM	#3
Scorch Senior Member Join Date: February 13, 2006 Location: Washington state Posts: 15,248	1- Check the bedding 2- Check the barrel inletting 3- Check the trigger 4- Check the scope 5- Check the scope bases 6- Do some load development 7- Check the action screw torque 8- Notice I have not gotten to "check the barrel" yet? The barrel is always what people point at, but is seldom the culprit. Early post-64 M70s were notorious for poor bedding and poor barrel inletting. Check the easiest to fix first, then worry about major overhaul. __________________ Never try to educate someone who resists knowledge at all costs. But what do I know? Summit Arms Services

November 10, 2014, 11:18 PM	#2
James K Member In Memoriam Join Date: March 17, 1999 Posts: 24,383	The rifle might not shoot for several reasons, but I rather doubt that that leade is the reason. How long have you had the gun? Has it ever shot well, or has it changed suddenly? What caliber is it? You say it doesn't shoot with commercial ammo? Does it shoot well with any ammo? What other areas have you tried, like checking the bedding or cleaning the barrel with an electronic cleaner? What does the barrel look like? Is the rifling strong? Have you checked the muzzle crown? Sorry to ask so many questions, but a Winchester 70 would take a lot of shooting to wear out the barrel or have enough throat erosion to make that kind of difference. Jim

November 12, 2014, 07:05 AM	#4
Dixie Gunsmithing Moderator Emeritus Join Date: April 27, 2013 Location: Ohio Posts: 1,923	I'm not sure what caliber that is, as it doesn't look to be a 30-06. Anyhow, manufacturers have been known to fudge that dimension to what they want, and that could be the case. Anyhow, how did you make the measurement, and what is the cartridge? Last, as mentioned above, there are several things to look at before the barrel throat, and most of the time, it is the stock or in the sighting.