How to measure Lead Length?
- Thread starter mao0720
- Start date
bigedp51
I don't use anything fancy, and by using the method below I found out my Savage .223 has a longer throat/lead length than both my AR15 5.56 rifles.
http://www.larrywillis.com/OAL.html
Read the link below and about the home made gauge on page 4.
http://www.gundigest.com/223-vs-5-56
Below is the gage mentioned on page 4, you can turn a bullet around base first in its case like the home made case tester at Larry Willis.
http://www.m-guns.com/tools.php
http://www.larrywillis.com/OAL.html
Read the link below and about the home made gauge on page 4.
http://www.gundigest.com/223-vs-5-56
Below is the gage mentioned on page 4, you can turn a bullet around base first in its case like the home made case tester at Larry Willis.
http://www.m-guns.com/tools.php
mao0720: Are you talking about freebore length? If so, that would be shown on the reamer print drawing.
I have FB length's for all my chambers, since they were cut with my reamers, but once the job is done & I've established my bullet seating depth to touch the lands, FB becomes meaningless, especially as erosion causes it to "grow" in length.
I have FB length's for all my chambers, since they were cut with my reamers, but once the job is done & I've established my bullet seating depth to touch the lands, FB becomes meaningless, especially as erosion causes it to "grow" in length.
Yes, I am talking freebore length. I was under the impression that that was synonymous with lead length or throat length. The reason I want to know is that the next time I order a new barrel, I am going to have the freebore reduced so that 130 and 140 berger VLD can touch the lands at mag length. I wanted to know what my freebore length is now so that I can start to figure out what I would like it to be on my next barrel.
mao0720: Tough for the individual (us) to come up with a really accurate dimension since we do not have the same machinest quality measuring tools that the reamer maker has.
When I spec out a new reamer, I choose my first bullet ( the "main" one), call Dave Kiff, give him the bullet # (for example: Berger 105 gr. #24428), tell him I want it seated to touch the lands, with the full diameter (.243") approx. .030" in front of the neck/shoulder junction. While on the phone, he will put that information into his optical comparator and have the exact freebore dimension/length that is required.
The same could be accomplished by loading a dummy round seated to the length you want it, and sending it to the reamer maker. When getting a new reamer I also request and receive a reamer print drawing, that remains with that reamer.
When I spec out a new reamer, I choose my first bullet ( the "main" one), call Dave Kiff, give him the bullet # (for example: Berger 105 gr. #24428), tell him I want it seated to touch the lands, with the full diameter (.243") approx. .030" in front of the neck/shoulder junction. While on the phone, he will put that information into his optical comparator and have the exact freebore dimension/length that is required.
The same could be accomplished by loading a dummy round seated to the length you want it, and sending it to the reamer maker. When getting a new reamer I also request and receive a reamer print drawing, that remains with that reamer.
Mao0720, good advice above. Here's another angle. Sinclair makes a "sinclair chamber length gauge" this gizmo fits into your case neck and is compressed into cartridge as bolt closes. This will give you a measurement from end of chamber mouth to bolt face. Then use Bigedp51's idea of chambering a flat based bullet backwards using your split case. the difference in the two measurements will be your free bore, leade, throat measurement. Hoping I'm right on at least ONE of the terminologies :
Cost for the "gizmo" $5.99... This would give you a good estimate of your particular free bore length. But other reamers will vary in length of neck. The optical comparator your best bet when the time comes.
Cost for the "gizmo" $5.99... This would give you a good estimate of your particular free bore length. But other reamers will vary in length of neck. The optical comparator your best bet when the time comes.bigedp51
Sinclair Chamber Length Gage
http://www.sinclairintl.com/reloading-equipment/measuring-tools/case-gauges-headspace-tools/sinclair-chamber-length-gage-prod32925.aspx
If you look below even a chamber cast wouldn't do you any good without special measuring equipment. You have freebore diameter, freebore length, and freebore angle.
I have one bolt action .223 and two AR15s, and there are so many chamber and throat/freebore types it boggles the mind for the .223/5.56. By doing what I stated above and looking at fired 5.56 cases from my .223 I knew the throat was made longer by company lawyers on my bolt action Savage.
See below and look at the OAL for the 80SMK in the various throats.
HOLLIGER ON .223/5.56 CHAMBERS
http://www.radomski.us/njhp/cart_tech.htm
http://www.sinclairintl.com/reloading-equipment/measuring-tools/case-gauges-headspace-tools/sinclair-chamber-length-gage-prod32925.aspx
If you look below even a chamber cast wouldn't do you any good without special measuring equipment. You have freebore diameter, freebore length, and freebore angle.
I have one bolt action .223 and two AR15s, and there are so many chamber and throat/freebore types it boggles the mind for the .223/5.56. By doing what I stated above and looking at fired 5.56 cases from my .223 I knew the throat was made longer by company lawyers on my bolt action Savage.
See below and look at the OAL for the 80SMK in the various throats.
HOLLIGER ON .223/5.56 CHAMBERS
http://www.radomski.us/njhp/cart_tech.htm
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.