Jumping a 105 gn. bullet, what is the impact on accuracy with difference lengths of free-bore? As an example, .115 FB compared to .135 FB? The seating depth changes, but.....?
Ben
Ben
6 Dasher free-bore
- Thread starter BenPerfected
- Start date
Terry,
I didn't word that clearly. The depth the bullet goes in the case varies at the same seating depth. What effect if any does this have on accuracy?
Ben
I didn't word that clearly. The depth the bullet goes in the case varies at the same seating depth. What effect if any does this have on accuracy?
Ben
Joe R
Gold $$ Contributor
Ben,
If I understand your question, you are asking whether the amount of jump that a bullet has to make affects accuracy, right? IMO the amount definitely has an impact on accuracy, that's why we spend so much time experimenting with seating depth.
I don't shoot a Dasher, but if I had a question I would start by PMing ShootDots (Ben Steinsholt) and dmoran (Donovan Moran). They are both proficient Dasher shooters I'm sure they can give you tons of specific info.
Kindest regards,
Joe
Joe and others,
I will try again. Does the length of the free-bore effect accuracy at the same seating depth. This assumes you have 2 or more barrels all the same except for a different length free-bore. Why do many gunsmiths order their reamers with different free-bores?
In other words, would two different chambers with the only change being the length of the free-bore make a difference at the target using the same bullet and same seating depth?
Ben
I will try again. Does the length of the free-bore effect accuracy at the same seating depth. This assumes you have 2 or more barrels all the same except for a different length free-bore. Why do many gunsmiths order their reamers with different free-bores?
In other words, would two different chambers with the only change being the length of the free-bore make a difference at the target using the same bullet and same seating depth?
Ben
Terry
Gold $$ Contributor
Ben
The selection of free-bore is a personal preference issue. The .104-.106 freebore was the standard for years. .130-.135 is now popular.
The critical issue is to keep the bullet out of the donut area, the shoulder/neck junction. If there is a donut it can effect accuracy.
The other benefit of the .130-.135 freebore is more case capacity. The negative is you run out of case to hold the bullet as the barrel wears. If you barrel wears .003 per 100 rounds fired .030 can get you more rounds before you run out of case.
Having said all of that I see no accuracy advantage of either one.
The selection of free-bore is a personal preference issue. The .104-.106 freebore was the standard for years. .130-.135 is now popular.
The critical issue is to keep the bullet out of the donut area, the shoulder/neck junction. If there is a donut it can effect accuracy.
The other benefit of the .130-.135 freebore is more case capacity. The negative is you run out of case to hold the bullet as the barrel wears. If you barrel wears .003 per 100 rounds fired .030 can get you more rounds before you run out of case.
Having said all of that I see no accuracy advantage of either one.
The longer freebore lets you get more velocity by giving you more capacity and using more powder. I use a .155 and it lets me get to 3050 easily with 105 to 108 grain bullets. Some times it lets you get to a higher accuracy node. It also keeps the pressure ring in the sized portion of the neck. It is bad if you push the pressure ring through the sized part and into an unsized portion. It is also bad to put it in a donut. Most competition shooters are now using .135 to .155. Matt
Guys,
Thanks so much for your posts. Today, my freebore is .135 and I am going to cross this off the list of things to worry about.
Ben
Thanks so much for your posts. Today, my freebore is .135 and I am going to cross this off the list of things to worry about.
Ben
Joe R
Gold $$ Contributor
Ben,
All of my barrels have shot best when I am in the lands. I measure with a hard jam then load a bunch rounds to that measure. I take my harbor press and Wilson die to the range and then start pushing the bullet further into the case in .003 increments until I find the spot that performs best and gives me the lowest SDs and ES.
When I first started shooting my Savage with 168 Sierra's the freebore was .098, as I have gone to custom rifles and heavier/longer bullets have had to increase the length of the freebore to maintain case capacity while seating the bullet still close to the lands. I learned many things by talking to Donovan. But I've also learned a great deal from Chris Long site. See http://www.the-long-family.com/optimal%20barrel%20time.htm. It is dense and quite a bit to digest.
Using Chris's theory you will find the accuracy nodes that Matt mentioned, a very important concept. Once you're in the node you will understand the importance of freebore. Not too long and not too short, but just right. You should have enough bearing surface to move the bullet out as the throat erodes. I believe this applies to all calibers, but my experience is limited to .308. I hope this helps.
Kindest regards,
Joe
All of my barrels have shot best when I am in the lands. I measure with a hard jam then load a bunch rounds to that measure. I take my harbor press and Wilson die to the range and then start pushing the bullet further into the case in .003 increments until I find the spot that performs best and gives me the lowest SDs and ES.
When I first started shooting my Savage with 168 Sierra's the freebore was .098, as I have gone to custom rifles and heavier/longer bullets have had to increase the length of the freebore to maintain case capacity while seating the bullet still close to the lands. I learned many things by talking to Donovan. But I've also learned a great deal from Chris Long site. See http://www.the-long-family.com/optimal%20barrel%20time.htm. It is dense and quite a bit to digest.
Using Chris's theory you will find the accuracy nodes that Matt mentioned, a very important concept. Once you're in the node you will understand the importance of freebore. Not too long and not too short, but just right. You should have enough bearing surface to move the bullet out as the throat erodes. I believe this applies to all calibers, but my experience is limited to .308. I hope this helps.
Kindest regards,
Joe
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