204 ruger rebarrelling opinion

[B23]

CZ 527's come with a lot of freebore. I don't know what the actual FB length was of the 527 Varmint model 204 Ruger I had but I measured COAL to touch w/32gr Vmax when I first got it and to just touching the lands it was 2.408 which is very long so it obviously had quite a bit of FB length. I have a Tikka Compact in 204 Ruger and it has plenty of FB as well but not as much as the CZ 527 I used to have did. My 20-222 has .030 of FB which I think is the most I'd ever want in any of these 20 cals that I'm not shooting anything heavier than a 40gr bullet.

With a 12 twist being marginal at best for the 40gr Vmax it makes zero sense why manufacturers continue to put 12tw barrels on factory rifles chambered in 204 Ruger.

 

[L.Sherm]

CZ 527's come with a lot of freebore. I don't know what the actual FB length was of the 527 Varmint model 204 Ruger

If memory serves me correct a saami 204 had .099 freebore.

 

[B23]

If memory serves me correct a saami 204 had .099 freebore.

Do you by chance know if there is a way to reverse engineer and figure out FB length if you know what the COAL of a certain bullet to touching the lands is?

 

[Rick in Oregon]

Do you by chance know if there is a way to reverse engineer and figure out FB length if you know what the COAL of a certain bullet to touching the lands is?

B23, if I understand your question, I use the old Stoney Point tool, now it's Hornady I believe, to figure that out with the bullet of choice, that tool and a dial caliper. Most 32gr bullets I've measured to touch the lands in a factory 204 chamber are at the point of either being out of the case, or so far out it's not viable to come close to the lands.

This is the reason I had a custom reamer ground so that any of my 32 or 39/40gr loads can touch the lands if I so desire. Most times it shoots best at around .005" off or just 'kissing' with that reamer in my 204RM.

 

[L.Sherm]

Do you by chance know if there is a way to reverse engineer and figure out FB length if you know what the COAL of a certain bullet to touching the lands is?

Berger has there bullet dimensions online, not sure about others.
Berger has the boatlail length, bearing surface and OAL, makes it easy subtracting boatail length from OAL then adding that to the base of the case to neck shoulder junction for OAL.
I'm sure with a print you could then.
Its not perfect for OAL but it will get you close.
Personally I like zero freebore on 17 and 20 cal up to 40 gr bullets on 20 cals

 

[B23]

B23, if I understand your question, I use the old Stoney Point tool, now it's Hornady I believe, to figure that out with the bullet of choice, that tool and a dial caliper. Most 32gr bullets I've measured to touch the lands in a factory 204 chamber are at the point of either being out of the case, or so far out it's not viable to come close to the lands.

This is the reason I had a custom reamer ground so that any of my 32 or 39/40gr loads can touch the lands if I so desire. Most times it shoots best at around .005" off or just 'kissing' with that reamer in my 204RM.

Rick, I'm asking if there is a mathematical formula or something else maybe that one can use to figure out what the actual freebore length of a persons rifle is if they measure and know what the COAL is with a specific bullet.

Example, I know my CZ 527 204 COAL to just touching the lands was 2.408 with a 32gr Vmax but that doesn't tell me what the actual FB length was. If there is a way to take that 2.408 number and reverse engineer it to figure out what the FB length is based on that I'd like to know how to do that but I'm not sure that's possible other than just guessing based on comparisons from knowing what other 204's had for a COAL to touch with the same bullet. Like say someone has a 20-222 and their COAL to touching the lands w/35gr Berger is nearly the same as mine is we could assume they have nearly the same FB length of 30thou that I do but again that's just a comparison not actually a formula. Hopefully that makes better sense of what I'm asking or did I just make it worse.

 

[chuckshooter]

Do you by chance know if there is a way to reverse engineer and figure out FB length if you know what the COAL of a certain bullet to touching the lands is?

yes, you can figure out fairly close. set calibers to .193 spin and mark the bullet in the calibers as close to perpendicular as you can. using that mark recalculate overall length to that mark, then deduct 1.876. that's the end of the camber including the part that goes from neck dia. to bore dia. free bore is the portion of the bore that is free of rifling. here's a few prints to look at

edit: I replaced the match print with a better copy. some info was lost converting from xls. to pdf.

 

[L.Sherm]

I use a whidden comparator that measures by using a bushing on the ogive for CBTO.
If you had one of these I think you could use a .198 bushing and measure CBTO and subtract that from 1.876 it would get you really close. The Horny ones I used to use were about .008 smaller than bullet size.

 

[chuckshooter]

here's the prints in jpg form. since most prints have a plus or minus .005 tolerances anyway. .193 or .198 should get you close . seating the bullet into the lands on a .204 is not always a good idea. there's a reason the factory rifles have so much free bore. probably pressure and then litigation. I have chambered one rifle with the reamer "204 ruger match" it shot the best group of any rifle I have ever shot and it was factory ammo, unfortunately it's not my rifle, so I can't tell you how a 32vmax would seat into it. but I can tell you the factory ammo did not have a hard bolt close, so it had enough freebore what ever enough is??.

 

[B23]

I use a whidden comparator that measures by using a bushing on the ogive for CBTO.
If you had one of these I think you could use a .198 bushing and measure CBTO and subtract that from 1.876 it would get you really close. The Horny ones I used to use were about .008 smaller than bullet size.

I'll try this on my 20-222 since I know exactly what the FB is on it and if I come up with something real close then I'll have a better idea of how accurate this is and if I get a number that's way off I'll know I did something wrong.

 

[L.Sherm]

B23 i just did some measuring with my whidden comparator on a 6.5 cartridge with a .261 bushing and my horny 6.5 one that measures. 255. The .006 difference made .052 in CBTO so that is a big difference. I believe measuring as close to the Ogive as possible will get you better results, its why I switched to the whidden so I can pick bushing to caliber specfic.

 

[RabbitSlayer]

I have a 527 in 17 hornet and I once had one in 223. I find the factory contour to be light enough to walk with it all day and heavy enough for PDs on the bench. Id probably just pay to match the factory contour.

 

[Fern]

Thank you all for the great advice and experiences.
I bought the rifle used so I honestly do not know how many rounds have been shot but have put 300-400 myself.
For the first time in past couple years I have seen the 39sbk and bought a good supply but I do not want to be in same position where you can find them.
40g vmax I was always able to find and about 50% less

 

[jepp2]

Example, I know my CZ 527 204 COAL to just touching the lands was 2.408 with a 32gr Vmax but that doesn't tell me what the actual FB length was. If there is a way to take that 2.408 number and reverse engineer it to figure out what the FB length is based on that I'd like to know how to do that but I'm not sure that's possible other than just guessing based on comparisons from knowing what other 204's had for a COAL to touch with the same bullet.

Here are my touch length measurements with Hornady 32 gr ZMAX (same as VMAX for me)

Lilja .204 Ruger AR15 Unknown FB	2.310” C​
Rem 700 VS SF II 204 RugerK Zero FB	2.324” C​
Cooper 204 Ruger Unknown FB	2.409” C​
Remington 700 VLS 204 Ruger Unknown FB	2.468” C​
DPMS 204 Ruger AR15 Unknown FB	2.412” C​
WOA 204 Ruger AR 15 0.100" FB	2.425” C​

 

[B23]

Here are my touch length measurements with Hornady 32 gr ZMAX (same as VMAX for me)

Lilja .204 Ruger AR15 Unknown FB	2.310” C​
Rem 700 VS SF II 204 RugerK Zero FB	2.324” C​
Cooper 204 Ruger Unknown FB	2.409” C​
Remington 700 VLS 204 Ruger Unknown FB	2.468” C​
DPMS 204 Ruger AR15 Unknown FB	2.412” C​
WOA 204 Ruger AR 15 0.100" FB	2.425” C​

Sooo based on knowing the last one has 100 thou FB and your OAL to touch is 2.425 and #2 has zero FB with a OAL to touch of 2.324 would it be somewhat safe to assume your Cooper has somewhere around 80 thou +/- FB??

 

[jepp2]

would it be somewhat safe to assume your Cooper has somewhere around 80 thou +/- FB??

I would place my bet that Cooper used a standard SAAMI reamer with 0.100" FB. I find enough variability in measuring touch length (excluding my own variability) that similar FB don't measure exactly the same with the bullet I am using.

I just knew like @Rick in Oregon said, with the standard 0.100" FB, you can't get close to the lands with many bullets.

 

[Fern]

I spoke with pax nor today to get some more info and they sent me the two prints for the reamers they use
Based on these two prints I am trying to figure out the freebore on each
What’s your preferences on finish ss polished bead blasted?
I think I am going to go with the recessed floorboard for crown keeping with the existing one
I just realized I forgot to ask them about skim bedding stock
I hand load my ammo and have only shot maybe one box of factory when I first got it and can’t tell you what I shot

 

[JB10]

Now this is what my gunsmith told me. The top spec is what is in a factory rifle. The bottom one is what they originally designed. Shorter throat getting those bullets closer to the lands. He has an original print reamer and has offered to set mine back to it but the thing shoots just fine the way it is. It just depends on id the bullet handles the jump

 

[HillbillyLongRifle]

I would go with the second print with zero freebore!

 

[Fern]

When I edited the pic I must have cropped out the top a bit but you can see where there is some pencil writing on the first pic.
They had that one labeled as match which I thought should have been the factory saami spec one