Jeff Porter
Gold $$ Contributor
TL/DR version of below...
What would cause the bullet to engage touch at 1.822" using the Hornady tool with a modified 6 BR case but show resistance to closing on the bolt until the same bullet was seated to 1.765" using a loaded round ?
Answer in Post #9. !!!!
I have been reloading for decades and have been using the Hornady/ Stony Point ( yes, I am that old) tool with good results on multiple rifles and multiple calibers. Yesterday, I ran into an issue for the first time where the CBTO ( Cartridge Base To Ogive) measurement I determined was not working in the rifle.
I had offered to do an initial work up for a friend on a new to them Eliseo R5 in 6 BR for sling shooting at Midrange and Long Range matches. I do not know what chamber was cut in the barrel beyond 6BR. I have been loading 6BRA for a while and have a general feel for what should be in the ball park for CBTO based upon my BRA data of 1.830 CBTO in that rifle with a 105 Berger.
I measured the CBTO with the same Copper Creek 6BR prepped case for the tool I use for my BRA as it indexes off of the neck shoulder junction. Using a Hornady 105 BTHP I measured 1.822" to touch by seating the bullet long in the tool with the cable locked, pushing to contact with the rifling then loosening the cable and pushing the case into the chamber and tightening the cable lock again. I found this technique to give me more repeatable results than setting bullet in sort and pushing into the rifling. This was in line with my expectations.
The gun owner provided some reloads 105 Berger and H4895 from the previous owner. I used these to zero the scope and get a baseline of performance. I took three shots to zero the NF scope and then shot a 3 shot group that went about 0.5 MOA. These chambered smoothly and had no resistance when closing the bolt. The looked stubby to me and measured only 1.700" CBTO with the tool I had and were running about 2755fps on the Xero chronograph.
For my first velocity check of four powder charges of Varget, I followed my usual protocol and dropped off about 0.020" from touch to 1.800" CBTO ( I like round numbers) and loaded 4 cases to that length. I noted that the bolt had some resistance closing like it was hitting a hard jam and seating the bullet deeper but was at a modest powder charge and had no pressure sign on the brass and extraction was smooth, no clickers.
I made an assessment from the velocity test and made my first load test of a three shot group using 29.7 Varget with 1.800" CBTO. I loaded the first round and noted the camming action on close... I decided to open the bolt and see if the bullet was getting engraved with rifling. and... you guessed it... pulled the case out and filled the action with Varget... After about 30 minutes of cleaning I could get the bolt closed with no kernels left in the locking lug recesses. Driving the stuck bullet out it appeared more like it was scuffed rather than engraved with rifling marks. I assumed this was from the brass pulling back when it was extracted.
I did not want to take the bolt apart at the range to do the wheeler method to find the touch CBTO but followed the procedure of loose seating a bullet until the bolt closed with no resistance.
I took that piece of brass and pushed a new bullet into it and coated it with black sharpie. Then loaded the chamber and closed the bolt. Same camming resistance felt at 1.800" - Using the cleaning rod to assist in the removal of the bullet and brass it measured about 1.775" with the sharpie marks more scratched around the bullet than engraved with rifling in the typical square blocks. I continued to seated the bullet in a bit deeper each trial until found I had to seat it to 1.765" to have the bolt close with no resistance.
I then used that data and ran a jump test with 0.010" Jam, and various distances off of 1.765" and found a winner at 2850 FPS. 0.030" off that shot 3 into one hole and repeated with a 5 shot group at about 0.4 MOA.
So after all that I am trying to figure out why I see a 0.055" difference in where the touch is with the tool and where the bolt closes with no resistance.
My best guess at this time is that long bearing surface of the Hornady 105 BT in combination with a very tight throat area that when being pushed by the ejector would bind the bullet enough to feel the resistance and allow the bullet to pull out with only 0.002" neck interference.
What else can you think of ?
What would cause the bullet to engage touch at 1.822" using the Hornady tool with a modified 6 BR case but show resistance to closing on the bolt until the same bullet was seated to 1.765" using a loaded round ?
Answer in Post #9. !!!!
I have been reloading for decades and have been using the Hornady/ Stony Point ( yes, I am that old) tool with good results on multiple rifles and multiple calibers. Yesterday, I ran into an issue for the first time where the CBTO ( Cartridge Base To Ogive) measurement I determined was not working in the rifle.
I had offered to do an initial work up for a friend on a new to them Eliseo R5 in 6 BR for sling shooting at Midrange and Long Range matches. I do not know what chamber was cut in the barrel beyond 6BR. I have been loading 6BRA for a while and have a general feel for what should be in the ball park for CBTO based upon my BRA data of 1.830 CBTO in that rifle with a 105 Berger.
I measured the CBTO with the same Copper Creek 6BR prepped case for the tool I use for my BRA as it indexes off of the neck shoulder junction. Using a Hornady 105 BTHP I measured 1.822" to touch by seating the bullet long in the tool with the cable locked, pushing to contact with the rifling then loosening the cable and pushing the case into the chamber and tightening the cable lock again. I found this technique to give me more repeatable results than setting bullet in sort and pushing into the rifling. This was in line with my expectations.
The gun owner provided some reloads 105 Berger and H4895 from the previous owner. I used these to zero the scope and get a baseline of performance. I took three shots to zero the NF scope and then shot a 3 shot group that went about 0.5 MOA. These chambered smoothly and had no resistance when closing the bolt. The looked stubby to me and measured only 1.700" CBTO with the tool I had and were running about 2755fps on the Xero chronograph.
For my first velocity check of four powder charges of Varget, I followed my usual protocol and dropped off about 0.020" from touch to 1.800" CBTO ( I like round numbers) and loaded 4 cases to that length. I noted that the bolt had some resistance closing like it was hitting a hard jam and seating the bullet deeper but was at a modest powder charge and had no pressure sign on the brass and extraction was smooth, no clickers.
I made an assessment from the velocity test and made my first load test of a three shot group using 29.7 Varget with 1.800" CBTO. I loaded the first round and noted the camming action on close... I decided to open the bolt and see if the bullet was getting engraved with rifling. and... you guessed it... pulled the case out and filled the action with Varget... After about 30 minutes of cleaning I could get the bolt closed with no kernels left in the locking lug recesses. Driving the stuck bullet out it appeared more like it was scuffed rather than engraved with rifling marks. I assumed this was from the brass pulling back when it was extracted.
I did not want to take the bolt apart at the range to do the wheeler method to find the touch CBTO but followed the procedure of loose seating a bullet until the bolt closed with no resistance.
I took that piece of brass and pushed a new bullet into it and coated it with black sharpie. Then loaded the chamber and closed the bolt. Same camming resistance felt at 1.800" - Using the cleaning rod to assist in the removal of the bullet and brass it measured about 1.775" with the sharpie marks more scratched around the bullet than engraved with rifling in the typical square blocks. I continued to seated the bullet in a bit deeper each trial until found I had to seat it to 1.765" to have the bolt close with no resistance.
I then used that data and ran a jump test with 0.010" Jam, and various distances off of 1.765" and found a winner at 2850 FPS. 0.030" off that shot 3 into one hole and repeated with a 5 shot group at about 0.4 MOA.
So after all that I am trying to figure out why I see a 0.055" difference in where the touch is with the tool and where the bolt closes with no resistance.
My best guess at this time is that long bearing surface of the Hornady 105 BT in combination with a very tight throat area that when being pushed by the ejector would bind the bullet enough to feel the resistance and allow the bullet to pull out with only 0.002" neck interference.
What else can you think of ?
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