load data and barrel length.

kilotanker22 · November 2, 2012, 02:33 PM

Hello all. Soon I think I will be loading a 300 rum with retumbo powder. I will be using data from hodgdon. I know hodgdon uses a 24 inch test barrel. My rifle will have a 26 inch heavy weight barrel. Would it be safe to assume that with the extra barrel length. I should at least be close to the data manuals speed?

**Unclenick** · November 2, 2012, 02:50 PM

QuickLOAD thinks that with a 180 grain bullet Retumbo in the large capacity case will add about 66 fps to the 24" barrel data. However, that assumes your chamber and bore are as tight as the test barrel and your freebore is no longer than the test barrel's chamber, none of which is normally true in a mass-produced firearm. So I would not be surprised if your real performance were down around that of the 24" barrel, though occasionally a gun can fool you and go the other way (have a "fast" barrel). So do your load workups while watching for pressure signs.

kilotanker22 · November 2, 2012, 03:08 PM

I understand the difference in tolerance and free bore. That is why I am assuming like stated earlier I would be very close to published load data.

The only rifle I have ever seen go a little faster is my win model 70 made by fn. It has a chamber tight enough that factory rounds chamber kinda snug.

November 2, 2012, 02:33 PM	#1
kilotanker22 Senior Member Join Date: October 14, 2012 Location: North Central, PA Posts: 2,117	load data and barrel length. Hello all. Soon I think I will be loading a 300 rum with retumbo powder. I will be using data from hodgdon. I know hodgdon uses a 24 inch test barrel. My rifle will have a 26 inch heavy weight barrel. Would it be safe to assume that with the extra barrel length. I should at least be close to the data manuals speed?

November 2, 2012, 02:50 PM	#2
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,061	QuickLOAD thinks that with a 180 grain bullet Retumbo in the large capacity case will add about 66 fps to the 24" barrel data. However, that assumes your chamber and bore are as tight as the test barrel and your freebore is no longer than the test barrel's chamber, none of which is normally true in a mass-produced firearm. So I would not be surprised if your real performance were down around that of the 24" barrel, though occasionally a gun can fool you and go the other way (have a "fast" barrel). So do your load workups while watching for pressure signs. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

November 2, 2012, 03:08 PM	#3
kilotanker22 Senior Member Join Date: October 14, 2012 Location: North Central, PA Posts: 2,117	unclenick. I understand the difference in tolerance and free bore. That is why I am assuming like stated earlier I would be very close to published load data. The only rifle I have ever seen go a little faster is my win model 70 made by fn. It has a chamber tight enough that factory rounds chamber kinda snug.