Pressure

[C.Smith]

So I have some questions about pressure. I had some loads of RL22 in my 7mmrm that I thought was a bad batch of powder, but it turns out I'm an idiot. Thought I would get that out of the way. I found this out when I loaded some new loads with a different brand powder and on the beginning load blew two primers and hit 3050 fps. So looking at my notes I used to load my bullets to 3.740" (this is using the Hornady measuring device I forgot the name, measures off the ogive). Current loads giving issues with RL 22 and now H1000 are 3.752". Can .012" make that much of a difference?

Corey

 

[TackDriver284]

What bullet weight are you using? What is the OAL of your chamber? I would seat bullets .020 off the lands for load development and adjust seating depths once a load is found. .012" is not much of an issue, just don't jam it into the lands.

 

[C.Smith]

160 grn accubonds is the bullet. I actually thought I was .040 off the lands but noticed I was .012 out from the year before. I changed powder lots at this time and thought that was the problem, and the only thing I changed. But looking at my notes I see that my seating depths are different, so I'm hoping that is it.

Corey

 

[TackDriver284]

For my 7 Mag, I liked the RL22 for weights of 140 to 150 and RL25 for weights of 160 to 180. RL25 worked better with my 168 VLD than the RL22, seems to push it faster with less pressure. I ran the 168 VLD at speeds close to 3,075 fps with no pressure signs ( some would say the fast velocity is a sign :lol: ) , but settled on 3,025 fps for best accuracy of .2 to .3 MOA.

 

[TXbaldhunter]

3.752 ???? Are you sure that's right? My 7mags with 160gr AccuBond are 3.299 over all length and Hornady Bullet Comparator length(from the base to the ogive)is 2.727.Your measurements are running about a half an inch longer.

 

[TackDriver284]

3.752 ???? Are you sure that's right? My 7mags with 160gr AccuBond are 3.299 over all length and Hornady Bullet Comparator length(from the base to the ogive)is 2.727.Your measurements are running about a half an inch longer.

You are right, I checked my notes on OAL length, it seems his OAL is way off or mistyped because mine is at 3.392 with the 168 VLD Bergers, and ogive at 2.713 , any other bullet would be shorter.

 

[C.Smith]

3.752 ???? Are you sure that's right? My 7mags with 160gr AccuBond are 3.299 over all length and Hornady Bullet Comparator length(from the base to the ogive)is 2.727.Your measurements are running about a half an inch longer.

I came up with up with 3.752. However that is the load that gives me issues. My notes from past loads that were not a problem were 3.740. This is pushing the bullet up until I feel it make contact, following the directions from the Hornady Bullet comparative. I don't feel anything until it is at 7.794 which I then backed off .040 to get 3.754. But you guys have me thinking I'm missing something. I have already pushed the bullets in to 3.740 where I have safely shot for a while and see what happens.

Corey

 

[TXbaldhunter]

OK here's the deal.A 7mag case is 2.5 inches.A 160gr AccuBond is 1.4075 inches.
2.5000 case
1.4075 bullet
3.9075 is the total of the two.If you subtract your total length of 3.752 from 3.9075 you get .1555,about 1/8 of and inch.The bullet has a boat tail,sothe bullet would not even be seated into the neck of the case at 3.752.

 

[C.Smith]

Well that's interesting now. I guess I need to look at what I'm doing a little bit closer, because as you wisely explained it does not add up. Thank you.

Corey

 

[TXbaldhunter]

I think I might have figured out what you are doing.If I zero my calipers closed,then add the Hornady comparator (It adds an inch) then measure one of my loaded rounds with a 160gr AccuBond,it measures 3.724.That is close to the reading your getting.You need to zero your calipers after the comparator is installed.By doing this,you are measuring from the base of the case to the ogive of the bullet.