Barnes TTSX Velocity loss ??

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Farmer001

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Just looking for some info on what could possibly be the problem on what I am experiencing. Followed recipe from Barnes on load data fora 7mmRM. Placed bullet COAL length close to what is mentioned which is close to .055 off the lands. Close enough to the reccomended spacing I thought. Found the best load for accuracy and placed 4 rounds in a 1 inch square. Boy I was happy as a pig in poop. Tried at the 300 yrd and this thing drops 14inches! Do not have a chrono but pluncked into ballistic table and shows 2200 to 2400 fps.
New brass trimmed to .010 bellow max length. Loaded right in the middle of spec grains with IMR 4350 powder. Went 4.5 grains above what worked best and primers started to show flattening. I sure like this bullet but this ribbed design and results has got me rattled.
 
Its not the bullet, its the cartridge. The 7mm needs to be run hard (not over pressure) to get results...Otherwise, its a .270...

Pretty hard to know what you're speed your running with no chrony, just going by a manual. Try a different powder, or buy a chrony.
 
I get the following on JBM's ballistc program with your drops:
130gr ttsx 2850fps
150gr ttsx 2750fps

Seems a little slow to me, but you need a chrony to really tell. I get just over 3000fps with 160gr accubonds out of my 7, so I would expect to get into that range with the 150gr ttsx.
 
Thx for the replies, will put thru a chrony to find out for sure, Not sure if I mentioned they are 140's also, will try the another ballistic software just to compare for the drop. I would have thought at 300 yrds with a 200yrd 0 would be closer to 6-7 inches drop. The groups were 2" high at 100. As for the quote the 7mm needs to be run hard I am going to assume higher velocity? I really like the bullet and am to stubborn to quit but will try some other bullets just to compare.
 
For many years the folks that did up the various manuals had trouble developing top speeds with the 7mm Rem. mag., they ran into pressure problems before they could get the advertised(factory) speeds. Quite often they would post a special note to this effect as the velocities were not much higher then the std. 270 Win. I'm sure this has been corrected with all the newer high performance powders.
 
Also be aware that the ballistic coefficient may be a fair bit optimistic (by say 0.025-0.030), which will start to have an effect out at 300yds. Did you also have all atmospheric conditions and the sight height correct in the ballistics calculator?

Mark
 
If you are sighted in at 2" high at 100, and it's dropping 14" below point of aim at 300, you are shooting that bullet about 300 or 400 fps too slow...:p
 
Am in the process of trying different powder to compare. Have tried 2 different ballistics programs with temperature/elevation settings and the results show that this bullets is going at least 400 fps to slow. The 4350 is a bit ambient senitive and there is a 3% loss from the factory. My 338 shoots awesome with the same batch of powder. Not given up yet as will try to push the bullet closer to the lands to minimize any losses to build up pressure without more powder. Barnes mentioned they have seen increased CUP pressure by doing this. The thing with these new bullet design is the ribbed design. If the explosive gases get past the first ring the rib acts as a area for the pressure to push back on, this would be compounded by the other 2 rings. Mind you this is just me thinking out loud.
 
try Rel22,.....I use 69grs in my 7 Mag...pushes the 140 TSX to near 3300...a friend has run up to 70grs in his 7 Mags and one of them runs near 3400 with a 140....that'll flatten your trajectory so you aren't shooting a 280....or a 7x57...
 
Farmer001 said:
The thing with these new bullet design is the ribbed design. If the explosive gases get past the first ring the rib acts as a area for the pressure to push back on, this would be compounded by the other 2 rings. Mind you this is just me thinking out loud.
Click to expand...

If the relief grooves filled with high pressure gas it will have no effect because the pressure pushes on both the front and rear edges the same, cancelling out any loss or gain.

Mark
 
Rembo said:
try Rel22,.....I use 69grs in my 7 Mag...pushes the 140 TSX to near 3300...a friend has run up to 70grs in his 7 Mags and one of them runs near 3400 with a 140....that'll flatten your trajectory so you aren't shooting a 280....or a 7x57...
Click to expand...

I can safely get 3050 fps with 140 gr bullets in my .280. Should be pretty easy to get to 3200-3300 with a 7 ram mag. From the ones I've seen or used they seem to work better with max loads.
 
RL 22 , never tried this powder willl give this a try, lots of info thx. I agree should be getting more velocity and should not be that hard. Slower burning powder may be the ticket.
 
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