I have a 308 10TR that I have been trying to develop a load for with AR Comp and 155 Scenars. The rifle's throat is quite short at 2.136" from the bolt face so I load them around 2.115" base to ogive for a 20 thou jump just to start development. With Lapua large primer brass at 41.1 grains I start to get ejector marks. This is around 2820 fps. Is lapua brass just soft or is it happening since I am loading them so short? With my Remington brass I know I could get higher speeds with no issues.
Is Lapua brass soft?
- Thread starter TRDJer
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Im not sure if this is the cause, but I recall seeing a chart that showed case water volume by brand for certain cartridges- lapua alwysbwas on the lower end ( had less internal volume) and remington and winchester had more. So less space with a certain powder charge equals more pressure. I haven’t found Lapua to be soft by my means. I also had a 10tr when they first came out- shot 168 match kings with 42.0 Gr varget very well- and my rifle also had a very short throat ( seems to be something savage does with a lot of their rifles).
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No lapua is the best. You can load it 50 times with super hot loads. Haven’t you read online.
Sarcasm aside I had primer pockets loosen up after 2 reloads of mild loads in 7mm-08 stamped brass
Sarcasm aside I had primer pockets loosen up after 2 reloads of mild loads in 7mm-08 stamped brass
I've read that an oil film on the brass or chamber walls can give you signs of excess pressure on the case head, such as ejector marks. The premise of the article I read was that if the case can't grip the chamber as it expands under firing pressure, more than normal force is transferred to the bolt lugs via the bolt face. Regardless of whether that's true or not, I make a habit of removing any oil from the chamber of a clean rifle before I start shooting.
Have you checked your headspace?
Have you checked your headspace?
The only brass harder than Lapua is military Lake City brass 5.56 and 7.62, I will assume your Canadian military brass is the same.
How Hard is Your Brass? 5.56 and .223 Rem Base Hardness Tests
http://bulletin.accurateshooter.com/2014/05/how-hard-is-your-brass-5-56-and-223-rem-base-hardness-tests/
I guess you can call me a cheap bastard, I just bought 300 once fired Lake City 7.62 cases and I'm in the middle of sizing, prepping and weight sorting these cases. Its my understanding the long range sniper ammunition comes from standard M80 cases that are weight sorted within a 2 grain weight span.
How Hard is Your Brass? 5.56 and .223 Rem Base Hardness Tests
http://bulletin.accurateshooter.com/2014/05/how-hard-is-your-brass-5-56-and-223-rem-base-hardness-tests/
I guess you can call me a cheap bastard, I just bought 300 once fired Lake City 7.62 cases and I'm in the middle of sizing, prepping and weight sorting these cases. Its my understanding the long range sniper ammunition comes from standard M80 cases that are weight sorted within a 2 grain weight span.
Velocity is another indicator of pressure, assuming the powder is not too fast for the application. The velocity looks low, so I doubt pressure is high.
If brass was soft. it would mark easily.
I have found lapua to take high pressure loads for many re-loads without issue.
If brass was soft. it would mark easily.
I have found lapua to take high pressure loads for many re-loads without issue.
I’m not sure if I somehow have a soft batch of brass or not. My other though would be just because I am loading so short that is jacking up pressure. I look at the velocities and powder volumes other people get with their Lapua brass and I know I could never get that high. At 42.0 grains (2850 fps) the case head smeared a little from the bolt face turning.
Below is a photo from accurateshooter.com and its reloading forum. The poster shot in long range competition and said he made a workup loads until he got brass flow into the ejector and then backed off 1 or 2 grains. This let this shooter find out the elastic limits of the brass and how much pressure the case could take before over stressing the case.
Bottom line if you are getting brass flow into the ejector and case head swipes your load is too hot. This can also be caused by a carbon buildup in the chambers neck, seating too deep, etc.
Did you start at the suggested start load and work up?
NOTE, if you just have a circular ring on the base of the case and no pimple like bulge the ejector hole may just have sharp edges and causing the ring on the case. This can be fixed by stoning the ejector hole circumference and polishing.
Bottom line if you are getting brass flow into the ejector and case head swipes your load is too hot. This can also be caused by a carbon buildup in the chambers neck, seating too deep, etc.
Did you start at the suggested start load and work up?
NOTE, if you just have a circular ring on the base of the case and no pimple like bulge the ejector hole may just have sharp edges and causing the ring on the case. This can be fixed by stoning the ejector hole circumference and polishing.
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The suggested load with a Federal case on the Alliant website is 43.2. I started at 40.2 and worked up in 0.3 steps until 42.0. This was loading with a 0.020" jump and 2.125" base to ogive (short Savage throat). This past weekend I loaded up 6 rounds of 39.9 and 6 rounds of 40.2 but at 0.010" of jump. With 40.2 grains and 0.020" of jump I was at 2780 fps. With 0.010" of jump it dropped to 2724 fps and ES of 29. With 39.9 grains I was getting 2715 fps (and an ES of 14). Both groups were just over an inch. The speeds I'm getting just don't seem to be normal but I am pretty new to reloading so this might just be a reality check and I might just have to deal with low speeds.
The throat of my rifle is 0.070" shorter than another 10TR in the family. I don't know if it would be an idea to see if I could get it reamed out by a smith or not. Depending on price it might be more worth while to ditch the factory barrel and get a good prefit. I'll see about getting a cheap iPhone borescope to check for carbon buildup. I could give up on AR Comp and try Varget. I could also give my usual Remington brass a try as with them I'm getting 2635 with a 175 TMK without issue with AR Comp. At this point I'm not sure where to go.
The throat of my rifle is 0.070" shorter than another 10TR in the family. I don't know if it would be an idea to see if I could get it reamed out by a smith or not. Depending on price it might be more worth while to ditch the factory barrel and get a good prefit. I'll see about getting a cheap iPhone borescope to check for carbon buildup. I could give up on AR Comp and try Varget. I could also give my usual Remington brass a try as with them I'm getting 2635 with a 175 TMK without issue with AR Comp. At this point I'm not sure where to go.
Sounds to me like that powder is a bit fast and likely double base high energy being aliant if you're really getting near 2800fps with only what a 24" barrel and 40-41gr... consider that most of us shooting 155's our of 30" barrels using 46gr of varget/N150 get around 2950-3000fps. We're pretty much all using Lapua brass in competition near or above its max and getting plenty of reloads out of it if its done right, its not the problem.
Instead of messing with that powder you should try a good proven 308win powder, Varget, N140, N150, that sort of thing, that's where you go from there.
Instead of messing with that powder you should try a good proven 308win powder, Varget, N140, N150, that sort of thing, that's where you go from there.
You mentioned smearing. That means the brass extruded. The velocity is not high, so either the brass is soft or the powder is too fast. I am not familiar with that powder, but I doubt a QC problem with Lapua.
I use N140, N150 Varget or RL15 to get 3000 fps with 155s (32" barl).
Try a known good powder and see if you can get more velocity without pressure signs.
I use N140, N150 Varget or RL15 to get 3000 fps with 155s (32" barl).
Try a known good powder and see if you can get more velocity without pressure signs.
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Recap:
24" Savage 10 TR with a short throat
155 Lapua scenar, Lapua brass, BR2 primer loaded to 2.125" base to ogive or ~2.750 COAL giving 0.010" jump
Update:
I switched over to Varget to see what velocities I could achieve without pressure signs. I went to the range two weeks ago and was able to get up to just over 2900 fps (45.1 grains) when I found ejector marks with the BR2 Primer. I was back at the range today where it was hot in the high 20s to low 30s. The ammo was in the shade the entire time and cool to the touch. While retesting some of the same loads in larger groups I was getting intermittent ejector marks around 2800 fps while using CCI magnum primers and 43.3 grains. I also brought along some factory Lapua ammo with the 155 scanar. The factory ammo was loaded to 2.788"and was jammed ~0.030" with the short throat of my barrel and running 2800-2830 fps with intermittent pressure signs.
It is looking like I will have to find a note in the lower 2700 fps (<43 grains) to have a load that wont spike in pressure in the heat. It also seems like regardless of which powder I have tried (8208 XBR, Ar Comp and now Varget) 2800 fps is the safe upper limit.
To revisit my earlier thought, is the fact that I have to load with a short seating depth due to the short throat causing me premature pressure issues or is what I'm experiencing fairly normal? I am considering having it reamed to allow for a longer seating depth to reduce pressures and to make it so that I can run factory ammo without it being jammed. Would this alleviate some of my issues or am I barking up the wrong tree and just need to stick with speeds around 2700 fps?
Alternatively I could switch to brass with a larger internal volume (Winchester or Remington) to try and drop pressures as well. I am also running a 178 Amax with 43.9 of Varget, BR2 primers and Remington brass around 2650fps without issue.
24" Savage 10 TR with a short throat
155 Lapua scenar, Lapua brass, BR2 primer loaded to 2.125" base to ogive or ~2.750 COAL giving 0.010" jump
Update:
I switched over to Varget to see what velocities I could achieve without pressure signs. I went to the range two weeks ago and was able to get up to just over 2900 fps (45.1 grains) when I found ejector marks with the BR2 Primer. I was back at the range today where it was hot in the high 20s to low 30s. The ammo was in the shade the entire time and cool to the touch. While retesting some of the same loads in larger groups I was getting intermittent ejector marks around 2800 fps while using CCI magnum primers and 43.3 grains. I also brought along some factory Lapua ammo with the 155 scanar. The factory ammo was loaded to 2.788"and was jammed ~0.030" with the short throat of my barrel and running 2800-2830 fps with intermittent pressure signs.
It is looking like I will have to find a note in the lower 2700 fps (<43 grains) to have a load that wont spike in pressure in the heat. It also seems like regardless of which powder I have tried (8208 XBR, Ar Comp and now Varget) 2800 fps is the safe upper limit.
To revisit my earlier thought, is the fact that I have to load with a short seating depth due to the short throat causing me premature pressure issues or is what I'm experiencing fairly normal? I am considering having it reamed to allow for a longer seating depth to reduce pressures and to make it so that I can run factory ammo without it being jammed. Would this alleviate some of my issues or am I barking up the wrong tree and just need to stick with speeds around 2700 fps?
Alternatively I could switch to brass with a larger internal volume (Winchester or Remington) to try and drop pressures as well. I am also running a 178 Amax with 43.9 of Varget, BR2 primers and Remington brass around 2650fps without issue.
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