A bit surprised as my buddy is playing with solids in a 300 NM and he has pretty minimal bullets and neck engagement with a similar freebore
It’s enough but barely.
- Thread starter b6graham
- Start date
It’s enough but barely.
Yup, I was surprised how long I could seat them without touching the lands on a standard 0.250” freebore.
So about pocket integrity: I am not convinced i am measuring web expansion correctly. I measured post firing and before FL sizing, and it seems you get a false measurement then (1.5 to 2 thou expansion, which seemed excessive). If i FL size the case, this reduces to 0.5 to 1.5 thou. What is the correct method?
The 300 WSM is a rebated case, so the rim is out of the way and not interfering with the micrometer. Before the first firing, Norma brass had web diameter (i picked the largest diameter near the case head) of 0.5480 to 0.5485 (with maybe +- 0.2 thou of possible operator error in my measuring technique). Post firing and post FL sizing that went up to 0.4590 to 0.5495, so most cases seems to expand between 1.0 and 1.5 thou on the first firing.
Second firing expands the case head much less, around 0.3 to 0.4 thou. Is that ok or too much?
Primer pockets are still holding primers, but primer seating force varies noticeably. The cases exposed to max loads during pressure testing feels less tight.
I have a set of go and no-go pin gauges for checking primer pockets from Ballistic Tools. No-go pin is 0.2059” and the go-gauge pin is 0.2093”. [Rexbeti micrometer with 5 digits after the zero (last digit is mostly useless), calibrated against a gauge block and checked for linearity against a Mitotoyo feeler gauge set.] The go-gauge is only able to go in a quarter of the way into the primer pocket. Actual Federal primers measure 0.2046” in diameter. Primer pocket measured with calipers (leas than perfect accuracy) is around 0.206 to 0.2065”. Looks like i still have 1.5 to 2.0 thou of interference fit. Feels adequate when i seat the primers.
Not seeing bright full moon ejector marks, but bolt lift is medium to hard at the top end. Primers have minimal cratering. Some minor muffin top effect, but there is still radius to the primers. [Curtis uses a 60 degree bolt throw, which tends to be harder than normal 90 degree actions. Not yet sure what would be a reliable pressure sign with the new magnum bolt.]
If i may ask for coaching:
1) What is typical case head expansion of a beltless magnum case on the first firing? What is max allowed?
2) What is max allowed expansion on subsequent firings if you want 8-12 reloads from your cases?
3) Best place/best method for measuring “case head expansion” (where on the case, and when: before or after FL sizing)?
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MPA chassis, Curtis Axiom action, switch barrel setup via West Texas Ordnance “switchlug” system, 300 WSM match chamber, 7.0 twist, 28” Spencer/MPA barrel, APW 5 port brake, chamber cut for 0.160” freebore. ATACR 5-25 SFP scope in Nightforce rings. Currently have a 20 MOA rail (needs 50 at least, but probably 60 MOA would be best). Accu-tac bipod. Weight kit installed after photo was taken: 24.5 lbs total weight.
Norma brass is on the soft side Typically with softer brass I prefer to fire a medium load first before doing pressure testing to help work harden the head. I’d bet you see your growth slow with 3rd firing and 4th.
Could always use the ball punch method and tighten up those looser ones
Could always use the ball punch method and tighten up those looser ones
By the way @Steel head you were right. I do have the .180 free bore not .250
I was measuring to the bore riding ring and not the bearing surface where it actually engraves. Had to jam one good to figure that out
I was measuring to the bore riding ring and not the bearing surface where it actually engraves. Had to jam one good to figure that out
How is that Spencer mpa barrel? Long wait times?
Too early to be truly sure, but: Very pretty and shiny inside (Teslong borescope), seems like they did a good lapping job.
It shot multiple 208 ELDMs into the same hole during fireforming of the new Norma brass, using a random starting load near minimum. Have not started load development yet, so will have to wait and see.
The 28” 7 twist is meant for 241 and 212 Seneca copper bullets as well as Warner Tool bullets like the 198 Flatline.
Have a second 8 twist (30”) for heavy lead core bullets (200 to 230 gn range). Takes 90 seconds to switch barrels at the range. Zero seems to hold within 2-3 clicks, if the threads are kept clean, usually well less than 1.0 MOA. I do not re-zero the rifle after a barrel swap, rely on the ballistic calculator to remember the scope offset. Then recheck zero at distance.
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By the way @Steel head you were right. I do have the .180 free bore not .250
I was measuring to the bore riding ring and not the bearing surface where it actually engraves. Had to jam one good to figure that out
Looks like you forgot about it and found it in the back haha it's so tempting
No, I knew about it all the time.
I used it to fix the 338 edge chamber because the the reamer I rented was terribly worn.
That reamer saved my bacon!
Are you doing your own barrels now?
Awesome man. That sure would be nice cut out time and a ton of money.
Yea
I’m far from what you’d call a machinist but I do have a fair amount of time on a lathe and mill.
We have a few lathes at work so I made spiders for one of them and bought some of the necessary tooling.
Basically my first barrel paid for the tooling.
Seems like it worked out great then. Cheaper and easier to try different cals too
I’m jealous the only barrels I’ve done my self I reamed the chamber by hand!
I’ve been looking for a lathe for a while now. Not just for guns but my chainsaw business as well
I do chainsaw porting. Lathe would help me shrink the combustion chamber. Shorten the deck and make pop up pistons
So what length you looking for.
I’d probably go 30-32”
So with the pva bashing threads last week I ordered some of these to play with, I didn't plan on playing with solids, but was a quick way to say thanks.
Now I shoot a 300NM and I'm looking for a good starting point. I have VV N560 and N570 to start.
The best I can find is PVA reccomends starting at 200gr load data and working up a load with starting at .020" jump.
So with N570 looks to be around 79-88gr
And N560 would be around 72-81gr
Does that seem right?
Thanks
Now I shoot a 300NM and I'm looking for a good starting point. I have VV N560 and N570 to start.
The best I can find is PVA reccomends starting at 200gr load data and working up a load with starting at .020" jump.
So with N570 looks to be around 79-88gr
And N560 would be around 72-81gr
Does that seem right?
Thanks
My load for these:
.300NM 28" 1:8 with 0.250 freebore
Lapua Brass
GM215M
89gr N570
3.90" COAL
3075fps
Note: I was able to push them hotter with up to 94gr, but pressure was getting up there. 89gr was very accurate and consistent with no flattened primers and no brass brutality.
I found that N565 also works, but you hit pressure a bit sooner. N560 is probably a bit too fast.
.300NM 28" 1:8 with 0.250 freebore
Lapua Brass
GM215M
89gr N570
3.90" COAL
3075fps
Note: I was able to push them hotter with up to 94gr, but pressure was getting up there. 89gr was very accurate and consistent with no flattened primers and no brass brutality.
I found that N565 also works, but you hit pressure a bit sooner. N560 is probably a bit too fast.
Thanks. I'll get a few loaded up and see how they work. They are long looks like I'm around 3.9825" coal to the lands.
I couldn't even get them to touch the lands - the bullet just fell out every time I got remotely close. So I'm jumping at least 0.1" but still getting really nice groups regardless.
Well. The since I had to jump these so far I couldn't get any real consistency with N570. My only single digit SD was at 87.5gr at 2970fps. The rest was in the 13-35 range. My group size wasn't anything to brag about. Might have been sub moa but close.
I had the same problem at the start until I used a tighter neck bushing and mandrel. It may just be me, but my setup preferred tight necks with these bullets.
Found similar results in a 338 Norma running solids.
The minimal neck grip to get a reasonable jump seemed to not want to produce a decent ES so we got a bushing that was 2 thou smaller and it immediately helped.
Probably going to try even a bit smaller bushing.
Can’t seem to get these 198’s to repeat. Had a half min group once. Now I’m back to 1” best it will do. Figured it was time for a clean. Took her down to bare metal verifying with bore scope. Still crap. Tried more neck tension today nope! Played with seating depth more and it got worse. Checked all screws and such nope all good. Gonna shoot my Berger load to make sure scope isn’t it.
I've heard of this a few times with the pva bullets. The hunting line seemed great but the few target ones I shot was a head scratcher.
No pressure. Went with the lower velocity node. Just couldn’t find a seating depth were they would tighten up better than 1” for 3 shots. Some groups where 3”. Tried from .010” off to .039” off in .003” increments
I may revisit them in hot weather. For now I’m done burning through components. I’ll shoot the vlds till I run out. Just opened my last 8#’er of h1000
300 Norma, chambered by PVA with Hawk Hill 1:7 twist @31", for the PVA 212's and 241's, as well as Cutting Edge's 230's
The 241's with that barrel like H50 BMG. At 91 gr, velocity was at 2780, .020 of the lands, .336 bushing, no pressure, but was at 102-ish% compressed load. Other powders that I have tried with this were D100 and RL26, both of these powders were almost identical in velocities, at 2980- 3001 FPS, which showed the first sign of lite pressure/ejector marks. However both of these powders were giving ES of 20 FPS, with .750 to 1.5 moa groups where as the 50 BMG would give 3 FPS ES over 5 shot strings and would produce groups less than 1.0 moa for all five shot string groups tried with 50 BMG
When ever the weather warms up and our daylight returns to interior AK, I'll give D100 and RL26 another look as well as RL50, N570, and RL 33. Again my goal is to be objective with this, finish up on the 241's and shoot them against the Cutting Edge 230's, and PVA's 212,and let the barrel tell me which bullet it likes at 100, then see how well all three print on paper at 1000, then see if all and or which stay stable below 1100 FPS and maintain/give the best consistency. (BC aint everything if they won't fly slow). Would like to have tried the CE 240's but they said in a phone conversation that the 240's require a 1:6 minimum twist. Will update in the spring.
Hello,
I'm curious if you had to use a special seating die with the seneca bullets. I'm worried about messing up the tips. I will be testing the 212s this summer.
I drilled out the front of the seating cup and it doesn’t bother the tip
Hopefully interior AK has heated up - and the mosquitoes are not up to Egyptian plague levels yet!
Any luck with the 241 Seneca bullet out of your Norma Magnum?
I got good results from 212’s, around 2950 fps (from IMR4350) from a 300 WSM built on an existing short action receiver, got 0.25-0.35” groups after seating dept optimization, but the 241’s were too heavy for my short fat baby case, speed was rather low even with a 28” barrel. I guess not enough case capacity (or maybe not the best choice of powder).
I have a friend that is shooting the 241’s from a 300wsm with great success with a 1-7 twist at around 2800 FPS from a 28” barrel. I’m pretty sure that he found RL26 as the powder of choice.
