.270 load development help with next step

[iXanadu]

Hey everyone,

I have almost reached the max powder recommended by the Nosler reloading guide but am way under the speed advertised. I'm trying to decide how much further I can safely push the load to high 2900's. I'm trying to develop a highly accurate load that can still hold a tight group at 300 yards.

Browning X-Bolt in .270c
2.853 OAL to lands per Hornady OAL gauge technique

Components:

H4831sc powder
Trimmed, prepped and neck sized once fired Win brass (same gun)
CCI 200 large rifle primers
Nosler 130g ballistic (hunting) bullet (will also develop AccuBond later)

All rounds were shot from bags so minimal user (some for sure) errror.

First trip to the range was to determine OAL. All rounds were loaded over 55g H4831 SC. I tried:

2.763 OAL (same as factory ammo)
2.840 OAL
2.847 OAL.

It was clear that 2.847 OAL was the best OAL with 2 in 1. 2.840 was a close second and I may go back to that after figuring out my powder charge.

Second trip all used 2.847 OAL and only varied with powder charge. This is where I need some advice for next step.

Data (pictures follow).

55g 2704, 2693, 2693, 2749 fps. 2709 avg 56 fps spread

57g 2818, 2836, 2807, 2824 fps. 2821 avg 29 fps spread

58g 2879, 2873, 2861, 2855 fps. 2867 avg 24 fps spread.

I'm new to this, but I can not see any pressure signs on any of the primers (see pics). I want upper 2900 fps, and the only thing I can figure (guess) is that my oal is reducing pressure and fps. Looking at the rate of speed increase, 59g will only put me at 2900. I guess I would be near 61g before getting 2990-3040 where I think I want to be. For the more experienced reloaders out there, especially for folks using same powder and components, if I use FPS and pressure signs as a gauge, can I push it past the book & how far do I dare?

Pics:

 

[super-7]

Just a couple things off the top of my head.
Verify your chrony is accurate, I run my 17 hmr over mine every time I set it up.
Set up at 12'-15' my chrony reads right around that 2550 fps @ 2500 ft of altitude.
Your altitude may play a factor and setting a chrony up under 10' can have effects from muzzle blast.
Barrel length , alot of the test barrels in many loading manuals are say slightly longer then a typical hunting barrel. On average 50 fps slower per inch shorter, it's a baseline.
I would say you are on the right track and I would also start moving up in 1/2 gr increments until you start to see pressure signs .
One thing you may want to try is switching to a magnum primer with 3 of each of you existing loads and see what difference it makes. Any time I start to creep toward that 60 gr mark with slower powders I prefer to do my development with a mag primer.

 

[iXanadu]

Just a couple things off the top of my head.
Verify your chrony is accurate, I run my 17 hmr over mine every time I set it up.
Set up at 12'-15' my chrony reads right around that 2550 fps @ 2500 ft of altitude.
Your altitude may play a factor and setting a chrony up under 10' can have effects from muzzle blast.
Barrel length , alot of the test barrels in many loading manuals are say slightly longer then a typical hunting barrel. On average 50 fps slower per inch shorter, it's a baseline.
I would say you are on the right track and I would also start moving up in 1/2 gr increments until you start to see pressure signs .
One thing you may want to try is switching to a magnum primer with 3 of each of you existing loads and see what difference it makes. Any time I start to creep toward that 60 gr mark with slower powders I prefer to do my development with a mag primer.

Thanks for the tips. I have no way of verifying my chrony. This was the first time I ever used it, and don't have anything with a known baseline. It was set 15-20' off the bench. I shoot from a covered area and have to locate the chromy forward to get the right light.

Nosler reloading book states 24" shilen barrel with a 1-10 twist. The X-Bolt has a 22" barrel with a 1-10 twist rate. So if there is a 50fps per barrel inch, 55g of h4831sc should drop from 2909 (book) to 2809 actual which is still 100fps faster than what I was able to measure at the same powder charge.

 

[Thebear_78]

Your col seem to be really short to me. I don't have my data handy but seem to remember my loads as all over the 3" mark with most up near 3.2"

Also you might try 7828 or re17 I've had good speeds with both of them

 

[iXanadu]

Your col seem to be really short to me. I don't have my data handy but seem to remember my loads as all over the 3" mark with most up near 3.2"

Also you might try 7828 or re17 I've had good speeds with both of them

Hi Bear,

The measurements are OAL. The OACL for this is a tad over the SAAMI specs.

You are right about other powders. I know there are other, maybe better powders, but I bought this up when it was the only thing I could find. I have 8lb's and feel I need to develop and shoot this first. When I looked in the Nosler book at tested powders, I googled each one. As luck would have it, H4831SC was the books listed "most accurate powder tested", and what I could find available.

 

[SJB358]

I think your fine moving in .5 grain increments. Your accuracy looks really good and your cases look fine as well. I'd be fine with pushing a little harder on them. Your going at it methodically so I see no reason to not push them into the upper 2900 range. Just about any 270 w/ H4831 should be entirely capable of attaining 3000 with a 130.

 

[DrMike]

Increase your charge in 0.5 grain increments, watching for pressure signs. At the first sign of pressure, drop back one grain for safety. This is the old standard methodology for working within a safe charge/pressure. The increase in velocity with increase charge shows no particular signs of plateauing at this point. You will see a plateau in velocity contra charge weight which is indicative of maximum effective charge. Even if pressure were still safe, you would gain nothing by continuing to increase powder charge. Keep your eye on the pressure signs and work up slowly. The reason Nosler speaks of their data as a guide, is that it is a guide. Your rifle will not likely duplicate their test conditions. You are crafting a load for your firing system. You are taking into account differences in lots of each of the components and differences in chamber dimensions. All these combine to create the particular conditions you observe whenever you fire the system. While velocity is not the ultimate proof of pressure, it can serve as a rough guide for you to help keep you from unsafe conditions. Half grain increments are less than one percent change, which should serve to keep you from a disastrous condition, provided the firing system itself is safe.

 

[iXanadu]

SBJ & Dr. Mike,

Thank you for the input. I think my next outing, I'll take three 4 round builds. 59gr (top of book), 59.5gr and 60gr. If 59 or 59.5 get it done I'll stop there. If not I'll run all three. I'll report back the results.

Broader questions. My objective is a highly accurate round (sub-moa) that will still hold a 1.5-2" group at 300 yards. I will be developing 2 cartridges, one with ballistic tips for target practice (they are cheaper) and one with AccuBond bullets for hunting. I've read similar threads here that they develop very similarly, and once dialed in, function well with the same sight picture. What I still don't have my arms around, is what fps do I need for hunting that will have sufficient ballistics to efficiently take a deer or bear down upon impact. Any hunters familiar with these rounds that understand ballistics enough to chime in?

PS: I understand shot placement - that is the reason for the "highly accurate" round development.

 

[SJB358]

Velocity within the bullets your talking about will whack deer off their hoofs out to alot longer than 300 yards. Bears, I wouldn't recommend shooting as far out, unless your hitting them with a heavier bullet. I use 1000ftlbs (at impact site) for deer and would probably stick with 1500ftlbs for bear. Not because it'll knock them off their feet, but typically, there will be enough bullet FPS and energy left to kill well.

Energy isn't a huge factor, but it is a good place to gauge your load. Unless you strike bone, putting an animal down everytime is probably more chance than anything else.

 

[DrMike]

SJB358 has given you the straight skinny. You do well to heed his advice at this point. You may or may not find that ABs and BTs are sufficiently identical to substitute. Ensure there are sufficient similarities in velocity/ballistics data to verify any effort to practise with one and hunt with the other.

 

[iXanadu]

Thanks guys. Where can I find an intro to ballistics so that I understand how a 130gr bullet at a stated velocity translates into ftlbs at impact?


Sent from my iPhone using Tapatalk

 

[SJB358]

Hornady ballistic calculator online or even the back of the older Nosler manuals have decent predictions.

Be careful, you could get addicted real quick. My wife thinks I go to work to feed my hunting and shooting habit!

 

[ColColt]

My best load with two 270's is the 130 gr Ballistic Tips and 59.5 gr H4831. I also get good accuracy with 48 gr IMR 4064. I've went up to a max of 60 gr H4831 but decided on the 59.5 gr load as it was consistently accurate enough for me giving sub MOA accuracy from an old 1952 M70 and a Lyman All American 4X Perma Center scope..

 

[ColColt]

I forgot to mention the good groupings with 4064. Not bad here but 48 gr was even better.

 

[SJB358]

Yup, that sorta load would do great stuff. Way to represent the 270!

 

[ColColt]

I know of someone that would be proud of the rifle and targets...wonder who?

 

[SJB358]

You know it!

 

[ColColt]

My hero since 1968. He's the one that turned me on to the 270.

 

[Rol_P]

Are there any factory loaded 130's that area advertised @ 3 000 fps that you could run over your chrony to see where they are in relation to your loads? That might be interesting if not definitive.. I agree with all the above suggestions. Good luck, Rol

 

[ColColt]

Winchester's 130 gr Power Point is rated at 3060 fps...pretty close.