Is magazine length screwing me?

[29aholic]

In the old days of shooting BR it didn't matter because I was shooting single shots loaded straight into the chamber. My old tried and trued method learned from Warren Page was to mock up a dummy round with an empty case with a bullet barely seated into the case mouth. Chamber that in rifle and close the bolt. The lands will then seat the bullet the rest of the way into the case. I would then set my seating die to the dummy then take one fill turn deeper on the die.

This worked great for years but now I am more interested in tactical type shooting which pretty much requires the use of a magazine.
I tried the above method with my SPS Tactical (I know I know, but the gun shoots) and the round would not even load into the factory magazine. I had a PTG Stealth DBM installed and that round will fit in the magazine but wont chamber out of it.

I loaded some rounds yesterday to about the maximum length I could get to feed out of the magazine.
The load was
41.5gr H4895
175gr SMK
Rem BR brass
CCI BR4 primers

Initial test results was ~1/2" for 10 shots. I didn't have the scope focused very well and I was shooting at basically a spray painted dot on a piece of cardboard.

1. Long way around to the question but does OAL really make that much difference?
2. Can you chamber one with a throat short enough you can seat to the lands and still be able to feed from a magazine?

Thanks in advance.

 

[InfScout1/69]

Is magazine length screwing me?

I would load your rounds to mag length so it chambers then play with the powder and do the ocw test and use what works best

 

[givey]

I would add that the 175SMK is a very jump tolerant bullet.

 

[29aholic]

I would add that the 175SMK is a very jump tolerant bullet.

How are the 155's with jump?

 

[djskit]

I load 175s at 2.8 OAL with 44.5 grains of varget and call it a day. I could not even tell you how far away they are from the lands because it does not appear to matter. The load shoots in every bolt 308 I have owned.

For my 6.5 creedmore, I load 0.015 off the land and have never felt compelled to change until about 2700 rounds and the throat lengthens then I re-evaluate. Last time it did that we were beyond mag length and had to dial back. But 3100 rounds and the rifle is still a boringly consisten 1/2 MOA.

 

[Darkphage]

OAL can make a big difference. To say that every gun will shoot best with the bullets jammed into the lands is probably an oversimplification. IF you will reload several lengths that will all feed from a magazine, you may find that at some length they shoot the best. My advice would be find what is the maximum length that will feed, then shorten the round by .005" then again by .005" more and so on down to the SAMMI specs for that cartridge. Try shooting them all and see which length your gun prefers, that will magazine feed. It is often the case that the lands are placed far enough out that you can't magazine feed the rounds and have them touching the lands. Its a pretty common problem.

I think that answers #1, as for #2 I would imagine it is possible to do what you asked, but I am not a gunsmith, and as such, have no solid knowledge to impart.

I hope that answers #1, if they all shoot about the same, then I would do what InfScout1 said and start playing with other factors to see if you can improve things.

Thanks,

Dark

 

[ptaylortx]

My aac-sd would shoot .75moa with a .010" jump and 2 moa inside mag length. I don't want a single shot rifle so I gave up and re barreled it.

 

[BapZander]

You mention that you loaded some rounds that fit in the mag, but wouldn't feed?

If this is the case, then typically the nose of the bullet is getting caught under the feed ramp. You can fix this by putting a small notch in the feed ramp:

I had to do this with my CDI bottom metal/Alpha mags to get max OAL for my loads. Have never had a problem feeding.

this pic is through the bottom metal with the barrel pointing north.

 

[givey]

29aholic;3156305]How are the 155's with jump?

I don't have any expeience with the 155's. I shoot both an Armalite AR10T and a Rem 700 AAC-SD in .308. My 700 will shoot 1/2MOA or better with Lapua brass and 43.1 or 44.3 of RL15, 175 SMK and FGMM primers at 2.81 and still fits in the mag well. The AR10 is a 1x11.25 twist and shoots Sierra 168 match kings in cloverleafs with 42.5 grains of RL15 Win Brass and FGMM primers. I'm not sure how playlortx got his to the lands in his AAC-SD, when I mearsured my chamber it would have left very little in bullet in the brass, have to love Remington chambers.

 

[DT1]

To the OP, if your rifle shot 1/2" groups (I assume at 100yds) with the load you describe under less than ideal conditions, I'd call it good and find something to worry about. 1/2 moa accuracy is plenty good for tactical, field precision type matches.

Load up a bunch of rounds and practice shooting off barricades, out of window ports, off of logs, barrels etc. Most importantly, get out and shoot some matches. That's how you'll get better. Good luck!

 

[29aholic]

To the OP, if your rifle shot 1/2" groups (I assume at 100yds) with the load you describe under less than ideal conditions, I'd call it good and find something to worry about. 1/2 moa accuracy is plenty good for tactical, field precision type matches.

Load up a bunch of rounds and practice shooting off barricades, out of window ports, off of logs, barrels etc. Most importantly, get out and shoot some matches. That's how you'll get better. Good luck!

Thanks, I know you are right. I do tend to get a little anal at times. I need to find some place around here to practice the tactical aspect on steel vs punching holes in paper.

 

[Hollywood 6mm]

You mention that you loaded some rounds that fit in the mag, but wouldn't feed?

If this is the case, then typically the nose of the bullet is getting caught under the feed ramp. You can fix this by putting a small notch in the feed ramp:

I had to do this with my CDI bottom metal/Alpha mags to get max OAL for my loads. Have never had a problem feeding.

this pic is through the bottom metal with the barrel pointing north.

I had this exact same problem, even when loading to mag length because my magazines allowed the round to walk forward enough in the magazine to get hung up under the feed ramp. Cutting open and reprofiling the feed ramp fixed that problem for me.

I also have an AAC-SD. With 175SMKs, I am loading them to ~2.925 OAL (base to tip) and getting them close to the lands but not touching. Once I did that(instead of loading 2.8"), I did see a fairly significant improvement in group sizes when I ran powder charges that hit the barrel nodes. Hornady match brass, 175SMKs, Winchester LR primers, and 44.4 or 45.4 grains of Varget are both capable of putting 5 rounds touching at 100 yards so long as I make sure the loose nut behind the trigger is properly secured first.