1903 A4 chamber question

[oneof79]

Just got myself a brand new 1903A4 replica. To break it in I shot some ammo I had loaded for my M1 Garand. It shot ok groups at 100 yards. I ordered a Hornaday case for my OAL gage, when it came in I found that the throat on this new rifle is so short that I cannot load 175 gr Sierra hpbtm bullets to book c.o.a.l. without cramming the bullet into the lands by .035.

Is the short throat normal for these rifles? What do I do about it? My options are, shoot shorter bullets, seat these bullets deeper and lighten the load some, or have a gunsmith work on it. Any one have any other suggestions.

 

[Boehlertaught]

Not that I ignore the text book OAL of rounds I load but I use the lengths as a guide only. For best results on any of my rounds I always seat the bullets where the base of the bullet is just a few thousands ahead of the cases shoulder to neck bend. When I say the bulletbase I don't mean the flat end of tube bullet, unless the bullet has a flat bottom. Your boat tailed bullets base, in my definition, is the point where the bullets largest diameter starts to taper to the boat tail. If you're using a powder that fills to or into the neck of the case I would change to another powder as you don't want to compress the load. Make a dummy round with the bullet seated as above and check how the round fitsnyour chamber.

 

[oneof79]

I hate experimenting. In this case I reduced the max book load by 10% then loaded 5 rounds. Added .75 grains to the minimum load and loaded another 5 rounds and so on. I have 6 sets of loads to try tomorrow. Hopefully I'll find something that will work without seeing signs of overpressure.
I have never had a rifle where the rifling started as close as this one does.

 

[Sanford]

Not particularly unusual and not uncommon with Sierra bullets - maybe because of the particular shape of the ogive? I've seen similar with their 168's but was able to close the bolt without an unreasonable amount of force so just shot them and they did well. I seem to remember some match shooters like to force the bullet into the lands a tiny bit for accuracy ... whether it actually matters or not I can't tell you.

 

[Boehlertaught]

Sanford I think you have a good point but I am nervous about jamming the bullet into the rifling. Even with a decent crimp you could get bullet setback and chamber pressure could go up just because because of the extra effort to launch the bullet.

 

[Sanford]

Sanford I think you have a good point but I am nervous about jamming the bullet into the rifling. Even with a decent crimp you could get bullet setback and chamber pressure could go up just because because of the extra effort to launch the bullet.

Would be a concern if you're nearing the maximum load. Think I'd probably double check the OAL with a caliper just to make sure that what I was seeing was coming from where I thought it was, too. Depending on the shape of the bullet it's possible for it to hit the lands even when the OAL is correct ... usually match stuff again, though.

As an interesting and possible irrelevant aside - some lots of the Greek HXP milsurp that CMP sells is known to run a bit long both to the datum line on the shoulder and OAL and can be booger to extract from an 03/03A3.

 

[oneof79]

I took my new loads out to the range yesterday and fired them. I have the bullets set back from the Sierra specs .050. Everything shot ok with out any signs of overpressure. One load shot at 100 yards gave me a group of about an inch. I think I'll go up and down a little from there and shoot some more next weekend. When I shot my "max" load, which was 1/2 a grain lower than book max the group opened up to nearly 2.5 inches.